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Himalayan Journal of Sciences Volume 5, Issue 7 (Special Issue), 2008 Himalayan Association for the Advancement of Science 2008

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PEER REVIEWED JOURNAL OF SCIENCE     I     Volume 5 • Issue 7 • 2008   I   |   ISSN 1727 5210
Extended Abstracts
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Volume 5 • Issue 7 (Special Issue) • 2008 • ISSN 1727 5210
The 23rd Himalayan - Karakoram - Tibet Workshop
8-11 august 2008
Leh, Ladakh
A.K. Jain, India
Mark E. Barley, Australia
Mary L. Leech, USA
Sandeep Singh, India (Organizing Secretary)
Sandeep Singh
Arvind K. Jain
Bharat B. Shrestha
Personal: US $ 25.00
Institutional: US $ 50.00
For HKT-23 Workshop Participants: IRs.1000.00
 The 23rd Himalayan - Karakoram - Tibet Workshop
ftn Karakoram Tibet Works h0.
Hosted by
The organizing committee of
The 23rd Himalayan - Karakoram - Tibet Workshop
Department of Earth Sciences
Indian Institute of Technology Roorkee
Roorkee, INDIA
Sponsored by
Council of Scientific and Industrial Research, New Delhi
Oil and Natural Gas Corporation, India
Ministry of Earth Sciences, Government of India
National Hydroelectric Power Corporation
Indian National Science Academy, New Delhi
International Lithosphere Program (ILP)
National Geophysical Research Institute, Hyderabad
The Himalaya-Karakoram-Tibet region is the most fascinating
and unique tectonic domain on Earth and is characterized by
numerous geodynamic processes. The orogen has developed
as a result of the interaction between the Indian and Asian
plates during the past 150 million years. The Tibetan Plateau,
popularly known as the "roof of the world," is marked
by doubling of crust and subduction-related magmatism,
and is currently undergoing an eastward extrusion along
major strike-slip and normal faults, east-west extension and
devastating earthquakes.
The juncture ofthe Tibet plateau and the zone of crustal
shortening (the Himalayas) is marked by the Karakoram fault
and the Shyok and Indus Tsangpo Suture Zones, where the
Neo-Tethyan oceanic lithosphere of the Indian Plate was
subducted beneath the Asian Plate. The subduction of this
ocean is manifested in the evolution ofthe Dras and Shyok
volcanic arcs, imbrication of sections ofthe oceanic lithosphere
of about 140-120 Ma, and deposition of trench sediments. All
this is followed sequentially by emplacement and intrusion
of calc-alkaline and Andean-type Trans-Himalayan batholiths
from Pakistan to the easternmost parts of the Himalaya in
Arunachal Pradesh. Once the Tethyan Ocean closed along the
suture zones, immense crustal shortening followed within the
Himalayan Collision zone to the south, with (i) continental
subduction ca. 57 Ma along the northern edge producing
ultrahigh pressure metamorphic terrain in Pakistan, India
and Nepal, (ii) intense remobilization, Cenozoic progressive
regional metamorphism and leucogranite generation from
the Proterozoic continental crust within the Himalayan
Metamorphic Belt (HMB), (iii) emplacement ofthe HMB
nappes along the Lesser Himalayan Proterozoic Sedimentary
Belt adjacent to the Main Central Thrust (MCT), (iv)
cooling and exhumation ofthe terrain due to tectonics and/or
monsoon precipitation and ensuing erosion, (v) deposition
and evolution of the Himalayan foreland basins, and (vi)
ongoing crustal deformation along major tectonic boundaries
resulting in the present-day seismicity.
The Himalayan orogen is also the cradle for new
geodynamic concepts such as the proposed role of deformation
processes in the inversion of prograde metamorphic
isograds including ductile shearing, leucogranite generation,
monsoon-controlled erosion and channel flow. For the uplift
of convergent orogenic belts, exhumation processes are
linked with erosion and/or tectonic activity for unroofing
the deeply-buried sequences, where one of the mechanisms
may dominate over the other. In mountainous and humid
active convergence zones, surface erosion processes require
concomitant removal of eroded detritus through an efficient
fluvial drainage system, which is an effective alternative to
tectonic exhumation in the modification of structural and
internal deformation patterns
Since the inception ofthe Himalayan-Karakoram-Tibet
Workshop in 1985, this platform has become an important
focus of discussion among active researchers from the
countries of the mountain chain as well as international
groups. The present workshop, the 23rd in the series, is
being held in the cold desert heartland of Ladakh, located on
the Indus Tsangpo Suture Zone and the extensive Andean-
type Ladakh Batholith, emplaced around 60 Ma at around
10 km depth.
Ladakh, the cold desert, consists ofthe two districts of
Leh and Kargil in State of Jammu and Kashmir. Leh with an
area of 45110 km2 makes it the largest district in the country
in terms of area. The Leh district has international borders
with Pakistan and China in the north and is bounded by
Lahul and Spiti region of Himachal Pradesh in southeast.
Ladakh lies on the rain shadow side ofthe Himalayan region
and has both arctic and desert climatic conditions, which
in combination with the high altitude, poor oxygen and
vegetation, low humidity as well as high solar radiation,
make the region inhospitable. In the background, the nine-
story Leh Palace is a distinguished historical monument of
the 17th century Tibetan architecture and is said to have
inspired the famous Potala Palace of Lahasa.
In ancient times, the present Leh district was a part
of Greater Ladakh from Kailash Mansarover to Swaat
(Dardistan) and was neither under the Domain ofTibet nor
under its influence. Lying on the ancient trade silk route
between Tibet and Central Asia, with the majestic Leh Palace
in the background, beautiful Leh is an ideal setting for this
workshop from the geological, historical, cultural, religious
and adventure points of view.
This volume of Himalayan Journal of Science contains
one hundred and twenty four extended abstracts, which will
be the subject of discussion during three-day presentation
during the workshop. One hundred and forty scholars have
responded to our call for the workshop, while about 120
delegates are likely to participate in the workshop.Out of
these, 40 delegates will join us to the Field Excursion through
the fabulous geology ofthe Indian and Asian plate margins.
The Organizing Committee expresses its deep sense of
gratitude to many organizations for their generous financial
support of this workshop and also travel assistance for many
participants. The Editorial Board ofthe Himalayan Journal
of Sciences has been most cooperative in their timely
publication of this volume. Finally, the workshop could
not have been held without the unwavering support of the
Indian Institute of Technology Roorkee.
Organizing Committee of the
23rd Himalayan-Karakoram-Tibet Workshop
Sandeep Singh
Arvind KJain
Mary L Leech
Mark E Barley
Himalayan Journal ofSciences (ISSN 1727 5210) is a peer-
reviewed multi-disciplinary journal published twice yearly.
HJS focuses on biodiversity, natural resource management,
ecology and environment, and other fields related to Himalayan
conservation, and develop-ment. HJS invites authors to
communicate their knowledge and uncertainties from all the
HJS publishes works in the following genres:
i) Research papers: report on original research
ii)   Review papers: thorough account of current developments
and trajectories in any field covered in the journal
iii) Articles: narrowly-focused account of a current development
in any field covered in the journal
iv)  Editorial: opinionated essay on an issue of public interest
v)   Essay: similar to editorial but longer and more
comprehensive; may include tables and figures
ft    Commentary and Correspondence: persuasive and informed
commentary on any topical issues or on articles published in
prior issues of the journal
vii) Policy: critical review of some topic of high public interest,
hybrid of essay and review article, with the basis of highly
valid facts and figures
vm)Resource review: evaluation of books, websites, CDs, etc.
pertinent to the scope of HJS
i x) Publication preview: description/epitome ofthe forthcoming
important books
x)   Calender: notice of forthcoming conferences, seminars,
workshops, and other events related to science and the
Permission to make digital or hard copies of part or all of
any article published in HJS for personal use or educational
use within one's home institution is hereby granted without
fee, provided that the first page or initial screen of a display
includes the notice "Copyright © 2008 by the Himalayan
Association for the Advancement of Science," along with
the full citation, including name of author(s). We assert the
authors' moral right to post their papers on their personal
or home institution's Web pages and to make and distribute
unlimited photocopies of their papers. In all ofthe above cases,
HimAAS expects to be informed of such use, in advance or as
soon as possible.
To copy or transmit otherwise, to republish, to post on
the public servers, to use any component of a paper in other
works, or to use such an article for commercial or promotional
purposes requires prior specific permission. HimAAS does not
grant permission to copy articles (or parts of articles) that are
owned by others.
Special Acknowledgments
In the business of dissemination of new knowledge relevant
to Himalaya, we are assisted in our publication and pre-
publication work by certain commercial collaborators. By
offering HJS generous discounts (and in some cases waiving
all fees), they have significantly reduced our publication costs.
We have tried to reciprocate in a small measure by including
notices of their services. Scanpro Pvt. Ltd. and Jagadamba
Press: Thank you for standing with us in this venture!
Printed at: Jagadamba Press
Hattiban, Lalitpur, Tel: 55250017, 55250018
Layout and Designed by Bharat Shrestha
Kathmandu, Nepal
Color separation: ScanPro Pvt Ltd.
Pulchowk, Lalitpur, Nepal
Tel: 5548861, 5551123, 5552335
This is a special issue ofthe Himalayan Journal of
Sciences, containing extended abstracts of papers
to be presented at the 23rd Himalaya-Karakoram-
Tibet Workshop to be held in Leh, Ladakh, India
August 08-11, 2008. The issue was produced
by guest editors and its contents have not been
subjected to peer review.
Volume 5
Issue 7 (Special Issue)
ISSN 1727 5210
Himalayan Journal
of Sciences
Volume 5, Issue 7, 2008
Page: 01-182
Cover Image
Leh Palace, Ladakh: the site of
23rd HKT Workshop. Courtesy
of Sandeep Singh.
Organizing Secretary, 23rd
Himalayan Karakoram Tibet
Published by
Himalayan Association for
the Advancement ofSciences
Lalitpur, Nepal
GPO Box No. 5275
extended abstracts
Scion Image Analysis in rocks ofthe hangingwall and foot wall ofthe MCT, central Nepal
Kamala Kant Acharya and Bernhard Grasemann,  Page 15
Geological setting ofthe Siang Dome located at the Eastern Himalayan Syntaxis
Subhrangsu K. Acharyyaand Puspendu Saha, Page 16
Geochemical-isotopic characteristics and K-Ar ages of magmatic rocks from Hundar valley,
Shyok Suture Zone, Ladakh.
TAhmad, S Sivaprabha, S Balakrishnan, NX Thanh, T' Itaya, HKSachan, D KMukhopadhyay and
P P Khanna, Page 18
New SHRIMP ages for Ladakh and Karakoram Batholiths - inherited zircons indicate
involvement of older crust
T Ahmad, L White, M Forster, T R Ireland and G Lister,  Page 19
Preliminary paleomagnetic study of Cretaceous dykes in SE-Tibet
E Appel, I Dunkl, E Ding, C Montomoli, R El Bay and R Gloaguen,  Page 20
Carbon and sulfur isotope records of Ediacaran carbonates of Lesser Himalayas: implications
on oxidative state ofthe contemporary oceans
DM Banerjee, Page 21
Kinematics ofthe crust in southern Tibet and Higher Himalayan
Crystalline -a paleomagnetic approach
Rachida El Bay, Erwin Appel, R Carosi, E Ding, D Istvan, R Gloaguen, C Montomoli, E Paudel and
B. Wauschkuhn, Page 22
White Sandstone in Subathu Sub-Basin: an example of tectonically driven forced regressive wedge
MKBera, A Sarkar and PP Chakraborty, Page 24
Evolution ofthe Lesser Himalaya
ON Bhargava and WFrank, Page 26
Bursting of glacial lakes—a consequence of global warming: a case history from the Lunana
area, Gasa Dzongkhag, Bhutan
ON Bhargava, SK Tangri and AK Choudhary,  Page 28
Implications of biostratigraphy in the Himalayan Paleogene Foreland Basin
SB Bhatia and ON Bhargava, Page 29
Spatio - Temporal Variation ofVegetation during Holocene in the Himalayan Region
Amalava Bhattacharyya and SKShah, Page 31
Songpan Garze fold belt: New petrological and geochronological data
Audrey Billerot, Julia de Sigoyer, S Duchene, O Vanderhaeghe and Manuel Pubellier, Page 32
extended abstracts Continued.
Crustal velocity structure from surface wave
dispersion tomography in the Indian Himalaya
Warren B Caldwell, Simon E Klemperer,
Shyam S Rai and Jesse F Lawrence, Page 33
Non-coaxial heterogeneous deformation in the Num
orthogneiss (Arun valley, Mt. Makalu area, eastern Nepal)
R Carosi, C Frassi, C Montomoli, PC Pertusati,
C Groppo, F Rolfo and D Visond, Page 34
Ductile-brittle deformation in the hanging-wall
ofthe South Tibetan Detachment System (Southern Tibet)
R Carosi, C Montomoli, E Appel, I Dunkl
and Ding Ein, Page 35
Three-Dimensional Strain Variation
across the Kathmandu Nappes: Insight to
Nappe Emplacement Mechanism
Deepak Chamlagain Page 36
Crustal configuration of NW Himalaya
based on modeling of gravity data
Chamoli Ashutosh, AKPandey, VP Dimri and P. Banerjee, Page 39
Tectonometamorphic evolution of collisional orogenic belts in
the Korean Peninsula: Implications for East Asian tectonics
Moonsup Cho, Page 40
The Sedimentary Record of Deglaciation in the Western
Himalaya recorded in the Indus Delta, Pakistan
PD Cliff E Giosan, IH Campbell, J Blusztajn, MPringle, AR Tabrez,
A Alizai, MM Rabbani and S Vanlaniningham,  Page 41
Seismic reflection evidence for a Dangerous
Grounds mini-plate in the South China Sea and
implications for extrusion tectonics in SE Asia
Peter CI ft, GH Lee, NA Due, U Barckhausen,
H Van Long, and Sun Zhen,  Page 42
Examination of relocated earthquake hypocenters
in the Pamir-Hindu Kush seismic zone using 3-D plots
SDas, Page 43
Unzipping Lemuria from its Himalaya
suture to understand mammalian origins
MaartenJ de Wit and Judith Masters, Page 44
Addressing Tectonic and Metamorphic
Controversy in the Pakistan Himalaya
Joseph A Dipietro, Page 45
Active tectonics and origin of Tso Morari Lake
observed by Remote sensing and GIS techniques
CS Dubey and DP Shukla, Page 47
Diagenetic and metamorphic overprint and deformation
history of Permo-Triassic Tethyan sediments, SE Tibet
Istvdn Dunkl, Ding Ein, Chiara Montomoli, Klaus Wemmer, Gerd
Rantitsch, Borja Antolin, Rachida El Bay and Erwin Appel, Page 49
Impact of coeval tectonic and sedimentary-driven tectonics on
the development of overpressure cells, on the sealing, and fluid
migration-Petroleum potential and environmental risks ofthe
Makran Accretionary Prism in Pakistan
N Ellouz-Zimmermann, A Battani, E Deville,
A Prinzohfer and J Ferrand, Page 50
The Tso Morari Nappe ofthe Ladakh Himalaya:
formation and exhumation
Jean-Luc Epard and Albrecht Steck, Page 52
Implications of geochemical signatures in the Trans-
Himalayan Lohit batholith, Arunachal Pradesh, India
TK Goswami, Page 53
Cretaceous - Tertiary carbonate platform evolution and the age
of India - Asia collision along the Ladakh Himalaya (NW India)
Owen R Green, Michael P Searle, Richard I Co field and Richard M
Coif Ad, Page 54
P-T evolution across the Main Central Thrust zone (Eastern
Nepal): hidden discontinuities revealed by petrology
Chiara Groppo, Franco Rolfo and Bruno Eombardo, Page 55
Kyanite-bearing anatectic metapelites from the Eastern
Himalayan Syntaxis, Eastern Tibet, China : textural evidence for
partial melting and phase equilibria modeling
Carl Guilmette, Indares Aphrodite, Hebert Rejean and
CS Wang. Page 56
New occurrence of eclogitic continental rocks in
NW Himalaya: The Stak massif in northern Pakistan
Stephane Guillot, Nicolas Riel, Keiko Hattori, Serge Desgreniers, Yann
Rolland, Jeremie Van Melle, Mohamad Eatif Allah B. Kausar and
Arnaud Pecher, Page 57
Evolution ofthe Indian Monsoon System and
Himalayan-Tibetan Plateau uplift during the Neogene
Anil K Gupta, Page 58
Structural and metamorphic equivalence across theLHS-HHCS
contact, Sikkim Himalaya - indicator of post-deformation
metamorphism or the wrong MCT?
Saibal Gupta and Suman Mondal,  Page 59
Continental Relamination Drives Compositional and
Physical-Property Changes in the Lower Crust
Bradley Hacker, Peter B Kelemen and Mark D Behn, Page 60
Comparison of regional geoelectric structure of Himalayan region
T' Harinarayana and RS Sastry,  Page 61
extended abstracts Continued.
Pre-collisional Crustal Structure Adjacent the Indus-Yalu Suture
T Mark Harrison, Donald J Depaolo and
Amos B Aikman, Page 62
Discovery of crustal xenolith-bearing Miocene post-collisional
igneous rocks within the Yarlung Zangbo Suture Zone
southern Tibet: Geodynamic implications
Rejean Hebert, E Guillaume, B Rachel, C Guilmette, E Bedard, C
Wang, T D Ullrich andjaroslav Dos tal, Page 63
Constraints to the timing of India-Eurasia collision
determined from the Indus Group: a reassessment
Alexandra E Henderson, Yani Najman, Randall R Parrish, Andrew
Carter, Marcelle Boudagher-Fadel, Gavin Foster, Eduardo Garzanti and
Sergio Andb, Page 64
Structure ofthe crust and the lithosphere in the
Himalaya-Tibet region and implications on the
rheology and eclogitization ofthe India plate
Gyorgy Hetenyi, J Vergne, John E. Ndbelek, R Cattin, F Brunet,
E Bollinger and M Diament, Page 65
Present-day E-W extension in the NW
Himalaya (Himachal Pradesh, India)
Esther Hintersberger, Rasmus Thiede, Manfred Strecker
and Frank Kriiger,  Page 67
3-D Velocity Structure ofthe Crust and upper
Mantle in Tibet and its Geodynamic Effect
Zheng Hongwei, He Rizheng, Zhao Dapeng,
Ei Tingdong and Rui Gao, Page 69
Electrical Structure of Garhwal Himalayan
region, India, inferred from Magnetotelluric
M Israil, DK Tyagi, PK Gupta and Sri Niwas, Page 70
Heterogeneous Himalayan crust using shear wave
attenuation in the Pithoragarh region of Kumaon
A Joshi, M Mohanty, AR Bansal, VP Dimri and
RKChadha, Page 72
Lithostratigraphy of the Naga-Manipur Hills (Indo-Burma
Range) Ophiolite Belt from Ukhrul District, Manipur, India
A Joshi and KT Vidyadharan, Page 73
Pre-Himalayan tectonometamorphic
signatures from the Kumaun Himalaya
Mallickarjun Joshi, Page 75
Northeast Tibetan Crustal Structure from
INDEPTH IV Controlled-Source Seismic Data
Marianne Karplus, S Klemperer, Z Wenjin, Wu Zhenhan, Shi Danian,
Su Heping, E Brown, Chen Chen, Jim Mechie,
R. Kind, F Tilmann, Yizhaq Makovsky, R Meissner,
and INDEPTH Team Page76
Geochronologic, structural and metamorphic
constraints on the evolution ofthe South Tibetan
detachment system, Bhutan Himalaya
Dawn A. Kellett, Djordje Grujic, Isabelle Coutand
and Clare Warren, Page 78
Paired terraces ofthe Seuti Khola, Dharan, eastern Nepal
M P Koirala, SK Dwivedi, P Dhakal, G Neupane, YP Dhakal, SP
Khanal, N K Regmi, G Ojha, S Shrestha and
RKDahal,   Page 80
Late Quaternary climatic changes in the eastern Kumaun
Himalaya, India as deduced from multi-proxy studies
BS Kotlia, J Sanwal, B Phartiyal, E MJoshi,
A Trivedi, and C Sharma,  Page 81
Palaeozoic granites and their younger components - A study of
Mandi and Rakcham granites from the Himachal Himalaya
A Kundu, NC Pant and Sonalika Joshi,  Page 82
Out-of-sequence deformation and expansion ofthe
Himalayan orogenic wedge: insight from the Changgo
culmination, south-central Tibet
Kyle P Larson and Laurent Godin, Page 84
Is the Ramgarh thrust equivalent to the
Main Central thrust in central Nepal?
Kyle P Larson and Laurent Godin, Page 85
Telescoping of isotherms beneath the South Tibetan
Richard D Law, MicahJJessup, Michael P Searle,
John M Cottle and David Waters, Page 86
Does the Karakoram fault interrupt mid-crustal
channel flow in the western Himalaya?
Mary E Leech, Page 88
Miocene exhumation ofthe granulite-eclogite ofthe
Ama Drime range (high Himalayas) through polyphased
syn-convergence normal faulting
Philippe Herve Eeloup, Elise Kali, N Arnaud, G Maheo and
E Boutonnet, Page 89
Lateral heterogeneity in lithospheric structure in SE Tibet
Anne Meltzer, Brian Zurek, Stephane Sol and
Lucy Brown, Page 90
Polyphase deformation history ofthe "Tibetan Sedimentary
Sequence" in the Himalayan chain (South-East Tibet)
Chiara Montomoli, E Appel, A Borja, I Dunkl, R El Bay,
Ding Ein and Gloaguen, Page 91
How significant is erosion in extrusion- insights from analogue
and analytical models
S Mukherjee, Hemin A Koyi, CJ Talbot and AKJain,  Page 92
extended abstracts Continued.
Flexural-slip folding and fold-accommodation faulting
in the Tethyan Sedimentary Zone, NW Himalayas
Dilip KMukhopadhyay, Page 93
The Paleogene record of Himalayan erosion;
Burma and Bangladesh
Yani Najman, R Allen, M Bickle, M BouDagher-Fadel,
A Carter, E Garzanti, M Paul, J Wtjbrans, Ed Willett,
G Oliver, R Parrish, S HAkhter, S Ando, D Barfod,
E Chisty, E Reisberg, G Vezzoli and J Uddin, Page 94
The Main Central Thrust Revisited:
New Insights from Sikkim Himalaya
Sudipta Neogi and VRavikant, Page 95
Deformation partitioning at the rupture front in NW Himalaya:
evidence from tectono-geomorphic and
paleoseismic investigations
Anand KPandey, Prabha Pandey, Guru Dayal Singh, GVRavi
Prasad, K Dutta and DKRay, Page 97
Geochemical characters of muscovite from the Pan African
Mandi Granite, and its emplacement and evolution
NC Pant andAKundu, Page 98
Segmented Nature ofthe Himalaya and Gangetic Plain
B Parkash, RS Rathor, AKAwasthi, P Pad, B Bhosle,
RPJakhmola, S Singh and VAcharya, Page 99
Significance ofthe clay mineral distribution
in the fluvial sediments ofthe Neogene
Himalayan Foreland Basin (central Nepal)
Pascale Huyghe, Romain Guilbaud, Matthias Bernet
and Ananta Prasad Gajurel, Page 100
Deformation and exhumation ofthe Higher and Lesser
Himalayan Crystalline sequences in the Kumaon region,
NW-Himalaya based on structural and fission-track analysis
Patel RC, Nand Eal and Yogesh Kumar,  Page 101
Tectonics vs. erosion: evidences from apatite
fission track and Rb-Sr (Biotite and Muscovite)
thermochronology Arunachal Himalaya
PebamJ, AKJain, R Kumar, Sandeep Singh
and Nand Eal, Page 103
Stress field evolution in the North West
Himalayan syntaxis (Northern Pakistan)
A Pecher, S Guillot, FJouanne, G Maheo, JE Mugnier,
YRolland, P Van derBeek and J Van Melle, Page 106
Soft sediment deformation structures in the Late Quaternary
sediments of Ladakh: evidence of multiple phases of
palaeoearthquakes in the North western Himalayan Region
Binita Phartiyal and Anupam Sharma, Page 107
Complex Seismic Discontinuities in the Mantle Transition
Zone beneath NW Himalaya and Ladakh- Karakoram
KS Prakasam, SS Rai, Keith Priestley and VK Gaur, Page 108
High Crustal Seismic Attenuation in Ladakh- Karakoram
SS Rai, Ahish, Amit Padhi and P Rajgopala Sarma, Page 109
The Deep structure of Western Himalaya - Ladakh-Karakoram
SS Rai, VK Gaur, Keith Priestley and Lev Vinnik, Page 110
Deep seismic reflection profiling over the
Siwalik fold belt of NW Himalaya
B Rajendra Prasad, V Vijaya Rao and HC Tewari, Page 111
Occurrence of Permian palynofossils from the Saltoro
Formation, Shyok-Suture-Zone, Ladakh Himalaya, India
Ram- Awatar, Page 113
Central crystallines as the exclusive source terrain
for the sandstone-mudstone suites of siwalik group:
geochemical evidence
Nikesh Ranjan and DM Banerjee, Page 114
Northern Margin of India in the Pre-Himalayan times
Vibhuti Rai and Aradhana Singh. Page 115
The petrogenesis of a crustal-derived Palaeoproterozoic Bomdila
orthogneiss, Arunachal Pradesh, NE Lesser Himalaya
Shaik A Rashid, Page 116
The great 1950 Assam Earthquake revisited: field evidences
of liquefaction and search for paleoseismic events
DVReddy, Pasupuleti Nagabhushanam, Devender Kumar,
BS Sukhija, PJ Thomas, AK Pandey, RN Sahoo,
GVRavi Prasad and KDatta, Page 117
Occurrences of sulphide minerals in the Stakand Tso
Morari eclogites: Implications for the behaviour of sulphur
and chalcophile elements in subduction zones
Nicolas Riel, Keiko Hattori, Stephane Guillot,
Mohamad Eatif and Allah B Kausar, Page 118
SHRIMP zircon ages of eclogites in the
Stak massif, northern Pakistan
Nicolas Riel, Keiko Hattori, Stephane Guillot, Nicole Rayner, Bill
Davis, Mohamad Eatif and Allah B. Kausar,  Page 119
Structural, paleogeographic and topographic evolution ofthe
northern Tibetan Plateau margin: Evidence from the southern
Tarim basin, northern Hexi Corridor, and Qaidam basin
Bradley D Ritts, Paul M Bovet, Malinda E Kent-Corson, Brian J
Darby, Jeremy Hourigan, Guangsheng Zhuang, StephanA Graham
and Yongjun Yue, Page 121
extended abstracts Continued.
New recognition of NNE-strike belt of negative
aeromagnetic anomaly in Tibetan plateau
HE Ri-Zheng, GAO Rui and ZHENG Hong-Wei, Page 123
Identification of necessary conditions for supershear wave
rupture speeds: Application to Californian and Asian Fault
David Robinson and Shamita Das, Page 125
Discovery of granulitized eclogite in North Sikkim expands
the Eastern Himalaya high-pressure province
Franco Rolfo, Rodolfo Carosi, Chiara Montomoli
and Dario Visond,  Page 126
Seismic Tomography of Garwhal-Kumaun Himalayas:
Is the basal detachment a wistful thinking?
S Mukhopadhyay, J Sharma and BRArora, Page 128
Lake-level changes in the past 50 ka reconstructed from
the lacustrine delta deposits in Kathmandu Valley, Nepal
Tetsuya Sakai, Ananta P Gajurel, Hideo Tabata, Nobuo Ooi and
Bishal N Upreti, Page 129
Mineralogy and Geochemistry of mafic to hybrid microgranular
enclaves and felsic host of Ladakh batholith, Northwest
Himalaya: Evidence of multistage complex magmatic processes
Santosh Kumar and Brajesh Singh,  Pagel30
Geochemistry and Petrogenesis of Granitoids from
Kameng Corridor of Arunachal Himalaya, Northeast India
Santosh Kumar and Manjari Pathak,  Page 132
Analysis of gravity and magnetic data along
Rumtse-Upshi-Leh-Kardung la and Rumtse-Upshi-
Igu-Shakti-Chang la - Durbuk profiles - Presence of
ophiolites within Ladakh batholith and suture zones
Rambhatla G Sastry and Md Israil, Page 133
Analysis of gravity and magnetic data along
Mahe-Sumdo-Tso Morari
Rambhatla G Sastry and Md Israil, Page 135
Anatomy, Age and Evolution ofthe Baltoro
granite batholith, Pakistani Karakoram
Michael Searle, Andrew Thow, Randall Parrish,
Steve Noble and David Waters, Page 137
Analysis of Climate change from high elevation sites
of North West Himalaya based on tree ring data
SK Shah, A Bhattacharyya and V Chaudhary, Page 138
Geo history of Tso-Morari Crystalline, Eastern Ladakh, India:
a plausible model for ultra-high pressure rocks in the Himalaya
Ram S Sharma, Page 139
Geochemistry of Late Quaternary Spituk palaeolake
deposit of Ladakh, NW Himalaya
Anupam Sharma and Binita Phartiyal, Page 141
Remote Sensing based Study of Retreat of and
Accompanying Increase in Supra-glacial Moraine
Cover over a Himalayan Glacier
A Shukla, RP Gupta and MKArora, Page 142
Vertical stratigraphic variations and sedimentation model
ofthe Lower Siwalik sequence in Kumaun Himalaya, India
UK Shukla and DS Bora. Page 143
Amphibole compositions as indicators of deep crustal
and mantle processes in subduction zones: case study -
Tso Morari metamafics, Ladakh, Himalaya
Preeti Singh, NC Pant, A Kundu, TAhmad
and PK Verma, Page 144
Tectonic Activity In The Ganga Plain
Foreland Basin During Quaternary
Indra Bir Singh, Page 145
Weathering in the Ganga Alluvial Plain:
Geochemical signatures linking of the Himalayan
source and the Bay of Bengal sink
Indra Bir Singh, Sandeep Singh and
Munendra Singh, Page 146
Geomorphic indicators of active growth and lateral propagation
of fault-related folds: Mohand Ridge anticline, NW Himalaya
Tejpal Singh and A. K Awasthi, Page 147
Neotectonic activity and its geomorphic response
in the Tangtse valley, Ladakh Himalaya
Vimal Singh, Page 148
Sediment sourcing in the Gangetic alluvium, Himalayan
Foreland Basin - competition between Himalayan
and cratonic hinterland
R Sinha, Y Kettanah, M R Gibling, S K Tandon, MJain, P S
Bhattacharjee, AS Dasgupta and P Ghazanfari, Page 149
Silurian acanthomorphitae acritarch from the Shiala
Formation, Tethys Garhwal Himalaya, India
HN Sinha, Page 150
Landslides in the Kashmir Earthquake of 8th October 2005
Amita Sinvhal, Ahok D Pandey and Sachin M Pore, Page 152
Neogene sedimentary evolution ofthe Guide Basin and its
implications on uplift ofthe NE Tibetan Plateau, China
Chunhui Song, Qingquan Meng, Xiaomin Fang, Shuang Dai and
Junping Gao, Page 154
A possible Permian suture in the Lhasa Block, Tibet:
Evidence from eclogite and probable ophiolite
Chen Songyong, YangJingsui, Ei Tianfu, Xu Xiangzhen,
Ei Zhaoli and Ren Yufeng, Page 155
extended abstracts Continued.
Long Term GPS Deformation
Rates in the Karakoram terrane of Ladakh
SrideviJade, VK Gaur, MSM Vijayan and
P Dileep Kumar, Page 156
The metamorphism ofthe Tso Morari
ultra-high pressure nappe ofthe Ladakh Himalaya
Albrecht Steck and Jean-Luc Epard, Page 157
The Tectonics ofthe Tso Morari Ultra High
Pressure Nappe in Ladakh, NW Indian Himalaya
Albrecht Steck and Jean-Luc Epard, Page 159
The Trans-Hudson Orogen of North America and the
Himalaya-Karakoram-Tibetan Orogen of Asia: Structural and
thermal evolution ofthe collisional lower and upper plates
Marc St-Onge, Michael Searle, Natasha Wodicka, Jeroen van Goof,
Adam Garde and David Scott, Page 161
Melting and Exhumation ofthe upper structural
levels ofthe Greater Himalaya Sequence and Makalu granite:
constraints from thermobarometry, metamorphic
modeling and U-Pb geochronology
Michael J Streule, Michael P Searle, Matthew
SA Horstwood and David Waters, Page 162
Strong ground motion observation and estimation:
From predictive relationships and
modelling to real-time shake maps
Suhadolc Peter, Costa Giovanni and
Moratto Euca, Page 163
Degree of Magnetic anisotropy as a strain intensity gauge:
An example from the Footwall of MCT Zone along
Bhagirathi valley, Garhwal Himalaya, India
Nihar R Tripathy and Tejpal Singh, Page 164
Petrology and geochronology of eclogitic and
retrograde micas from Tso Morari UHP
Complex, Ladakh Himalaya
Igor M Villa, Julia de Sigoyer and
Stephane Guillot, Page 167
Examining the Tectonic Wedging
Hypothesis in the NW India Himalaya
A Alexander G Webb and An Yin, Page 168
Tectonic sequence diagrams and the constraints
they offer for the structural and metamorphic
history ofthe Kullu Valley, NW India
L White, G Lister, M Forster and TAhmad, Page 169
Different eclogite types from the Pakistan Himalaya
and implications for exhumation processes
Franziska DH Wilke, Patrick J O sBrien and
M Ahmed Khan, Page 170
River discharge and erosion rates in the
Sutlej basin, NW Himalaya
Hendrik Wulf and Dirk Scherler Page 172
The Central Crystallines around Hapoli,
Subansiri, Eastern Himalayas
An Yin, CS Dubey, AAG Webb, PK Verma,
TKKeltyand TM Harrison, Page 174
Surface-tectonic coupling at the Namche Barwa -
Gyala Peri massif and geologic hazards associated with a
proposed dam on the Yarlung-Tsangpo river in SE Tibet
Peter Zeitler, Anne Meltzer, Brian Zurek, Lucy Brown,
Noah Finnegan, Bernard Hallet, Page Chamberlain,
William Kidd and Peter Koons,  Page 176
Paleomagnetic and Geochronologic Results From Late Paleozoic
and Mesozoic Rocks ofthe Central Tibet: Implications for the
Paleogeography ofthe Qiangtang Terrane
Xixi Zhao, Pete Eippert, Rob Coe, Chengshan Wang, Zhifei Liu,
Haisheng Yi, Yalin Ei, Bin Deng, and Igor Villa,  Page 177
Whole-rock elemental and zircon Hf isotopic geochemistry of
mafic and ultramafic rocks from the Early Cretaceous Comei
large igneous province in SE Tibet: constraints on mantle source
characteristics and petrogenesis
Di-Cheng Zhu, Xuan-Xue Mo, Zhi-Dan Zhao, Yaoling Niu and
Sun-Ein Chung,   Page 178
Scion Image Analysis in rocks of the hanging wall and foot wall
of the MCT, central Nepal
Kamala Kant Acharya* and Bernhard Grasemann
Department of Geodynamics & Sedimentology, Structural Processes Group, Vienna University, AUSTRLA
For correspondence, email:
In central Nepal, the Kathmandu Crystalline Thrust Sheet comprises rocks ofthe Higher Himalayan Crystalline, overlying lower
metamorphic grade rocks of the Nawakot Complex, separated
by the Main Central Thrust (MCT). All these rocks, which are
sometimes combined in the 'Kathmandu Nappe', have been folded to form the NW-SE trending, essentially upright Mahabharat
Synform. A public downloading software Scion imaging has been
used to quantitative image analyse of thin sections from the area
especially in the vicinity of the thrust. Scion Image is an image
processing and analyzing program (
Images of seven thin sections from different parts of central
Nepal were analysed using Scion Image. These thin sections were
prepared from the three samples collected from the hanging wall
i.e. Kathmandu Complex rocks and four samples from the foot
wall i.e. Nawakot Complex rocks ofthe MCT. The ellipse major
axis, ellipse minor axis, and orientation of the ellipse major axis
of quartz and feldspar grains were measured using this software
from the thin sections. The ellipticity and Bretherton shape index
were calculated from the obtained values.
The analysis shows that, rocks of the Nawakot Complex
(Lesser Himalaya) record a monoclinic symmetry while rocks ofthe
Kathmandu Complex (Higher Himalaya) record an orthorhombic
symmetry In one sample collected from the thrust zone of the
MCT, quartz grains show orthorhombic while feldspar grains show
monoclinic symmetry In all the samples feldspar behave as a rigid
particle whilst quartz grains show evidence of ductile deformation.
Flattening and elongation of quartz grains is strong parallel to the
foliation. Rocks ofthe Kathmandu Complex and ofthe MCT thrust
zone show higher rheological role of quartz than in rocks ofthe
Nawakot Complex. Some rocks ofthe Kathmandu and Nawakot
Complex shows asymmetry indicating non-coaxial deformation.
Other possible indicators of non-coaxial deformation, such as
extensional crenulation cleavage, S-C shear bands, porphyroclasts
with asymmetric pressure shadows and porphyroblasts with
curved inclusion trails have also been observed in thin-sections.
The strain partitioning between individual phases, typical of lower
metamorphic grade rocks such as the chlorite grade Nawakot
Complex diminishes as the metamorphic grade increases to garnet
and biotite grade in the Kathmandu Complex and deformation
becomes more nearly homogenous. In the sample from MCT zone,
where both quartz and feldspar grains have been analysed, feldspars
show a higher ellipticity than quartz. The average ellipticity of
quartz in all of these rocks is more or less similar but in feldspar
rocks ofthe Kathmandu Complex shows higher average ellipticity
than rocks ofthe Nawakot Complex. Comparatively feldspar grains
show higher variation in ellipticity and Bretherton Shape Index
than that of quartz. In these rocks, shear sense indicators show
both pure shear flattening fabrics and non-coaxial south-directed
simple shear fabrics.
From these observations, it can be said that rocks of both
the hanging wall and footwall show a significant pure shear
component early in the deformation and simple shear component
during exhumation. Therefore, the MCT can be characterized
as Stretching Fault Thrusting (Means 1989), where wall rocks
lengthen perpendicular to the shear direction, and MCT partially
acted as Stretched Fault Thrust.
Geological setting of the Siang Dome located at
the Eastern Himalayan Syntaxis
Subhrangsu K. Acharyya* and Puspendu Saha
Department of Geological Sciences, Jadavpur University, Kolkata 700032, INDIA
For correspondence, email:
The Siang Dome located at the Eastern Himalayan Syntaxis is
a large structure involving entire Himalayan packet from the
Paleogene rocks to the south at the core ofthe Siang Window to
the ophiolitic suture rocks and the Trans-Himalayan granitoids
around Tuting at its northern periphery. About a kilometer thick
shear zone with intense granitic injection is exposed in the Siang
River section located at the tectonic base of the Yang Sang Chu
Fm., overriding the Central Crystallines. This zone is tentatively
equated to the South Tibetan Detachment. Marcoscopically
the Himalayan thrust pile at the Siang Dome has a prominent
orogen-transverse antiformal structure trending NW-NNW. It
is truncated to the west by the N to NE trending Tuting-Basar
dextral fault. The Siang Window at the core exposes a duplex
antiform of Paleogene rocks that are placed beneath the low grade
Proterozoic Himalayan rocks tectonically separated by the arched
splay ofthe MBT roof-thrust.
Two structurally discordant units frame the Siang
Window. The crystalline thrust packet and the subjacent Lesser
Himalayan thrust sheets of low-grade Proterozoic and locally
present Permian metasediments on the hangingwall ofthe arched
MBT to the north constitute one congruous unit and preserve
identical structure. The duplex antiform of the Paleogene rocks
beneath the arched MBT, which are further truncated to the south
against the Neogene Siwalik Sub-Himalayas by the ENE-SSW
trending and north dipping frontal MBT and North Pashighat
Trust (NPT) represent the other tectonic unit. The antiform of
Paleogene rocks are dissected by subsidiary imbricate faults that are
oblique to both MBT at the roof and NPT at the floor, truncating
and dislocating MBT, but remaining asymptotic to NPT. These
are responsible for generating the Siang duplex antiform and its
northern fault bend antiformal closure (Figure 1, 2). Tuting-Basar
tear fault also breeches folded thrusts, and off sets the Siang and
the Namche Barwa Domes at its northeastern end, whereas, to
the south the frontal Gondwana thrust belt, frontal belt MBT and
MFT remain unaffected, and therefore represent the youngest
thrust structures.
The lower unit of the Paleogene sequence at the Siang
Window, the base of which is not yet well defined, is mainly
composed of white to pink colored, skolitho-bearing and mature
Miri like quartzite. It is also frequently intruded by dykes and
sills feeding the overlying Abor Volcanics. The stratigraphic base
of this quartzite with type Miri Quartzite is yet to be defined.
Calcareous bands or limestones occurring at the upper part
of this quartzite and at the lower parts of the Abor Volcanics
have yielded rich larger foraminifera record characterized by
Assilina depressa, A.  regularia,  Orbitosiphon cf tibetica, Nummulites
thdicus etc., indicating Late Paleocene to Early Eocene age. The
Yinkiong Formation overlying the volcanics consists of mainly
argillo-arenaceous volcanisediments with marl and limestone
intercalations. Foraminifera assemblage in these, characterized
by Nummulites atacicus, N. maculatus, Asilina spira, A daviesi, A
subassamica, indicate Early to Mid Eocene age (Acharyya 1994,
2007). The MBT zone between the early Paleogene rocks and the
overriding pre-Tertiary rocks, particularly the Permian Gondwana
rocks, Proterozoic quartzite-dolostone bearing Buxa like rocks,
often develop melange with tectonic assemblage of these rocks.
Narrow zones of intermixed Permian and Eocene fossils are
recorded from frontal belt MBT zones, which extend over 250
km (Acharyya 1994).
The Himalayan crystalline thrust tectonically floored by the
MCT has many similarities with typical features of the Type-C
crystalline Thrust Sheets as recognized by Hatcher and Hooper
(1992). The foreland thrusts are driven ahead of Type C sheets
as crystalline and foreland thrust merge into the Coulomb wedge
of the foreland. At the Eastern and NE Himalayas located in
Darjeeling-Sikkim area and Arunachal Pradesh, the pile of thrust
sheets, from higher to lower structural levels comprising the
crystalline, the low-grade Proterozoic metamorphic rocks, Late
Paleozoic metasediments and the Neogene floor sediments, are
cofolded together. The macroscopic folds in the former area have
orogen-parallel and transverse trends. In the present area, the latter
are the dominant fold style. In mesoscopic scale four generations
of folds have been recognized from the former area and broadly
similar fold styles are also inferred from the Siang Dome, but here
the orogen parallel early folds are generally rotated to orogen-
transverse orientation. The earliest Fl folds are tight isoclinal with
axial plane cleavage which is the main cleavage/schistocity SI. Fold
axes generally trend northward. Stretching lineation and mullions
denoting transport direction of thrusts are developed parallel to
Fl axes, but the latter often show variable trends. The Fl are well
developed in the Paleogene rocks, particularly in the Yinkiong
Formation. F2 folds developed on SI are generally asymmetric,
upright, inclined to recumbent in geometry. Often there is
development of spaced cleavage S2, and striping, and mineral
lineation. F3 fold are open, upright and trend NW-NNW. In the
present area because of superposition, F2 and F3 fold axes are both
transversely oriented and are thus often difficult to differentiate.
Evidence of F2-F3 cross folding in the Paleogene rocks of the
Siang Window is revealed by the presence ofwell formed dome
structures at the top section ofthe Miri Quartzite (sensu lato) and
basal sections ofthe Abor Volcanics (Figure 1, 2). The presence of
co-axial folding of Fl by F3 is recorded from single outcrops. The
latest F4 fold structures are generally orogen-parallel in trend, but
have recumbent geometry with subhorizontal axial plane. These
are better developed in zones of steeply dipping sheet schistosity
and bedding. The F4 folds are not recorded from the Tertiary
sediments, whereas, Fl to F4 affect the thrust pile of Proterozoic,
Late Paleozoic and Paleogene rocks. Therefore, Fl to F4 folds are
late- to post-thrust structures (Acharyya 2007).
The buried basement ridge of the Shillong-Mikir massif
in NE India, trends NE-N-ward and finally plunges beneath
the Siang Window. Regional trend and depths to basement
immediately south of the Siang Window are obtained from
seismic reflection data (Baruah et al. 1992). The Paleogene rocks
in the Siang Window are trust over the Neogene pile and older
sediments overlying the basement (Figure 1). Some test wells
on north bank of Brahmaputra River have also confirmed the
presence of late Paleocene-early Eocene marine shelf sediments.
Lateral continuity and thickening sequence ofthe Eocene marine
shelf in Arunachal Sub-Himalayas, around the Siang Window
is strongly indicated by the presence of thrust slivers of Eocene
sediments and presence of similar marine fauna in them, which
occur close to and beneath MBT zone from widely separated
FIGURE 1. Simplified geological map of the Siang Dome and foothill
plains. Regional Depth contours in km close to basement in the foothill
plains and Basement Ridge Axis are based on reflection seismic data
after Baruah et al., 1992. - 1-High-grade rocks and gneisses (Central
Crystallines), 2a- Low-grade quartzite-dolomite metasedimets (Buxa
Fm., equivalent, Proterozoic), 2b- Low-medium grade meta-argillite
(Proterozoic), 3- Miri Quartzite (? Early Paleozoic), 4- Late Plaeozoic
Gondwana equivalent metasediments, 5- Paleogene rocks, 6a- Tectonised
early Neogene sediments in the northern belt (Lower Siwalik), 6b- Late
Neogene (Upper and Middle Siwalik) in the southern belt, 7- Low- to
high-grade graphitic metasediments (Yang Sang Chu Fm.), 8- Mafic and
ultramafic rocks (Ophiolite), 9- Trans-Himalayan granitoids and gneisses.
Abbreviations: MBT- Main Boundary Thrust, NPT- North Pashighat Thrust,
MCT- Main Central Thrust, STD- South Tibetan Detachment, A- Along, B-
Basar, D-Dibrugarh, G- Garu, P-Pashighat, T-Tuting, Y-Yinkiong.
sections. The thrust arcuation ofthe Siang Window located at the
Eastern Himalayan Syntaxis was therefore influenced initially by
the involvement of the subsurface indenture of the NE leading
edge of Indian continent, which acted as an oblique crustal ramp
over which the pile of Himalayan nappes climbed. A basement
saddle and depression occurs instead south of western part ofthe
Siang Window and the complementary synform located further
west (Acharyya 2007). The geometry of the Siang Dome was
modified subsequently by ductile deformations.
Acharyya SK. 1994. The Cenozoic foreland basin and tectonics of the
Eastern Sub-Himalaya: problems and prospects. Himalayan Geology
Acharyya SK. 2007. Evolution ofthe Himalayan Paleogene foreland basin,
influence of its litho-packet on the formation of thrust-related
domes and "windows in the Eastern Himalayas — A review. Journal of
Asian Earth Sciences 31: 1-17
Baruah JMB, Handique GK, Rath S, Malhck RK. 1992. Exploration for
Palaeocene-lower Eocene hydrocarbon prospects in the eastern parts
of Upper Assam basin. Indianjournal of Petroleum Geology 1: 117-129
Hatcher RD (Jr) and Hooper RJ. 1992. Evolution of crystalline thrust
sheets in the internal parts of mountain chains. In: Mc Clay KR.
(ed.), Thrust tectonics, Chapman and Hall, London p 217-233
\ T\V\5bVNa
/        1             7
■ 2830'
1  Vi
)             N
5b\            p     5c
15c i?n f~y/
1/                    ^fc/r
5b\ \^"N
SN]    2a
7 Za'nNX         5b         "V
F-41XV.        V
^ ^  2a            Y,5b,
r 2a R|
Its             iSM
&*^    * 11
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FIGURE 2. Simplified geological map ofthe Siang Window. Legend
same as in Figure 1. Paleogene rocks differentiated to: 5a- Quartzite
(Late Paleocene-Early Eocene: may include older Lower Paleozoic
Miri Quartzite), 5b- Abor Volcanics, 5c- Yinkiong Fm.
Geochemical-isotopic characteristics and K-Ar ages of magmatic
rocks from Hundar valley, Shyok Suture Zone, Ladakh
T Ahmad1*, S Sivaprabha2, S Balakrishnan3, N X Thanh4, T Itaya4, H K Sachan5,
D K Mukhopadhyay2 and P P Khanna5
1 Department of Geology, University of Delhi, Delhi, INDIA
2 Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee, INDIA
3 Department of Earth Sciences, Pondicherry University, Pondicherry, INDIA
4 Research Institute of Natural Sciences, Okayama University of Science, Okayama, JAPAN
5 Wadia Institute of Himalayan Geology, Dehradun, INDIA
For correspondence, email:
Hundar section rocks of the Shyok Suture Zone comprise
predominantly diorite, granodiorite with minor gabbro-dolerite,
two types of granite, volcano-clastic sediments and tuffs that are
intruded by diabasic dykes. Diorite samples contain pyroxene,
amphiboles and plagioclase as major phases. Quartz and alkali
feldspar, showing myrmekitic intergrowth are found in granites.
Gabbro-dolerite comprises feldspar, biotite, hypersthene and
hornblendes. Andesitic dykes have euhedral plagioclase phenocryst
within fine-grained groundmass.
Major and trace element display trends expected for igneous
rocks from mafic to felsic compositions. Data indicate fractionation
of olivine, pyroxene, feldspars and Fe-Ti oxide phases during
evolution ofthe magma. Normalized REE plots depict light REE
enrichment and middle - heavy REE moderate fractionation. Multielement patterns also display enrichment of large ion lithophile
elements (LILE) and depletion of high field strength elements
(HFSE) with significant negative Sr and Eu anomalies.
Hundar samples do not define any collinear array for Rb-Sr
or Sm-Nd isotope evolution indicating multiplicity of sources for
magmas. S^ (t = 100) varies from +3.7 to -7.4, while the e& varies
from -7 to +50. 6Nd vs. 6Sr diagram plots for Hunder samples
partly overlaps the mantle array and partly that of Ladakh pluton.
The samples of Ladakh pluton have extended €Nd and €Sr values
up to -8 and +165 respectively. Probably magmas ofthe Hundar
section were variably contaminated by enriched and long lived
continental crustal components.
Eight samples from the Hundar section yield K-Ar ages from
60.8 Ma to 65.8 Ma. The medium-grained granite shows younger
age (60.8 and 61.8 Ma) compared to the coarser-grained granite of
63.9 Ma. Three coarse-grained diorite samples yield the age from
64.4 to 65.8 Ma. Two microdiorite samples in the center of Hundar
section yield the age of 64.0 and 64.4 Ma. The coarse grained granite
samples having magma mingling structure with the microdiorite
gives the similar ages of 63.9 and 64.4 Ma respectively. Two coarse
grained diorite display the oldest age (65.8 Ma) in the area. These
age data indicate that the magmatic rocks ofthe Hundar section are
much older than the dominant magmatic phase (—58 Ma) ofthe
Ladakh batholith and therefore could be unrelated.
New SHRIMP ages for Ladakh and Karakoram Batholiths
inherited zircons indicate involvement of older crust
T Ahmad1*, L White2, M Forster2, T R Ireland2 and G Lister2
1 Department of Geology, University of Delhi, Delhi, INDIA
2 Research School of Earth Sciences, The Australian National University, Canberra, AUSTRALIA
For correspondence, email:
We report new U-Pb zircon SHRIMP ages for the Ladakh and
Karakoram batholiths. The samples ofthe Ladakh Batholith were
collected from the Khardung La and Chang La tops and those of
the Karakoram Batholith were collected along the Tangtse gorge
and Darbuk-Shyok section.
Separated zircon crystals display zoned zircon crystals
typically observed in igneous rocks. The age obtained for the
Khardung La and Chang La top samples is circa 58 Ma. These
ages are similar to the age data published by earlier workers,
confirming a strong phase of magmatism in the Ladakh Batholith
at approximately 58 Ma. No inherited older zircons were observed
in these samples, confirming the observations of earlier studies.
A Karakoram Batholith sample was collected near Tangste
Gompa. This sample is a coarse grained porphyritic granite and
gave an age of circa 32 Ma. One zircon grain from this sample
gave a late Permian age, and this may indicate the involvement of
older crust in the batholith.
Muscovite-biotite-garnet bearing leucocratic granite dykes are
best exposed in the Tangtse gorge where many leucocratic granitic
dykes dissect each other (Figures 1 and 2). One sample was collected
from near the middle ofthe gorge between the northern and southern
strands ofthe Karakoram fault. This sample gave an age of circa 18 Ma.
This is consistent with earlier published age data that was associated
with movement on the Karakoram fault.
Another sample of the Karakoram Batholith was collected
further to the north, near the Karakoram fault. This sample has
gneissic characteristics and is richer in mafic phases (biotite -
hornblende). The age of this sample is circa 102 Ma. This age is
consistent with data published by earlier workers indicating that
there was also a major magmatic phase in the Karakoram Batholith
at around 102 Ma.
One leucocratic granitic dyke sheet sampled between
Darbuk and Shyok villages has a mixture zircon crystals that
gave a range of ages. Some of these zircon grains are possibly
inherited. These range of ages found in these samples range
between 15 Ma and 97 Ma. All of these dates have been reported
from at least one of the other sampled localities by various
methods. Interestingly several grains gave ages that have not
been previously reported (ranging between 250 - 970 Ma).
These older ages may indicate that older crust was involved in
the generation of part ofthe Karakoram Batholith (possibly the
southern portion ofthe Tibetan slab?). Recent suggestions that
collision was as late as 35 Ma may need more consideration in
the light of magmatic zircon ages of 32-36 Ma.
FIGURE 1. Leucocratic granitic dykes, Tangtse gorge
FIGURE 2. Close up of Figure 1
Preliminary paleomagnetic study of Cretaceous dykes in SE-Tibet
B Antolin1*, E Appel1, I Dunkl2, L Ding3,  C Montomoli4, El Bay1 R and R Gloaguen5
1 Institutf. Geowissenschaften, Sigwartstrasse 10. D-72076 Tubingen, GERMANY
2 University of Gottingen, Goldschmidtstrasse 3, D-37077 Gottingen, GERMANY
3 Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Shuangqing Rd. 18, Beijing 100085, CHINA
4 University of Pisa, via S. Maria 53, 56126 Pisa, ITALY
5 University of Freiberg, Bernhard-von-Cottastrasse 2, 09596 Freiberg, GERMANY
For correspondence, email:
The SE Tibetan area is a key region to better understand Tibetan
Plateau formation. Lateral motion is evident by the alignment
of major rivers in Southeast Asia and GPS velocities indicating
motion around and away from the Eastern syntaxis. We try to find
vertical axes rotations utilizing paleomagnetic studies combined
with geological-petrological investigations to clarify the process
of uplift of the Himalaya-Tibetan Plateau in the south eastern
A total of 17 sites with about 10 cores per site were drilled in
Lower Cretaceous diorite dykes. These dykes intruded widespread
into the Triassic flysch ofthe Tethyan Himalaya. A total of 11
dykes were drilled in Nagarze area and 6 sites more to the east
(south of Tsetang-Gyaca) (Figure 1).
Rock magnetic analysis demonstrates the presence of
pyrrhotite as the principle carrier ofthe remanence. IRM saturates
from 300 mT to 500 mT and thermal demagnetization of SIRM
is mainly achieved around the Curie temperature of pyrrhotite
(325°C). Most of the samples show also a decay of the SIRM
around 580°C indicating the additional presence of magnetite.
The values of the intensity of the natural remanent
magnetization varies strongly from 0.5 to 446 mA\m. In about
50% ofthe samples it is possible to isolate a significant pyrrhotite
component, usually unblocking between 250°C and 350°C.
Equal area projection mostly shows a scattered distribution ofthe
pyrrhotite components. In three sites the characteristic pyrrhotite
remanence components are well grouping and in four sites a
small circle distribution can be observed. We relate the origin of
the pyrrhotite remanence to last metamorphic cooling in the area
(K/Ar ages indicate —24 Ma). Sulphor for pyrrhotite formation
has been likely delivered from the adjacent schists during peak
metamorphism. The remanence is therefore probably secondary,
26° N
FIGURE1. Simplified geological map of the East Himalaya and
SE-Tibet (modified after Yin and Harrison 2000). HFT, Himalaya
Frontal Thrust; MCT, Main Central Thrust; HHM, High Himalaya
Metamorphic rocks; STDS, South Tibetan Detachment System;
THS, Tethyan Himalayan Sequences; YTS, Yarlung Tsangpo Suture
zone; LB, Lhasa Block; Z, locality of Tsetang or Zetang. The black
rectangle indicates the studied area.
either beinga the rmore mane nee or a the rmo-chemical remanence.
More paleomagnetic analysis is required to elucidate vertical axes
rotations in SE-Tibet.
Yin A and TM Harrison. 2000. Geologic evolution of the Himalayan-
Tibetan orogen. Annual Reviews in Earth and Planetary Sciences 28:
Carbon and sulfur isotope records of Ediacaran carbonates
of Lesser Himalayas: implications on oxidative state of the
contemporary oceans
DM Banerjee
Department of Geology, University of Delhi, Delhi-110007, INDIA
High resolution geochemical data from fossil-poor Blaini-Krol
and fossiliferous Lower Tal succession in the Lesser Himalayas
closely conform to the geochemical trends demonstrated by
the rock sequences at Oman, Newfoundland, South China and
Western United States. Geochemistry of all these known Ediacaran
sections suggest long term oxidation of the terminal Proterozoic
oceans which led to gradual depletion of dissolved organic carbon
reservoir. It is interpreted that the increase in the dissolved
organic carbon was responsible for the radiation of acritarchs
and algal population (McFadden et al 2008). Such coupling of
oceanic oxidation event and the evolution of organisms can be
suggested only when chemostratigraphy is adequately supported
by biostratigraphy. Lower Himalayan sections do not offer such an
opportunity due to low suphate but high sulfide contents in the
Krol carbonates and the consequent paucity of preserved organic
life in these strata. The Krol basin carbonates show fairly stable
organic carbon isotopes, but three profound negative carbonate
carbon excursions and a positive excursion close to the rock
junction of Lower Tal phosphorite. Two of these excursions are
associated with facies changes, hence suspected to be artifacts,
while one negative excursion in the transgressive facies represent
biogeochemical anomaly co relatable through different continents
(Kaufmann et al. 2006). On the other hand, sulfate sulfur isotopes
associated with the carbonates are compatible with large buffered
dissolved organic carbon reservoir and low sulfate concentrations
but high sulfide sulfur. Sharp negative isotopic shift in the upper
part of the Krol succession therefore records pulsed oxidation
of the deep oceanic dissolved organic carbon reservoir, leading
to sudden proliferation of small Shelly Fossils and associated
eukaryotic diversity in the Lower Tal phosphate/Chert which
followthe sharp negative carbonate carbonexcursion. Two negative
excursions in the lower Cambrian Tal succession reflect changes
in the oceanic chemistry while one small excursion is an artifact
and influenced by the facies. On the other hand, at the bottom
ofthe whole succession, representing the end phase ofthe Blaini
Formation, a prominent negative carbonate carbon excursion has
matching trends in most ofthe continents and reflects last phase
ofthe glacial activity in the terminal Proterozoic time.
McFadden KAJ Huang, X Chu.G JiangAJ Kaufinan and C Zhou. 2008. Pulsed
oxidation and biological evolution in the Ediacaran Doushantuo Formation.
Proceedings National Academy ofSciences L7S^4,105(9): 3197-3202
Kaufman AJ,GJiang,N Christie-Blick,DM Banerjee.VRai. 2006. Stable isotope
record of the terminal Neoproterozoic Krol platform in the Lesser
Himalayas of northern India. Precambrian Research 147:156-185
Kinematics of the crust in southern Tibet and Higher Himalayan
Crystalline -a paleomagnetic approach
Rachida El Bay*1, Erwin Appel1, Rodolfo Carosi2, Lin Ding3, Dunkl Istvan4, Richard Gloaguen5,
Chiara Montomoli2, Lalu Paudel6 and Bastian Wauschkuhn5
1 Institute for Applied Geoscience, University of Tuebingen, GERMANY
2 Departimento di Scienze della Terra, University of Pisa, ITALY
3 Institute of Tibetan Plateau Research, Chinese Academy of Sciences, CHINA
4 Geoscience Center, University of Goettingen, GERMANY
5 Institute for Geology, Technical University of Freiberg, GERMANY
6 Central Dept. of Geology, Tribhuvan University, Kathmandu, NEPAL
For correspondence, email: rachida.el-bay
Secondary pyrrhotite remanences from the Tethyan Himalaya
acquired duringEocene (western Himalaya) and Oligocene to early
Miocene (central and eastern Himalaya) were evaluated for block
rotations. Oroclinal bending is well reflected by paleomagnetic
data in the western part ofthe Himalaya also showing a uniform
counterclockwise rotation of India versus the Tethyan Himalaya.
In contrast, data from the central part and preliminary results
from the eastern part indicate an abrupt change to unexpected
clockwise rotations versus India where oroclinal bending would
predict no rotation or slight counterclockwise rotations (Schill et
al. 2004). It can be hypothesized that these clockwise rotations are
a result of a large dextral shear zone related to lateral extrusion of
the Tibetan Plateau, with an onset in central Nepal. However, the
existing gap in suitable data from the eastern part ofthe Himalaya
was hindering a closer evaluation of this question. The hypothesis
is reconsidered in the light of new findings.
In southern Tibet field work has been carried out on an E-W
section between 86° and 89°E (Figure 1) encompassing the Nayalam
section, the Karta valley, the Dinggye extentional zone and the Yadong/
Pagri area. Low grade Ordovician to Mid-Triassic metacarbonates
and slates were sampled. The south Tibetan series are bounded to
the south by the South Tibetan Detachment System (STDS) and to
the north by the Yarlung Tsangpo Suture Zone (YTSZ) and there is
a widespread occurrence of north Himalayan gneiss domes. The S-
N transect at ca. 87°E is ranging from few km south of Lukla (Solu
Khumbu, HHC) to Lhatse close to the YTSZ. Sampling included
the high grade metamorphic gneisses from the HHC, the Tethyan
sedimentary series (Ordovician to Carboniferous) and the upper
Triassic flysch between Tingri and Lhatse.
The mechanism of secondary remanence acquisition in low-
grade metamorphic rocks of the Tethyan Himalaya is quite well
understood. Pyrrhotite is formed during prograde metamorphism.
A thermoremanence is blocked during last cooling if the peak
metamorphic temperature has reached the Curie temperature
(Tc) of pyrrhotite (ca. 320 °C). If the peak temperature was lower
than Tc a thermo-chemical mechanism is likely and the time of
remanence acquisition might predate the cooling age. For these
reason we applied illite crystallinity and K/Ar dating to determine
peak metamorphic temperatures and ages of metamorphic cooling.
In the high grade gneisses ofthe HHC pyrrhotite is believed to be
formed during the transition from ductile to brittle deformation
(retrograde stage). A thermoremanence is likely acquired and its age
11 lkm
FIGURE 1. Shutle
Radar Topography
Mission (SRTM)
image from
the study area
showing sampled
E-W traverse and
S-N transect
will correspond to the age ofthe last metamorphic cooling event.
"Anomalous" inclinations, indicating strong tilting after
remanence acquisition, are observed across the E-W traverse.
Taking into account the proximity of the sampled sites to the
STDS, especially at the Nyalam section (Nyalam detachment)
and in the Karta valley, a regional trend linked to a "folded" STDS
can be assumed. Therefore, remanence acquisition predates the
onset ofthe STDS or is coeval with it.
Remarkably, remanences are mainly dispersed on small
circles with a tilt axis oriented approximately in N-S direction.
This is not in agreement with long-wavelength tilting parallel to
the strike ofthe main Himalayan tectonic units. It can be suggested
that this small-circle distribution is an expression of doming in
the crust (caused by channel flow?).
Inclinations at Nyalam section and Karta valley indicate a
second phase of tilting superposed to the E-W tilting.
Small circle analysis (Waldhor et al. 2006) enables
quantification of vertical axis rotation. A clockwise rotation is
evident along the S-N transect at ca. 87°E at Karta valley and further
north in the flysch series between Tingri and Lhatse. First results
from the northern part of the HHC in Khumbu area indicate
a pattern of rotation comparable to those observed at the Karta
valley. Counterclockwise rotation obtained for the Dinggye- and
Yadong/Pagri areas are in contradiction with the above mentioned
hypothesis of a uniform large dextral shear zone.
In summary, the hypothesis of a large dextral shear zone
linked to the extrusion of the Tibetan Plateau can be yet not
proved or rejected. A major effect attributed to a normal fault/
thrust system became more evident.
Schill E, E Appel, C Crouzet, P Gautam, F Wehland and M Staiger. 2004.
Oroclinal bending and regional significant clockwise rotations ofthe
Himalayan arc — constraints from secondary pyrrhotite remanences.
Geological Society of America Special Publication on orogenic curvature
Waldhor M and E Appel. 2006. Intersection of remanence small circles:
new tools to improve data processing and interpretation in
paleomagnetism. Geophysical Journal International 33-45
White Sandstone in Subathu Sub-Basin: an example of
tectonically driven forced regressive wedge
MK Bera1*, A Sarkar1 and PP Chakraborty2
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur—721302, INDIA
2 Department of Applied Geology, Indian School of Mines, Dhanbad 826 004, INDIA
Corresponding author: e-mail:
Sediments ofthe Himalayan peripheral foreland basin, developed
due to progressive thrust-loading (DeCelles and Giles 1996,
Dickinson 1974) and subsequent exhumation/upliftment of the
mountain chain, records signature of hinterland tectonics visa-vis basin filling processes. The synchroneity of the foreland
sediments with widespread early Oligocene glaciation suggests
that hypothesis of tectonics-climate connection, whereby the
cooling was driven by drop in atmospheric C02 via enhanced
silicate weathering ofthe rising Himalayan orogen (Raymo and
Ruddiman 1992, Pagani et al. 2005), has considerable merit. As a
test-case Paleogene Sub-Himalayan foreland sediments of marine
Subathu and continental Dagshai formation rocks were studied to
identify the teleconnection between tectonics and climate, if any.
The Subathu-Dagshai transition here is marked by the presence
of a —31 Ma old (Najman et al. 2004) characteristic quartz rich
mature sandstone locally termed as the 'White Sandstone".
It marks the termination of marine Subathu Formation and
initiation of continental molasses Dagshai Formation and
represents an important evolutionary stage in the geodynamic
history of the foreland basin (DeCelles and Giles 1996, Sinclair
1997). However, the status of White Sandstone has always been
uncertain varying between marine Subathu (a beach or tidal flat;
Singh and Khanna 1980, Srivastava and Casshyap 1983) to fluvial
Dagshai (Najman et al. 2000, 2004). Further, raging debates exist
about the possible continuity/discontinuity between Subathu and
Dagshai formations (see Bera et al. 2008 and references therein).
Since the White Sandstone plays a crucial role in this debate the
present study focused on process based sedimentology of this
unit. Detailed bed form geometry and sedimentary structure
shows that the White Sandstone unit is made up of three distinct
components viz., Lower shoreface (between fair weather wave
base and storm wave base), Upper shoreface (above fair weather
wave base) and Foreshore/beach. Lower shoreface deposits are
characterized by intercalation of centimeter thick fine sand and
shale couplets, although definite signature of hummocky cross
stratified (HCS) unit is not recorded in the present study. These
units lie between two erosional surfaces. The lower erosional
surface is sharp and it places the units directly over the offshore/
shelf sediments. Presence of gutter cast and rip-up clast at the
base of these units suggest the lower erosional surface must be a
storm weather wave base or regressive surface of marine erosion
(RSME) (Plint 1988). The upper erosional surface is marked
by the truncation of the fine sand shale intercalation of lower
shoreface with decimeter thick lenticular unit of upper shoreface
and dips towards the basinal depocenter. The presence of this
surface above basal RSME allowed us to interpret it as a fair
weather wave base or "surf diastem" (of Swift et al. 2003). Recent
studies (Fraser et al. 2005, Tamura et al. 2007) show that this fair
wave base is an important component of shoreface sand deposits,
as it helps in assessing the change in progradation of the upper
shoreface deposits during forced regression. Our study shows
that the basal RSME is not a single erosional surface developed
due to fall in storm wave base; at places, where lower shoreface
is absent, fair weather wave base amalgamates with it. The
amalgamation depends upon the preservation of lower shoreface
which, in turn, governed by both sediment supply and rate of
sea level fall during forced regression. As mentioned earlier, the
upper shoreface deposits are characterized by the decimeter thick
lenticular sandy units. The meter thick thinning and finning
upward nature of these lenticular beds and internal truncation of
these bed sets suggest its probable longshore bar origin (Tamura
et al. 2007). The presence of wave ripples on top ofthe beds and
foreshore/beach deposits above it indicate its upper shoreface
environment. The foreshore/beach deposits are characterized
by decimeter thick parallel bed sets with very low angle cross
stratification and sometimes show parting lineation. This unit
is overlain by either interfluve sediments with extensive caliche
development or cut by Dagshai channel sandstone. The presence
of basal RSME and fluvial incision and/or caliche development on
the top of white sandstone unit indicate it as a product (an FSST
wedge) of forced regression (Hunt and Tucker 1992, Catuneanu
2002). Our spatially extensive new petrographic dataset suggest
a sudden increase in metamorphic detritus from the White
Sandstone unit onwards indicating initiation of exhumation of
the Himalayan metamorphic core during this time. Our study has
three important implications. First, the —31 Ma white sandstone
is marine not fluvial and hence the unconformity occurs above it
not below. Second, the forced regression was possibly tectonically
driven due to sudden hinterland uplift. Third, the timing of this
tectonically driven forced regression coincides with the rapid
rise in sea water Sr isotope ratio (from 0.7077 to 0.708) further
strengthening the hypothesis that uplift driven silicate shedding
might have causal link with the early Oligocene cooling.
BeraMK, A Sarkar, PP Chakraborty, RS Loyal and P Sanyal. 2008. Marine
to continental transition in Himalayan foreland. Geological Society of
America Bulletin. (In press).
Catuneanu O. 2002. Sequence stratigraphy of clastic systems: Concepts,
merits, and pitfalls. Journal of African Earth Sciences 35: 1—43
DeCelles PG and KA Giles. 1996. Foreland basin systems. Basin Research
8: 105-123
Dickinson WR.  1985. Interpreting provenance relations from detrital
modes of sandstones. In: Zuffa GG  (eds) Provenance of arenites:
Dordrecht, NATO ASI series C, 148, D. Reidel p333-361
Fraser C, PR Hill and M Allard. 2005. Morphology and facies architecture
of a falling sea level strandplain, Umiujaq, Hudson Bay, Canada.
Sedimentology 52: 141—160
Hunt D. and ME Tucker. 1992. Stranded parasequences and the forced
regressive "wedge systems tract: Deposition during base level fall.
Sedimentary Geology 81: 1—9
Najman Y, M Bickle and H Chapman. 2000. Early Himalayan exhumation:
Isotopic constraints from the Indian foreland basin. Terra Nova 12: 28-34
Najman Y,  K Johnson,  N White and G  Oliver.  2004. Evolution of
Himalayan foreland basin, NW India. Basin Research 16: 1—24
Pagani M, JC Zachos, KH Freeman, B Tripple and S Bohaty. 2005. Marked
decline in atmosphere carbon dioxide concentrations during the
Paleogene. Science 309: 600-603
Plint AG. 1988. Sharp-based shoreface sequences and 'offshore bars' in
the Cardium Formation of Alberta: Their relationship to relative
changes in sea level. In: Wilgus CK, BS Hastings CGStC Kendall,
HW Posamentier, CA Ross and JC Van Wagoner (eds), Sealevel
changes—An integrated approach. SEPM (Society for Sedimentary Geology)
Special Publication 42: 357—370
Raymo ME and WF Ruddiman. 1992. Tectonic forcing of late Cenozoic
climate. Nature 359: 117-122
Sinclair HD. 1997. Tectonostratigraphic model for underfilled peripheral
foreland basins: An Alpine perspective. Geological Society of America
Bulletin 109: 324-346
Singh HP and AK Khanna. 1980. Palynology of the Paleogene marginal
sediments of Himachal Pradesh, India. Lucknow. Proceedings Fourth
International Palynological Conference 1: 462^471
Srivastava VK and SM Casshyap. 1983. Evolution of the pre-Siwalik
Tertiary basins of Himachal Himalaya. Journal of Geological Society of
India 24: 134-147
Tamura T, F Nanayama, Y Saito, F Murakami, R Nakashima and K
Watanabe. 2007'. Intra-shoreface erosion in response to rapid sea-
level fall: depositional record of a tectonically uplifted strand plain,
Pacific coast of Japan. Sedimentology 54: 1149—1162
Swift DJF^ BS Parsons, A Foyle and GF Oertel. 2003. Between beds and
sequences: stratigraphic organization at intermediate scale in the
Quarternery ofthe Virginia coast, USA. Sedimentology 50: 81—111
Evolution of the Lesser Himalaya
ON Bhargava1* and W Frank2
1   103, Sector 7, Panchkula 134109, India, 253/8 Ferrogasse Vienna 1040, AUSTRIA
For correspondence, e-mail:
The earliest rocks found in the Lesser Himalaya are gneisses
and crystallines in which the 1860 Ma Jeori-Wangtu-Bandal
Granite-gneiss Complex (JWBC) is intrusive. It forms the
basement complex for the oldest Lesser Himalayan rocks and
are a possible extension of the Peninsular rocks. In stratigraphic/
parautochthonous position it is found only in the Himachal and
J&K (Kishtwar). In the Eastern Himalaya, the basement rocks
occur as tectonic slivers. Once the JWBC was cratonised there
was a formation of paleosol prior to the 1800 Ma rifting. The
JWBC is also involved in thrusting and forms a tectonic marker
(Baragaon/Gahr) throughout the Himalaya.
The history of the Himalaya commenced with a rifting
manifested by 1800 Ma Rampur and equivalent volcanics. This
event created a shallow marine basin in which the Rampur Group
and equivalent sequences (Sundernagar, Dharagad, Berinag,
Kuncha, Daling, Shumar groups) along with tholeiites were laid.
Duration of the Rampur Group sedimentation is uncertain, but
the basin certainly terminated prior to 1500 Ma i.e. the age of
the basal part of the overlying Shali Group and its equivalents.
The Kulu Thrust sheet involving the JWB basement was possibly
nucleated between 1800 Ma and 1500 Ma.
After a hiatus, the sedimentation ofthe carbonate sequences
of the Shali and equivalent successions (Larji, Deoban, Calc
"Series", Nawakot, Baxa) took place. The stromatolites in
these 3000 m thick carbonate sequences, indicate an age range
between 1500-1000 Ma. It looks improbable that only 3000
m thick sequences should have been deposited during 500 Ma
time-span, which almost equals the entire Phanerozoic. Several
sedimentological breaks in between the carbonate sequences
are probable and many of the shale horizons in these carbonate
sequences may represent paleosols.
The carbonate sedimentation ceased with another rifting
around 1000 Ma. The rifting caused outpouring ofthe Tattapani
and Peontra tholeiitic volcanics. The rise of thermal dome formed
the Chaur Granite. TheJutoghThrust Sheetwas possibly nucleated
at this juncture. The raised Rampur and Deoban and equivalent
terrains provided clasts to the Basantpur and Mandhali diamictites
culminating in the deposition ofthe Simla-Jaunsar groups in the
same basin. The detrital mica in the Sanjauli Formation (Simla
Group) and Nagthat Formation (Jaunsar Group) are 860 Ma old,
thus indicating these formations to be younger to this age. The
mica and illite have chemical signatures ofthe Erinpura Granite.
This basin was possibly confined mainly between Nepal and
Jammu, as its equivalents are not known in the Eastern Himalaya.
The sedimentation possibly terminated around 750 Ma to allow
time to raise the Simla and Jaunsar groups and their consequent
extensive erosion before the sedimentation of 700-650 Ma Blaini
sequence. This regression was accompanied by rising of upland
between the Himalaya basin and the Aravalli terrain.
The clasts in the glaciomarine Blaini diamictites are from
the Himalayan source, suggesting the glaciers to have emanated
from the raised Simla-Jaunsar upland, which had cut off supply
from the peninsular part. There were two glaciations intervened
by an interglacial period. After the deposition ofthe cap carbonate,
there was a regression and the basin was confined to a smaller part
in which Infra-Krol and Krol sequences were deposited. At the
termination ofthe Krol sedimentation, close to the Precambrian-
Cambrian boundary, the Outer Krol Belt part was raised and the
Tal sedimentation continued in the Krol Basin sited over the
Jaunsar Group. This basin too was confined mainly between
Nepal and Himachal. Upwelling currents from an open sea, as
indicated by presence of cerium, concentrated the phosphorite in
the Tal Group. The open sea was separated from the Tal Basin by
a submarine ridge. Another basin towards SE ofthe Krol basin
was created, in which the Chilar Formation was deposited. The
Chilar quartzitearenites enclose 1860 Ma detrital mica, whereas
the Tal quartzitearenite have 860 Ma detrital mica. Presence of
age specific micas in the Chilar and Tal sediments indicates that
a barrier separated the basins of these two formations to preclude
intermixing of micas of two different ages. The Outer Krol Belt,
which lacks the Tal sediments, formed this barrier. The Tal basin
relatively subsided, which resulted in greater depth of burial,
leading to higher grade of anchimetamorphism in the Jaunsar
Group as compared to the Simla Group. The Tal quartzarenites
are younger than 525 Ma—the age of enclosed detrital zircons.
Zircons of the same age are found in the Middle Cambrian
Kunzam La Formation of the Tethyan Himalaya also, thereby
indicating a common provenance. The submarine ridge referred
to above, mainly made up of Vaikrita Group with Early Palaeozoic
granites, became aerial and contributed sediments to the Tal basin
as well as the Kunzam La basin on the Tethyan side during the
Middle Cambrian.
The Tal basin terminated around 520 Ma due to late
Cambrian thrusting event, which was experienced over the entire
length ofthe Himalaya. Suturing in the northern part ofthe then
Indian Plate caused this tectonic event. The folds generated during
this event are co-axial with the Himalayan folds. The suturing
and resultant thrusting caused a regional hiatus covering the Late
Cambrian and generation of Early Paleozoic granites all over the
Himalaya in the Vaikrita Crystalline. The Vaikrita Thrust Sheet
too was nucleated at this time and on its back carried the Kunzam
La basin, which contributed clasts to the Thango Formation of
the Tethyan basin.
After this event the Lesser Himalayan terrain became a
positive area, with drainage heading towards the Tethyan part.
At the beginning of the Permian, associated with rifting in the
Gondwanaland, old lineaments, mainly in the present foothill
parts opened and provided pathway to Permian sea right from
Arunachal to Uttarkhand. The sea lasted only during the Early
Permian, its withdrawal coinciding with Midian regression and
sedimentological break in the Tethyan part. Thereafter Lesser
Himalaya again became a positive area.
The rifting/drifting during Cretaceous again re-opened old
lineaments for the transgression of Late Cretaceous Sea between
Uttarkhand and Arunachal. The sea withdrew around 70 Ma.
Thereafter erosion in subtropical climate led to the formation
of bauxite. The subduction of the Indian plate had already
commenced, the Lesser Himalayan part arched and the foreland
basin formed at the present foothill region; its embayments
extended quite far over the Mesoproterozoic carbonate belts
and Neoproterozoic Simla-Krol, Cambrian Tal, Permian Bijni
and Cretaceous Nilkanth parts. The Subathu sediments derived
material from the northern and partly from southern (peninsula)
sources and from the Wazirstan-Khost area. The sedimentation in
a marine basin continued up to 44 Ma, thereafter (Passage Beds)
the paralic conditions set in that lasted till 40 Ma. In shallower
part of the basin there was a break in sedimentation during the
Late Eocene. The thrust sheets, which were nucleated in the
Precambrian times were reactivated and were partly bared. The
Dagshai and equivalent basins were mainly deposited in estuaries
and extensive flats. The Dagshai and the Passage Beds had their
provenance in sedimentary sequences and also from the rising
crystalline thrust sheets. The overlying Kasauli Formation
represents brackish water environment with distinct supply
mainly from the low grade crystalline. As the thrust sheets further
emerged as a consequence of continued subduction ofthe Indian
Plate, these advanced towards the south and the foreland basin
shifted towards farther south in which typical molassic sediments
ofthe Siwalik were deposited.
Due to impact of advancing crystalline thrust sheets the
Shali and Simla groups' rocks moved partly over the Paleogene of
the foreland basin and Krol Belts slid on their floors as superficial
thrust sheets. The Late Cambrian folds, which are co-axial
with the Himalayan folds, got accentuated and also selectively
overturned, whereas the Himalayan folds (e.g. Jutogh, Krol,
Tons and Kulu thrusts) remained largely open and upright. The
Himalaya acquired the present elevation and various weathering
processes became active, with the removal of overburden due to
extensive erosion the stresses were released and various faults
were reactivated from time to time.
Bursting of Glacial Lakes-- A Consequence of Global Warming:
A Case History from the Lunana Area, Gasa Dzongkhag, Bhutan
ON Bhargava1, SK Tangri2 and AK Choudhary3
1 103 Sector 7, Panchkula 134109, INDIA
2 3 Sector 33, Chandigarh, INDIA
3 Resident Geologist, Tala Hydroelectric Project Authority, Tshimalakha, Chimakoti, BHUTAN
The lower reaches of the Lunana area expose multiple folded
migmatite and biotite gneiss ofthe Thimphu Group, extensively
intruded by granitic and pegmatitic rocks. This sequence in the
upper reaches of the Table Mountain is overlain by the Tethyan
The straight course ofthe Pho Chhu between Luggye and
Lhedi lakes in the Lunana area is probably controlled by a fault. A
N-S strike-slip fault during Quaternary seems to have formed the
Raphstreng Lake as a pull apart sag-pond.
Severe hot summers during the year 1994 led to excessive
melting of glaciers. The exceptional melting contributed
enormous amount of melt water to the lake basins, which caused
breach of the morainic dam and consequent enlargement of the
outlet ofthe Luggye Tsho and the Tshopda Tsho. The breach was
followed by floods on October 7, 1994,. These floods destabilized
the slopes on either bank of the Pho Chhu near Tshopda Tsho
outlet making them prone to landslides. The flash floods also
eroded the left lateral moraine ofthe Raphstreng Tsho, which had
disturbed the original angle of repose. The Raphstreng area is also
prone to ice avalanches, rock glaciers, surge of which can damage
the rim and also cause spillover of water.
The morainic material comprises poorly graded gravel,
deficient in finer fraction. The unit weight or in place density ofthe
material and permeability values varies from 17.67 kN/m3 to 19.66
kN/m3 and 7.39 to 8.36 Lugeon respectively in the Raphstreng
Tsho, 24.66 kN/m3 and 1.81 Lugeon in the Thorthormi Tsho and
21.39 kN/m3 and 1.14 Lugeon in the Lyggey Tsho. The permeability
values suggested semi-pervious nature ofthe material. The values of
cohesion and friction angle are 0.02 kN/cm2 and 370 respectively.
The mitigating measures suggested were: (i) management
of active landslide in the Tshopda-Tsho-Thorthormi Tsho
complex, (ii) construction of dykes, check dams and (iii) partial
draining of the Raphstreng Tsho complex and construction of
dykes and check dams in Thnza-Tshoju complex. Plantation along
the slopes, regular monitoring of the lakes, seismic and microclimatic observations are recommended as long term measures.
These measures were implemented in the years 1996-97. Since
then the lakes of this area have remained intact.
Implications of biostratigraphy in the Himalayan Paleogene
Foreland Basin
SB Bhatia1* and ON Bhargava2
1 441 Sector 6, Panchkula-134109, INDIA
2 103 Sector 7, Panchkula-234109, INDIA
For correspondence, email:
The paper discusses the role and significance of biostratigraphy
in deciphering the structures, facies models and dating event
stratigraphic surfaces of the intricately deformed Paleogene
sediments comprising the Subathu, Dagshai and Kasauli
formations (Late Thanetian-Early Miocene) of the Surajpur
Tectonic Unit of the Himalayan Foreland Basin. The larger
foraminifera, particularly the Nummulitdae, which occur in
great abundance in distinct foraminiferal bands in the Subathu
Formation are chronologically significant and facilitate recognition
of Shallow Benthic Faunal Zones (SBZ-Serra-Eel et al. 1998)
throughout the Tethyan Zone, including the Himalayan Foreland
Basin (Bhatia and Bhargava 2005, 2006).
In the case ofthe structurally deformed Paleogene sediments
of the Surajpur Tectonic Unit (Mukhopadhyay and Misra,
2005), it is all the more imperative to identify and recognize the
biostartigraphically significant foraminifera and other taxa to
determine the younging direction of the beds. Failure to do so
led Raiverman and Raman (1971), Singh (1996) and Raiverman
(2002) to erroneous conclusions by suggesting an inter-tonguing
relationship between the various exposed green Subathu (G1-G5)
and the red Dagshai sediments (R1-R5) on the Simla-Bilaspur
Highway, implying thereby that the G1-R1-G2-R2... sequence
was towards the younging direction. This concept was soon
contradicted by Batra (1989) on the basis of the faunal zones,
which were repeated in all the G1-G5 units clearly suggesting that
they were all of the same age (Late Cuisian-Early Lutetian) and
that the repetition of the red and green beds was due to folding
and faulting. Later works of Bagi (1992), Najman et al. (1993)
and others confirmed this view. Singh's (1996) work, based
on the premise that the increase of the proloculus size in the
megalospheric generation (Form A) in larger foraminifera, is of
phylogenic significance, is misconstrued in as much as it relies
on the proloculus-size increase in a single species-identified by
him as Nummulites atacicus, which neither corresponds in size to
the types from Europe nor to the Shallow Benthic Zone (SBZ)
8, Middle Ilerdian, of which it is one ofthe characteristic zonal
fossil. The bulk of larger foraminifera in the exposed Subathu
Formation- G1-G5 in the Bilaspur-Simla Highway are of
Middle-Late Cuisian (SBZ 11-12) and Early Lutetian age (SBZ
13 = Assilina spira abrardi = Zone III of Batra, identified by him
as Assilina blondeaui.
The inter-tonguing concept of green Subathu and red
Dagshai was extended to embrace the grey facies of the Kasauli
Formation also in the section near Charring Crossing in Dagshai
Cantonment (Raiverman 2002, p. 12, figs. 2.1, 2.5c). This would
seem to imply that the Kasauli Formation, generally accepted to
be of Early Miocene age, is roughly homotaxial with the Early to
Middle Eocene Subathu Formation—an untenable stratigraphic
situation. We critically examined the Charring Crossing section
and did not find any evidence of interfingering between the green
and red Subathu (actually the Passage Beds with characteristic
molluscs) and the grey beds of the Kasauli Formation. On the
contrary, the two are juxtaposed along a thrust plane as evidenced
by profuse silckensides observed in all the rocks, particularly
the sandy beds exposed in this section. The Subathu Formation
along with the overlying Dagshai Formation, exposed north and
northeast of the Charring Crossing, was found to have ridden
over the Kasauli Formation along a ramp-flat-ramp thrust, which
may be designated as the Dagshai Thrust.
In so far as the relationship between the various morphotypes
of the Nummulitidae (Nummulites and Assilina and various
paleofacies models) are concerned, the workby Luterbacher (1984)
in Southern Pyrenees shows a correlation between morphological
characters (size and shape, whether lenticular or flat discoidal),
classified into four morphotypes and the established facies models
in the Paleogene of the Pyrenees. Our work in the Kaushalia
River section shows that the beds ofthe lowermost SBZ 10 (Early
Cuisian) containing Nummulites planulatus and N. burdigalensis
burdigalensis were deposited in a beach, prodelta setting, while
those of SBZ 11 and 12 (Middle to Late Cuisian) with abundant
A. laxispira, A. cuvillieri, besides bryozoa, crabs etc., in a lagoon to
bay carbonate shoal setting, and those of SBZ 13 (Early Lutetian)-
A. spira abrardi bed (flat discoidal >8 mm diameter) in a beach,
shore face, near shore shoal environment.
The larger foraminiferal fauna thus corroborates the views
expressed three decades earlier on sedimentological criteria by
Singh (1978) that most ofthe Subathu sediments were laid down
in shelf mud, tidal flats, and coastal sand bars. This view has
stood the test of the time as confirmed by several workers from
the homotaxial beds in Jammu, Hazara-Kashmir Syntaxis and
Nepal. These homotaxial beds were deposited in a shallow, wave
and storm dominated tidally influenced lagoon/barrier beach with
near shore carbonate-shoal setting.
The above conclusions are in stark contradiction to the
contention of Bera et al. (2008) of documenting for the first
time large varieties of basinal turbidites in the Subathu—an
interpretation that is not corroborated by sedimentological and
paleontological evidences. The occurrence of hummocky cross-
bedded sandstones (Late Cuisian) immediately below the A spira
abrardi bed in the Kaushalia River section (Bagi 1992) and in the
oyster-bearing beds in the Jammu sector (Singh and Andotra,
2000) testify to frequent storm events in the Subathu basin. We
are also in strong disagreement with the conclusion of Bera et
al. (2008) that "Fixing an age for the termination of marine beds,
based on reworked fossils (e.g. A. spira) in calciturbidite units
is not justifiable and the upper limit of the Subathu Formation
must be significantly younger than ca 44 Ma." In support ofthe
above contention, Bera et al. (2008) have shown the occurrence of
A. spira in a calciturbidite bed at the base ofthe black grey Subathu
shale in most of their sections, which is hypothetical, factually
incorrect and militates against the basic principles of stratigraphy.
The surmise of Bera et al. (2008) regarding the upper age limit
of Subathu is not borne out by the fossil records in the overlying
Passage Beds, which delimit the termination of HST, including
the Passage Bed around ca 40 Ma (Bhatia and Bhargava 2005).
The A. spira abrardi bed (SBZ 13) in the Subathu Formation in
all the sections occurs in the same chronological order above the
beds containing foraminifera of Cuisian age (SBZ 12) as it does
elsewhere in the Tethyan Zone (European biozonation), hence
could not be reworked by any stretch of imagination.
In so far as the Event Stratigraphic framework is concerned,
the entire Subathu sequence including the coal and carbonaceous
shale at the base and the Passage Beds at the top represent
Highstand Systems Tract (HST), the maximum flooding surface
(MFS) is seen in sections where the base is exposed, viz., Jammu,
Kakra and other sections and is represented by the occurrence of
limestone beds containing Daviesina garumnensis (Bhatia and
Bhargava 2005, 2006) representing SBZ 4 of Late Thanetian age.
We concur with Bera et al. (2008) that the ubiquitous
white sandstone bed in the Kaushalia River and other sections,
occurring at the top of the Passage Beds with a sharp contact, is
of marine origin and that it represents the Falling-Stage Systems
Tract (FSST) in the Event stratigraphy framework. However, we
disagree with their age assignment of 31 Ma to the white sandstone
and of 28 Ma to the overlying Dagshai, as none of these dates are
corroborated with the fossil record (Bhatia and Bhargava 2005).
Bera MK, A Sarkar, PP Chakraborty, RS Loyal and P Sanyal. 2008. Marine
to continental transition in Himalayan Foreland. Geological Society of
America (In Press, available On Line)
Bhatia SB and ON Bhargava. 2005. Regional Correlation ofthe Paleogene
sediments ofthe Himalayan Foreland Basin. Palaeontological Society of
India, Special Publication 2: 105-123
Bhatia  SB   and  ON  Bhargava.   2006.   Biochronological  continuity  of
the   Paleogene   sediments   of  the   Himalayan   Foreland   Basin:
paleontological and other evidences. Journal of Asian Earth Sciences
26: 477-487
Bhatia SB and ON Bhargava. 2007. Reply to Y.Najman, 2007, Comments
on "Biochronological continuity ofthe Paleogene sediments ofthe
Himalayan Foreland Basin: paleontological and other evidences"-
Bhatia,  S.B. and Bhargava, O.N.,  2006, Journal of Asian Earth
Sciences. 26,477-487. Journal of Asian Earth Sciences 31: 87-89
Luterbacher H   1984.  Palaeoecology of foraminifera in  Paleogene  of
Southern  Pyrenees.  Bentho's  83.  Second International Symposium
Benthic Foraminifera April 1983 p389-392
Mukhopadhyay DK and P Misra. 2005. A balanced cross section across the
Himalayan frontal fold-thrust belt, Subathu area, Himachal Pradesh,
India: thrust sequence, structural evolution and shortening. Journal
of Asian Earth Sciences 25: 735-746
Spatio - Temporal Variation of Vegetation During
Holocene in the Himalayan Region
Amalava Bhattacharyya* and Santosh K Shah
Birbal Sahni Institute of Palaeobotany 53, University Road, Eucknow-226 007, INDIA
* For correspondence, email:
Palaeovegetation records derived from pollen assemblages provide
potential information on palaeoclimate due to its characteristically
multivariate and multiscale nature with respect to both temporal
and spatial scales. A good number of studies on climate changes
based on palynology are available from the higher elevation sites of
the Himalaya, but these are mostly from its Northwestern part and
data from the Northeast Himalayan region are scanty. This paper
gives a glimpse of paleovegetation-palaeoclimate changes in the
alpine Himalayan region during the Holocene based on evidence
of pollen data from sub-surface sediments. Further, interpretation
of fossil pollen data based on the calibration of modern climate
vs. modern pollen data could be used in quantitative climate
reconstruction from the pollen diagrams of this region have also
been emphasized
In general in the Northwest Himalayan region, the climate
was warm-moist during most part of Holocene with short phases
interruption of colder and drier climate around 8.3-7.3 ka B.R, 6 -
~3 ka B.R and 850 years B.R In contrary data from the Northeast
Himalaya is available only for Late Holocene, around 1.8 Ka
B.R the climate was comparatively warmer and moister similar
to condition prevailing at present. There is further amelioration
of climate around 1.1 Ka B.R corresponding to Medieval warm
period. Around 0.55 Ka B.R there is a trend towards cooler and
comparatively less moist climate corresponding to the little Ice
Age. This is followed by an amelioration of climate comparable to
present day climatic condition.
Songpan Garze fold belt: New petrological
and geochronological data
Audrey Billerot1*, Julia de Sigoyer2, Stephanie Duchene3, Olivier Vanderhaeghe1
and Manuel Pubellier2
1 G2R, Nancy Universite, FRANCE
2 ENS-CNRS, Labo. Geologic, 75005-Paris, FRANCE
For correspondence, email:
The Songpan Garze fold belt, located in the north Tibet, is the
most enigmatic block ofthe Tibetan plateau. It is located between
the Qaidam block (to the North), the Qiangtang block (to the
South) and the Yangtze block (to the East). It has been accreted
to Eurasia during the Indosinian orogeny in the upper Trias.
The Songpan Garze block mainly consists of deformed Triassic
flyschoid sediments (5-15 km thick). Many granitoids cross
cut the Songpan Garze flysch. Some of them present the same
isotopic signature than the Yangtze block basement (Zhang et al.
2006, Zhang et al. 2007). The Songpan Garze block is interpreted
as a relict of the Yangtze peninsula, crushed between Qaidam and
Qiantang blocks during the PaleoTethys closure. Songpan Garze
sediments were deposited as submarine fan in the depression
comprised between the converging blocks (Roger et al. 2008).
In the Danba area (Sichuan Province China), north-west to
the Longmen Shan belt (that represents the eastern boundary ofthe
Tibetan plateau) high grade metamorphic rocks are outcropping.
Those metamorphic terrains could represent a cross section of
exhumed deep structure ofthe Songpan Garze block. Petrological
and geochronological studies carried on by Huang et al. (2003a)
and Huang et al. (2003b) show a polyphased metamorphic
evolution. Ml stage is characterized by the occurrence of kyanite
and garnet (3-5 kb 570-600°C). It is dated at 204-190 Ma and is
thus related to the Indonisian orogeny. M2 stage is characterized
by heating, rocks reached the sillimanite grade and migmatitic
conditions (4.8-6.3 kb 640-725 °C)(Huang et al., 2003b) and is
dated at 168-158 Ma. However, Wallis et al. (2003) obtained an age
of 65 Ma (on monazite that contain inclusions of sillimanite) for a
high grade metamorphism event close to Danba. The question of
the age of high temperature is then a matter of debate.
In the Quingaling dome (North Danba), migmatites of
sedimentary rocks are observed. Field observations suggest that
migmatization also affected metabasic intrusions. We are processing
a petrogical and geochemical study on this metamorphic dome in
order to precise the successive P-T conditions, and to determine if
the basic intrusions are the cause of heating or if they are affected
by the migmatization (partial melting or crystallization).
Moreover, cathodoluminescence observations of zircons
from a leucosome ofthe Quingaling dome reveal growth zoning
that correspond to different step of crystallisation. We interpreted
them as metamorphic overgrowth around an inherited core.
The different sub-domain will be dated by U-Pb dating (SIMS
Cameca 1270).
Huang, M., Maas, R., Buick, LS. and Williams, I.S., 2003a. Crustal
response to continental collisions between the Tibet, Indian, South
China and North China blocks: geochronological constraints from
the Songpan-Garze Orogenic Belt, Western China. Journal Of
Metamorphic Geology 21(3): 223-240
Huang, M.H., Buick, LS. and Hou, L.W, 2003b. Tectonometamorphic
evolution of the eastern Tibet Plateau: Evidence from the central
Songpan-Garze Orogenic Belt, western China. Journal Of Petrology
44(2): 255-278
Roger, F., Jolivet, M. and Malavieille, J., 2008. Tectonic evolution ofthe
Triassic fold belts ofTibet. Comptes Rendus Geoscience 340: 180-189.
Wallis, S. et al., 2003. Cenozoic and Mesozoic metamorphism in the
Longmenshan orogen: Implications for geodynamic models of
eastern Tibet. Geology 31(9): 745-748
Zhang, H.F., Harris, N., Parrish, R. and Zhang, L., 2006. Association of
granitic magmatism in the Songpan-Garze fold belt, eastern Tibet
Plateau: Implication for lithospheric delamination. Geochimica Et
Cosmochimka Acta 70(18): A734-A734
Zhang, H.F. et al., 2007. A-type granite and adakitic magmatism association
in Songpan-Garze fold belt, eastern Tibetan Plateau: Implication for
lithospheric delamination. Lithos 97(3-4): 323-335
Crustal velocity structure from surface wave dispersion
tomography in the Indian Himalaya
Warren B Caldwell1*, Simon L Klemperer1, Shyam S Rai2 and Jesse F Lawrence1
1 Department of Geophysics, Stanford University, CA 94305-2215, USA
2 National Geophysical Research Institute, Hyderabad 500007, INDIA
For correspondence, email:
A network of 15 broadband seismographs in a —500 km long, N-S
array recorded 12 months of data in 2002-2003 (Rai et al. 2006).
The array traverses the NW Himalaya, from the Indian plain in
the south, across the Indus-Tsangpo Suture and the Tso Morari
Dome, to the southern flank of the Karakoram in the north.
Magnetotelluric (MT) studies in this region reveal low-resistivity
zones which may be indicative of fluids, graphite, or partial melts
in the mid-crust. We have tested these hypotheses by creating 1-D
models of crustal shear wave velocity. The models contain low-
velocity zones at 25-40 km depth; these may be indicative of fluids
or partial melts.
Our models are obtained by inverting group velocity dispersion
curves of Rayleigh waves in the period range of roughly 4—60
s. Numerous magnitude 4 events, several magnitude 5 events,
and one magnitude 6 event occurred 900 km or less from the
array. We find dispersion curves by analyzing the z-component
of fundamental mode Rayleigh waves using Robert Herrmann's
Computer Programs in Seismology (Herrmann and Ammon
2002). We invert the dispersion curves using these programs to
create 1-D models of crustal shear wave velocity structure. The
inversion is done to 150 km depth, but we consider only the upper
60 km ofthe models.
Our results reveal, as expected, demonstrably different crustal
structure in the Indian shield and the Himalaya and Tibetan Plateau,
and our 1-D models suggest that a low-velocity zone is present
immediately north ofthe Indus-Tsangpo Suture (Figure 1).
Future work
We are currently performing tomographic inversions for the region
using these data. These results will offer resolution not available in
our 1-D models. The 1-D results, with their simpler underlying
assumptions, will provide a test ofthe tomography results.
Herrmann, RB and CJ Ammon. 2002. Computer Programs in Seismology:
Surface Waves, Receiver Functions and Crustal Structure. St. Louis
University, St. Louis, MO.
Compu terPrograms. html.
Rai SS, K Priestley, VK Gaur, S Mitra, MP Singh and M Searle. 2006.
Configuration of the Indian Moho beneath the NW Himalaya
and Ladakh. Geophysical Research Letters 33 (L15308): doi:10.1029/
2.9     3       3.1     3.2     3.3     3.4    3.5     3.6     3.7
Velocity, Vs [km/s]
FIGURE 1. Upper: Locations of seismograph stations and
epicenters of earthquakes scaled by magnitude (all magnitudes
are between 3.8 and 6.4). Lines are earthquake paths used for
this study. We designate 3 principal geologic regions: 'Tibetan
Plateau,' 'Indus-Tsangpo Suture' (ITS), and 'Himalaya.' Lower:
Mean of the shear wave velocity models in each regional
group. Line styles follows the map. Event-station paths in the
thrust and foreland basin (dotted lines) show a normal velocity
profile that increases with depth. Event-station paths north of
the ITS in the Gangdese Batholith (gray solid lines) show the
highest velocity, and, along with paths from the Tibetan Plateau
(dashed lines), have a low-velocity zone at 30-40 km. Event-
station paths in the ITS (black solid lines) have a pronounced
low-velocity zone at 25-30 km.
Non-coaxial heterogeneous deformation in the Num orthogneiss
(Arun valley, Mt. Makalu area, eastern Nepal)
R Carosi1*, C Frassi1, C Montomoli1, PC Pertusati1, C Groppo2, F Rolfo2 and D Visona3
1 Department of Earth Sciences, University of Pisa, Via S. Maria, 53 1-56126 Pisa, ITALY
2 Department of Mineralogical and Petrological Sciences, University of Torino, Via Valperga Caluso 35, 1-10125 Torino, ITALY
3 Department of Mineralogy and Petrology, University ofPadova, Garibaldi 37 35122 Padova, ITALY
For correspondence, email:
In the Arun and Barun valleys the upper portion of the Lesser
Himalayan section is made up by the Num orthogneiss. It is a
3-4 km thick unit of granitic augen gneiss with bands of kyanite-
flogopite schists (Lombardo et al. 1993). It records a non-
coaxial deformation related to its involvement within the Main
Central Thrust zone that produced an heterogeneous mylonitic
deformation with rotated feldspar porphyroclasts, bookshelf
structures and localized shear bands with a prominent top-to-the
SW sense of shear. The base ofthe Num orthogneiss is the Main
Central Thrust I (MCT I, sensu Arita 1983).
Micaschists and/or micaceous levels are often intercalated
within the Num orthogneiss, being parallel to the mylonitic foliation.
Two different kinds of micaceous levels have been recognized:
Type a: derived from sedimentary levels deformed and
transposed within the orthogneiss. They often contain
garnet and could be referred to Kushma and/or Seti
Formations (Goscombe and Hand 2006);
Type b: decimetric- to metric-thick micaceous levels
with the same mineral assemblage as in the orthogneiss
but showing a strong grain size reduction and mica
enrichment along the main foliation.
In Type b levels strain increases from the mylonitic
orthogneiss toward the micaceous levels as highlighted by strong
grain size reduction of feldspar crystals and development of
polycristalline quartz ribbons; small-size tourmaline crystals are
still present.
A conspicuous enrichment in muscovite and biotite has
been observed along the shear planes and sometimes gneiss is
transformed into phyllonites.
Microstructural studies revealed that many of the micaceous
intercalations within Num orthogneiss are the product of the
localization of non-coaxial deformation during the evolution of
deformation in the MCT zone.
Arita K. 1983. Origin of the inverted metamorphism of the Lower
Himalayas, Central Nepal. Tectonophysics 93: 43-60
Goscombe B and M Hand. 2006. Gondwana Research 10: 232-255
Lombardo B, P Pertusati and ABorghi. 1993. Geology and tectono-magmatic
evolution of the eastern Himalaya along the Chomolungma-Makalu
transect. In: Treloar P J and Searle M P: (eds.) Himalayan Tectonics
Geological Society, London Special Publication 74: 341—355
Ductile-brittle deformation in the hanging-wall of the South
Tibetan Detachment System (Southern Tibet)
R Carosi1*, C Montomoli1, E Appel2, I Dunkl3 and Lin Ding4
1 University of Pisa, ITALY
2 University of Tubingen, GERMANY
3 University of Gottingen, GERMANY
4 Instititute of Tibetan Plateau Research, CAS, Beijing, CHINA
For correspondence, email:,
The SouthTibetanDetachment System (Burget al. 1984, Burchflel
et al. 1998) is characterized by a lower ductile shear zone, an upper
low-angle normal fault and high-angle normal faults (Carosi et al.
1998, Searle 2003). The low-angle normal fault puts in contact the
base of the Tibetan Sedimentary Sequence with the high-grade
sillimanite-bearing schists and mylonitic leucogranites of the
Greater Himlayan Sequence and, in several places, the intervening
North Col Formation. In the Rongbuck valley, Sa'er and Nyalam
areas (southern Tibet) a sharp contact of the low-angle normal
fault is associated to breccias and cataclasites.
Samples collected from the Ordovician rocks up to Triassic
rocks reveal that temperature increases toward the bottom ofthe
Ordovician limestone. Localized high-strain zones have been
recognized in the Ordovician limestone where it is transformed
in calcmylonites. Calcite crystals show a shape preferred
orientation and grainsize reduction in cm-size bands and show
mechanical twins mainly of Type II with lesser amount of Types
I and III (Passchier and Trouw 2006) suggesting a temperature of
deformation in the range of 200-300°C.
Ductile deformation at the base of the limestone is
heterogeneous and gives rise to mylonitic bands post-dating DI
folds. Quartz and calcite displacement-controlled fibres around
pyrite crystals, asymmetric tails around polycristalline calcite or
calcite/dolomite aggregates, foliation boudinage and asymmetric
boudinage of calcite veins confirm a top-to-the NE sense of
shear, in agreement with the movement of the South Tibetan
Detachment System.
Moving to the Silurian, Devonian and Carboniferous
sequences primary structures are well-preserved and deformation
mechanisms show a sharp transition to low-temperature
mechanisms, being pressure-solution dominant both in limestone,
sandstones and conglomerates. In limestone pressure solution is
linked to the development of calcite veins nearly perpendicular to
pressure solution seams showing cross-cutting relationships.
The ductile shear zones recognized at the base ofthe Tibetan
Sedimentary Sequence cannot be attributed to the thickening
stage (with south verging deformation and lithostatic load ofthe
overlying Tibetan Sedimentary Sequence) but it is related to the
earlier ductile activity ofthe South Tibetan Detachment.
Further brittle deformation of the South Tibetan
Detachment System localized mainly at the base ofthe Ordovician
limestone giving rise to breccias, cataclasites and ultracataclasites.
However, "ghosts" of recrystallized pseudotachilites, preserving
the geometry of injection veins, have been detected even in the
underlying mylonitic granites in the Nyalam section, testifying
their involvement in brittle deformation.
BurgJP, M Brunei, D Gapais, GM Chen and Liu GH. 1984. Deformation
of leucogranites of the crystalline main central thrust sheet in
southern Tibet (China). Journal of Structural Geology 6: 535-542
Burchflel BC, Z Chen, KV Hodges, Y Liu, LH Royden, R Carosi, B
Lombardo, G Molli, G Musumeci and PC Pertusati. 1998. The
South Tibetan Detachment System in the Rongbuk valley, Everest
region. Deformation features and geological implications. Journal of
Asian Earth Science 16: 299-311
Changrong D and L Xu. 1992. The South Tibetan Detachment System,
Himalayan Orogen: extension contemporaneous with and parallel to
shortening in a collisional mountain belt. Geological Society of America
Special Paper 269: 41 p
Passchier CW and RJ Trouw. 2006. Microtectonks, Springer Verlag, Berlin,
Heidelberg. 366 p
Searle MP, RL Simpson, RD Law, RR Parrish and DJ Waters. 2003. The
structural geometry, metamorphic and magmatic evolution of the
Everest massif, High Himalaya of Nepal—South Tibet. Geological
Society [London]Journal 160: 345—366
Three-Dimensional Strain Variation across the Kathmandu
Nappes: Insight to Nappe Emplacement Mechanism
Deepak Chamlagain
Department of Environment Science, Amrit Science College, Tribhuvan University, Kathmandu, NEPAL
For correspondence, email:
The Main Central Thrust (Mahabharat Thrust of Stocklin 1980)
is one ofthe key thrusts in central Nepal Himalaya to understand
the nappe tectonics because it is considered that MCT acted as a
glide plane for the thrust sheets, which traveled more than 100 km
towards south over the LHS forming a large folded-thrust sheet
called Kathmandu Nappe. Much ofthe research has been focused
on structural and kinematic analysis ofthe MCT zone, a root zone
ofthe Kathmandu Nappe. These studies have confirmed a top-
to-the south directed sense of shear in the MCT zone, which is
associated with the emplacement of Kathmandu Nappe. Although
large-scale geometry of the Himalayan thrust sheets and nappes are
relatively understood, features ofthe internal deformation are not
well understood in terms of strain geometry. Several studies have
shown that the pattern ofthe internal deformation varies between
thrust sheets because it depends on pressure, temperature, and
complex tectonic boundary condition. Although strain analysis
bears important clues to understand internal deformation, there
is still lack of studies across the Himalaya nappes. It is, therefore,
necessary to address several problems like (1) three-dimensional
strain geometry, (2) relation between inverted metamorphism
and strain pattern, (3) precise kinematic model to reveal nature of
internal deformation and emplacement mechanism. These issues
are certainly useful to decipher tectonics ofthe Himalayan nappes
and thrust sheets. This study, therefore, mainly attempts to discuss
above-mentioned issues using structural data, three-dimensional
strain geometries, and metamorphism across the MCT and basal part
ofthe Kathmandu Nappe in central Nepal Himalaya (Figure 1).
Structural Geology
In the study area, the MCT is only a major thrust that served as
a glide plane along which Kathmandu Nappe has been emplaced
towards south from its root zone. It carried Precambrian to
Devonian rocks over the Lesser Himalaya. Although displacement
magnitudes are difficult to determine for the MCT, 100 km was
estimated at least (Johnson et al. 2001). The entire thrust sheet has
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FIGURE 1. Geological map of central Nepal
(modified after Stocklin 1980). MCT: Main
Central Thrust, MBT: Main Boundary Thrust,
OST: Out of sequence thrust. Rectangles
show studied areas.
an oval shape structure and convex towards the foreland, which
is folded giving rise to large synclinorium. Along the Malekhu
Khola section, complete sequences of both footwall and hanging
wall are well exposed. About 100 m thick mylonite, and phyllonite
zones characterize MT zone, where thrust related structures are
abundant. In the study area, the NE-SW trending MCT represents
thin ductile zone with the highest degree of finite deformation.
It is distinctly marked by a penetrative foliation, and stretching
and mineral lineation. Deformation fabric intensities are generally
homogeneous at the outcrop scale. Foliation within the quartzites
and schists is defined by aligned biotite and muscovite, and the
mineral lineation is defined by streaking of mica domain in
foliation surfaces in schists and in quartzites by quartz grain-shape
alignment. In the footwall, platy phyllites display lineation with
south-southwest plunge and the foliation planes in the footwall
block show steep dipping towards south. Near to MCT, mylonitic
quartzite is characterized by the strong stretching lineation with
southwest plunge. The S-C fabrics at the MT zone show top-to-
the-south directed shear sense (Johnson etal. 2001). At the central
part of thrust zone, quartz veins are often folded asymmetrically
and the axial plane is sub-parallel to the foliation plane. Garnet
grains of centimeter scale are normally present in the MT
zone. At the base of the hanging wall, the garnetiferous schist
(Raduwa Formation) is well foliated with poorly developed linear
structures. Foliation plane is dominantly dipping towards south
excluding area at the proximity of MCT. At least three phases
of deformation can be documented: first (DI) development of
SI parallel to So. Second (D2) phase is mostly observed along
the Mahesh Khola and is characterized by the tight folds and
lineations, which moderately plunge toward southwest. The
axial planes of these folds are slightly oblique to the SI foliation
and, S2, a new schistosity is incipiently developed along the axial
plane ofthe F2 folds. F2 fold is considered as a refolding ofthe Fl
folds. The D3 deformation phase is characterized by the F3 and
consists of crenulation cleavages with easterly or southeasterly
plunges and steeply dipping axial plane trending east-west or
northwest-southeast. The linear structure associated with the
D3 deformation is roughly considered parallel to the axis of the
Mahabharat synclinorium which trends east southeast. Structural
data support a single nappe model considering Mahabharat Thrust
as a southern continuation of the MCT, which acted as a glide
plane for Kathmandu Nappe.
Three-Dimensional Strain Geometry
Three-dimensional strain data show heterogeneous strain field
both in footwall Lesser Himalayan sequence (LHS) and hanging
wall (Kathmandu Nappe). In the footwall Nadai amount of
strain intensity ( ) varies from 0.396 at the base to 0.575 adjacent
to the MCT whereas in the Kathmandu Nappe, it varies from
0.345 to 0.946. In general, the footwall block shows increasing
trend of value towards MCT whereas in the Kathmandu Nappe
increases away from the MCT (Figure 2). Lower value of at the
base of the Kathmandu Nappe is due to thermal relaxation that
led to a low temperature dynamic metamorphism and plastic
deformation after the emplacement of hot Kathmandu Nappe.
The complex patterns of orientation ofthe strain ellipsoids are due
to superposition of strain partitioning mechanisms on different
scales, which have also created a complex regional strain variation
in terms of magnitude. The shape, orientation of strain ellipsoids,
and   mesoscale   structural   data   indicate   transpressional   strain
field in the MCT zone. The dominancy of prolate type strain
ellipsoids suggest simple shear model for the footwall LHS. In
the hanging wall, however, strain field is dominantly oblate type
with few prolate types suggesting pure shear with a thrust parallel
shortening model (Figure 2). For the both walls computed k-
values have revealed non-plane strain deformation for the MCT,
which is apparently consistent with several fold-and-thrust belts
on the earth.
Emplacement Mechanism
Various models have been designed to explain the exhumation of
the HHCS e.g. (a) rigid extrusion (b) ductile channel extrusion
or channel flow (c) Ductile extrusion by general shear. None of
the models are able to show complete scenario ofthe exhumation
mechanism of the HHCS. Recently, Channel flow model is
widely used but also a matter of strong debate. This model for the
Himalaya-Tibet orogenic system are particularly intriguing because
of the proposed link between channel flow and ductile extrusion
driven by focused precipitation/denudation at the Himalayan
topographic front (Beaumont et al. 2001). The primary drivers for
channel flow in the Himalayan-Tibetan Orogen are (1) unusually
weak zones that exist in the crust at different depths throughout
I langing wall (Kalhmandu Nappe)
Hanging wall (Kathmandu Nappe)
FIGURE 2. Variation of strain parameters
across the MCT (a) Galchhi area (b) Malekhu
area. Note that measured distance (in meter)
is normal to the MCT.
the modern Tibetan Plateau, and (2) that gravitational/pressure-
driven flow. Based upon results from the INDEPTH studies,
Nelson et al. (1996) proposed that crust on the leading edge ofthe
subducting Indian plate partially melts below the Lhasa terrane, and
flows southward toward the Himalayan orogenic front, where it
is denudationally extruded between the coeval MCT and STDS
as Higher Himalayan rocks. Harrison (2006) opposed this concept
because their 'bright spots' restricted to a single rift and evidence
that they represent aqueous fluids rather than molten silicate; the
seismogenic nature of Moho in southern Tibetan and 3He/4He
data indicates the presence of mantle heat and mass in the rift valley.
Therefore, any melt present is due to late Neogene calc-alkaline
magmatism and is supported by the lack of Tertiary migmatites
in the crustal section exposed in the uplifted rift flank of the
Yangbajain graben. The absence of Gangdese zircon xenocrysts in
the Higher Himalayan rocks and the broadly coherent stratigraphy
further put question on validity of channel flow model. Further,
the model must explain observed geological relationships in the
nappes composed of rocks of HHCS. For example in central Nepal
the MCT juxtaposes hangingwall rock that consists ofthe Higher
Himalayan rocks (Bhimphedi Group of Stocklin 1980) against LHS
rocks. However, there is no evidence of normal fault equivalent
to STDS that serves as an upper bounding fault for the extruding
channel. Therefore, the lack of an upper bounding shear zone
clearly suggests that existing channel flow models that describe the
emplacement of HHCS rocks in the High Himalaya may not apply
to the Kathmandu Nappe. Gross stratigraphic relationships within
the well-bedded Bhimphedi Group appear to be intact and in the
more quartz-rich lithologies, primary sedimentary structures such
as cross-beds and ripple marks can be observed (Stocklin 1980). If
rocks ofthe Bhimphedi Group flowed within a channel, it is highly
likely that original stratigraphic relationships and sedimentary
structures would have been obscured. Further, central Nepal
Himalaya doesn't show the coupling between the climate and
tectonics, posing question on validity of the channel flow model.
Rather, structural and three-dimensional strain data support the
general shear extrusion model proposed by Vannay and Grasemann
Beaumont C, RA Jamieson, MH Nguyen and B Lee. 2001. Himalayan
tectonics explained by extrusion of a low-viscosity crustal channel
coupled to focused surface denudation. Nature 414: 738-742
Harrison TM. 2006. Did the Himalayan Crystallines extrude partially
molten from beneath the Tibetan Plateau? In LawRD, MP Searle and
L Godin (eds.) Channel Flow, Ductile Extrusion and Exhumation
in Continental Collision Zones. Geological Society, London, Special
Publications 268: 237-254
Nelson KD and others.  1996. Partially molten middle crust beneath
southern Tibet; synthesis of Project INDEPTH results. Science 214:
Stocklin J. 1980. Geology ofthe Nepal and its regional frame. Journal ofthe
Geological Society of London 137: 1-34
Vannay J-C and B Grasemann. 2001. Himalayan inverted metamorphism
and syn-convergence extension as a consequence of a general shear
extrusion. Geological Magazine 138: 253-276
Crustal configuration of NW Himalaya based on modeling of
gravity data
Ashutosh Chamoli1*, AK Pandey1, VP Dimri1 and P Banerjee2
1 National Geophysical Research Institute, Hyderabad- 500 007, INDIA
2 Wadia Institute of Himalayan Geology, Dehradun- 248 001, INDIA
For correspondence, email:
The crustal structure of the Himalayan fold-thrust belt in
NW Himalaya is constrained using spectral analysis, wavelet
transform (WT) and forward modeling of the Bouguer gravity
anomaly. The data covers the Himalayan range from the Sub
Himalayan zone in the hanging wall of Himalayan Frontal
Thrust (HFT) to the Karakoram fault across the Indus Tsangpo
Suture Zone (ITSZ), along about 450 km long (projected
distance), the Kiratpur-Manali-Leh-Panamik transect. The
spectral analysis of power spectrum of the gravity data yielded
three layer interfaces. The short wavelength data is modeled on
the basis of density contrast across the litho-tectonic boundaries
and regional structural geometries along the profile section.
The average depth and  location obtained  using the wavelet
transform (WT), which shows good correlation with the major
mapped tectonic boundaries including intracrustal/subcrustal
faults in space scale domain. The long wavelength gravity data
is analysed using coherence method for isostatic compensation
to obtain the average depth of effective elastic thickness. The
Moho configuration and the locus of flexure of Indian crust is
constrained using forward modeling incorporating information
from other studies. The Moho depth increases from 40 to 75 km
towards north with the locus of flexure of Indian crust beneath
the Lesser Himalayan zone. The combination of forward
modeling and WT analysis of the data gives insight into the
subsurface extent and geometry of regional structures for the
first time from the NW Himalaya.
Tectonometamorphic evolution of collisional orogenic belts in
the Korean Peninsula: Implications for East Asian tectonics
Moonsup Cho
School of Earth and Environmental Sciences, Seoul National University, Seoul, 151—747, KOREA
The Korean Peninsula consists of three Precambrian massifs
(Nangrim, Gyeonggi and Yeongnam massifs from north to south),
bisected by two Phanerozoic fold-thrust belts (Imjingang and
Ogcheon belts). Tectonometamorphic evolution of these terranes
is of prime importance for understanding the continental growth
of East Asia. In particular, the eastward extension ofthe Dabie-Sulu
collisional belt between North and South China cratons, across
the Korean Peninsula towards Japan, has been discussed by many
workers but still contentious. In this study I review the Permo-
Triassic collisional orogeny recorded in the Korean Peninsula.
The Ogcheon fold-thrust belt consists of the Taebaeksan
basin and the Ogcheon metamorphic belt, which are in fault
contact. The Paleozoic formations in the Taebaeksan basin are well
correlated with those of the North China craton. On the other
hand, the Ogcheon metamorphic belt comprises Neoproterozoic
(ca. 750 Ma) to Paleozoic meta-sedimentary and -volcanic
sequences which may belong to the South China craton. Regional
metamorphism has produced the Barrovian-type assemblage at
peak metamorphic conditions estimated to be 4.2-9.4 kbar and
490-630°C. This syn-tectonic metamorphism in association
with the Ogcheon orogeny was dated at ca. 280 Ma. During the
subsequent Indosinian (Songrim) orogeny at ca. 250-220 Ma, the
Ogcheon metamorphic belt experienced the greenschist-facies
metamorphism and was thrust over the Taebaeksan basin along
brittle-ductile shear zones.
The Imjingang belt, commonly known as an extension ofthe
Dabie-Sulu belt, consists primarily of Barrovian-type metapelites,
calc-silicate rocks and garnet amphibolites. Biotite poikiloblasts
ofthe metapelites initially grew between two contractional events
(Dn-1 and Dn), and was subsequently overgrown during Dn
by crack-filling mechanism. On the other hand, the growth of
poikiloblastic garnet started after Dn-1, and predominated during
Dn. The garnet porphyroblast partly replaced biotite at the post-
Dn stage. Peak temperatures were estimated at 450-700°C, and
metamorphic pressures apparently increase from ca. 8 kbar in
the garnet zone to ca. 11 kbar in the kyanite zone. The matrix of
the kyanite-zone schist, however, records much lower pressure
of 5-7 kbar, suggesting a clockwise P-T path. The timing for
high-P peak metamorphism was dated at ca. 250 Ma, whereas
relatively rapid cooling through ca. 500-300°C took place at
230-220 Ma. The latter was associated with Dn+1 responsible
for rapid exhumation along a ca. 20 km-wide ductile shear zone.
The clockwise P-T-t history is similar to that documented in not
only the basement gneisses ofthe Gyeonggi massif but also high-
P schists in the Alps. It is thus likely that the whole peninsula,
including Phanerozoic fold-thrust belts and Precambrian
basement massif, has experienced a crust thickening during the
Permo-Triassic orogeny, and that the Dabie-Sulu collisional belt
continues towards the Korean Peninsula.
The Sedimentary Record of Deglaciation in the Western
Himalaya recorded in the Indus Delta, Pakistan
PD Cliff*, L Giosan2, IH Campbell3, J Blusztajn2, M Pringle4,
AR Tabrez5, A Alizai1, MM Rabbani5 and S Vanlaniningham1
1 School of Geosciences, University of Aberdeen, UK
2 Woods Hole Oceanographic Institution, USA
3 Australian National University, Canberra, AUSTRAELA
4 Massachusetts Institute of Technology, Cambridge, MA, USA
5 National Institute of Oceanography, Clifton, Karachi, PAKISTAN
For correspondance, email:
The retreat of icesheets following the end of the Last Glacial
Maximum (LGM) might be expected to have caused a significant
change in the nature of erosion in the Western Himalaya.
We investigated the nature of this changing erosion and the
stratigraphic record ofthe transition by drilling in the Indus delta
of Pakistan. A section dating back to —14 ka was recovered and
dated by 14C AMS methods. The delta appears to have been built
in two prograding stages, separated by a transgressive surface
dated at around 8 ka. Curiously the delta and shoreline migrate
oceanwards during the fastest stages of eustatic sealevel rise prior
to 9 ka (Giosan et al. 2006). This requires strongly accelerated
sediment delivery at this time, much as seen in the Bengal delta.
Provenance analysis shows that this sediment is newly eroded in
the Early Holocene and is not simply glacial sediments that are
transported to the ocean at that time. Nd isotope analysis provides
an overview of how erosion patterns change. The greatest isotopic
shift is seen before —10 ka, coincident with summer monsoon
intensification (Clift et al. 2008). The direction of isotopic change
is towards more continental, radiogenic values. A combination
of Ar-Ar mica and single grain zircon dating indicates that the
proportion of Lesser Himalayan material increases sharply at this
time, largely at the expense ofthe Karakoram and Trans Himalaya.
These more northerly ranges are still heavily glaciated and appear
to have dominated the erosional flux to the delta prior to the
Holocene. Glaciation was not so important in driving erosion
in the western Himalaya, but may have more important in the
wetter East. At the LGM glaciers did not extend much further
than presently seen, largely because the climate was very arid at
this time. Glaciers never covered the Lesser Himalaya, so that
the pulse in erosion after 14 ka from these ranges is not due to
glacial retreat. Instead we suggest that it is the intensified summer
monsoon that caused both the faster overall rate and the change
in the patterns of erosion. The Lesser Himalaya and the southern
flanks of the Greater Himalaya are the recipients of the greatest
amounts of summer rain. The fact that the Lower Holocene
sediment is isotopically distinct from LGM sediment shows that
reworking of older sediment is minimal. Transport times from
source to the delta sink are short, at least less than the resolution
ofthe age control (—1000 yr), as provenance and climate appear to
change in parallel. However, sediment now on the seafloor ofthe
Indus Canyon has a glacial Nd isotope character and confirms that
sediment flux to the deep ocean ceased no later than the Bolling-
Allerod. As a result the sediment record of Himalayan erosion
preserved in the Indus Fan is buffered and lags the erosion events
by at least —10 k.y. Marine data suggest that much ofthe sediment
now found in the delta and on the Pakistan Shelf is eroded during
sealevel fall and has low preservation potential over long periods
of geologic time, largely because tectonic subsidence in the delta
region is now slow.
Clift PD, L Giosan, J Blusztajn, IH Campbell, C Allen, AR Tabrez, M
Danish, MM Rabbani, A Alizai, A Carter and A Luckge. 2008.
Holocene erosion of the Lesser Himalaya triggered by intensified
summer monsoon. Geology 36 (1): 79-82
Giosan L, PD Clift, J Blusztajn, A Tabrez, S Constantinescu and F Filip.
2006. On the control of climate- and human-modulated fluvial
sediment delivery on river delta development: The Indus. Eos,
Transaction of American Geophysical Union 87(52): OS14A-04
Seismic reflection evidence for a Dangerous Grounds
mini-plate in the South China Sea and implications for
extrusion tectonics in SE Asia
Peter Clift12*, Gwang H Lee3, Nguyen Anh Due4, Udo Barckhausen5, Hoang Van Long1 and Sun Zhen2
1 School of Geosciences, University ofAberdeen, Aberdeen, AB24 3UE, UNITED KINGDOM
2 Key Laboratory ofthe Marginal Sea Geology. South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164# Xingangxi Road,
Guangzhou, 510301, CHINA
3 Department of Environmental Exploration Engineering, Pukyong National University, Busan 608-737, KOREA
4 Vietnam Petroleum Institute, Yen Hoa, Cau Giay, Hanoi, VIETNAM
5 BGR, Federal Institute for Geosciences and Natural Resources, Stilleweg 2, 30655 Hannover, GERMANY
For correspondance, email:
The collision of India and Asia has caused large strike-slip faults
to form in East Asia, resulting in the "extrusion" of crustal blocks
towards the southeast since the Eocene as a result ofthe indentation
of rigid India into Asia (Peltzer and Tapponnier 1988, Tapponnier
et al. 1982). It has been suggested that the South China Sea
opened as a result of relative motion between a rigid Indochina
(Sundaland) block and China (Briais et al. 1993). Alternative
models propose that rifting and seafloor spreading were driven by
trench forces to the south (Morley 2002, Taylor and Hayes 1980).
We test these competing models by analysis of seismic reflection
profiles across the boundary between Sundaland and the southern
rifted margin, known as the Dangerous Grounds. We show that
the southern boundary ofthe Dangerous Grounds is a subduction
zone that jammed in the Middle Miocene (Hutchison et al. 2000).
To the west the Dangerous Grounds is bounded by a strike-slip
zone, also active until —16 Ma, that becomes diffuse south ofthe
now inactive South China Sea seafloor spreading centre. We place
the western edge ofthe Dangerous Grounds just to the east ofthe
Natuna Arch (Lupar Line). The West Baram Line is confirmed
as originating as a major strike-slip fault within the Dangerous
Grounds and continuous with Red River Fault Zone. Because the
Dangerous Grounds were independent of Sundaland until —16
Ma its motion cannot have been constrained by motion of this
block, making extrusion impossible as a mechanism to rift the
South China Sea. SE motion by both the Dangerous Grounds and
Sundaland suggests subduction forces were the primary trigger
for plate motions. Our reconstruction places a —280 km upper
limit on the motion on the Red River Fault, and a —1400 km
width to the paleo-South China Sea. This value is intermediate
between the low estimates of Searle (2006) and the higher values
of > 1000 km (Tapponnier et al. 1990).
Briais A, P Patriat and P Tapponnier. 1993. Updated interpretation of
magnetic anomalies and seafloor spreading stages in the South
China Sea: implications for the Tertiary tectonics of Southeast Asia.
Journal of Geophysical Research 98: 6299-6328
Hutchison CS, SC Bergman, DA Swauger and JE Graves. 2000. A
Miocene collisional belt in north Borneo: uplift mechanism and
isostatic adjustment quantified by thermochronology. Journal qf the
Geological Society 157: 783-793
Morley CK. 2002. A tectonic model for the Tertiary evolution of strike-
slip faults and rift basins in SE Asia. Tectonophysics 347(4): 189-215
Peltzer G and P Tapponnier. 1988. Formation and evolution of strike-slip
faults, rifts, and basins during the India-Asia Collision: an experimental
approach. Journal qf Geophysical Research 93: 15085-15117
Searle MR 2006. Role ofthe Red River Shear zone, Yunnan and Vietnam,
in the continental extrusion of SE AsitL.Journal ofthe Geological Society
Tapponnier R et al. 1990. The Ailao Shan/Red River metamorphic belt;
Tertiary left-lateral shear between Indochina and South China.
Nature 343(6257): 431-437
Tapponnier P, G Peltzer, GAY Le Dam, R Armijo and PR Cobbold. 1982.
Propagating extrusion tectonics in Asia: New insights from simple
experiments with plasticine. Geology 10: 611—616
Taylor B and DE Hayes. 1980. The tectonic evolution of the South
China Basin. In: D Hayes (ed), The Tectonic and Geologic Evolution of
Southeast Asian Seas and Islands. Geophysical Monograph. American
Geophysical Union, Washington DC, p89—104
Examination of relocated earthquake hypocenters in the Pamir-
Hindu Kush seismic zone using 3-D plots
S Das
Department of Earth Sciences, University of Oxford, Oxford OXI 3PR, UK
Reliably relocated earthquake hypocenters in the Pamir-Hindu
Kush region for about 1700 earthquakes deeper than 50 km, are
examined using 3-D color plots. The hypocenters define an single
contorted "S" shaped seismic zone, 700 km long and no more
than 30 km wide and with most activity concentrated in the 100-
300 km depth range. The main features observed are:
the continuous steepening ofthe north dipping Hindu Kush
seismic zone as we move eastwards towards the Pamirs;
the southeast dipping Pamir seismic zone;
the curvature and forking of the subducting slab at
depths greater than 200 km within the eastern part of
the Hindu Kush seismic zone;
the very abrupt cutoff in intermediate depth seismicity
at 90-110 km depth with no extension to shallower
depths, under the Pamirs, suggesting that the slab has
become decoupled from the surface deformation;
e) the unusual horizontal T-axes for intermediate depth
earthquakes of the Pamir seismic zone, which align
with its curvature, suggesting that this region is under
horizontal compression. The study shows that the
seismic zone under the Hindu Kush has stress axes
which follow the classical pattern for subducting slabs
controlled by gravity, whereas the Pamir region has
horizontal T-axes that follow the trend ofthe contorted
seismic zone. We suggest that the Pamir seismic zone is
a remnant slab has been completely overturned and torn
away from the Hindu Kush slab, to be in the current
south dipping geometry, as a result of flow in the upper
mantle. The 3-D plots will be shown as computer
animations at the conference.
Unzipping Lemuria from its Himalaya suture to
understand mammalian origins
Maarten J de Wit1* and Judith Masters2
1 AEON —Africa Earth Observatory Network and Department of Geological Sciences, University of Cape Town, Rondebosch 7700, SOUTH AFRICA
2 Department of Zoology, University ofFort Hare, Private Bag X1314, Alice 5700, SOUTH AFRICA
For correspondence, email:
Information relating to the suturing history between India and Asia
is crucial to understanding the historical biogeography of living
mammals. It is particularly relevant to understanding the origins
of Madagascar's mammal fauna that contributes to the island's
standing as one ofthe worlds' biodiversity hotspots. Evolutionary
biologists are strongly divided as to the timing and place of the
origins of extant mammalian orders. Most palaeontologists stand
by the opinion that living mammal orders arose after the K/T
boundary (66 Ma) in the northern hemisphere, while molecular
phylogeneticists push these divergences back into the Cretaceous
(>100 Ma) and favour a southern hemisphere origin. Recent
discovery of an ungulate fossil at about 65 Ma in peninsular India
supports the molecular argument. Within the circa 40 Ma period
that separates the two estimates, the global palaeobiogeography of
the Indian Ocean changed dramatically as continents moved and
oceans evolved rapidly during the final break-up of Gondwana and
the suturing between India and Asia. A detailed understanding of
the movement and suturing history of India will allow biologists
to formulate more robust scenarios of early mammalian dispersal,
and perhaps identify, finally, the places of origin of major mammal
The precise extent of palaeo-continental lithosphere north
of India that vanished following the sub-continent's collision with
Asia is poorly quantified. Argand, in 1922, assumed it stretched all
the way from northern India, then in the southern hemisphere as
part of Gondwana, to Asia. He called this landmass Lemuria and
predicted that during continental drift away from Gondwana, much
of Lemuria was thrust beneath Asia. We know this to be incorrect
in detail today, but the concept is still with us. Yet facts about the
chemical and physical composition of this continental shelf to the
north of paleo-India are few. There is also a lack of consensus on
the precise timing (and possible along-strike diachronous events)
of docking and final suturing between Lemuria and Asia. The
fragmentation history of Gondwana and the evolution of the
Indian Ocean are now well-enough understood to re-evaluate
evidence for transient land bridges, given the unlikelihood of cross-
water dispersals of early mammals between different fragments of
Gondwana, and especially between Africa, Madagascar and India.
Resolution of the uncertainties associated with India's accretion
to Asia by geologists and geophysicists will enable biologists to
unravel one of the great long-standing debates in natural history
that dates back to the heydays of AR Wallace and C Darwin, i.e.
the colonization of Madagascar. In this presentation we outline
the major controversies relating to this problem, and show how a
detailed analysis ofthe events that occurred along the length ofthe
suture will contribute to resolving this debate.
Addressing Tectonic and Metamorphic Controversy in the
Pakistan Himalaya
Joseph A Dipietro
University of Southern Indiana, Dept. of Geology, 8600 University Blvd., Evansville, IN 47712, USA
Some of the more controversial or less agreed upon aspects of
the Pakistan Himalaya include the absolute age (or ages) of
metamorphism, the cause of metamorphism, the location (or
existence) of the MCT, the existence of the STDS or STDS-
equivalent extensional faulting, the correlation of stratigraphy and
tectonostratigraphic zones, and transport direction. In this paper I
address some of these in an attempt to summarize the geology of
the Pakistan Himalaya.
It must first be pointed out that the geology is not perfectly
continuous across Pakistan. There is a discontinuity located along
the western margin ofthe Hazara syntaxis. It was shown as a major
fault by Wadia (1931) who bent it northeastward and extended it
all the way to the Kohistan arc. Part of this fault was mapped by
Bossart et al. (1986) as the 'mylonite zone.' Later workers ignored
Wadia's interpretation and, within about 5 km ofthe Kohistan arc,
bent the fault eastward to connect with the Batal thrust, referring
to its entire trace as the MCT. DiPietro and Pogue (2004) argued
in support of Wadia's interpretation and referred to it as the
Jhelum-Balakot fault. This fault effectively divides the Pakistan
Himalaya into an eastern half (the Naran region), and a western
half (the Western Hinterland) (Figure 1).
All known occurrences of eclogite are in the Naran region
on the upper plate ofthe Batal thrust. According to DiPietro and
Pogue (2004), the Batal thrust is truncated at the Jhelum-Balakot
fault, offset southward, and reappears in the Western Hinterland as
the Banna thrust which, itself, terminates against the Indus suture
zone on the east side ofthe Indus Syntaxis. Irregardless of whether
the Batal and Banna faults correlate, the relationships indicate that
nearly the entire Western Hinterland is structurally below the
Batal thrust. In the Naran region, the Batal thrust is interpreted
as extending eastward into the mountains and metamorphic rocks
south of Nanga Parbat. This is not the MCT.
An important distinction must also be made between thrust
faults that underlie the Indus Suture Zone, and the Kohistan fault
which underlies the Kohistan arc. Foliation in graphic schists
at the top of the Indian plate are continuous with chlorite and
talc schists that form the matrix rock in the Indus Suture Zone.
Additionally, the suture zone is folded about late-metamorphic
F3 folds. This implies that Indian plate rocks were underthrust
beneath the suture zone prior to and/or during regional foliation-
forming metamorphism. The Kohistan fault, by contrast, truncates
foliation in both the suture zone and Indian plate and truncates
the late-metamorphic F3 folds that deform the suture zone. The
fault cuts across strike such that suture zone rock is absent in the
Indus Syntaxis region and in the area north ofthe Malakand fault
slice. The assumption that there was simultaneous transport and
emplacement of the Indus Suture Zone and the Kohistan arc is
incorrect. Thrusting of Kohistan played no role in the prograde
metamorphism ofthe Western Hinterland.
The only major thrust faults in the Western Hinterland
are the Banna thrust in the east, and the Malakand thrust in the
west. Both are syn-metamorphic and both are folded by late-
metamorphic F3 folds. They appear to have been active during
activity in the suture zone. Significant shortening may have been
accommodated along these thrust faults but neither extend across
the hinterland. Both truncate against the suture zone or Kohistan
fault. The remainder of the Western Hinterland appears to have
acted as a single coherent block throughout metamorphism
that remained largely autochthonous prior to middle Miocene
displacement along the Panjal—Khairabad thrust. This is indicated
by Permian and Mesozoic stratigraphic rock units that can be
traced continuously across the hinterland. Wadia (1934) mapped
what he referred to as a Paleozoic unconformity below Permian
Panjal Volcanics in the region surrounding the Kashmir Basin. He
showed that the age of rocks directly below the unconformity vary
considerably from middle Paleozoic to what are probably Lower
Proterozoic. Wadia implicitly showed that the Kashmir region
contains a coherent stratigraphy of (probable) Early Proterozoic
age to Mesozoic age that would later correlate with parts of the
Lesser Himalayan, Greater Himalayan, and Tethyan Himalayan
sequence. This stratigraphy is likely present in the Naran and
Nanga Parbat regions and is unquestionably present in the
Western Hinterland. Intrusive rock, such as Lesser Himalayan,
Ulleri-equivalent, Kotla orthogneiss, and Greater Himalayan 500
Ma orthogneiss, are also present. The Panjal-Khairabad thrust
forms the southern boundary of the Western Hinterland and is
considered to be the western continuation ofthe MCT. Greater
Himalayan stratigraphy, and 500 Ma orthogneiss, are both absent
south of the thrust. This fault, however, is post-metamorphic,
appears to have initiated later than the Central Himalayan MCT
and does not show nearly the displacement.
It has been assumed that transport of both the Indus
Suture Zone and the Kohistan arc was in a southward direction
presumably because both are oriented roughly east-west, faulting
in the Pakistan foreland is toward the south, and the most obvious
lineations within the western Hinterland are oriented generally
north-south. Detailed analysis does not support this conclusion.
The most widespread lineation is a north-south crenulation of the
regional foliation associated with late-metamorphic F3 folds. These
folds deform the suture zone and are truncated by the Kohistan
fault. They are not valid indicators of transport direction for either
tectonic terrane. South-directed thrusting in the foreland also is not
relevant because it is younger than displacement on the Kohistan
fault. Syn-metamorphic transport of the Indus Suture zone and
Banna thrust zone is inferred to be toward the SW or WSW based
on westward vergence of large-scale syn-metamorphic F1/F2 folds
and on stretching lineations which, although variable, are dominantly
oriented NNE-SSW The Kohistan arc was transported in a different
direction. Enematic indicators along the fault consistently show
thrust and dextral strike-slip displacement with ESE to E-directed
transport. This is consistent with the Naran region where early SW-
transport and then SE-transport is also reported (Greco et al. 1989).
The southern termination ofthe Kohistan fault in the western part of
the hinterland is interpreted to be a right-slip sidewall ramp such that
the Kohistan arc never advanced much farther south on the Indian
plate than its present position. This fault likely remained active until
late Oligocene or early Miocene when south vergence first began
in the hinterland. Although active in the foreland since middle
Miocene, south vergence presently is not active in the hinterland.
The 2005 Kashmir earthquake revealed the Bagh blind fault with
southwestward transport that cuts across all earlier structures.
The Kohistan fault has been interpreted as a major
extensional fault equivalent with the STDS even though it is
located north of the Indus Suture Zone (not within the Indian
plate). The evidence, however, is not convincing. Detailed analysis
of the fault zone at three locations in the Western Hinterland
provides evidence that long-term and final displacement was in
the form of thrusting or dextral strike-slip faulting. The Kohistan
fault in the Naran and Nanga Parbat regions has been overprinted
by the Balakot, Diamir, and Raikot fault zones. All three faults
are north to northwest-striking with southeast or east-side-up
reverse displacement that places Indian plate rocks structurally
above the Kohistan arc. None appear to be extensional.
The age of metamorphism in the Western Hinterland is
poorly constrained. Flat hornblende Ar-Ar spectra vary from
67 to 31 Ma with additional dates circa 175 Ma and 1900 Ma
(Treloar and Rex 1990). Zircons from the post-metamorphic
Malakand granite recently gave a well defined IA-ICPMS age of
32.7±0.5 Ma (unpublished data). Smith et al. (1994) reported a
zircon rim SHRIMP age of 47±3 Ma from the same granite. The
disparate ages, and the description that their rock is deformed,
suggests that Smith et al. (1994) may have dated a metamorphic
overgrowth from the nearby Chakdarra orthogneiss. Zircons
from another post-metamorphic intrusion, the Khar Diorite,
gave a well defined LA-ICPMS age of 48.1 ±0.8 Ma (unpublished
data). This rock intrudes the suture zone (not the Indian plate)
near Afghanistan at the structural top of the metamorphic pile.
Collectively, the Western Hinterland has yielded detrital zircons
from circa 2200 to 2930 Ma; igneous zircons circa 1850, 825,
500, 270, 48 (within the suture zone), and 33 Ma; metamorphic
zircons circa 2175, 262, and 89 Ma; and possible metamorphic
zircon overgrowths circa 47 and 40 Ma (DiPietro and Isachsen
2001). These data suggest only that metamorphism was active
during middle Eocene (49-37 Ma) and that there may have been
multiple metamorphic episodes during late Mesozoic/Cenozoic
and earlier. This is broadly consistent with ages obtained in the
Naran region. More work is required to constrain the timing of
metamorphism relative to fabric development.
In summary, the cause of metamorphism in the Western
Hinterland is underthrusting beneath the Indus Suture Zone prior
to, and/or during, the middle Eocene. The Kohistan arc arrived
post-metamorphic, after development of F3 folds that deform
the suture zone. Neither produced south-verging structures in
the Western Hinterland. The Western Hinterland consists of
conformable Lesser, Greater, and Tethyan stratigraphy that, with
the exception of the Banna and Malakand thrusts, remained
coherent throughout deformation.
Bossart P, D Dietrich, A Greco, R Ottiger and JG Ramsay. 1988. The
tectonic   structure   of  the   Hazara-Kashmir   syntaxis,   Southern
Himalayas, Pakistan. Tectonics 7: 273-297
DiPietro JA and CE Isachsen. 2001. U-Pb zircon ages from the Indian
Plate in northwest Pakistan and their significance to Himalayan and
pre-Himalayan geologic history. Tectonics 20: 510-525
DiPietro JA and KR Pogue. 2004. Tectonostratigraphic subdivisions ofthe
Himalaya: A view from the west. Tectonics 23: TC5001 doi:10.1029/
2003TC001554 20
Greco A, G Martinotti, K Papritz, JG Ramsay and R Rey. 1989. The
crystalline   rocks   of the   Kaghan   Valley   (NE-Pakistan).   Eclogae
Geologicae Helvetiae 82: 629-653
Smith HA, CP Chamberlain and PK Zeitler. 1994. Timing and duration
of Himalayan metamorphism within the Indian plate, northwest
Himalaya, Pakistan .Journal of Geology 102: 493-508
Treloar PJ and DC Rex. 1990. Cooling and uplift histories ofthe crystalline
thrust stack ofthe Indian plate internal zones west of Nanga Parbat,
Pakistan Himalaya. Tectonophysics 180: 323-349
Wadia DN. 1931. The syntaxis ofthe northwest Himalaya: Its rocks, tectonics
and orogeny. Records ofthe Geological Survey qf India 65: 189-220
Wadia DN. 1934. The Cambrian-Trias sequence of northwest Kashmir
(parts of the Mazaffarabad and Baramula District). Records qf the
Geological Survey qf India 68: 121-146
Si,   t? ^ 74 y
Afghjn ston'
r    -v
j^^ Arc Complex
v    v    ' \y_-      v    v    v    v,
FIGURE 1. Simplified map ofthe
Pakistan Himalaya. Black areas
are lenses of suture zone rock.
B-Banna Thrust; Bg-Bagh Fault;
Bg'-Bagh Blind Fault; D-Diamir
Fault; J-Jalalabad Basin; JB-Jhelum-
Balakot Fault; K-Khairabad thrust;
KF-Kohistan Fault; M-Malakand
Fault Slice; MBT-Main Boundary
Thrust; MCT-Main Central Thrust;
P-Panjal thrust.
Active tectonics and origin  of Tso Morari Lake observed by
Remote sensing and GIS techniques
Chandra Shekhar Dubey and Dericks Praise Shukla
University of Delhi, Delhi-1100 07, INDIA
Large-scale landscaping processes become strongly influenced
by tectonic and geomorphological changes caused to a great
degree, by the vertical morphotectonic and climatic zoning which
gradually took place on the slopes ofthe rising mountain ranges.
The development ofthe relief in the northern and central parts of
these mountain ranges and near Tso-Morari area the Tibet displays
strong exhumation evidences of deep crustal material as well as
the features of horizontal movements ofthe nappe type followed
by tectono-geomorphic features of faulting with pronounced
differential uplifts on faults, during the Quaternary.
The Tso Morari lake is located between latitude 32° 40'-33°
15' N and longitude 78° 15' -78° 25' E, which is about 220 km
southeast of Leh in the northwestern Himalaya at an altitude of
4900 m and close to the ISZ (Figure 1).
In the present study, we have attempted to identify active
faults, tilting of deposits and Neotectonic origin of Tso Morari
lake having a dimension of 3 km X 8 km with the help of
Remote  sensing and  GIS. The  study also  demonstrates that
geomorphological and structural inferences are possible using
high resolution TERRA Satellite (ASTER) as well as 30 meter
Landsat 7 ETM+ and pseudo Landsat covers of 1990 TM and
2000 ETM data for the arid, often inaccessible and complex
terrain ofthe northwestern Himalaya (Figure 2).
The north-south transect passing near Tso Morari Lake
suggest that the SW-directed North Himalayan nappe stack
(comprising the Mata, Tetraogal and Tso Morari nappes) was
emplaced and metamorphosed by c. 50-45 Ma, and exhumed to
moderately shallow depths (c.10 km) by c. 45-40 Ma. From the
mid-Eocene to the present, exhumation continued at a steady and
slow rate except for the root zone ofthe Tso Morari nappe, which
cooled faster than the rest ofthe nappe stack (Schlup et al. 2003).
The Ladakh region ofthe northwestern Indian Himalaya is rich in
quaternary deposits but it has not received much attention. The region
was under the influence of tectonic activity and cold climate during the
late Quaternary times. Tectonic activity at 50,000 years BL? 35,000 years
BP and 25,000 years BP has been recorded (Phartiyal et al. 2005).
FIGURE 1. Location of the Area
FIGURE 2. Geology and Tectono-Geomorphology of the Area
This fact is corroborated by Aspect at 1° and Grain
classification map derived from SRTM Digital Elevation Model
(DEM) using MICRODEM software. Also medium sized recent
earthquake activity lie linearly on the fault (source USGS database).
It is important to note that most of the recent seismic activity is
limited to south ofthe direction of flow of NW-SE trending river
also changed from NNW-SSE to almost NE-SW feeding the Lake.
This fault seems to be younger and active and hence has displaced
the N-S trending Tso Morari fault (Figure 3).
The LANDSAT ETM 2000 and TM 1990 alongwith the
Google earth and NASA world wind pseodo landsat covers depict
the damming of the NW-SE trending River on N-S to NNW- SSE
trending fault passing upto Kaurik, Leo and Sangla valley (Singh
et al. 2007 and this study) and its tributaries by debris avalanches
/deposits initiated mainly by tilting of fan due to tectonic
Activity along the WNW-ESE fault lineament. Another
prominent feature of this fault is that is cuts the fan at the mouth
of Tso Morari lake in such a way that the northern portion takes a
concave shape while the southern portion takes a convex shape. The
aspect and grain size classification marks the extent ofthe fault which
is well corroborated by the microseismic events draped from google
earth over the fault depicting neotectonic activity (Figure 4).
The Tso Morari lake in this region is formed in the late
Quaternary due to the damming ofthe NW-SE trending River and
its tributaries by debris avalanches/deposits initiated mainly by tilting
of fan due to tectonic activity along the WNW-ESE fault lineament.
The seismic activity on this fault is related to neotectonism.
Phartiyal B, AAnupam Sharma, R Upadhyay, Ram-Awatar and AK Sinha. 2005
Quaternary geology, tectonics and distribution of palaeo- and present
fluvio/glacio lacustrine deposits in Ladakh, NW Indian Himalaya—a
study based on field observations. Geomorphology 65 (3-4): 241-256
Schlup M, A Carter, M Cosca and A Steck. 2003. Exhumation history
of eastern Ladakh revealed by 40Ar/39Ar and fission-track ages:
the Indus River—Tso Morari transect, NW Himalaya. Journal qf the
Geological Society qf London 160(1): 385-399
Singh S and AK Jain. 2007. Liquefaction and fluidization of lacustrine deposits
from Lahaul-Spiti and Ladakh Himalaya: Geological evidences of
paleoseismicity along active fault zone Sedimentary Geology 196: 41-SI
FIGURE 3. A) DEM of the Area B) Aspect at 10 of
the area showing tilted Fan
'\%S%*<" ■*■■
FIGURE 4. Grain size classification map and fault draped on
Google showing microseimicity on the identified fault by
remote sensed and GIS dataset.
Diagenetic and metamorphic overprint and deformation history
of Permo-Triassic Tethyan sediments, SE Tibet
Istvan Dunkl1, Ding Lin2, Chiara Montomoli3, Klaus Wemmer1, Gerd Rantitsch4, Borja Antolin5,
Rachida El Bay5 and Erwin Appel5*
1 University of Gottingen, GERMANY
2 Instititute of Tibetan Plateau Research, CAS, Beijing, CHINA
3 University of Pisa, ITALY
4 University ofEeoben, AUSTRIA
5 University of Tubingen, GERMANY
For correspondence, email:
We have studied the deformation history and the grade and
age of metamorphic overprint of the folded and imbricated
Permo-Triassic limestone and flysch sequences of the Tethyan
Himalaya in several strike-perpendicular profiles in SE Tibet in
order to supply time and temperature constraints for a running
paleomagnetic study and to describe the behaviour ofthe hanging
wall of STDS.
The longest profile (ca. 40 km) runs from Tsetang to the
SW and exposes mainly Triassic flysch. The deformation at the
southern part is weak, big-scale, south-vergent isoclinal folds
are characteristic foliation associated to folds is mainly a stilolitic
surface withdominantpressure solution. At the northernpartofthe
profile a second, top-to-north folding event generated a complex
deformation pattern and locally intense neo-crystallization of
illite-sericite, gives rise to a fine continuous foliation parallel to
axial planes of folds. The applied methods were "illite crystallinity"
(results are expressed as Kiibler Index: KI), vitrinite reflectance
(VR), K/Ar geochronology and microtectonic analyses. The
appearance ofthe Tethyan sedimentary formations suggests a very
wide range of overprint: in some sites fossiles and sedimentary
micromorphological elements are well preserved, while in other
tectonic blocks the formations experienced metamorphism in
greenschist facies. The analytical results reflect well the variable
overprint: VR ranges from 1.8 % to the graphite stage, and KI ranges
from 0.38 to 0.17°. The majority of K/Ar results is interpreted as
mixed age, because the shift of apparent ages between 106 Ma and
24 Ma shows good correlation with decreasing KI. The most re-
crystallized samples (KI ca. 0.17°) show no reaction after ethylen-
glycol treatment and they have uniform K/Ar ages in the <2 /xm
and <0.2 /xm grain size fractions around ca. 24 Ma. We suppose
that these ages are close to the climax ofthe second, top-to-north
folding event. Probably the structural block in the middle ofthe
Tsetang profile showing the highest degree of metamorphism is
structurally related to the Yalar Xiangbo dome.
Late orogenic large-scale deformations have been recorded
in many areas of the Tethyan Himalaya by stable secondary
magnetizations residing in pyrrhotite and postdating main
Himalayan folding. In SE Tibet, however, a complex magnetic
behaviour (noisy demagnetization, scattering remanence directions,
very variable pyrrhotite content) is observed and paleomagnetic data
have to be analyzed and interpreted with thorough selection criteria
based on the thermal history and deformation style.
Impact of coeval tectonic and sedimentary-driven tectonics on
the development of overpressure cells, on the sealing, and fluid
migration -Petroleum potential and environmental risks of the
Makran Accretionary Prism in Pakistan
N Ellouz-Zimmermann, A Battani, E Deville, A Prinzohfer and J Ferrand
IFP, Dir of Geology, 1-4 av de Bois-Preau, 92856 Rueil-Malmaison, cedex FRANCE
The tectonic evolution of the Makran accretionary prism is
resulting from the continuous subduction to the North of the
Arabian/Indian plates below the Eurasian blocks. Subduction
processes started during Cretaceous time, and the tectonic
accretionary prism developed progressively southeastward. The
3D evolution of the prism is not only controlled by tectonic
processes (architecture ofthe slab, changes in orientation & speed
of convergence), but also by the strong impact ofthe sedimentary
parameters on the deformation style. Structural architecture
results from the N-S shortening ofthe sediment deposited in the
migrating trench, which are scrapped over an oceanic (to the west)
and a stretched continental crust (to the East close to transform
fault system). To understand the present-day 3D architecture
and the localization of overpressure zones it is obvious that
sedimentary origin and rates as well as the place were sediment
deposited is a first order parameter.
Sedimentary supply
History of the sedimentation in the Pakistani Makran can be
described in two large periods:
(1) Since Eocene times, the Makran trench was progressively
filled by erosion products, which have been conveyed by the
paleo-Indus River (from Himalayan erosion). The deltaic to
deep-slope sediment progressively involved in the deformation,
were coming successively from the deposition ofthe Himalayan
detritics forming the Katawaz delta (Paleogene times), and the
paleo-Indus delta (up to Middle-Miocene times).
(2) During Middle Miocene times, due to the reorganisation ofthe relief along the transform fault system, a drastic
change occurred inducing the transfer ofthe Indus River East of
the Kirthar-Sulaiman Ranges. From this time, the sedimentary
detritics were produced by the erosion ofthe prism itself.
From this time, the deposition of the Himalayan-derived
sediment has been transferred south of the Murray Ridge to the
present-day position Indus delta.
Structural evolution
The complex tectonic style ofthe prism is characterized by: (1) a
basal decollement level located within Paleogene or Cretaceous
series, which deepens progressively from 6-8 km at the
deformation front down to ll-12km depth onshore; (2) an internal
structure depending on several parameters: the lithology which is
controlled by the regional and/or local depositional environment
(determining the extension of secondary "decollement levels");
and the sedimentary loading which control the dynamics of the
pressure conditions.
We infer than the deformation propagation is directly linked
to the origin, rate and location ofthe sediment deposits, which has
changed through times:
* during the 1st period, all the sedimentary input arrived
from the Eastern back-side of the growing prism, and were
deposited laterally along the trench.
* duringthe2nd period, a large part ofthe sedimentation was
directly transferred all along the Makran, from the northern Inner
units (backside) to the south. Sediment series were, either trapped
in small or large "piggy-back basins" (developed as a platform)
on the frontal units, or supplied by a diffuse hydrographic net,
through small rivers and canyons across the frontal units up to
the abyssal plain.
Mud volcanoes and overpressure generation
Based on field data, re-processed seismic data, and new bathymetric
and seismic data acquired in 2004 during the CHAMAK
oceanographic survey, regional sections have been analyzed
(Ellouz-Zimmermann et al 2007). A couple of local detachments
have been observed above the late Cretaceous-Early Paleogene
basal one. Close to the shelf area, the disharmonic late Miocene
slope series can be considered as the uppermost detachment
level, along with the compressive but also extensive deformation
propagated, introducing a disconnection between surface and
Middle Miocene structures.
The huge sedimentary loading superimposed to the regional
shortening conditions, contributed to develop overpressure
conditions within Late Miocene (Parkini fm) at depth. Linked
with these deep pressure cells, fluid and mud mobilization have
been recognized at surface. Onshore in the Coastal Range, a
spectacular "belt" of active mud volcanoes outlined the episodic
decompression processes, and expelled products, mud and fluids
(i;e. water and gas) represent a "window" for the deep processes.
Mud, and fluids (waters and gas) have been sampled and analyzed
on several of these mud volcanoes, as well as in the core samples
from the CHAMAK survey.
Analytical results
The origin ofthe mineral fraction ofthe mud expelled in the mud
volcanoes has been attributed to the late Miocene series (from
nannoplancton datings).
Geochemical analyses (including noble gas isotopes) of
the gas sampled from three mud volcanoes and one gas seepage
indicate a thermogenic signature, showing that source-rocks have
generated gas at depth. Meanwhile, the other samples from coastal
mud volcanoes show a bacterial signature, as well as offshore from
long cores (sampled with the Calypso of Marion Dufresne II on
BSR). Spatial organization ofthe "thermogenic signature" mud
volcanoes implies a connection with deeper levels than Parkini
Fm, probably linked with fluid migration along major faults.
Thermal variation of the heat flow have been calculated
over the frontal Makran zone, on the base of 1) ofthe geothermic
gradient calculated on thermal T°C measurements sampled on
the Chamak cores, 2) then calibrated on the present-day heat flow
values with conductivity parameters from BGR measurements
and 3) finally along seismic profiles, interpolated with the largely
recognizable BSR (Bottom-simulating-reflectors) modeling using
the previously determined conductivity parameters.
Integrating the structural, sedimentological and geochemical new
results, we propose a conceptual model of the architecture of
the structural traps-reservoirs system and of the fluid migration
mechanisms in the Pakistani Makran accretionary prism.
The Tso Morari Nappe of the Ladakh Himalaya:
formation and exhumation
Jean-Luc Epard1* and Albrecht Steck2
1 Institut of Geology and Paleontology, University of Lausanne, Anthropole, CH-1015 Lausanne, SWITERLAND
2 Institut of Mineralogy and Geochemistry, University of Lausanne, Anthropole, CH-1015 Lausanne, SWITZERLAND
For correspondence, email:
The Tso Morari Nappe is one ofthe North Himalayan nappes and
is characterized by ultra-high pressure metamorphic rocks. It is
composed of graywackes, slates, sandstones and dolomites ofthe
Upper Haimantas and Karsha formations (Vendian-Cambrian).
It includes also metabasites. The Tso Morari anatectic granite
is dated at 479 Ma (Ordovician, Girard and Bussy 1999) and is
intrusive in the Haimantas and Karsha formations. It contains
basic dikes, perhaps in part cogenetic. The Tso Morari Nappe
is characterized by high to ultra-high pressure metamorphic
paragenesis (de Sigoyer at al. 1997, Mukherjee and Sachan 2001)
dated at 53 Ma (Leech et al. 2005). Eclogites are absent ofthe
surrounding units. Static eclogite facies crystallization preserves
folded boudins of metabasites in the Tso Morari granite. These
structures predate the HP metamorphism and can be interpreted
as deformation of cogenetic dikes in relation with the Tso Morari
granite intrusion. Only sparse deformational structures can be
attributed to the ultra-high pressure event.
The main schistosity SI is associated to an E-directed
stretching lineation LI with top-E shear indicators. In general, this
is a strong deformation dominated by mylonitic structures. Strain
is however heterogeneous and relatively large area of massive,
non-deformed granite can be observed. This deformation is
related to mineral assemblages ofthe amphibolite facies attesting
a pressure drop and a temperature increase. It is interpreted as
associated to the nappe extrusion. A younger deformation D2 is
characterized by a N-S trending stretching lineation L2 with top-
S shear indicators. This deformation is developed at the upper
part of the Tso Morari nappe and can be found in the higher
Tertaogal and Mata nappes. It has been observed also at the
front ofthe North Himalayan nappes in the Lingti Valley (Epard
and Steck 2004). It is interpreted as related to an early phase of
north-directed underthrusting of the Tso Morari Nappe below
the Tetraogal and Mata nappes. This is coherent with the early
N movement of India below Asia (Patriat and Achache 1982).
The D2 deformation is superimposed by the D3, L3 deformation
with top-SW shear indicators. It is associated to the main phase
of North Himalayan nappes emplacement and is a shared
structure in the North Himalayan nappe stack. Barrovian regional
metamorphism is coeval to the extrusion ofthe Tso Morari Nappe
and its incorporation into the North Himalayan nappe stack. It
reaches amphibolite facies in most area ofthe Tso Nappe except
the eastern part, close to the colder rocks ofthe Indus Suture Zone
where it reaches only higher greenschist facies. This is due to a
more rapid extrusion of this part ofthe nappe and is responsible
for the first warping of the Tso Morari Nappe (Schlup et al.
2003). This first warping has been emphasized by NE verging
backfolding already described by Steck et al. (1998) and also by
structures related to neotectonics. The superposition of these
structures leads to the present day dome structure. These tectonic
structures are compatible with a late, NW-SE striking dextral
shear zone, parallel to the Indus Suture Zone. They consist in
large E-W trending, en-echelon, open folds as well as N-S striking
normal faults. Additional new structural and metamorphic data,
as well as a compilation ofthe published data on the Tso Morari
nappe can be found in Epard and Steck (2008).
de Sigoyer J, S Guillot, J-M Lardeaux and G Mascle. 1997. Glaucophane-
bearing eclogites in the Tso Morari dome (eastern Ladakh, NW
Himalaya). European Journal qf Mineralogy 9: 1073-1083
Epard J-L and A Steck. 2004. The eastern prolongation ofthe Zanskar Shear
Zone (Western Himalaya). Eclogae Geologicae Hehetiae 97: 193-212
Epard J-L and A Steck 2008. Structural development of the Tso Morari
ultra-high pressure nappe of the Ladakh Himalaya. Tectonophysics :
Girard M and F Bussy. 1999. Late Pan-African magmatism in the Himalaya:
new geochronological and geochemical data from the Ordovician
Tso Morari metagranites (Ladakh, NW India). Schweizerische
Mineralogische und Vetrographische Mitteilungen 79: 399-417
Leech ML, S Singh, AKJain, SL Klemperer and RM Manickavasagam.
2005. The onset of India-Asia continental collision: Early, steep
subduction required by the timing of UHP metamorphism in the
western Himalaya. Earth and Planetary Science Letters 234: 83-97
Mukherjee BK and HK Sachan. 2001. Discovery of coesite from Indian
Himalaya: A record of ultra-high pressure metamorphism in Indian
Continental Crust. Current Science 81: 1358-1361
Patriat P and J Achache. 1984. India-Eurasia collision chronology has
implications for crustal shortening and driving mechanism of plates.
Nature 311: 615-621
Schlup M, A Carter, M Cosca and A Steck 2003. Exhumation history
of eastern Ladakh revealed by 40Ar/39Ar and fission track ages:
The Indus river-Tso Morari transect, NW Himalaya. Journal qf the
geological Society qf London 160: 385-399
Steck A, J-L Epard, J-C Vannay, J Hunziker, M Girard, A Morard and
M Robyr. 1998. Geological transect across the Tso Morari and Spiti
areas: The nappe structures ofthe Tethys Himalaya. Eclogae Geologicae
Helvtiae 91: 103-121
Implications of geochemical signatures in the Trans-Himalayan
Lohit batholith, Arunachal Pradesh, India
TK Goswami
Department of Geology, JB College, Jorhat, Asam, INDIA
The Trans Himalayan Lohit batholith studied both in the Lohit and
Dibang valley gives an insight as far as the source characteristics of
magma and the possible evolutionary trend. The batholth represents
at least four phases of intrusion representing changing sources of
magma generation. The early gabbro-quartz diorites are followed by
trondhjemite and followed by intrusions of leucogranites towards
the end phase. The aplite and the pegmatite dykes finally intruded
all the earlier intrusive. The rocks are metaluminous and mostly
calc-alkaline and a few early gabbros also show tholeitic parentage.
Gabbro-quartz diorites form a single group with the Si02 range
from 40.34 to 59.64 %. Leucogranites show high values of Rb, Ba
and KjO Four samples of diorites and granodiorites have 87Sr/86Sr
initial ratios from 0.7039 to 0.7061, suggesting the upper mantle
could be the source of the granitoids. Two samples of leucogranite
with high and very high 87Sr/86Sr initial ratios 0.7079 and 0.7144
indicate that they are the products ofthe melting ofthe crustal rocks.
In the Walong area dextral shearing might be synchronous with the
intrusion ofthe copious volume ofthe leucogranites into the earlier
rocks. In the Dibang valley, leucogranites near Dumbuen invariably
follow the right lateral shearing in the earlier intrusives. Leucogranite
intrusion might be associated with the collision induced shearing
towards the later stages in the thick continental crust.
Cretaceous - Tertiary carbonate platform evolution and the age
of India - Asia collision along the Ladakh Himalaya (NW India)
Owen R Green1*, Michael P Searle1, Richard I Corfield2 and Richard M Corfield1'3
1 Department of Earth Sciences, University of Oxford, Oxford OX1 3PR, UK
2 BP Amoco Exploration, Farburn Industrial Estate, Dyce, Aberdeen AB21 7PB, UK
3 Department of Earth and Environmental Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
For correspondence, email:
The India - Asia collision resulted in the formation and uplift of
the Himalaya and enhanced uplift of the Tibetan plateau. The
transition from marine to continental facies within the Indus
- Yarlung Tsangpo suture zone and along the northern margin of
the Indian plate provides the most accurate method of dating the
closure of Tethys Ocean separating the Indian and Asian plates. The
use of shallow water, carbonate platform-dwelling larger benthic
foraminifera provides the means for defining 20 shallow benthic
zones (SBZ) ranging from the base of the Paleocene up to the
Eocene-Oligocene boundary (Serra-Kiel, et al. 1998), and is applied
to Cretaceous-Tertiary rocks of the Ladakh Himalaya. Indirect
methods of dating the collision such as palaeomagnetism (Zhu et
al. 2005), dating the UHP metamorphism along the north margin
of India (Leech et al. 2005), dating the youngest subduction-related
granites along the southern margin of Asia (Weinberg and Dunlap
2000) or dating the post-orogenic Indus Molasse Group deposits
within the suture zone (Aitchison et al. 2007), cannot provide such
a precise or reliable age of collision. Ophiolite obduction onto the
Indian passive margin occurred during the latest Cretaceous and
pre-dated initial collision of the two continental plates (Corfield
et al. 1999). Unconformities occur beneath the Late Maastrichtian
Marpo Formation, and beneath the Danian Stumpata Formation
on the shelf and beneath the Upper Paleocene Sumda Formation
in the suture zone. Stratigraphic and structural data from the Indian
plate continental margin in the Ladakh and Zanskar Himalaya,
NW India, suggest that the final marine sediments were shallow
marine limestones containing a diverse assemblage of larger
benthic foraminifera (Figure 1) deposited during the planktonic
zone P8/shallow benthic zone SBZ10, corresponding to the Cusian
stage of the late Lower Eocene (Ypresian), 50.5 Ma. A regional
unconformity across shelf and suture zone above these rocks
marks the beginning of continental red-bed deposition (Chulung-
la and Nurla Formations). The age ofthe final marine sediments
is similar in Waziristan (NW Pakistan) to the west, and the south
Tibet region to the east, suggesting that there was no significant
diachroneity along the Indus -Yarlung Tsangpo suture zone. South
of the Himalaya in the Hazara syntaxis, Pakistan, the youngest
marine sediments correspond to Nummulite bearing limestones of
the shallow benthic zone SBZ10, and planktonic foraminifera P7
zone (52-51 Ma). The timing of closure of Neo-Tethys between
India and Asia corresponds closely to the ending of subduction-
related granodiorite - granite magmatism along the Ladakh -
Gangdese batholith (southern, Andean-type margin of the Asian
plate) and precedes the drastic slowing of the northward drift of
India. Continental fluvial - deltaic red-beds unconformably overlie
all marine sediments, both in the suture zone and along the north
Indian plate margin.
Gil. Plukloaic    SKL1. Assiliaai
IcrammilL-ia [MxCuCytlina
CM  Awilina UMl
Kt.<ib. Numfltuliies tc   Cjffl Alwolina ft
BBm »MII Slope -"j™ Inner shallow plslfonr,
FIGURE 1. Diagrammatic reconstruction of the carbonate platform of
the Cusian stage of the late Lower Eocene (Ypresian) illustrating the
relative positions of the foraminiferal biofacies present along the Indian
plate margin (Samples from exposures at: G = Gongma, KL = Kesi La,
MA = Marling, SKL = Stumpata).
Aitchison JC,JR Ali andAM Davis. 2007.When andwhere did India and Asia
collide? Journal qf'Geophysical Research 112: doi: 10.1029/2006JB004706
CorfieldRI, MP Searle and OR Green. 1999. Photang thrust sheet: an accretionary
complex structurally below the Spontang ophiolite constraining timing
and tectonic environment of ophiolite obduction, Ladakh Himalaya, NW
lnditL.Journal ofthe Geological Society, London 156:1031-1044
Leech ML, S Singh, AKJain, SL Klemperer and RM Manickavasagam.
2005. The onset of India-Asia continental collision: Early, steep
subduction required by the timing of UHP metamorphism in the
western Himalaya. Earth and Planetary Science Letters 234: 83-97
Serra-Kiel J, L Hottinger, E. Caus, K Drobne, C Ferrandez, AKJauhri,
G Less, R Pavlovec, J Pignatti, JM Samso, H Schaub, E Sirel, A
Strougo, Y Tambareau, J Tosquella and E Zakrevskaya. 1998. Larger
foraminiferal biostratigraphy ofthe Tethyan Paleocene and Eocene.
Bulletin de la Societegeologiaue de France 169: 281-299
Weinberg RF and WJ Dunlap. 2000. Growth and deformation of the
Ladakh Batholith, Northwest Himalayas; implications for timing of
continental collision and origin of calc-alkaline batholiths. Journal qf
Geology 108: 303-320
Zhu B, SF Kidd, DB Rowley, BS Currie and N Shafique. 2005. Age of
initiation of the India-Asia collision in the East-Central Himalayas.
Journal qf Geology 113: 265-285
P-T evolution across the Main Central Thrust zone (Eastern
Nepal): hidden discontinuities revealed by petrology
Chiara Groppo1*, Franco Rolfo12 and Bruno Lombardo2
1 Dipartimento di Scienze Mineralogiche e Petrologiche, University of Torino, ITALY
2 Istituto di Geoscienze e Georisorse, CNR — Section of Torino, ITALY
For correspondence, email:;
Identifying the location and nature ofthe Main Central Thrust Zone
(MCTZ) is a major challenge in most of the Himalayan chain. As
a contribution to clarifying this geopuzzle, a number of metapelite
samples were selected for petrologic studies along a transect on
the eastern flank ofthe 'Arun Tectonic Window" (Bordet 1961) in
eastern Nepal. The results provide information on the distribution of
the Lesser Himalaya and MCTZ in a relatively poorly known area.
Both to the west and east of the study area, the classical
Makalu and Kangchendzonga transects (Brunei and Kienast 1986,
Lombardo et al. 1993, Meier and Hiltner 1993, Pognante and
Benna 1993, Goscombe and Hand 2000, Goscombe et al. 2006)
show metamorphic units characterized by a well-documented
inverted metamorphism, with a general increase of metamorphic
grade northward from lower (Lesser Himalaya) to higher (Higher
Himalaya Crystallines - HHC) structural levels across the MCTZ
(e.g. Le Fort 1975, Arita 1983, Valdiya 1983, Hodges et al. 1998,
Inger and Harris 1992, Vannay and Hodges 1996).
Metamorphic assemblages in the studied metapelites range
fromthe low-gradechloritezone (Chi +Wm + Qtz+P1 ± Ctd ± Mn-
rich Grt), to the medium-grade staurolite (Wm+Bt+Grt + St) and
kyanite (Wm+Bt + Grt+St+Ky) zones, up to the sillimanite zone
(Wm+Bt+Grt + Sil+Pl±St±Ky) and a further zone of partial
melting with the appearance of K-feldspar and the breakdown of
white mica. The P-T evolution of 5 metapelite samples collected
at different structural levels has been reconstructed in detail using
the modern petrological approach of P-T pseudosections, and
considering the possible chemical fractionation of the bulk rock
composition due to the presence of zoned porphyroblasts (e.g.,
The resulting P-T paths may be grouped in three different families:
(i) the structurally lower Lesser Himalayan samples show
a prograde P-T path characterized by an increase in both P and T,
up to peak metamorphic conditions of 550°C and 0.65 GPa;
(ii) two structurally intermediate samples preserve relics of
a prograde history characterized by heating and decompression
from 550°C, 1.0 GPa to 620°C, 0.8 GPa and from 570°C, 1.1 GPa
to 650°C, 0.9 GPa, respectively, showing a similar exhumation
history characterized by cooling and decompression along the
same metamorphic gradient;
(iii) the structurally higher samples consist of mostly
unzoned minerals and well equilibrated assemblages that do
not preserve relics of their prograde metamorphic history. Peak
metamorphic T and P of these two samples are higher than the
structurally lower MCTZ samples: 650°C, 0.7 GPa, but still inside
the white mica stability field, and ~ 780°C, 1.0 GPa, beyond the
stability limit of white mica and in the melt-bearing field.
The different P-T paths inferred for the studied
metapelites suggest the presence of important metamorphic
discontinuities that are not structurally evident in the field
because   the   regional   metamorphic   fabric   mainly  developed
during late deformation events. The first discontinuity found
may correspond to the MCT in the classical sense of Heim and
Gansser (1939) as it juxtaposes the medium-grade metamorphic
units of the MCTZ, characterized by a clockwise P-T path
with heating during decompression followed by cooling and
decompression, over the Lesser Himalaya sequence, which only
preserves prograde metamorphism characterised by an increase
in both P and T. A second discontinuity, at a higher structural
level, separates units of the MCTZ from overlying metapelites
that were metamorphosed at higher T and relatively lower P.
Arita K.   1983.  Origin  of the inverted metamorphism  of the Lower
Himalayas, Central Nepal. Tectonophysics 93: 43—60
Bordet R 1961. Recherches geologiaues dans VHimalaya du Nepal, region du Makalu.
Paris: Editions du Centre National de la Recherche Scientifique. 275 p
Brunei M andJR Kienast. 1986. Etude petro-structurale des chevauchements
ductiles himalayens sur la transversale de l'Everest-Makalu (Nepal
oriental). Canadian Journal ojEarth Sciences 23: 1117—1137
Goscombe B and M Hand. 2000. Contrasting P-T paths in the Eastern
Himalaya,   Nepal:   inverted   isograds   in   a   paired   metamorphic
mountain bcltjournal qf Petrology 41: 1673—1719
Goscombe B, D Gray and M Hand. 2006. Crustal architecture ofthe Himalayan
metamorphic front in eastern Nepal. Gondwana Research 10: 232—255
Heim A and A Gansser. 1939. Central Himalaya: geological observations ofthe
Swiss expedition 1936. Memoir Society Helvetica Science Nature 73: 1—245
Hodges KV S Bowring, K Davidek D Hawkins and M Krol.  1998.
Evidence for rapid displacement on Himalayan normal faults and
the importance of tectonic denudation in the evolution of mountain
ranges. Geology 26: 483— 486
Inger S andNBWHarris. 1992. Tectonothermal evolution ofthe High Himalaya:
geochemical and sedimentological evidence. Geology 10: 439-452
Le Fort R 1975. Himalayas: the collided range. Present knowledge ofthe
continental arc. American Journal qf Science 275: 1^4
Lombardo B, P Pertusati and ABorghi. 1993. Geology and tectono-magmatic
evolution of the eastern Himalaya along the Chomolungma-Makalu
transect. Geological Society qf London, Special Publication 74: 341—355
Meier K and E Hiltner. 1993. Deformation and metamorphism within the
Main Central Thrust zone, Arun tectonic Window, eastern Nepal.
Geological Society qf London, Special Publication 74: 511—523
Pognante U and P Benna. 1993. Metamorphic zonation, migmatization,
and leucogranites along the Everest transect (Eastern Nepal and
Tibet): record of an exhumation history. Geological Society qf London,
Special Publication 74: 323—340
Valdiya KS. 1983. Tectonic setting of Himalayan granites. In: Shams FA
(ed), Granites qf Himalayas Karakorum and Hindu Kush, Lahore Punjab
University, 39—53
Vannay JC and KV Hodges.  1996. Tectonometamorphic evolution of the
Himalayan metamorphic core between the Annapurna and Dhaulagiri,
central Nepal/owm^/ qf Metamorphic Geology 14: 635-656
Kyanite-bearing anatectic metapelites from the Eastern
Himalayan Syntaxis, Eastern Tibet, China : textural evidence for
partial melting and phase equilibria modeling
Carl Guilmette1*, Indares Aphrodite2, Hebert Rejean1 and CS Wang3
1 Departement de Geologic et de Genie Geologique de I'Universite Laval, Quebec, QC, CANADA, G1K7P4
2 Earth Sciences Department, Memorial University of Newfoundland, St-John's, NL, CANADA, A1C5S7
3 School of Earth Sciences and Mineral Resources, China University of Geosciences, Xueyuan Road #29, Beijing PEOPLE'S REPUBLIC OF CHINA
For correspondence, email:
The Eastern Himalayan Syntaxis (EHS), or Namche Barwa
antiform, Tibet, China, marks the eastern termination of the
Himalayan Range. In the EHS, the overall E-W trending India-
derived Higher Himalayan Crystallines are bent in a N-S
orientation and are actively indenting and exhuming into and from
underneath the Asian-derived rocks ofthe Lhasa terrane, strongly
altering the otherwise linear trend ofthe Yarlung Zangbo Suture
Zone (YZSZ). As reflected by its tormented landscape, the EHS
is characterized by extreme denudation and exhumation rates. Up
to now, no consensus has been made on the metamorphic history
ofthe metamorphic core ofthe EHS, and the mechanisms that
drove its burial and exhumation are still strongly debated.
In the core ofthe EHS, rare kyanite-bearinganatectic paragneisses
locally occur as boudins within sillimanite-bearing paragneisses.
Worldwide, kyanite-bearing anatectic rocks are seldom found and
such an occurrence within a young and active orogenic belt provides
both an excellent opportunity to study partial-melting of aluminous
paragneisses in the kyanite stability-field and a unique insight into the
evolution ofthe Himalayan range and Tibetan Plateau.
Previous studies described kyanite-bearing boudins
found at the foot of the Namche Barwa massif, near the locality
of Zhibai (Liu and Jhong 1997 and references therein, Burg
et al. 1998), in the core ofthe EHS. These rocks consist of an
early HP-granulite assemblage (garnet-kyanite-biotite-quartz-
plagioclase-K-feldspar-rutile) variably overprinted by a late high
temperature but lower pressure assemblage including sillimanite
pseudomorphs after kyanite cordierite-spinel coronas after
sillimanite and orthopyroxene coronas after garnet. These studies
outlined the unique character of these rocks and tentatively
estimated P-T conditions for peak and retrograde metamorphism.
However, partial melting was not taken into account, leading to
much controversy on the peak conditions (amphibolite vs HP-
granulite facies) and therefore on the maximum depth of burial.
In the present study, we describe kyanite-bearing anatectic
paragneisses from the NW side of the Yarlung Zangbo River, in
the western rim ofthe EHS. These rocks were found at the eastern
end of an E-W cross-section that in an eastward direction crosses
granitic batholiths of the Lhasa terrane, metamorphosed and
deformed units of the YZSZ and a metasedimentary sequence.
This sequence is characterized by an eastward increasing
metamorphic grade going from 2-micas garnet schists through
garnet-kyanite-staurolite gneisses and sillimanite-bearing gneisses
to kyanite-bearing anatectic gneisses. At the outcrop scale, the
kyanite-bearing rocks occur in the same setting as the boudins
described in the inner core. However, they lack the late lower-P
high-T overprint, being devoid of corona assemblages.
In this contribution, we present textural evidences for partial-
melting of these rocks in the kyanite stability field supported by phase
equilibria modelling with THERMOCALC. The studied rocks have
broadly pelitic to semi-pelitic compositions and are characterised by the
assemblage garnet-kyanite (±sillimanite)-biotite-quartz-plagioclase-
K-feldspar±rutile/ ilmenite with sillimanite locally occurring as
pseudomorphs after kyanite. Although the rocks are strongly deformed,
melt related textures are locally preserved in the matrix as (1) fine
grained feldpar-rich domains corroding relict coarser grained quartz
ribbons and (2) films and pockets of randomly oriented fine grained
biotite and feldspars surrounding corroded kyanite. However, melt
related textures are best preserved in polymineralic inclusions within
garnet porphyroblasts, consisting of rounded quartz and /or squeletal
biotite surrounded by optically continuous pools of feldspar, with
crystalline garnet faces towards the inclusions. All the above textures
are consistent with the continuous reaction biotite+kyanite + quartz ±
plagioclase=garnet+melt±K-feldspar (RI) which marks the entrance
to the HP-granulite lacies. In addition retrograde textures related to
melt crystallization are observed in form of biotite-fibrolite aggregates
locally corroding garnet rims and suggesting that the melt solidified in
the sillimanite stability field.
Phase equilibria modelling in the NCKFMASTHO system
with THERMOCALC is in progress. Preliminary pseudosections
built with the bulk compositions of one pelitic and one semi-
pelitic sample show that for these rocks the biotite-kyanite-garnet-
quartz-plagioclase-K-feldspar-liquid-rutile +/- ilmenite field in
which reaction RI operates, occurs within the P-T range of— 800-
875°C and —10-17 kbar. In addition these pseudosections show
topologies that are consistent with substantial melt loss during
prograde metamorphism. Preliminary minimum P-T estimates of
— 13.5-14.5 kbar and —830°C are inferred for the metamoorphic
peak based upon the the intersection of composition isopleths
reflecting the grossular contents and XFe of homogeneous cores
of garnet in the metapelitic sample. Subsequent solidification
of melt in the sillimanite stability field implies strong post-peak
decompression at high temperatures.
BurgJ-P, P Nievergelt, F Oberli, D Seward, P Davy, J-C Maurin, Z Diao
and M Meier. 1998. The Namche Barwa syntaxis: Evidence for
exhumation related to compressional crustal folding. Journal qf Asian
Earth Sciences 16: 239—252
Liu Y and D Zhong. 1997. Petrology of high-pressure granulites from the
eastern Himalayan syntaxis.Journal qf Metamorphic Geology 15: 451^66
New occurrence of eclogitic continental rocks in NW Himalaya:
The Stak massif in northern Pakistan
Stephane Guillot,*1 Nicolas Riel1, Keiko Hattori2, Serge Desgreniers3, Yann Rolland4,
Jeremie Van Melle1, Mohamad Latif5, Allah B Kausar5 and Arnaud Pecher1
1 University of Grenoble, OSUG - CNRS, BP 53, 38041 Grenoble cedex 9, FRANCE
2 University of Ottawa, Dept of Earth Sciences, Ottawa, Ontario, CANADA KIN 6N5
3 University of Ottawa, Dept of Physics, Ottawa, Ontario, CANADA KIN 6N5
4 University of Nice, Geosciences Azur - CNRS, 06108 Nice Cedex 02, FRANCE
5 Geological Survey of Pakistan—Northern Area, PlotN". 84, H-8/1, Islamabad, PAKISTAN
For correspondence, email:
Three occurrences of ultrahigh pressure (UHP) rocks have
been recognized along the Himalayan belt. In southern Tibet,
Yang et al. (2007) documented diamond- and coesitebearing
chromitites from the Lobuosa ophiolite in the Indus-Tsangpo
Suture zone (ITSZ). Coesite-bearing eclogites are reported in
the Tso Morari and Kaghan massifs in NW Himalaya (O'Brien
et al. 2001, Mukherjee et al. 2003 2005) in the ITSZ ofthe Main
Mantle Thrust (MMT). The latter occurrences are the products
ofthe subduction ofthe margin ofthe Indian continent between
57 and 44 Ma (Leech et al. 2005, Parrish et al. 2006, Guillot et al.
2008). We report a new occurrence of eclogitic rocks from the
Stak area where pyroxenite boudins with a retrogressed eclogitic
assemblage were described by Le Fort et al. in 1997. This massif
east of the Nanga Parbat-Haramosh anticline consists of garnet-
bearing orthogneisses, metasediments, and marbles intruded by
dykes of boudinaged garnet-bearing metabasites. The metabasites
have similar chemical composition as the basalts of the Panjal
Traps and this association ofthe metabasites with metasediments
suggest that the rocks represent the western margin ofthe Indian
continent, similar to the UHP massifs at Kaghan (Chaudhry and
Ghazanfar 1987) and Tso Morari (Guillot et al. 1997). The rocks
in the Stak area have undergone at least two phases of folding.
The youngest event is defined by NE oriented steep folds (up to
100m in size) with axial plane dipping — 60° towards the NW.
Asymmetrical folds indicate the top verging to the SE, which is
likely related to the exhumation ofthe Nanga Parbat-Haramosh
block (Argles and Edwards 2002). The deformation ofthe MMT
also affected the area, which resulted in alternating layers of
weakly metamorphosed rocks of the Ladakh arc and strongly
metamorphosed Indian continental rocks.
The Stak massif contains well preserved eclogitic assemblage;
garnet (Pyr34), omphacite (Jd46), phengite, Ca carbonate (most
likely aragonite). The presence of coesite is suspected because the
peakmetamorphic condition is in the stability field of coesite, greater
than 2.7 GPa, based on the bulk and garnet compositions. Rims of
garnet contain inclusions of phengite and dolomite, clinopyroxene
(Jd24) and plagioclase (Ab80). Omphacite in the matrix is altered
to a symplectic mixture of Na-Ca clinopyroxene (Jdl8) and albite,
indicating that the  retrogression under eclogitic conditions at
~1.8±0.1 GPa and 650-700°C. The late folding developed under
amphibolitic facies conditions as marked by pargasitic amphibole,
biotite and ilmenite and later the crystallization of hornblende. The
assemblages indicate that the folding took place during a pressure
decrease from 11 to 8 kbar and a temperature decrease from 700
to 600°C. Finally late localized millimetric shear bands defined by
calcite and chlorite developed at the ductile-brittle transition under
greenschist facies conditions.
A few Ar-Ar biotite ages have been obtained in this study,
and the data suggest that the Stak massif was cooled below 350°C
before 20- 10 Ma, which corresponds to the exhumation of the
Nanga Parbart Haramosh anticline (Zeitler et al. 2001). The Stak
massif shares many features with the Kaghan massif including
lithologies, location in the MMT and the mineral chemistry. The
similarities suggest that the Stak-Kaghan massifs were possibly
once a continuous UHP unit and later separated by the Plio-
Miocene uplift of the Nanga Parbat Haramosh block. If this
hypothesis is correct, the size of the Kaghan-Stak UHP massif
(> 500 km2) is comparable to those ofthe Western Gneiss region
of Norway and the Dabie-Sulu region in China. This will be
tested by the data of our on-going studies including new micro-
Raman spectometry, SHRIMP ages of zircon and Ar-Ar ages of
amphibole, biotite and white micas.
Argles TW and MA Edwards. 2002. Journal qf Structural Geology 24: 1327-1344
Chaudhry MN and M Ghazanfar. 1987. Geological Bulletin University qf
Punjab 22: 13-57
Guillot S et al. 1997. Contribution to Mineralogy and Petrology 128: 197-212
Guillot S et al. 2008., Tectonophysics: doi:10.1016/j.tecto.2007.11.059
Kaneko Y et al. 2003. Journal qf Metamorphic Geology 21: 589-599
Le Fort P et al. 1997. Compte Rendus de I'Academie des Sciences, Paris 325: 773-778
Leech ML et al. 2005. Earth and Planet Science Letters 234: 83-97
Mukheerjee B et al. 2005. Geologie Alpine 44: 136
Mukheerjee B et al. 2003. International Geology Review 45: 49-69
O'Brien P et al. 2001. Geology 29: 435-438
Parrish R et al. 2006. Geology 34: 989-992
Yang JS et al. 2007. Geology 35: 875-878
Zeitler PK et al. 2001. Tectonics 20: 712-728
Evolution of the Indian Monsoon System and Himalayan-Tibetan
Plateau uplift during the Neogene
Anil K Gupta
Department of Geology and Geophysics, Indian Institute of Technology
Kharagpur- 721 302, INDLA
The Indian monsoon also known as the South Asian monsoon is
an important feature of the climate system, marked by seasonal
reversals in the wind direction with southwesterly winds in
summer and northeasterly winds in winter. The summer
monsoon plays an important role in global hydrological and
carbon cycles, and affects climate and societies over a large part
of Asia between 35°N and 10°S. The monsoon is the lifeline to
the people of Asia as region's food production and water supply
are largely dependent on the summer monsoon rains. Thus the
Indian monsoon constitutes a critical resource for the region's
largely agrarian economies.
Considerable efforts have been made toward high resolution
(high density sampling of the marine cores) reconstruction of
proxy records of monsoon that have helped in the understanding
of monsoon evolution, its variability over various time scales, and
forcing factors that drive the monsoon on orbital and sub-orbital
time scales. However, there are still unresolved questions as to
the timing of the advent of the modern monsoon and driving
mechanisms of monsoon variability. The elevated heat source
ofthe Himalayas and the Tibetan Plateau is of vital importance
for the establishment and maintenance of the Indian summer
monsoon circulation through mechanical and thermal factors.
But there are different propositions about the attainment ofthe
critical elevation by the Himalayas and the Tibetan Plateau to drive
the Indian monsoon, ranging from 35 to 7.5 Ma (Table 1). While
the marine records indicate a major shift in the monsoon system
between 9 and 8 Ma, the continental records suggest a range from
22 to 7.5 Ma during which time the monsoon may have evolved.
The model studies, on the other hand, put the origin farther back
in time at — 35 Ma. Recent study from China suggests a wet phase
in the early Miocene and beginning of an arid phase (weakening
ofthe summer monsoon) across 13-11 Ma (Hanchao et al. 2008).
Thus to resolve these issues, a coordinated effort is required to
analyze and compare high resolution records from marine cores
from high sedimentation areas ofthe Arabian Sea and the Bay of
Bengal as well as continental records of continuity.
Gupta AK RK Singh, E Thomas and S Joseph. 2004. Indian Ocean high-
productivity Event (10-8 Ma): Linked to Global Cooling or to the
Initiation ofthe Indian Monsoons? Geology 32: 753-756
Hanchao J, J Ji and Z Ding. 2008. Cooling-driven climate change at 12-
11 Ma: multiproxy records from a long fluviolacustrine sequence at
Guyuan, Ningxia, China. Palaeo3 In press
TABLE 1. Evidence and timing of the Himalayan Uplift and Monsoon Intensification (Modified from Gupta et al. 2004)
Rowley and Currie 2006
Oxygen isotope
Tibetan Plateau
Ramstein etal. 1997
Monsoons and Paratethys retreat
Guo et al. 2002
China loess deposits
Monsoon climate
Wang 1990
Sediments in China
Clift and Gaedicke 2002
Indus Fan sediments
Erosion and weathering
Clift et al. 2002
South China Sea smectite mineral
Precipitation and monsoons
Spicer et al. 2003
Fossil flora
Himalayan elevation and monsoons
Coleman and Hodges 1995
Himalayan elevation
Blisniuk etal. 2001
Himalayan uplift and monsoons
Chen et al. 2003
Oceanic microfossils
Monsoons and upwelling
Dettman et al. 2001
Isotopes and land
An et al. 2001
Land and marine sediments
Uplift and onset of monsoons
Kroon et al. 1991
Oceanic microfossils
Monsoons and upwelling
Filipelli 1997
Weathering and sediments
Quade etal. 1989
Isotopes and flora
Structural and metamorphic equivalence across theLHS-HHCS
contact, Sikkim Himalaya - indicator of post-deformation
metamorphism or the wrong MCT?
Saibal Gupta* and Suman Mondal
Department of Geology and Geophysics,
Indian Institute of Technology Kharagpur, Kharagpur— 721 302, INDIA
For correspondence, email:
In the Sikkim Himalaya, the contact between the base ofthe Lingtse
Gneiss (an augen gneiss body at the base ofthe Higher Himalayan
Crystalline Sequence, HHCS) and the metapelitic schists of the
Lesser Himalayan Sequence (LHS) has been considered to be
the Main Central Thrust (MCT). The region is characterized
by an inverted metamorphic sequence, with the index minerals
chlorite to sillimanite appearing at progressively at higher structural
levels across the sequence. The study has been conducted along
the North-Sikkim Highway (NH -31A), and focuses along the
contact zone between HHCS and LHS. Structural studies reveal
that the contact zone is a ductile shear zone (the MCT zone)
dominated by a single penetrative fabric (S2) trending NW-SE
and dipping northeast. This corresponds to a second deformation
event that affected lithounits on either side of the contact. Since
the intersection lineation between the earlier fabric in both units
(SI) and S2 is identical, it is inferred that the earlier fabrics in the
HHCS and LHS had similar disposition prior to D2 deformation.
A third deformation event (D3) is recorded in the mica schists of
the LHS, but this is confined to lower structural levels. The late S3
foliation related to this event cuts across the earlier SI and S2 fabrics
in the LHS. Microstructural relationships between the mineral
phases and deformation fabrics, and zoning characteristics of garnet
indicate a progressive metamorphic history from the syn-Dl to
post-D2 period. Peak metamorphic conditions in both the HHCS
and the LHS were attained after D2 deformation, and there appears
to be no significant difference in the estimated peak P-T (~ 7 Kb,
650°C) across the MCT zone. The pressures and temperatures
have been estimated through both conventional thermobarometric
techniques and THERMOCALC, and the interpretations cannot
be attributed to flaws in the applied methodology, as suggested by
some workers. Thus, the estimated conditions are considered to be
realistic. The lack of any detectable difference in peak metamorphic
conditions that followed D2 deformation in both units may
indicate that the entire metamorphic development is independent
of and unconnected to, movement along the MCT. Alternatively, it
is possible that the observed shear zone does not correspond to the
MCT at all, and that the MCT in this sector needs to be relocated.
The latter possibility appears to be supported on structural grounds,
since the structural orientation of pre-D2 fabrics in the HHCS and
LHS are interpreted to be similar. A more comprehensive study is
being undertaken across the sequence to confirm one or the other
Continental Relamination Drives Compositional and Physical-
Property Changes in the Lower Crust
Bradley Hacker,* Peter B Kelemen and Mark D Behn
University of California, Santa Barbara, CA,93109-9630,   USA
For correspondence, email:
A long-standing paradigm for the genesis and evolution of Earth's
continental crust holds that the crust is andesitic and reached
this composition in the 'subduction factory' by delamination or
foundering of a dense, mafic or ultramafic component into the
mantle from the base of initially basaltic arc crust. However, the
range of suggested compositions for the lower crust and our
incomplete understanding of subduction-zone processes render
this paradigm non-unique. Recent discoveries from (ultra)high-
pressure xenoliths and terranes, combined with re-evaluation of
methods for inferring lower crustal compositions from seismic
velocity data, show that "relamination" of buoyant, subducting
continental crust may be an efficient means of altering the
composition ofthe lower crust.
Ultrahigh-pressure   terranes   show   that   large   areas
(> 60,000 km2) of continental crust are subducted to depths > 100
km where they undergo heating to temperatures of 600-1000°C
for periods of up to 20 Myr. Xenoliths from the Pamir show that
subduction erosion can drag continental rocks to depths >90 km
and temperatures of ~1200°C. In both settings, devolatilization
and melting transform cold, hydrous, low-density crust into
hot, less hydrous residues. Felsic and intermediate rocks attain
densities similar to the middle-lower continental crust; buoyancy
may drive such rocks to rise through the mantle to pond at the
Moho or higher crust levels. The calculated seismic wavespeeds
of such material are indistinguishable from the bulk lower crust.
Both ultrahigh-pressure continental subduction and subduction
erosion operate at rates of 1—1.5 kmVyr, such that over the
lifetime of Earth either could have led to large-scale 'continental
relamination', refining the composition and physical properties of
the continental lower crust.
Comparison of regional geoelectric structure of Himalayan region
T Harinarayana and RS Sastry*
National Geophysical Research Institute, Hyderabad — 500007, INDIA
For correspondence, email:
In order to understand the regional tectonics of the Himalayan
region, a few geotransects have been carried out along different
transects in India and also in Nepal. The prominent among
them are wide band magnetotelluric soundings along Panamik-
Leh-Bara-la-chala, Una-Mandi, Siliguri-Gangtok-Lachung,
Joshimath-Gaucher in India and also in Central Nepal.
These studies are carried out as a part of deep crustal
investigations for better understanding of the seismotectonics of
the region. Additionally, several other deep geoelctric studies are
carried out using wide band digital magnetotelluric investigations
for geothermal exploration in Puga, Ladakh region, Tapovan-
Vishnugad and Lohari-Nag-Pala regions in Uttaranchal, Kullu-
Manali-Manikaran, Sutlej Spiti valley regions in Himachal Pradesh.
The major geological features in the study region are Munciari,
vaikrita thrust and other expressions of main central thrust. These
geotrasects have shown anomalous conductive features at mid-lower
crustal depths. This feature in relation to the regional tectonics and
seismo tectonics ofthe regions is discussed.
Pre-collisional Crustal Structure Adjacent the Indus-Yalu Suture
T Mark Harrison1*, Donald J Depaolo2 and Amos B Aikman3
1 Institute of Geophysics and Planetary Physics, UCLA, Los Angeles, CA 90095, USA
2 Earth and Space Science & LBL, University of California, Berkeley, CA 94720, USA
3 Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, AUSTRALIA
For correspondence, email:
Understanding the evolution ofthe Indus-Yalu Suture (IYS) has
significance well beyond its key role in recording events of the
Indo-Asian collision. Although this continent-continent collision
is likely just reaching middle age, the IYS is already largely bereft
of ophiolitic rocks and the adjacent subduction complex is
completely absent. This serves as a powerful cautionary example
to those who see the apparent absence of ophiolites in Archean
terranes as counterevidence of plate tectonics. Knowledge
of the pre-collisional geometries of India and Asia is vital to
assessing when collision began and how much convergence
was accommodated by thickening, extrusion, or delamination.
However, post-collisional thrusting and strike-slip faulting have
transmogrified the suture zone to such an extent that little can
be learned about syn-collisional crustal structure from its direct
study. In light of these limitations, we have investigated rocks
adjacent the IYS isotopically with a view to inferring crustal
thickness through time. Nd isotopic data from K-T granitoids in a
N-S traverse near Lhasa show a pronounced gradient in eNd, with
mantle-like values adjacent to the IYS ( + 5) and £Nd as -12 at —120
km north of the suture. This type of spatial gradient in eNd is
interpreted as reflecting decreasing mantle input/increasing crustal
assimilation due to progressively thickened crust (i.e., higher
lower crustal temperatures enhance crustal assimilation). Using a
calibrated crustal thermal model, we can then relate £„,, to crustal
thickness. A test of this model may be possible using the recently
calibrated zircon thermometer as crystallization temperature
spectra and inheritance patterns are characteristic of specific
assimilation scenarios. Our preliminary results suggest that the
strong continentward gradient in assimilation is due to a gradually
decreasing mantle magma flux and increasing crustal thickness;
from <20 km adjacent the IYS to >50 km in the northern portion
of the Gangdese Batholith where the granitoids are essentially
100% crustal melts. South of the suture, emplacement of the
44±1 Ma Dala granites into highly deformed Tethyan Himalaya
units indicates that significant crustal thickening had occurred
there prior to 'hard collision'. However, no current model for
evolution ofthe IYS yet explains why such magmas should appear
south ofthe suture. The similarity of £Nd in the Dala granites and
Lhasa terrane crustal melts is consistent with lower crustal flow
southward across the IYS, but more likely reflects the origin of
the Lhasa terrane and Tethyan Himalaya as adjacent blocks in the
northern Gondwana Supercontinent.
Discovery of crustal xenolith-bearing Miocene post-collisional
igneous rocks within the Yarlung Zangbo Suture Zone southern
Tibet: Geodynamic implications
Rejean Hebert1*, Lesage Guillaume1, Bezard Rachel1, Carl Guilmette1, Emilie Bedard1, Chengshan
Wang2, Thomas David Ullrich3 and Jaroslav Dostal4
Departement de geologic et de genie geologique, Universite Laval, Quebec, QC, G1K7P4, CANADA
Research Center for Tibetan Plateau Geology, China University of Geosciences, 29 Xueyuan Road, Haidian District, 100083 Beijing, CHINA
Department of Earth and Ocean Sciences, The University of British Columbia, Vancouver, BC, V6T 1Z4, CANADA
Department of Geology, Saint Mary's University, Halifax, NS, B3H3C3, CANADA
For correspondance, email:
The Neo-Tethys Ocean has been consumed into north-dipping
intra-oceanic and active margin subduction zones. Post-collisional
potassic to ultrapotassic magmatism occurred between 11.8 and
17 Ma. No such magmatism was reported within the YZSZ. The
purpose of this presentation is to document, for the first time, the
2006-2007 discovery of Miocene magmatic rocks within the YZSZ.
A 12.9 Ma ultrapotassic dyke cutting through th Xigaze flysch and
containing crustal xenoliths have been reported by Chan et al.
(2007, HKTW22). The igneous rocks crop out in the Saga and
Sangsang areas about 600 and 450 km west of Lhasa respectively.
They consist of intrusions cutting through the ophiolitic upper
mantle at Sangsang and the ophiolitic melange and ophiolitic crust
at Saga. The phenocrysts are made of amphibole and F-bearing
biotite (Mg# 0.3-0.6; F up to 2.56 wt. %), phlogopite, K-feldspar
(°r85-6i)' Plagioclase (An,7J, garnet (Al79_59Gr5_26Sp512Py11_3, and
pleonaste set in quartz-rich albite-oligoclase, apatite, and zircon
fine-grained matrix. Partly resorbed xenocrysts of garnet (Al67
74G r5 ySp042Py2819). The xenoliths contain various amounts of
K-feldspar (Or55 60), plagioclase An5 57), brown and green biotite
(Mg# 0.42-0.85), rare phlogopite, kyanite, garnet (A1J6 77Gr219Sp5
6Py316), quartz, muscovite, corundum, rutile, pleonaste, ilmenite,
magnetite, hematite, magnesiohastingsite, epidote. Plagioclase
grains contain up to 0.2 wt. % BaO and 0.47 wt. % SrO The
mineral chemistry of the xenoliths suggest that the high-Al
content could be related to partial melting extraction of migmatitic
liquids and the ferromagnesian assemblage correspond to basaltic
The geochemical data reveal that the host rocks are
trachyandesites and trachydacites. The range in composition is:
44,5-64,7 wt. % Si02, 15,3-18 wt. % AL03, 1,5-5,2 wt. %, MgO,
1,4-11,7 wt. %, CaO, 2,5-4,9 wt. % KjO, and 3,1-5,6 wt. % Na20.
The intrusive rocks belong to the shoshonitic clan in terms of
KjO vs Na20 and KjO vs Si02 relationships and to ultrapotassic in
the CaO vs ALP3 space but have K20/Na20 <2 (0.5-1.7). Trace
elements show high contents in Ba (703-1288 ppm), Ce (48-137
ppm), La (up to 73 ppm), Rb (up to 201 ppm), Sr (262-1498
ppm), and Zr (148-230 ppm). The rocks show large variations in
Ba/Nb (34-117), Rb/Ba (5-15), Sr/Y (20-105) but uniform Rb/Sr
(0.14-0.18) and La/Ce (0.5-0.6). 143Nd/144Nd ratios vary from
0,512167 to 0.512439 and time corrected -9,01 to -3,71. Strongly
fractionated Zr/Y ratios (11-18), high concentrations of LaPM
(42-117), CepM (21-75), Ti and other incompatible elements
negative YNd, and their similarities to the average of the upper
continental crust, suggest these rocks were largely derived from
a continental source with possible lower crustal and lithospheric
mantle components. They are likely derived from post-collisional
partial melting of lower to middle crustal material underlying the
YZSZ. 40Ar-39Ar geochronology on magmatic amphibole and
biotite points to a Middle Miocene age, making them the youngest
igneous rocks reported within the YZSZ. The presence of magma
at depth south of the Gangdese belt by Miocene time could have
an impact on further modeling of crustal thermal behaviour. The
trachyandesites and trachydacites provide a unique window allowing
a probe into the deep Indian crust underlying Tibet Plateau.
Constraints to the timing of India-Eurasia collision determined
from the Indus Group: a reassessment
Alexandra L Henderson1*, Yani Najman1, Randall R Parrish2, Andrew Carter3, Marcel le Boudagher-
Fadel3, Gavin Foster4, Eduardo Garzanti5 and Sergio Ando5
1 Department of Environmental Science, Lancaster University, Lancashire, UK
2 NERC Isotope Geosciences Laboratory, British Geological Survey, Nottingham, UK
3 Department of Earth Sciences, University College London, University of London, UK
4 Department of Earth Sciences, Wills Memorial Building, University of Bristol, UK
5 Dipartimento di Scienze Geologiche e Geotecnologie, Universita Milano-Bicocca, Milano, ITALY
For correspondence, email:
The Indus Group is a Tertiary aged sequence composed of marine
and terrestrial sedimentary rocks which were deposited in an
evolving late-forearc to intermontane basin setting during the
initial phases of Indian-Asian continental collision (Brookfield
and Andrews-Speed 1984, Van Haver 1984, Searle et al. 1990,
Sinclair and Jaffey 2001, Clift et al. 2002). For this reason, the
Indus Group provides the earliest record of erosion from the
Himalayas. Clift et al. (2002) have constrained the age of collision
by determining the lowermost stratigraphic point in the Indus
Group that contains detritus from both Indian and Asian plates,
and also by identifying where the Asian plate derived Indus Group
unconformably overlies Indian plate margin sediments. The
Chogdo Formation, dated by an overlying limestone at older than
54.9 Ma (O Green, unpublished data cited in Sinclair and Jaffey
2001) is identified by Clift et al. (2001), to be the oldest unit ofthe
Indus Group to contain detritus from both the Indian and Asian
plates, and to stratigraphically overly Lamayuru Group Indian slope
turbidites and Jurutze forearc basin rocks, thereby pinpointing the
timing of continental collision to the Late Paleocene. However,
despite its importance, these previous evaluations of the Indus
Group have been hampered by poor stratigraphic knowledge and
uncertain lateral correlations, largely due to the relatively complex
deformation ofthe rocks and poor biostratigraphic control.
We use a combination of geological mapping,
biostratigraphy, faciesanalysis, petrography, bulkrockgeochemistry,
and isotopic characterisation of single detrital grains to 1) create
an accurate and more widely representative stratigraphy for the
Indus Group, 2) determine the nature of the contacts which
separate the overlying Indus Group from underlying Indian
and Asian Plate formations and 3) determine the provenance of
the Group, in particular the stratigraphic level within the Indus
Group at which both Indian and Asian plate detrital minerals
occur together, in order to constrain the time of collision and
discover which geological terranes where exhumed and actively
eroded during the early stages of the Himalayan orogeny. Our
Initial analyses indicate that the Chogdo Formation may not be as
widely occurring as previous interpretations have led to believe;
partly due to obscured tectonic contacts and problems with lateral
correlations along strike. Therefore certain formations which
are currently identified as belonging to the Chogdo Formation
may well be younger (<48.6 Ma; Wu et al. 2007) Indus Group
formations. Reassessment of constraints to the timing of India-
Asia collision as determined from the Chogdo Formation is
Brookfield ME and CP Andrews-Speed. 1984. Sedimentology,
petrography and tectonic significance ofthe shelf, flysch and molasse
clastic deposits across the Indus suture zone, Ladakh, NW India.
Sedimentary Geology 40: 249—286
Clift PD, N Shimizu, GD Layne and J Blusztajn. 2001. Tracing patterns of
erosion and drainage in the Paleogene Himalaya through ion probe
Pb isotope analysis of detrital K-feldspars in the Indus Molasse,
India. Earth and Planetary Science Letters 188: 475^91
Clift PD, A Carter, M Krol and E Kirby. 2002 Constraints on India-
Eurasia collision in the Arabian sea region taken from the Indus
Group, Ladakh Himalaya, India. In: Clift PD, D Kroon, C Geadicke
and J Craig (eds), The Tectonic and Climatic Evolution ofthe Arabian Sea
Region. Geological Society Special Publication 195: 97-116
Searle MP, KT Pickering and DJW Cooper. 1990. Restoration and
evolution of the intermontane molasse basin, Ladakh Himalaya,
India. Tectonophysics 174: 301—314
Sinclair HD, and N Jaffey. 2001. Sedimentology of the Indus Group,
Ladakh, northern India; implications for the timing ofthe initiation
ofthe palaeo-Indus River. Journal qf the Geological Society qf London
158: 151-162
Van Haver T. 1984. Etude stratigraphiaue, sedimentologiaue et structurale d'un
bassin d'avant arc: Exemple du bassin de Vlndus, Ladakh, Himalaya [Ph.D
dissertation]. Grenoble, France: Universite de Grenoble:204 p
Wu FU, PD Clift and JH Yang. 2007. Zircon Hf isotopic constraints on
the sources ofthe Indus Molasse, Ladakh Himalaya, India. Tectonics
26: TC2014
Structure of the crust and the lithosphere in the Himalaya-Tibet
region and implications on the rheology and eclogitization of
the India plate
Gyorgy Hetenyi1+*, JerOme Vergne1x, John L.
Bollinger3 and Michel Diament4
Nabelek2, Rodolphe Cattin1, Fabrice Brunet1, Laurent
Laboratoire de Geologic, Ecole Normale Superieure, CNRS — UMR 8538, 24 rue Lhomond, 5005 Paris, FRANCE
College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis OR 97331, USA
Laboratoire de Detection et de Geophysique, CLA, BP12, 91680 Bruyeres-le-Chatel, FRANCE
Institut de Physique du Globe de Paris, 4 placeJussieu, 75252 Paris, FRANCE
Present address: Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, Leeds, UK
Present address: Ecole et Observatoire des Sciences de la Terre, Strasbourg, FRANCE
For correspondence, email:
The Himalayas and the Tibetan Plateau are considered as the
classical case of continental collision. The geophysical, geological
and geochemical observations in this region as well as numerical
modelling studies have been interpreted in the frame of different
models of plateau formation, including continental subduction
(Tapponnier et al. 2001, Haines et al. 2003), crustal thickening
(England and Houseman 1986), and underplating (Argand 1924,
Barazangi and Ni 1982, Owens and Zandt 1997). In the meantime,
due to the uneven coverage and resolution of the data over the
plateau, some fundamental questions concerning the evolution
of the region's lithosphere are still pending. What are the main
structural features ofthe collision zone? How do new constraints
on structure influence our understanding of rheology? What are
the physical processes which play a major role in the evolution of
this system?
The "Himalayan-Tibetan Continental Lithosphere in
Mountain Building" (Hi-CLIMB) project provides new data
to bring answers to the questions on structure. This passive
seismological experiment deployed a large number of broadband
stations at 255 sites during three years. More than 150 closely
spaced (4-9 km) stations form the main profile, spanning on 800
km along 85°E, across the Himalayas and the southern half of the
Tibetan Plateau. The remaining sites were deployed more sparsely
and allow to map lateral structural variations. The large amount
of data (1.5 terabyte), the high-frequency receiver functions and
the use of multiply converted waves result in a detailed image of
lithospheric structures at all scales. Two ofthe main results are as
(1) We observe shallow and localized low-velocity layers
in the Tibetan crust. These features, previously referred to as
"bright spots", have a limited size both horizontally (—50 km)
and vertically (—10 km). This, together with estimates of average
crustal VP/VS-ratios between 1.7 and 1.8, does not support the
presence of widespread partial melt. Moreover, the position of
these low-velocity zones is strongly correlated to extensional
grabens, which supports their localized occurrence, and suggests
a rifting mechanism for their presence.
(2) Our images show underthrusting of the Indian lower
crust beneath most of Lhasa block. The high resolution of the
images allow to clearly follow the Moho ofthe India plate: its
geometry descends smoothly beneath the Himalayas, reaching a
maximum depth of—73 km b.s.l. at the Yarlung-Tsangpo suture,
and then continues sub-horizontally for further —200 km to the
North. The underthrusting is identified by the appearance of a
second interface —15 km above the Moho, which is related to the
top ofthe lower crust undergoing eclogite facies transformation
(see below).
The conducted receiver function analyses also allow to:
(3) map faults at shallow (—3-4 km) depth in Nepal;
(4) follow the Main Himalayan Thrust from its shallow
part to its deep and ductile continuation;
(5) trace the main lithospheric boundary between India and
Eurasia at about the centre ofthe plateau (south of and beneath
the Banggong-Nujiang suture);
(6) conclude that the main sutures at the surface have no
pronounced signature at depth;
(7) show that the upper mantle discontinuities at 410 and
670 km do not seem to be affected by the ongoing orogeny
The obtained information on the geometry ofthe structures
are then used to bring answers to the questions on rheology and
major physical processes.
The improved image on the flexural shape beneath the
foreland basin allows to re-assess the rheology ofthe India plate
using thermo-mechanical modelling. This reveals that flexural
and thermal weakening causes decoupling of the lithospheric
layers, which results in a south-to-north decrease ofthe effective
elastic thickness. To explain the support ofthe Tibetan Plateau's
topography as well as regional isostasy in the Himalayas, a strong
upper mantle is required (Hetenyi et al. 2006).
The geometry of underplating is combined with density
models to reproduce observed Bouguer anomaly data. These
models shows that localized densification of the Indian lower
crust is occurs where it reaches its maximal depth. This effect
is associated to eclogitization. Using thermo-kinematic and
petrological models, we investigate the thermal field and pressure-
temperature-density relations assuming different hydration levels,
respectively. The results suggest partial hydration of the Indian
lower crust, and kinetical hindrance of its eclogitization compared
to phase equilibria. This overstepping is explained by the absence
of free water in the system, and subsists until dehydration reactions
occur at higher P-T conditions (Hetenyi et al. 2007).
Argand  E.   1924.   La  tectonique   de   l'Asie.   In:   Congres   Geologique
Internationale, Bruxelles,   Compte rendus de la Xllle session  1:
Barazangi M and J Ni. 1982. Velocities and propagation characteristics of
Pn and Sn beneath the Himalayan Arc and Tibetan plateau: possible
evidence   for   underthrusting  of Indian   continental   lithosphere
beneath Tibet. Geology 10(4): 179-185
England P and G Houseman. 1986. Finite strain calculations of continental
deformation. 2: Comparison "with  the  India-Asia collision  zone.
Journal of Geophysical Research 91(B3): 3664—3676
Haines SS, SL Klemperer, L Brown, GRJingru, J Mechie, R Meissner, A
Ross and WJ Zhao. 2003. INDEPTH III seismic data: from surface
observations to deep crustal processes in Tibet. Tectonics 22(1): 1001
Hetenyi G, R Cattin, J Vergne and JL Nabelek. 2006. The effective elastic
thickness ofthe India Plate from receiver function imaging, gravity
anomalies and thermomechanical modelling. Geophysical Journal
International 167(3): 1106-1118
Hetenyi G, R Cattin, F Brunet, L Bollinger, J Vergne, JL Nabelek and M
Diament. 2007. Density distribution ofthe India plate beneath the
Tibetan Plateau: geophysical and petrological constraints on the
kinetics of lower-crustal eclogitization. Earth and Planetary Science
Letters 264(1-2): 226-244
Owens TJ and G Zandt. 1997. Implications of crustal property variations
for models of Tibetan plateau evolution. Nature 387(6628): 37—43
Tapponnier P, ZQ Xu, F Roger, B Meyer, N Arnaud, G Wittlinger and JS
Yang. 2001. Oblique stepwise rise and growth ofthe Tibet plateau.
Science 294: 671-1677
Present-day E-W extension in the NW Himalaya
(Himachal Pradesh, India)
Esther Hintersberger1*, Rasmus Thiede2, Manfred Strecker1 and Frank Kriiger1
1 Department of Geosciences, University of Potsdam, GERMANY
2 Department of Geology, ETH Zurich, SWITZERLAND
For correspondence, email:
During the evolution of most major orogens, both
contemporaneously developed compressional and extensional
structures have been documented. Thus, localized extension
within an overall compressional setting seems to be a fundamental
process for the evolution of orogens, however, their kinematic
linkage is still debated. Since the Indian-Eurasian collision, the
Himalayan mountain belt has formed as the southern termination
of the Tibetan Pleteau. While at present day, thrusting at lower
elevations within the Lesser Himalaya is observed (Bilham et al.
1997, Lave and Avouac 2000), several generations of extensional
structures have been detected in the high-elevation regions ofthe
Higher Himalaya, both parallel and perpendicular to the strike of
the orogen, which are the following: (1) The Southern Tibetan
Detachment System (STDS), the most prominent example for
orogen-perpendicular extension, was active during the Miocene
(around 25 to 19 Ma, Burchfield et al. 1992) and potentially locally
reactivated during the Quaternary (Hogdes et al. 2001, Hurtado et
al. 2001). (2) Orogen-parallel extension is observed along roughly
N-S striking normal faults and graben systems whose onset is
mainly constraint to 15-12 Ma (e.g., Fort et al. 1982, Burchfield et
al. 1991, Wu et al. 1998, Murphy et al. 2000, Hogdes et al., 2001,
Garzione et al. 2003, Thiede et al. 2006). Earthquake information
(e.g., Pandey et al. 1999) and fault-plane solutions (Harvard catalog,
Molnar and Lyon-Caen 1989) infer that they are recently active. To
explain the kinematic linkage between extensional structures in an
overall compressional settting, several models have been developed,
the most important ones are: (a) radial extension (Molnar and
Lyon-Caen 1989), (b) gravitational collapse (Molnar and Chen
1983, Royden and Burchfield 1987), (c) the partitioning of oblique
convergence (McCaffrey 1996, McCaffrey and Nabelek 1998), and
(d) arc-shaped, convex-southward propagation (Ratschbacher et
al. 1994). Alternatively, local extension due to metamorphic dome
formation has also been invoked (Aoya et al. 2005). However, the
interpolated deformation patterns of these models are not consistent
to focal mechanisms of larger earthquakes (Harvard Catalogs) and
regional GPS measurements (Banerjee and Burgmann 2002) in the
Sutlej-Spiti River Valleys and the Garhwal in the NW Himalaya
(India) .These data sets reveal ongoing E-W extension in this area.
In contrast to model predictions, however, this direction is neither
parallel nor perpendicular to the NW-SE regional shortening
direction. Therefore, currently available models of extensional
faulting within the Himalaya apparently do not reconcile the
observations in this part ofthe mountain range and alternative, less
ambiguous mechanisms have to be involved.
Here we present new geological and geophysical data
sets such as newly calculated earthquake fault-plane solutions,
new structural geological mapping, fault kinematic analysis of
hundreds of brittle faults, and satellite imagery analysis covering
the area between the Tso Morari Lake in the Tibetan Himalaya
in the north and the mountain front in the Garhwal Himalaya in
the south. The data sets that we obtained allow us to get a detailed
overview ofthe extensional deformation history in this area and to
try to reveal the underlying driving mechanism. In the following,
we describe the data sets in detail.
We observed that globally recorded seismicity data is
arranged in a narrow N-S striking swath ranging from the Tso
Morari Lake in the Tibetan Himalaya almost to the mountain front
in the Garhwal Himalaya (NEIC Catalog). Earthquake fault-plane
solutions, however, are only available for the northern part of our
study area extending between the Tso Morari Lake and the Spiti
River Valley. Therefore, we used several medium-size earthquakes
recorded during the last 20 years to determine new earthquake
fault-plane solutions using a moment tensor inversion technique.
All together, we now have an extended and detailed data set available
reaching from the Lesser Himalaya in the south to the suture zone
in the north and are able to provide much more detailed view into
the recent deformation ofthe Himalayan wedge. All the new data
suggest consistently recently ongoing E-W extension.
Furthermore, in the northern part of the study area,
between the Spiti River Valley and the Tso Morari, we found
new undescribed large N-S striking normal faults up to 10 km
length separating basement rocks from sedimentary deposits. By
analyzing high-resolution satellite imagery (LandSat, ASTER,
GoogleEarth) we reveal that normal faults have played an integral
role during the development of local sedimentary basins. In
addition, we have observed structures such as steeply dipping,
mainly N-S striking normal faults with displacements in the
range of mm deforming fluvial fans and lake deposits in the Spiti
River Valley. Inferring the age of these deposits to Quaternary, the
normal faults document E-W extension during this time span.
By compiling earlier published data (Anand and Jain 1987, Singh
and Jain 2006), we were able to extend the record of sedimentary
deposits affected by normal faulting further south into the thrust
belts in the Garhwal Himalaya.
We have mapped extensional structures in the Garhwal
Himalaya and the Sutlej River Valley and compiled them with
structures already shown in geological maps (e.g., Steck et al. 1998,
Neumayer et al. 2004, Thiede et al. 2006). We found large N-S
striking normal faults with gouge zones up to 3 m in width which
are observed mainly in a narrow band between 78° and 78.5° E.
They are generally associated with steep slickensides indicating dip-
slip faulting and E-W extension with limited offset. New-grown
micas on the fault plane and within the fault gouge indicate that
these faults have their origin in the brittle-ductile transition zone.
However, we cannot be absolutely sure whether this limitation
on such a small swath is really related to focused concentration of
deformation or this is only an artifact due the restricted accessibility
in the field area. In addition, small brittle normal fault planes on
outcrop scale with displacements up to several cm cover the whole
region from Tibetan Himalaya down to the mountain front. These
densely spaced, steeply to the W and E dipping structures crosscut
all older structures related to the shortening in the mountain
belt. To analyze fault kinematic data (strike and dip of the fault,
slip direction and sense of slip) for these small fault planes, we
determined approx. 30 pseudo fault-plane solutions using the
program TectonicsFP (Ortner et al. 2002). The results indicate a
regional E-W oriented extension arranged in a diffuse N-S trending
swath, overlaying other deformation patterns, e.g., orogen-parallel
and orogen-perpendicular extension along the lower-elevation
parts ofthe study area. The consistency with fault-plane solutions
derived from seismicity data shows that E-W extension in the area
between the Tso Morari and the Garhwal Himalaya seems to be a
long-lasting and consistent phenomenon.
Combining all these data sets reveals that there is ongoing
extension in the Sutlej-Spiti River Valleys and the Garhwal
Himalaya, which is aligned in an overall N-S striking zone. Our
compilation of geological and geophysical data sets suggest that E-
W extension spreads almost over the entire mountain range from
the Tibetan Himalaya in the north to the thrust belt in the south
and seems to be a long-lasting phenomenon rather than a localized
disturbance in the regional deformation pattern. Crosscutting
relationships indicate that this extensional deformation phase here
is younger than the extensional deformation phases described at the
beginning. Furthermore, this extensional direction is neither parallel
nor perpendicular to the regional shortening direction. Therefore,
models explaining orogen-parallel or orogen-perpendicular
extension are not able to explain the observed extension. We
derive a model that proposes a southward propagation ofthe E-W
extension from the Tibetan Plateau into the Himalayan mountain
range. In this model, the Karakorum fault, a large strike-slip fault
separating the Himalaya and the Tibetan Plateau, would not be
able to accommodate the whole E-W extensional deformation in
the Tibetan Plateau. Therefore, a part of this extension would be
compensated in N-S striking normal faulting in the NW Himalaya,
where our study area is located.
Ananad A and AK Jain. 1987. Earthquakes and deformational structures
(seismites) in     Holocene sediments from the Himalayan-Andaman
Arc, India. Tectonophysics 133: 105-120
Aoya M, S Wallis, K Terada, J Lee, T Kawakami, YWang, and M Heizler.
2005. North-     South extension in the Tibetan crust triggered by
granite emplacement. Geology 33(11): 853-856
Banerjee P and R Biirgmann. 2002. Convergence across the Northwest
Himalaya  from   GPS  Measurements.   Geophysical Research Letters
29(13): doi: 10.1029/2002GL015184.
Bilham R, K Larson, J Freymueller and Project Idylhim Members. 1997.
GPS measurements of present-day convergence across the Nepal
Himalaya. Nature 386: 61- 64
Burchflel BC, Z Chen, LH Royden, Y Liu and C Deng. 1991. Extensional
development of Gabo Valley, Southern Tibet. Tectonophysics 194: 187-193
Burchflel BC, Z Chen, K Hodges, Y Liu, LH Royden, C Deng and J Xu.
1992. The South Tibetan Detachment System, Himalayan Orogen:
Extension contemporaneous "with and parallel to  Shortening in a
Collisional Mountain Belt Geological Society of America Special Paper 269.
FortM, P Freytet and M Colchen. 1982. Structural and Sedimentological
Evolution ofthe Thakkho la-Mustang Graben (Nepal Himalayas).
Zeitschriftfiir Geomorphologie 42: 75-98
Garzione CN, PG DeCelles, D Hodkinson, R Ojha and B Upreti. 2003. E-
W Extension and Miocene Environmental Change in the Southern
Tibetan Plateau: Thakkhola graben, Central Nepal. Geological Society
of America Bulletin 115(1): 3-20
Hogdes KV, Hurtado JM and KXWhipple. 2001. Southward Extrusion ofFibetan
Crust and its effect on Himalayan Tectonics. Tectonics 20(6): 799-809
Hurtado JM, KV Hodges and KX Whipple. 2001. Neotectonics of the
Thakkhola Graben and implications for Recent activity on the South
Tibetan Fault System in the central Nepal Himalaya. Geological
Society of America Bulletin 113(2): 222-240
Lave J and JP Avouac. 2000. Active folding of fluvial terraces across the
Siwalik Hills, Himalayas of central Nepal. Journal of Geophysical
Research 105: 5735-5770
McCaffrey R. 1996. Estimates of modern arc-parallel strain rates in fore-
arcs. Geology      24(1): 27-30
McCaffrey R and J. Nabelek. 1998. Role of oblique convergence in the
active deformation of the Himalayas and Southern Tibet Plateau.
Geology 26: 691-694
Molnar P and WP Chen. 1983. Focal depths and fault-plane solutions of earthquakes
under the Tibetan plateau Journal of Geophysical Research 88:1180-1196
Molnar P and H Lyon-Caen. 1989. Fault-plane solutions of earthquakes
and active tectonics ofthe Tibetan Plateau and its margins. Geophysical
Journal International 99: 123- 153
Murphy M, A Yin, P Kapp, TM Harrison, D Lin and G Jinghui. 2000.
Southward Propagation ofthe Karakoram Fault System, Southwest
Tibet: Timing and Magnitude of Slip. Geology 28(5): 451-454
Neumayer J, G Wiesmayr, C Janda, B Grasemann and E Draganits. 2004.
Eohimalayan fold and thrust belt in the NW-Himalaya (Lingti-Pin
Valleys): Shortening and depth to detachment calculation. Austrian
Journal of Earth Sciences 95/96: 28-36
Ortner H, F Reiter and P Acs. 2002. Easy handling of tectonic data: the
programs TectonicVB for Mac and TectonicsFP for Windows.
Computers and Geosciences 28: 1193-1200
Pandey MR, RP Tandukar, JP Avouac, J Vergne and Th Heritier. 1999.
Seismotectonics of the Nepal Himalaya from a local seismic
network. Journal of Asian Earth Sciences 17(5-6): 703-712
Ratschbacher L, W Frisch, GH Liu and CS Chen. 1994. Distributed deformation
in Southern and Western Tibet during and after the India-Asia Collision.
Journal of Geophysical Research (Solid Earh) 99(B10): 19917-19945
Royden L and BC Burchfield. 1987. Thin-skinned N-S extension "within
the convergent Himalayan Region: Gravitational collapse of a
Miocene topographic front. In: Continental Extensional Tectonics,
Blackwell Scientfie Publications: 611-619
Singh S and AK Jain. 2006. Liquefaction and fluidization of lacustrine
deposits from Lahaul- Spiti and Ladakh Himalaya: Geological
evidences of paleoseismicity along active fault zone. Sedimentary
Geology 196(1-4): 47-57
Steck A, JL Epard, JC Vannay, J Hunziker, M Girard, A Morard and M
Robyr. 1998. Geological transect across the Tso Morari and Spiti
areas: the nappe structures ofthe Tethys Himalaya. Eclogae geologicae
Helvetiae 91: 103-122
Thiede R, J Arrowsmith, B Bookhagen, M McWilliams, E Sobel and M Strecker.
2006. Dome formation and extension in the Tethyan Himalaya, Leo Pargil,
northwest India. BuUetin of Geological Society of America 118: 635-650
WuC,KNelson,GWortman,S Samson,YYue,J Li,WKiddandMEdwards.
1998. Yadong Cross Structure and South Tibetan Detachment in the
East Central Himalaya (89° - 90° E). Tectonics 17: 28-45
Zhang P, Z Shen, M Wang, W Gan, R Biirgmann, P Molnar, Q Wang,
Z Niu,J Sun,JWu, S Hanrong and Y Xinzhao. 2004. Continuous
deformation ofthe Tibetan Plateau from Global Positioning System
data. Geology 32(9): 809-812
3-D Velocity Structure of the Crust and upper Mantle
in Tibet and its Geodynamic Effect
Zheng Hongwei1*, He Rizheng2, Zhao Dapeng\Li Tingdong2and Rui Gao2
1 Department of Geophysics, Peking University, Beijing 100871, CHINA
2 Institute of Geology, Chinese Academy of Geological Science, Beijing 100037, CHINA
3 Research Center for Prediction of Earthquake & Volcanic Eruptions, Graduate School of Science, Tohoku University, Sendai 980-8578, JAPAN
For correspondence, email:
The crust and upper mantle structure under Tibet is the direct
result of the India plate subducting and colliding with the
Eurasian plate. 3-D seismic velocity structure of the crust and
upper mantle under Tibet was determined by using the Tomo3D
tomography program developed by Prof. Dapeng Zhao (Zhao et
al. 1992, 1994). In the tomographic inversion we used 139,021 P-
wave arrival times from 9649 teleseismic events recorded by 305
seismic stations. The major results of this study (Zheng 2006) are
summarized as follows:
1) The Tibetan crust velocity structure is generally consistent
with the surface tectonic features which are oriented nearly east-
west. But the main trend of the velocity anomalies in the upper
mantle is generally oriented in the north-south direction. The
location of the NNE strike low-velocity zone is consistent with
the N-S strike negative aeromagnetic data.
2) Low-velocity anomalies in the crust are clearly visible
under the Himalaya Mountain.
3) Our tomographic images show that the Indian lithospheric
mantle subducting angles are different under different areas, but
their front locations are all beneath the Qiangtang terrain. The
tomographic images (Figure 1) along 88°E show that the Indian
lithospheric mantle is underthrusting northwards with a dip angle
of about 22° beneath the center of Qiangtang terrane at about 34°N
latitude, and its frontier has reached to the deep part ofthe upper
mantle. The tomographic images along North-East profile show
that the Indian mantle has nearly horizontally underthrusted under
the Tibet from Ganges plain to 33°N. Then, the Indian mantle
broke off down to the asthenosphere and caused the asthenophere
upwelling. The top shows the surface topography. The tectonic
lines are the same as those in Figure 1. The middle panel shows
tomography. White circles show local earthquake hypocenters.
The dash lines indicate the estimated upper and lower boundaries
ofthe subducting Indian lithospheric mantle. The low-left panel
shows the P-wave velocity perturbation scale. The low-right panel
shows the location of profile AB along 88° E.
4) There is a huge low-velocity body (Wittlinger et al.,1996)
which looks like a mantle plume beneath the Qiangtang terrain.
Such a prominent low-velocity body is impossible to be the partial
melting products. It is speculated to be either the subducted
delamination of the Indian lithospheric mantle according to its
location and extending depth with Qaidam block holding back
the thermal disturbance in the area, and so resulting in higher
temperature which begets fallingvelocity or be the mantle upwelling
materials along the surface of Indian lithospheric mantle.
'■•'*— "^
>r        W
AY,/ (*>
-.1    -2
P-wavc vt
•1    1
2    .1
I -•'!■
36* ifh
.-■*    -I"  V      LTV' I..
FIGURE 1. P-wave tomographic image of the subducting Indian
lithospheric mantle along profile AB.
This workwas supported by grants from National Natural Science
Foundations of China (No. 40404011-40774051), 2007 Year ofthe
Basic outlay of scientific research work from Ministry of Science
and Technology ofthe People's Republic of China, International
Cooperative Project from Ministry of Science and Technology
of the People's Republic of China-No.2006DFA21340, Open
Fund (No. GDL0602) of Geo-detection Laboratory Ministry of
Education of China, China University of Geosciences.
Zhao DP, A Hasegawa and S Horiuchi. 1992. Tomographic Imaging of P
and S wave velocity structure beneath Northeastern Japan. Journal qf
Geophysical Research 97(B13): 19909-19928
Zhao DP; A Hasegawa and H Kanamori. 1994. Deep structure of Japan
subduction zone as derived from local, regional, and teleseismic
events. Journal qf Geophysical Research 99 (Bll): 2313-2329.
Wittlinger G, F Masson and G Poupinet. 1996. Seismic tomography of
northern Tibet and Kunlun; evidence for crustal blocks and mantle
velocity contrasts. Earth and Planetary Science Letters 139: 263-279.
Zheng HW. 2006. 3-D velocity structure qf the crust and upper mantle in Tibet
and its geodynamic effect. Ph. D. thesis in Chinese, Beijing: Chinese
Academy Geological Sciences.
Electrical Structure of Garhwal Himalayan region, India, inferred
from Magnetotelluric
M Israil*, DK Tyagi, PK Gupta and Sri Niwas
Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee- 247667, INDIA
*For correspondence, email:
Magnetotelluric investigations have beencarried out in the Garhwal
Himalayan corridor to delineate electrical structure of the crust
along a profile extending from Indo-Gangetic Plane to Higher
Himalayan region in Uttarakhand, India. The profile passing
through major Himalayan thrusts: Himalayan Frontal Thrust
(HFF), Main Boundary Thrust (MBT) and Main Central Thrust
(MCT), and is nearly perpendicular to the regional geological
strike. These Himalayan thrusts are broadly parallel to each other,
steeper near surface and become shallow with the depth until they
merge with the detachment surface. The main tectonic elements
of Garhwal Himalayan region have an average strike of NW-SE
(Kbattri 1992). Magneto-variation (MV) studies (Aroraetal 1982),
were carried out over a rectangular array of 24 stations in the
Siwalik Himalayan region, indicated the presence of a conductive
anomaly, which they interpreted as an extension of the Aravallis
and referred to as Trans Himalayan conductor. Subsequently,
MT investigations were carried out by Gupta et al (1994) in the
Siwalik region over 150 km long Mohand - Ramnagar profile to
determine the thickness of Siwalik sediments. They recorded MT
data in the frequency range 0.01-100 Hz using short period MT
system and estimated geoelectric strike of N 800 W on the basis of
simple rotation of impedance tensor
We have conducted a Broadband MT survey in the Garhwal
Himalayan corridor during 2004-06, data were recorded in the
frequency band 1000 - .001 Hz. The locations ofthe 44 stations
are shown in figure 1. The paper presents the electrical structure of
the crust along the profile inferred from the 2D smooth inversion
of MT data.
The recorded time domain data were transformed to the
frequency domain impedance tensor and subsequently used
to determine intrinsic dimensionality and directionality of the
geological structure with respect to the geographical coordinate
system. We have used Groom and Bailey (1989) tensor
decomposition as implemented by McNeice and Jones, 2001
in strike code provided by Alan G. Jones. The decomposition
analysis suggests an average strike direction of N 700 W for entire
profile. The measured responses are rotated in the estimated strike
direction to obtain TE and TM response for inversion.
Smooth inversion of only TE mode, TM mode and joint
TE and TM responses have been done so as the final model
incorporates the important features of both TE and TM responses.
The main results are given in figure 2 which presents (i) 2D
70<V0"K    WW'S    90WE       .
11 FT
WjC*ict             r\
7        ^bttr    MBT        _/~"H
Mil | x^-^fL-J    /
RamnngarS.         S     A, r*
INDIA V^1    y
\      J        Legend       \
■ Sin ill ami             \
■■ Til rust
70 0"0"E    80 0"0"E    WOVE
•   i
7B°00"E 7BD30,0,,E 79°0'0"E
-*.   * 3 0«BsLZ]8EZ)'Q8CZI«nitlEIZ)" d'1
FIGURE 1. Location the
study area (geological
map compiled from Virdi,
1988, Sorkhabi et al. 1999,
Kumar et al. 2002). 1- MT
Sites; 2- Thrust; 3- Cities;
4- Dehra Dun Reentrant;
5- Blaini-lnfrakrol-Krol;
6- DaMTha; 7- Garwhal
Nappe; 8- Jaunsar-
Simla (Undifferentiated);
9- Sunder Nagar-
Berinag Groups;
10- Undifferentiated
Metamorphics; 11-
Undifferentiated Tertiaries;
12- Piedmont zone. MT
data collected in the
Indo-Gangetic Plains,
Siwalik, Lesser and Higher
Himalayan region in
Garhwal Himalaya.
Q m
20    40    60    80   100   120   140   160
Distance (km)
FIGURE 2. 2D resistivity models of Roorkee-Gangotri profile in Garhwal Himalaya corridor with (i) elevation profile on the top, (ii) 2D smooth geoelectric model
obtained from the joint inversion of TE, TM responses (iii) the local seismicity (hypocenters) locations plotted as circles in the model, (iv) locations of 27 MT
sites indicated by vertical bar, (v) the major Himalayan thrusts (HFT, MBT, MCT).
smooth geoelectric model obtained from the joint inversion of TE
and TM responses (ii) the local seismicity (hypocenters) plotted as
circle in the electrical model, (iii) elevation profile, (iv) locations
of 27 MT sites, used for 2D inversion, indicated by vertical bar,
(v) the major Himalayan thrusts.
The electrical model shows a shallow conductive structure
(<50Q/n) mainly confined in the southern part ofthe profile
located in Indo-Gangetic Plane (IGP) and Lesser Himalayan
(LH) region. The conductive structure is extended to a depth of
6 km. Geologically, the zone corresponds to the loose sediments,
mollasse ofthe Miocene and younger age, transported from Higher
Himalayan region. Resistive structure (1000 (lm) underneath
the near surface conductive sediments is interpreted as electrical
image ofthe Indian crust. Low resistivity (<5flm) zone present
below MCT. This zone is a typical example of low resistivity
zone in mid crustal region invariably observed in Himalayan
region. This zone also appears to coincide with the location of
hypocenter of local earthquake. The conducting zone appears to
be related with the strain accumulation zone in Himalayan region
for future earthquakes. This conductive zone is analogous to the
similar conductive zone reported in the central Nepal - Himalaya
profile (Lemonnier et al. 1999). The MCT zone falls in high heat
flow area, majority of hot spring are concentrated around this
zone, might be associated to this low resistivity zone. Resistive
feature underlying the low resistivity zone in mid crustal depth is
interpreted as the electrical image of north dipping Indian Plate.
Arora B R, F E M Lilley, M N Sloane, B P Singh, B J Srivastava and S N. Prasad
1982. Geomagnetic induction and conductive structures in northwest
India; Geophysical Journal qf Royal Astronomical Society 69: 459-475
Groom RW and RC Bailey. 1989. Decomposition of Magnetotelluric
impedance tensors in the presence of local three-dimensional
galvanic distortion -Journal qf Geophysical Research 94: 1913-1925
Gupta G, SG Gokarn and BP Singh 1994. Thickness of the Siwalik
Sediments in the Mohand-Ramnagar region using magnetotelluric
studies; Physics ofthe Earth and Planetary Interiors 83: 217-224
Khattri K N. 1992. Local seismic investigations in the Garhwal-Kumaun
Himalaya. Mem. Geol. Soc. India, 23, pp. 45-66
Kumar R, S K Ghosh, S J Sangode and V C Thakur. 2002. Manifestation
of Intra — Foreland thrusting in the Neogene Himalaya foreland
basin fi\\;Journal qf Geological Society qf India 59: 547-560
Lemonnier C, Marquis G, Perrier F, AvouacJ P, Chitrakar G, Kafle B, Sapkota
S, Gautam U, Tiwari D and Bano M 1999 Electrical structure ofthe
Himalaya of central Nepal: high conductivity around the mid-crustal
ramp along the MHT; Geophysical Research Letters 26: 3261-3264
McNeice G W and A G Jones. 2001. Multisite, multifrequency tenser
decomposition of magnetotelluric data. Geophysics 66: 158-173
Sorkhabi R B, E Stump, K Foland and A K Jain. 1999. Tectonic and
cooling history ofthe Garhwal Higher Himalaya (Bhagirathi Valley):
constraints from thermochronological data; Gondwana Research
Group Memoir 6: 217-235
Virdi N S. 1988. Pre — Tertiary geotectonic events in the Himalaya; Z. geol.
Wiss, Berlin 16: 571-585
Heterogeneous Himalayan crust using shear wave attenuation in
the Pithoragarh region of Kumaon
A Joshi1*, M Mohanty2, AR Bansal3, VP Dimri3 and RK Chadha3
1 Indian Institute of Technology, Roorkee, Roorkee 247 667, Uttarakhand, INDIA
2 Department of Science and Technology, Government of India, New Delhi, INDIA
3 National Geophysical Research Institute, Uppal Road, Hyderabad, INDIA
For correspondence, email:
Pithoragarh district of Uttarakhand Himalaya, which lies in the
border region of India and Nepal, falls in the seismically active
zone of the seismic zoning map of India. Under a major DST
sponsored project a network of eight strong motion stations has
been installed in this region since March 2006. This paper presents
a method of finding shear wave quality factor 'Qp(f)' from strong
motion data recorded by this network. The method used for this
study is based on modified technique, given by Joshi (2006).
Data of local noise recorded at various stations have been utilized
for the purpose of site survey and average value at each station
is used for correcting the accelerograms for site amplifications.
Based on availability of data, hypocentral parameters and clear S
phases from horizontal component of 37 strong motion records
from six stations have been used for in this work. The output
of this inversion gives Qp (f) relation and corner frequencies of
earthquake at different stations. Low value of coefficient (< 200)
and high frequency dependence (>.8) in the Qp(f) relationships
obtained at different stations suggest that the region is seismically
and tectonically active and is characterized by large number of
heterogeneities. Obtained Qp (f) are used to compute source
spectrum of S wave from the accelerogram and are compared with
theoretical Brune's source spectrum of corner frequency obtained
from inversion. Comparison of source spectrum obtained from
the corrected accelerograms with the theoretical Brune spectrum
shows that this technique has potential to give reliable Qp(f) and
source parameters ofthe studied earthquakes using records from
single station. Using the obtained Qp(f) values at different stations
at different frequencies an average Qp(f) relation of 50F °8 has been
obtained for Pithoragarh region of Kumaon Himalaya. Obtained
relations not only explain the complexities and heterogeneities of
earth crust in Himalaya, it can be used as an input for simulation
of strong ground motion in this region.
Lithostratigraphy of the Naga-Manipur Hills (Indo-Burma Range)
Ophiolite Belt from Ukhrul District, Manipur, India
A Joshi1* and KT Vidyadharan2
1 Geological Survey of India, NH-5P, NIT Faridabad-121001, Haryana, INDIA
2 310, Block "B", Maharaja Residency, Balmatta Road, Hampankatta, Mangalore-575001, INDIA
For correspondence, email:
Two late Mesozoic ophiolite belts occur along the eastern margin
ofthe Indian plate. The eastern or Sumatra belt is poorly exposed
whereas the western or the Indo-Burma Range (Naga-Manipur
Hills) ophiolite belt is well preserved particularly in the Myanmar
bordering terrain of Manipur. The NE-SW trending western belt
extends in the states of Nagaland and Manipur and is about 200 km
wide in north before splitting into thin slices towards south. This
study delineates the lithostratigraphic ensemble of the ophiolite
belt in the northernmost part of Manipur in Ukhrul district while
discussing its petrology and tectonic implications.
Three major lithopackages have been mapped in this
area. From west to east these comprise a thick, folded pile of
Paleogene sediments, which are tectonically juxtaposed with
an ophiolite suite followed by feebly metamorphosed pelagic
cover sediments (Figure 1). The sedimentary rocks in the west
include shale-siltstone rhythmites with minor sandstone (Disang
Group) representing distal shelf facies that grades upward to a
conglomerate-grit-sandstone-coal streaks-bearing shallow marine
to fluviatile sequence (Barail Group). The upper part of Disang
Group depicts an olistrostromal zone with olistoliths of mainly
fossiliferous limestone, varying in dimensions from a few meters
to more than 0.5 km. The foraminiferal assemblage of limestone
suggests a wide, upper Cretaceous (Maastrichtian) to Oligocene
age range supporting their exotic nature in the melange zone
(Vidyadharan and Joshi 1984, Vidyadharan et al. 1989).
The ophiolite suite exhibits a dismembered sequence with
alternating slices of variable dimensions including ultramafics,
mafic differentiates and volcanics. Harzburgite is the dominant
lithology of the ultramafic clan followed by volumetrically
insignificant dunite, and pyroxenite. All ultramafic variants depict
various stages of serpentinization with development of magnetite,
talc and a typical ribbon and mesh texture. Chromite occurs as
massive chromitite bands (metallurgical to refractory grade),
nodular pods and disseminations. A significant feature of the
peridotite associationis the occurrence of thin, discontinuous lenses
of coarse, dark coloured garnet bearing ultramafic segregations,
with diopside, grossular-almandine garnet, magnesio-hastingsite
and rutile as the other major minerals, in the northeastern part of
this area. These rocks show strong enrichment of CaO and severe
depletion of MgO from the host peridotites besides higher values
for AL03, Ti02, Na20, KjO and resemble the metarodingite
formed by extensive Ca metasomatism during serpentinization
of the host rocks followed by high pressure recrystallization
(Evans et al. 1979). Mafic differentiates are represented mainly
by gabbros and plagiogranite. Prolonged rodingisitization of these
rocks is displayed by the presence of chlorite, epidote, zoisite
and calcite. Massive to amygdaloidal, low MgO basalts showing
intersertal and glomeroporphytitic textures represent the volcanic
rocks besides a few occurrences of volcanic agglomerates.
The easternmost unit of this area exposes oceanic pelagic
cover sediments comprising mainly phyllite, quartzite, bedded
radiolarian chert and limestone. These have undergone low
grade metamorphism and also incorporate tectonic slices of the
ophiolite suite.
Olistrostromal Upper
Disang Formation
Lower Disang Formation
Barail Group
Disang Group
| X45 I Strike and Dip of Foliation
I ^40 I Strike and Dip of Bedding
P^l Fault
Phyllite, Bedded chert, ] Oceanic Pelagic Sediments i ^.i Antiform
Limestone I -^   I
I iLx*| Synfomn
1^1   Spot Height (M)
(mainly Basalt]
|L3III|   Metarodingite
(mainly Harzburgite)
[■■■]   Ultramafics
Ophiolite Suite
FIGURE  1.  Geological  map of the area around  Ukhrul,  Naga-
Manipur Hills, Manipur (Modified after Vidyadharan et al. 1989).
Absence of dyke swarms and the chemistry ofthe volcanic
rocks indicates an ocean island or seamount type of setting for this
belt, whereas presence of metarodingite and glaucophane-bearing
schists further north in Nagaland suggests a complex subduction
process. Linear zone of negative gravity anomalies over the
western ophiolite belt has been explained by shallow nature of
these nappes, while linear gravity high over the eastern belt makes
it the site of the of the root zone of the eastern suture of Indian
plate (Acharyya et al. 1990, Acharyya 2007, Sengupta, 1990).
Acharyya SK, KKRay and DKRoy 1990. Tectono stratigraphy and emplacement
history of the ophiolite assemblage from the Naga Hills and Andaman
Island Arc, India Journal ofthe Geological Society qf India 33: 4-18
Acharyya   SK.   2007.   Collisional   emplacement  history  of the   Naga-
Andaman ophiolites and the position of the eastern Indian suture.
Journal ofthe Asian Earth Sciences 29: 229-242
Evans BW, V TrommsdorfFand W Richter. 1979. Petrology of an eclogite-
metarodingite  suite  at Cima  di  Gagnone,   Ticino,   Switzerland.
American Mineralogist 64:15-31
Vidyadharan KT and AJoshi. 1984. Unpublished Geological Survey qf India
Report. 42p
Vidyadharan KT, AJoshi, S Ghosh, MP Gaur and R Shukla. 1989. Manipur
ophiolites: Its geology, tectonic setting and metallogeny In: Ghose NC
(ed.) Phanerozoic ophiolites qf India. Patna: Sumna Publication. pl97-212
Pre-Himalayan tectonometamorphic signatures from
the Kumaun Himalaya
Mallickarjun Joshi
Department of Geology, Banaras Hindu University-221005, INDIA
E-mail: m
It is necessary to resolve the relative contributions of the
Himalayan and Pre-Himalayan tectonometamorphic signatures
for refinement of the existing models for the evolution of the
Himalaya. An attempt has been made for the Lesser Himalayan
metamorphics exposed in the Kumaun Himalaya to identify the
Pre-Himalayan deformations and metamorphisms. The isoclinal
Fl folds and the tight to isoclinal F2 folds in the Lesser Himalayan
metamorphics ofthe Kumaun Himalaya can be safely inferred to
be distinctly Pre-Himalayan as the 560±20 Ma old Champawat
Granitoides and its equivalent Almora Granite (Rb-Sr dating,
Trivedi et al. 1984) intrude the F2 folds.
The metamorphics comprising the Almora Group of rocks
have been subjected to green schist facies to upper amphibolite
facies metamorphism (Ml) reaching temperatures of > 700°C
and pressures of 7.4±0.5 kbar (Joshi and Tiwari 2004). Four
metamorphic zones, viz. chlorite-biotite, garnet- biotite, kyanite -
biotite and sillimanite K-feldspar zone have been identified in the
Almora Group of rocks. These metamorphics can be demonstrated
in the field to gradually increase in metamorphic grade from the
chlorite zone ofthe green schist facies to the K-feldspar sillimanite
zone ofthe upper amphibolite facies comprising gneisses through
a migmatite zone in the Champawat, Almora, Dwarahat and
Dudatoli regions. Thus, these sillimanite K-feldspar gneisses are
evidently a product of the culmination of metamorphism and
have been dated at 1860±50 Ma by Trivedi et al. (1984) by Rb-Sr
dating. The metamorphic sequence both in the southern flank,
viz. Champawat and Almora areas and in the northern flank, viz.
south of Someshwar and Dwarahat areas have been affected by Fl
and F2 folding which has led to a repetition of isograd surfaces
across north - south transects.
This folded sequence in the southern flank of the Almora
Nappe has been intruded by 560 ±20 Ma granitoids. This hot
intrusion of granitoids has left a well preserved contact aureole
in the Champawat area (Joshi et al. 1994) and the Almora area
(Joshi and Tiwari 2007). The well preserved randomly oriented
chloritoids and andalusites overprinting the regional schistosity
(S2) clearly show that the regional metamorphism is older
than the 560±20 Ma contact metamorphism (M2). This fact
is further corroborated by the age of the gneisses around 1860
Ma, which have formed as an end product at the culmination of
regional metamorphism. Thus it is highly likely that the age ofthe
dominant regional metamorphism is also close to 1860 Ma.
The two stage garnet growth in these metamorphics is
suggestive of a polymetamorphic history of the area and it is
likely that the outer rim ofthe garnet formed during the Tertiary
(Himalayan) metamorphism (M3). It can be safely inferred that
the dominant regional metamorphism in the Almora Group of
rocks is of Pre- Himalayan (Pre- Cambrian) age and the Himalayan
metamorphic imprint in the Almora Nappe was of lower grade
and in all likelihood did not exceed the garnet grade.
Joshi M, BN Singh and OP Goel. 1994. Metamorphic conditions from the
aureole rock from the Dhunaghat area, Kumaun Lesser Himalaya.
Current Science 67(3): 185-88
Joshi M and AN Tiwari. 2004. Quartz c-axes and metastable phases in
the metamorphic rocks of the Almora Nappe: evidence of Pre-
Himalayan signatures. Current Science 87(7): 995-999
Joshi M and AN Tiwari. 2007. Folded metamorphic reaction isograds in
the Almora Nappe, Kumaun Lesser Himalaya: Field evidence and
tectonic implications.N. Jb. Geol. Palaont. Abh. 244: 215-225.
Trivedi JR, K Gopalan and KS Valdiya. 1984. Rb-Sr ages of granites within
Lesser Himalayan Nappes, Kumaun Himalaya, Journal ofthe Geological
Society qf India 25: 641-654
Northeast Tibetan Crustal Structure from INDEPTH IV Controlled-
Source Seismic Data
Marianne Karplus1, Simon Klemperer1,*, Zhao Wenjin2, Wu Zhenhan2, Shi Danian2, Su Heping2,
Larry Brown3, Chen Chen3, Jim Mechie4, Rainer Kind4, Fred Tilmann5, Yizhaq Makovsky6, Rolf
Meissner7 and INDEPTH Team
1 Department of Geophysics, Stanford University, CA 94305-2215, USA
2 Chinese Academy of Geological Sciences (CAGS), Beijing 100037, CHINA
3 Department of Earth and Atmospheric Sciences, Cornell University, NY 14853, USA
4 GeoForschungsZentrum (GFZ), Telegrafenberg, 14473 Potsdam, GERMANY
5 Department of Earth Sciences, Cambridge University, Cambridge CB3 OEZ, ENGLAND
6 School of Marine Sciences, University of Haifa, Haifa 31905, ISRAEL
7 Institute of Geosciences, Christian Albrechts University, Kiel, GERMANY
For correspondence, email:
Since 1992, project INDEPTH (International Deep Profiling of
Tibet and the Himalaya) geoscientists from Chinese, American,
British, German, and Canadian institutions have collaborated
to collect high-quality seismic, MT, and geologic data along a
roughly north-south transect from the Himalaya to northern
Tibet. The current field effort from 2007-2009, INDEPTH IV,
targets the NE margin ofthe plateau, with goals of testing models
of subduction (relict and current) near the Kunlun and Jinsha
sutures and probing the deep geometry of key features such as
the Kunlun and Altyn Tagh Faults. Our new datasets are intended
to shed light on the possible existence of a lower-crustal flow
channel beneath northern Tibet, analogous to the weak (and
flowing?) lower crust evidenced by INDEPTH observations of
mid-crustal low seismic velocities, seismic bright spots and high
electrical conductivities (Nelson et al. 1996) in southern Tibet.
INDEPTH IV further aims to evaluate the possible subduction of
Asian crust from the north beneath the Kunlun suture (Kind et al.
2002) and to probe whether the Kunlun and Jinsha sutures act as
crustal-scale faults.
Active seismic experiment, summer 2007
The INDEPTH IV active-source seismic experiment spans
270 km from the Qaidam Basin (Figure 1), across the North
Kunlun Thrusts, the Kunlun Mountains, the North and South
Kunlun Faults onto the Tibetan Plateau. The recording spread
consists of four elements: 1) a wide-angle deployment of 295
IRIS PASSCAL Texan seismometers at 650 m spacing, 2) a near-
vertical deployment of 655 Texans at 100 m spacing, 3) an adjacent
deployment of a 1000-channel Sercel cabled spread with 50 m
geophone spacing, and 4) an overlapping three-component array
(48 Geophysical Instrument Pool Potsdam and SEIS-UK short-
period and broadband instruments at 5-6 km spacing). Sources
included five large shots (each 1000-2000 kg explosives) roughly
evenly spaced along the profile, augmented by —110 small shots
(each —60-80 kg) nominally spaced at 1 km in the central part of
the profile.
We are using two-dimensional ray-tracing to model basin
and basement refractions, and lower-crustal and Moho reflections
to determine the crustal velocity structure. The preliminary model
compiled incorporates a southward-thinning low-velocity Qaidam
84' 88' 62' 96' I00- 104-
Qiangtang Terrane
FIGURE 1. (a) Locations of INDEPTH I-IV transects spanning Tibetan
Plateau, (b) Topographic map of northeast Tibet showing the locations
of INDEPTH IV Texan and Sercel (continuous line of black dots)
receivers, three-component short-period (diamonds) and broadband
instruments (triangles), and small (circles) and large shots (stars).
basin, unusually low crustal velocities of 6 km/s compatible with
older controlled-source observations further south and east in
Tibet (e.g. Klemperer 2006), lower-crustal reflectors beneath the
Plateau, and Moho depths of 50-55 km beneath the Qaidam Basin
in the north. Near-vertical data from the small shots contains
unusually strong s-wave arrivals as well as fault-plane reflections:
reflectors at about 6 seconds beneath the Kunlun front range
that we interpret as decollement horizons of the North Kunlun
Passive seismic experiment, 2007-2009
The passive seismic effort is cored by dense, linear broadband
seismic arrays (59 stations at —5 km spacing) deployed across
the Jinsha and Kunlun sutures. Depth-domain teleseismic
receiver-function processing from these arrays should allow
detailed mapping of the Moho, the base of the lithosphere, and
possibly subducted elements of Asia. This high-resolution passive
profiling is complemented by a large areal array simultaneously
deployed across NE Tibet by the ASCENT (Array Seismology
Collaborative Experiments in Northeastern Tibet) consortium.
Data from these passive deployments is scheduled for retrieval in
summer 2008.
Other studies: Geology, thermochronology & magnetotellurics
INDEPTH Sino-US field parties will investigate shortening and
strike-slip deformation near the seismic transects in 2008, using
thermochronologic and stratigraphic studies to investigate timing
of shortening and total offset on different strands of the Kunlun
fault. MT surveys are planned for 2009 across the Kunlun and
Altyn Tagh Faults. These new data will augment the INDEPTH
III profile, which showed that the middle crust is conductive as far
north as the Kunlun Fault, although with less extreme conductivity
values than in southern Tibet (Wei et al. 2001).
Kind R and 10 others. 2002. Seismic images of crust and upper mantle
beneath Tibet: Evidence for Eurasian plate subduction. Science 298:
Klemperer SL. 2006. Crustal flow in Tibet: geophysical evidence for the
physical state of Tibetan lithosphere, and inferred patterns of active
flow. In: RD Law, MP Searle and L Godin, eds., Channel flow, ductile
extrusion and exhumation in continental collision zones, Geological Society
London Special Publication 268: 39-70
Nelson KD and 28 others. 1996. Partially molten middle crust beneath
southern Tibet; synthesis of Project INDEPTH results. Science 274:
Wei W and 14 others. 2001. Widespread fluids in the Tibetan crust. Science
292: 716-718
Geochronologic, structural and metamorphic constraints on the
evolution of the South Tibetan detachment system,
Bhutan Himalaya
Dawn A Kellett1*, Djordje Grujic1, Isabelle Coutand2 and Clare Warren13
1 Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, CANADA
2 Universite des Sciences et Technologies de Lille 1, UFR Sciences Terre (SN5), UMR 8157 du C.N.R.S., 59655 Villeneuve d'Acq Cedex, FRANCE
3 Department of Earth and Environmental Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, ENGLAND
For correspondence, email:
Geodynamic models of collisional orogenesis provide predictions
about the provenance and pressure-temperature-time-deformation
(PTtD) history of material within exposed crustal-scale structures.
Focused field studies across relevant natural analogues provide
the requisite data against which these models must be tested.
Here we present structural, geochronologic, thermochronologic,
thermometric and thermo-barometric data from transects across the
South Tibetan detachment system (STDS) in Bhutan (Figure 1) and
compare them to model predictions for the equivalent structures in
numerical geodynamic models (e.g., Jamieson et al. 2006).
The STDS in Bhutan occurs as two discrete detachments
(Hollister and Grujic 2006) similar to the STDS in eastern
Nepal (Searle et al. 2003). The upper detachment appears to be a
brittle-ductile normal fault, which juxtaposes the poly-deformed
Tethyan sediments
*-       upper 5TD
Chekha Formation
*-       lower STD
Greater Himalayan Sequence
*-       upper MCT
Jaishidanda Formation
*-       lower MCT
Lesser Himalayan Sequence
\f Kanfcarpv nzum (7500 m) \
Jt -'
FIGURE 1. Geological map of Bhutan, with field areas enclosed in boxes. K, klippen of Chekha Formation; STDu, upper South
Tibetan detachment; STDI, lower South Tibetan detachment; MCT, Main Central thrust; MBT, Main Boundary thrust; MFT, Main
Frontal thrust. From Hollister and Grujic 2006 and unpublished data.
metasedimentary Chekha Group against unmetamorphosed
Tethyan sedimentary rocks. The timing of motion along the upper
detachment has been constrained to < 12-11 Ma in northern
Bhutan by U-Pb zircon dating of cross-cutting leucogranites
(Edwards and Harrison 1997, Wu et al. 1998).
The lower detachment is a ductile, top-to-the-north shear
zone separating high-grade metamorphic rocks of the Greater
Himalayan sequence (GHS) in the footwall from the Chekha
Group in the hangingwall. It is characterized by pervasive intrusion
of multi-generational Tertiary leucogranite dikes and sills. These
granite bodies have been variably boudinaged and folded by the
detachment. SHRIMP-RG U-Pb dating combined with trace
element geochemical analysis of concentrically-zoned magmatic
zircon rims indicates pre- to syn-deformational emplacement
and crystallization of the leucogranite dikes into Chekha Group
rocks during —23-16 Ma, reflecting ductile motion along the
lower South Tibetan detachment since at least 16 Ma. Porous,
inclusion-rich, U-rich zircon cores may indicate early magmatic
crystallization of zircon within a highly-fractionated partial melt
between 30 and 20 Ma.
Ti-in-zircon thermometry of dated zircon rims suggests
slow cooling during zircon crystallization from ~650°C to
~500°C between 23 and 16 Ma. Crystallization temperatures are
well below the closure temperature for Pb diffusion in zircon,
suggesting that the spread of ages reflects protracted crystallization
during the Early Miocene. 40Ar/39Ar step-heat ages from bulk
separate igneous muscovite from the leucogranite dikes (same
samples) indicate rapid cooling to below ~350°C, and hence
cessation of ductile shearing by —13-11 Ma. Apatite fission track
data indicate that the lower detachment reached 110-120°C at 5-8
Ma, thus the cooling rate slowed slightly into the Late Miocene.
The peak temperature gradient across both strands of
the STDS in NW Bhutan has been determined by Raman
spectroscopy of carbonaceous material and conventional
thermobarometry in low- and high-grade metamorphic rocks,
respectively. Peak temperatures in the Tethyan sequence increase
down-section from ~200°C in the core of a map-scale syncline
(Figure 1) to ~400°C in the hanging wall of the upper STDS.
Temperatures in the structurally-highest Chekha Group rocks are
>400°C, but not substantially higher than Tethyan sedimentary
rocks, suggesting throw on the upper STDS is not significant.
Peak temperatures continue to increase down-section across
the lower STD to 600-750°C in the structurally lowest CG and
highest GHS rocks respectively. These are higher temperatures
than the Ti-in-zircon rim temperatures suggest, indicating that
the leucogranites intruded during cooling and exhumation.
The metamorphic sequence across both strands ofthe STDS
is right-way-up, from granulite-facies rocks in the uppermost
Greater Himalaya sequence through amphibolite facies in the
Chekha Group and into structurally-highest, unmetamorphosed
Tethyan sedimentary rocks, confirming the normal sense of
shearing observed through the sequence. The lower detachment
was most likely active during the Early to Mid-Miocene, and
marks the protolith and rheological boundary between the upper
(Chekha Group) and middle (GHS) crust. The upper detachment
was most likely active since Late Miocene and has contributed
to the tectonic denudation of the rocks beneath, as reflected by
the rapid cooling ofthe lower detachment during Late Miocene.
These PTtD data provide crucial constraints on the choice of an
appropriate geodynamic model for the evolution ofthe Tibetan-
Himalayan orogen.
Jamieson RA, C Beaumont, MH Nguyen and D Grujic. 2006. Provenance of
the Greater Himalayan Sequence and associated rocks: Predictions of
channel flow models. In: Law R, MP Searle and L Godin (eds), Channel
flow, ductile extrusion, and exhumation in continental collision zones,
Geological Society, London, Special Publications 268: 165-182
Edwards MA and TM Harrison. 1997. When did the roof collapse? Late
Miocene north-south extension in the high Himalaya revealed by Th-Pb
monazite dating ofthe Khula Kangri Granite. Geology 25(6): 543-546
Hollister LS and D Grujic. 2006. Pulsed channel flow in Bhutan. In: Law
R, MP Searle and L Godin (eds), Channel flow, ductile extrusion,
and exhumation in continental collision zones, Geological Society,
London, Special Publications 268: 415-423
Searle M, RL Simpson, RD Law, RR Parrish and DJ Waters. 2003. The
structural geometry, metamorphic and magmatic evolution of the
Everest massif, High Himalaya of Nepal-South 'Tibet. Journal qf the
Geological Society, London 160: 345-366
Wu C, KD Nelson, G Wortman, SD Samson, YYue, J Li, WSF Kidd and MA
Edwards. 1998. Yadong cross structure and South Tibetan Detachment
in the east central Himalaya (89°-90°E). Tectonics 17(1): 28-45
Paired terraces of the Seuti Khola, Dharan, eastern Nepal
Matrika Prasad Koirala123*, Sunil Kumar Dwivedi123, Prakash Dhakal3, Ghanashyam Neupane3,
Yadav Prasad Dhakal3, Suresh Prasad Khanal3, Niraj Kumar Regmi3, Gobinda Ojha3, Suchita
Shrestha3 and Ranjan Kumar Dahal13
1 Department of Geology, Tri-Chandara Campus, Tribhuvan University, Kathmandu, NEPAL
2 Simulation Tectonics Laboratory, Faculty of Sciences, University of the Ryukyus, Nishihara, Okiwana, 901-0213, JAPAN
3 Central Department of Geology Tribhuvan University, Kathmandu, NEPAL
For correspondence, email:
Terraces are the geomorphic units once occupied by the rivers.
When a river cuts down into its flood plain, the former alluvial
surface is no longer flooded and is left as a more or less flat
terrace above the new level of the river. If the downcutting
resumes, a second pair of terrace may then be left on the valley
side. Terrace mapping on the riverside is important in evaluating
the environmental impact of the river to the adjacent area. The
suitability of area to a particular landuse, and the possible action
of river on the adjacent area of the river can also be understood
from the terrace mapping. About 4 km stretches of the Seuti
Khola, east of the Dharan Bazar has been mapped to illustrate
the terrace patterns associated to this stream. The Seuti Khola is
a hilly stream, characterized by low discharge during dry season,
but tremendously high flow during rainy time. The river valley is
wide (> 150 m) consisting of boulder-cobble beds. The stream
valley has gradient of about 2°. Within the mapped area the river
channels drops from 480 m elevation at upper reaches to 340 m
elevation at the lower reaches. This provides high energy to the
river during high discharge level that is capable of transporting
boulder-sized clasts.
Four levels of terraces on each side has been identified and
mapped on either side. The terraces are of paired type, thus can
be individually recognized on either side. These terraces are well
developed, and can easily be recognized as being successive steplike geomorphic units. Lower Terrace (T ) is about 5 to 10 m
above the present river channels. This terrace is distributed within
elevation range of 350 - 400 m. The Lower Middle Terrace (T2)
is distributed within 370 - 440 m level. Upper Middle Terrace
(T3) is situated between 390 - 460 m levels. Similarly, the Upper
Terrace (T ) is identified above 410 - 550 m level.
The terraces of the Seuti Khola might be the evidence of
the neo-tectonic activity in the Himalayan realm. The terraces
along this stream are resulted due to the recent upliftment ofthe
area. The terrace forming material is characterized by the north-
tilting loose boulder-beds exposed on the steep riverbank scarps.
This may be due to the rapid upward and southward movement
associated with the Himalayan Frontal Thrust (HFT) that carries
the Sub-Himalaya as hanging wall, onto the footwall of the
Terai sediments. The continuous upliftment provides the extra
elevation to be undercut by the stream.
Late Quaternary climatic changes in the eastern Kumaun
Himalaya, India as deduced from multi-proxy studies
Bahadur Singh Kotlia1*, Jaishri Sanwal1, Binita Phartiyal2, Lalit Mohan Joshi1, Anjali Trivedi3 and
Chhaya Sharma3
1 Department of Geology, Kumaun University, Nainital, 263002, Uttarakhand, INDIA
2 Birbal Sahni Institute of Pdaeobotany, University Road, Lucknow, 226007, INDIA
3 Department of Geology, Lucknow University, Lucknow, 226 007, INDIA
For correspondence, email:
An event of neotectonic activity on an NE-SW trending
subsidiary fault in the zone of E-W running intracrustal
boundary thrust (South Almora Thrust) in the Champawat
district of eastern Kumaun Himalaya resulted in creation
of a lake at ca. 21.5 BP. The lake was drained out in the late
Holocene leaving behind a 5.0 m thick sedimentary sequence
of mostly black and carbonaceous mud indicating at the base a
minor magnetic reversal between 20.5-19.7 ka BP. The profile,
studied by using multi-proxies (e.g., carbon isotopes, pollen
analysis, palaeo and mineral magnetism and clay minerals)
has recorded globally well established abrupt climatic events
in the last 20,000 years, such as, LGM, Older Dryas (OD),
Younger Dryas (YD), Holocene warming, 8.2 ka and 4.2 ka
events. Most events, estimated assuming the invariable rate of
sediment accumulation for similar lithologies, may be related
to the rapid changes in the local climate and albedo structure.
We suggest that the ITCZ may have played a key role to control
the behavior of south-west monsoon from LGM onwards.
Palaeozoic granites and their younger components - A study of
Mandi and Rakcham granites from the Himachal Himalaya
A Kundu*, NC Pant and Sonalika Joshi
Geological Survey of India, NH-5P, NIT Faridabad-121001, Haryana, INDIA
For correspondence, email:
Several occurrences of Palaeozoic granites are recorded from the
Lesser Himalayas as well as from the Higher Himalayas (Miller
et al. 2001). From Himachal many such bodies have been dated
(Bhanotetal. 1979, Frank etal. 1977, Jager etal. 1971, Kwatra etal.
1986, Pognante et al. 1990, Kwatra et al. 1999, Kundu et al. 2006).
All of these bodies are deformed and several occur in the vicinity
of Main Central Thrust (MCT). Studies have indicated presence
of more than one granite type in most of these occurrences
(e.g. Gupta 1974, Chatterjee 1976) but definitive reference to
the Himalayan orogeny has generally been lacking. The present
work supplements the earlier field and petrographic classification
with rigorous mineralogical including rare earth element (REE)
bearing mineral data for the two Paleozoic granites of Mandi and
Rakcham and show association of younger granites with these
Four petrographic variants of Mandi granites can be
identified (Chatterjee 1976). These are as follows.
1. Porphyritic granite: With two mica and two feldspar. The
ratio ofthe micas number to feldspar phenocryst vary The other
mineral phases are quartz, ilmenite, sphene, epidote, zircon,
secondary muscovite, chlorite, monazite, allanite, zircon, apatite
and fluorite.
2. Fine grained porphyritic granite: Two mica two feldspar
granite and mineralogy similar to the porphyritic granite but has
distinctly finer ground mass size and less phenocrysts.
3. Trondjhemite/albite granite: Leucocratic rock with one
feldspar (albite) and one mica (muscovite). Other minerals are
quartz, rare biotite, chlorite, wolframite, iron oxides, monazite,
fluorite, apatite and tourmaline.
4. Leucogranite/tourmdinegranite: Two feldspar and one mica
(muscovite) granite, some outcrops have significant amount of
tourmaline (more than 1%). Quartz, k-feldspar, albite, tourmaline,
muscovite, fluorite, monazite etc. In Rakcham occurrence three
variants are identifiable namely 1. porpyritic granite: two feldspar
biotite granite, 2. granodiorite and 3. trondjhemite. The latter
two variants are subordinate and the major constituent is the
porphyritic granite. Magma mingling is indicated by the presence
of mafic pillows in the Mandi occurrence (Miller et al. 2001).
Mandi Occurrence: In porphyritic granite plagioclase has a
range of composition. The larger grains of plagioclase are zoned
with core composition (An29) being more calcic than the rim
(An23). Finer grained matrix grains are less calcic (Anl2) and
inclusion of plagioclase within K-feldspar is nearly pure albite.
Biotite has a highFe content (Fe/Fe+Mg~ 0.73). The fine grained
porphyritic granite has nearly albitic plagioclase and the biotite is
more Fe rich (Fe/Fe+Mg~ 0.780). In trondjhemitic granite the
albite is the main feldspar and muscovite is the only mica present.
The iron content ofthe muscovite in this variant is over 3 times
that ofthe same mineral in other varmints of Mandi occurrence.
Enclaves present in the Mandi occurrence include enclaves of
host rock (schist) engulfed by the granite during ascent, mica-rich
coarse grained small rounded to oval lumps of restite material,
fine grained, melanocratic commonly angular small sized dioritic
rocks and oval to elongated, pillow shaped, melanocratic, up to 5
m in size mafic rocks (basalts). In diorite biotite as phenocrysts are
more magnesium (Fe/Fe+Mg~ 38) than those in the groundmass
(Fe/Fe+Mg~ 48). Anorthite content of plagioclase is ~ An37. In
contrast the mafic rock has higher Ca in plagioclase (An70) and
lower Fe in biotite (Fe/Fe+Mg~ 18). Most Fe rich composition
of biotite in enclaves is observed in restite (Fe/Fe+ Mg~ 72), while
the plagioclase in this is most albitic (Anl8).
Rakcham Occurrence: In porphyritic granite perthitic K-
feldspar is the dominant mineral while plagioclase is relatively
finer grained and subordinate. Biotite is the main mafic mineral.
Muscovite is of two generations. Composition of the host in
perthitic K-Feldspar has significant Na content (Ab~8%).
Anorthite content of plagioclase varies from oligoclase to andesine.
Plagioclase is locally zoned in granodiorite and has higher calcium
(An44), biotite is the main mafic and the muscovite content is
very low. Garnet and alanite is present occasionally. Trondjhemite
is relatively finer grained variant and is made up dominantly of
quartz, plagioclase and muscovite with rare biotite. Plagioclase is
Ca-poor (albite to oligoclase). Monazite in the porphyritic granite
from Rakcham is a Ce-monazite.
Chemical dating of both Mandi and Rakcham granite bodies
has been carried out. In a euhedral monazite enclosed within
quartz, chemical age determination yielded an age of 462 Ma with
a standard deviation of 44 Ma (Kundu et al. 2006). This compares
well with the reported Rb/Sr age of 453±9 Ma for the Akpa, a
granite body possibly part of Rakcham granite and 477±29 Ma
for Rakcham (Kwatra et al. 1999). Indications of Teritiary ages is
obtained from two samples in the Rakcham area thus describing
coexistence of Himalayan granite in this Pan-African age granite
complex. In Mandi, the dominant granite (porphyritic granite)
gives Pan-African age (514 Ma with a standard deviation of 49 Ma),
which compares well with the reported age data for this occurrence
(Jageretal. 1971,Mehta, 1977, Miller etal. 2001). However, effects
of resetting of ages of monazite and commensurate mineralogical
transformations record imprints of Tertiary geological events. It
is possible that besides the presence of Tertiary granite, formation
of trondjhemite may also be linked to the Himalayan mountain
building processes in Mandi and Rakcham occurrences.
BhanotVB, AKBhandari, VP Singh and AKKansal. 1979. Geochronological
and geological studies of granites of Higher Himalaya, NE of
Manikaran, H. P. Journal ofthe Geological Society of India 20: 90-94
Chatterjee BC. 1976. Petrology and structural geology of the Mandi
granite, Mandi district, Himachal Pradesh. Geological Survey of India
Miscellaneous Publications 24: 302-315
Frank W, A Gansser and V Trommsdorff. 1977. Geological observations
in the Ladakh area (Himalaya): a preliminary report. Schweizerische
Mineralogische und Petrographische Mitteilungen 57: 89-113
Gupta LN. 1974. Petrology of Mandi granites and associated rocks. Center
of Advanced Studies, Punjab University, Chandigarh 10: 95-108
Jager E, AK Bhandari and VB Bhanot. 1971. Rb-Sr age determinations on
Biotites and "whole rock samples from the Mandi and Chor granites,
Himachal Pradesh, India. Ecologae Geologica Helvetia 64(3): 521-527
Kwatra SK, VB Bhanot, RK Kakar and AK Kansal. 1986. Rb-Sr radiometric ages
ofthe Wangtu Gneissic complex , Kinnaur District, Higher Himachal
Himalayas. Bulletin Indian Geological Association 19(2): 127-130
Kwatra SK, S Singh, VP Singh, RK Sharma, B Rai and N Kishore. 1999.
Geochemical and geochronological characteristics ofthe early Palaeozoic
granitoids from Sutlej-Baspa Valleys, Himachal Himalayas. In: Jain AK
and RM Manickavasagam (eds). Geodynamics ofthe N-W Himalaya.
Gondwana Research Group Memoir No.6:145-158
Kundu A, S Joshi, NC Pant and D Bhatnagar. 2006. Electron microprobe
dating technique- critical evaluation and application for a Pan-
African granite from the Himachal Himalayas. Indian Journal of
Geochemistry 21(1): 211-230
Mehta PK. 1977. Rb-Sr geochronology of the Kulu-Mandi belt: its
implication for the Himalayan tectonogenesis. Geologische Rundschau
66(1): 156-175
Miller C, M Thorn, W Frank, B Graseman, T Klotzh, D Gunth and
E Draganits. 2001. The early Palaeozoic magmatic event in the
Northwest Himalaya, India: Source, tectonic setting and age of
emplacement. Geological Magazine 138(3): 237-251
Pognante U, D Castelli, P Benna, G Genovese, F Oberali, M Meier and
Tonarini S. 1990. The crystalline units ofthe high Himalayas in the
Lahaul-Zanskar region (northwest India): Metamorphie-tectonic
history and geochronology of the collided and imbricated Indian
plate. Geological Magazine 127: 101-116
Out-of-sequence deformation and expansion of the
Himalayan orogenic wedge: insight from the Changgo
culmination, south-central Tibet
Kyle P Larson* and Laurent Godin
Department of Geological Sciences and Geological Engineering, Queen's University, CANADA
For correspondence, email:
The Changgo culmination, one of a series of granitic and/or
metamorphic domal structures that crop out along the North
Himalayan antiform, comprises a multi-phase, foliated granitic
core surrounded by a polydeformed metasedimentary carapace.
The carapace of the Changgo culmination consists of two
structural domains. The upper domain is characterized by vertical
thickening recorded as large-scale, close-to tight overturned,
south-verging folds while the lower domain is characterized by a
dominant transposition foliation. The contact between the metasedimentary cover and the granitic core is marked by a >300 m thick
top-to-the north sense shear zone. The shear zone predominantly
consists of mylonitized pelitic schist, but also contains 30-50 m
thick lenses of sheared leucogranite. One of these leucogranite
lenses has been dated as 35.35 ±0.37 Ma based on U-Pb SHRIMP
analyses. The main phase of the igneous core of the Changgo
culmination is a foliated alkali-feldspar porphyritic granite, which
has been dated using spot U-Pb SHRIMP analyses as 22.78±0.91
Ma. Quartz c-axis petrofabrics measured in specimens of this
foliated granite yield a top-to-the south shear sense. Undeformed
aplite dykes that cut the foliated porphyritc granite yield a U-Pb
TIMS monazite age of 22.08±0.19 Ma. 40Ar/39Ar cooling ages of
specimens sampled from both the meta-sedimentary carapace and
igneous core of the Changgo culmination range between ca. 20
Ma and 16 Ma. The cooling ages young with increasing structural
depth towards the center ofthe culmination.
The tectonic evolution of the  Changgo culmination is
interpreted to comprise three main episodes.
1) Crustal thickening through folding of the carapace: This
episode is equivalent to Eohimalayan events described elsewhere
along the orogen and, as in those events, it is interpreted to result
in prograde metamorphism and melt formation. The sheared
leucogranite lenses dated at ca. 35 Ma are interpreted to have
formed during this episode.
2) Horizontal stretching and extrusion of the mid-crust:
Subsequent to initial crustal thickening, or perhaps as a response
to crustal weakening associated with earlier deformation, the
mid-crustal core ofthe Himalayan-Tibetan orogen was extruded
southward. The transposition foliation developed in the Changgo
area, which is associated with a top-to-the-south shear sense in the
granite core, is thought to reflect deformation during extrusion.
In many areas along the Himalaya this extrusion is coincident
with significant anatexis and formation of plutons. The Changgo
granite is interpreted to have formed during the later stage of this
episode at 22.78±0.91 Ma. Top-to-the-south shear ended prior to
the intrusion of aplite dykes at 22.08±0.19 Ma. These dykes are
nonetheless deformed adjacent to the top-to-the north shear zone
at the core/carapace interface. This shear zone, therefore, must
have been active after the intrusion of the dykes. Deformation
in the shear zone took place at 520±50°C according to quartz
petrofabric analysis and likely ceased prior to cooling through
a calculated muscovite closure temperature of 414±21°C
at 18.43 ±0.25 Ma. Based on shear sense, structural position
and chronology, the shear zone at the core/carapace contact
is interpreted to be a branch of the South Tibetan detachment
system (STDS).
3) Out-of-sequence exhumation: The late-stage evolution
of the Changgo culmination is interpreted to reflect out-of-
sequence deformation within the Himalayan system. In central
Nepal, southward extrusion of mid-crustal material between
the STDS and the Main Central thrust ceased by ca. 19 Ma as a
result of insufficient gravitational potential to drive the southward
expansion ofthe orogenic wedge. The exhumation ofthe Changgo
culmination, shortly thereafter, is interpreted to reflect the out-
of-sequence rebuilding ofthe Himalayan wedge. Subsequent to
the exhumation of the Changgo area, in-sequence deformation
began to propagate southward as reflected in the ca. 16 Ma
exhumation ofthe Chako antiform, and then the cooling ofthe
central Nepalese frontal Himalaya (in the Annapurna region) at
ca. 14-15 Ma (Figure 1). The orogenic wedge continued its lateral
growth with the development ofthe Lesser Himalayan duplex and
the succeeding activation of the Main Boundary thrust, thereby
completing the transfer of slip from the kinematically unfavorable
Main Central thrust.
Lateral spreading of the
orogenic wedge and initiation ofthe
Main Boundary thrust
16Ma    18Ma
FIGURE 1. Diagram depicting the southward progression of cooling ages
in the central Nepalese Himalaya. Assuming a constant rate of erosion
cooling ages are interpreted to reflect the lateral spreading of the orogenic
wedge after out-of-sequence rebuilding. Grey represents past structures,
black represents active structures. MBT, Main Boundary thrust; MCT, Main
Central thrust; STDS, South Tibetan detachment system.
Is the Ramgarh thrust equivalent to the Main Central
thrust in central Nepal?
Kyle P Larson* and Laurent Godin
Geological Sciences & Geological Engineering, Queen's University, Kingston, CANADA
For correspondence, email:
Recent studies ofthe Main Central thrust (MCT), as exposed in
the Nepalese Himalaya, have attempted to elucidate its character,
contentious definition and locality (e.g. Searle et al. 2008,
Imayama and Arita 2008). Examination of vertical exposures in
the Budhi Gandaki and Darondi rivers, which drain the Manaslu-
Himal Chuli massif, supported by detailed thermobarometry and
microstructural analyses provide the means to critically evaluate
the applicability of such studies.
The Ramgarh thrust is defined in western Nepal as the
fault that juxtaposes green-schist facies rocks on top of lower-
grade Lesser Himalayan series rocks. The Ramgarh thrust has
not been mapped previously in the Budhi Gandaki or Darondi
valleys; however, it has been inferred in the adjacent Annapurna
and Langtang Himalaya. The geology of the Budhi Gandaki
and Darondi valleys is dominated by a >30 km thick package
of transposed medium-to high grade metamorphic rock of the
Greater Himalayan series. The upper boundary of the highly
strained section is the base ofthe top-to-the-north sense shears
zone of the South Tibetan detachment system, while the lower
boundary of the highly strained package is interpreted to be the
MCT using the definition of Searle et al. (2008). In the Budhi
Gandaki, rocks in the hanging wall of the MCT show evidence
of Tertiary metamorphism, display abundant C/S/C fabrics, yield
quartz c-axis crystallographic preferred orientations that suggest
horizontal stretching, and contain partial melt at higher structural
levels. Rocks below the MCT often preserve primary sedimentary
features such as bedding, contain abundant detrital porphyroclasts,
and are characterized by large-scale folding indicative of vertical
thickening. Mapping the MCT at the base of the transposed,
pervasively deformed rock package