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Palynology, thermal maturation, and time temperature history of three oil wells from the Beaufort-Mackenzie.. 1988

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Paiynology, Thermal Maturation, and Time Temperature History of Three Oil Wells from the Beaufort - Mackenzie Basin by Robert Douglas For man B.Sc. (Honours) University of British Columbia. 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF SCIENCE in THE FACULTY OF GRADUATE STUDIES Department of Geological Sciences We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October. 1988 © Robert Douglas Forman, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of <^£"O^CC/<^/iC Se/^s/C^S The University of British Columbia Vancouver, Canada DE-6 (2/88) ABSTRACT Palynological and maturation data are combined to reconstruct the burial and thermal history of three oil wells in the Beaufort-Mackenzie Basin. From south to north, the three wells are Netserk F-40, Tarsuit A-25, and Orviiruk 0-03. Each well was examined palynologically and zoned based on species ranges of pollen, spores, fungi, and algal cysts. Using local extinction events of zonally diagnostic species to define the tops of intervals, seven informal palynozones are presented: Laevigatosporites (Pleistocene); ChenopodipoJlis (Pliocene to early Pleistocene); Ericipites (middle to late Miocene); SelenopemphJx-\ (middle to late Oligocene); Integricorpus (early Oligocene); AraJiaceoipoJlenites (late Eocene to early Oligocene); Pistlllipollenites (middle Eocene). Correlations within the basin indicate that the proposed zonation may be useful for local correlations. Correlations outside the basin indicate that the palynological assemblages from the Beaufort-Mackenzie Basin may not be as isolated and endemic as first thought. A high recovery of algal cysts is attributed to less harsh maceration techniques, and confirms a significant population of cysts from a region in which they were formerly believed to be relatively scarce. The paiynology does not exhibit an increase in marine influence with decreasing proximity to the basin margin. Instead it shows a consistent, strong terrestrial influence throughout each well. The large terrestrial discharge from the Mackenzie River is interpreted to have masked the effect of basin proximity on the paiynology of the area. The study wells are dominated by terrestrial Type III organic matter. Recycled and terrestrial inert material often make up over 95 % of the residues. These results support a terrestrial source for the offshore oils in the Beaufort - Mackenzie Basin. There is a small but consistent presence of potential oil-generating material throughout each well (amorphous and liptinite). The liptinite is largely composed of pollen grains, spores, and leaf cuticle. Algal cysts are present but less abundant. If the observed amounts of amorphous and liptinite material continue to some ii depth, where the required level of thermal maturation might be reached, these sediments could act as source rocks for hydrocarbons. The rare occurrence of resinite in the study wells questions the resinite source theory for the hydrocarbons in the basin The sediments in each of the three study wells are immature to total depth, and could not be the source of Tertiary oils in the Beaufort - Mackenzie Basin. The levels of maturity in the wells, and the low maturation gradient calculated for Netserk F-40 (0.07 Ro/km), suggest that thermal maturation will only be achieved at much greater depths. This is most likely due to rapid sedimentation rates in the basin during the Tertiary. By combining the zonations from Chapter 3 with the maturation data from Chapter 4, the burial and thermal history of each study well is reconstructed. Using a modified version of Lopatin's method, paleo-geothermal gradients are calculated for each well. In each case, the gradient that best accountes for the measured maturities is 15 °C/km. The calculated gradient is approximately 1/2 to 1/3 of the present geothermal gradients for the wells. The gradient is in agreement with those previously calculated from similar basins, and is considered responsible for the failure of any of the study wells to encounter effective source rocks. Source rocks of Tertiary oils in the Beaufort-Mackenzie Basin will only exist at greater depths than those encountered in this study. Prospective targets may therefore be located adjacent to sites where vertical migration of hydrocarbons is likely, such as steeply-dipping faults. iii TABLE OF CONTENTS Abstract ii List of Tables vii List of Figures .viii Acknowledgement xi CHAPTER 1. INTRODUCTION 1 1.1 introductory Statement 1 1.2 Regional Setting 1 1.3 Exploration History 4 1.4 Purpose 7 1.5 Study Area 8 CHAPTER 2. GEOLOGICAL HISTORY OF THE BEAUFORT-MACKENZIE BASIN..... 11 2.1 Tectonic Development 11 2.2 Structure 13 2.3 Stratigraphic History 16 2.4 Tertiary Lithostratigraphy 17 CHAPTER 3: PALYNOSTRATIGRAPHY 26 3.1. Introduction 26 3.2. Previous Work 27 3.3. Methods 31 3.31.Sample preparation 31 3.3.2.Analytical Techniques 32 3.3-2.1. Recognizing contemporaneous palynomorphs ....32 3.3.2.2. Palynological interval zones 34 iv 3.4. Results 35 3.4.1. Palynological zonation 35 3.4.2. Correlations between the three study wells 50 3.4.3. Correlations with other Tertiary zonations in northern, western and eastern Canada 51 3.4.4. Comparison with previous palynological zonations from the Beaufort-Mackenzie Basin 54 3.4.5. Nearshore-offshore effects on palynology 56 35.Summary and Conclusions 58 CHAPTER 4: ORGANIC GEOCHEMISTRY 60 4.1 Thermal maturation 60 4.1.1. Introduction 60 4.1.2. Methods -. 63 4.1.2.1. Thermal Alteration Index (TAD 63 4.1.2.2. Vitrinite Reflectance 65 4.1.2.2.1. Sample Preparation 65 4.1.2.2.2. Analytical Techniques 65 4.1.3. Results 69 4.1.3.1. Thermal Alteration Index (TAD 69 4.1.3.2 Vitrinite Reflectance 70 4.1.4. Summary and Conclusions 75 4.2. Organic Matter Type (OMT) 75 4.2.1. Introduction 75 4.2.2. Methods 77 4.2.3. Results and Discussion 77 v CHAPTER 5: TIME-TEMPERATURE MODELLING 84 5.1. Introduction 84 5.2. Methods 86 5.3. Results and Discussion 92 CHAPTER 6: SUMMARY AND CONCLUSIONS 98 BIBLIOGRAPHY 101 APPENDIX A: SPECIES LISTS 115 A. 1. Composite species list - Alphabetical 116 A.2. Composite species list - Taxonomic 122 APPENDIX B: RAW ORGANIC MATTER ANALYSIS DATA 128 APPENDIX C: PLATES 134 vi LIST OF TABLES Table 31 Ratio of terrestrial species versus marine species 57 Table 4.1 Comparison of TAI and Vitrinite Reflectance scales 63 Table 4.2 Total depth versus maximum attained TAI values 70 Table 5.1: Correlation of TTI, Ro, and TAI with several important stages of oil generation and preservation (after Waples, 1980) 85 Table 5-2: Comparison of paleogeothermal gradients calculated by Lopatin's method, those calculated from present day down hole temperatures, and those reported by Judge and Bawden (1987), and theASPG( 1976) .....91 Table 53: Geothermal gradient (G) versus slope for:l. calculated geothermai gradients (Lopatin model), and 2. the measured gradient from vitrinite analysis for Netserk F-40 91 Table 5.4: Comparison of paleogeothermal gradients for Netserk F-40 derived by four different methods 92 Table 5.5: Cumulative TTI and maximum paleo - temperatures, assuming a paleogeothermal gradient of 15 °C/km 97 Table B.l: Percentage Organic Matter Types for Imperial Netserk F-40 (raw data) 129 Table B.2: Percentage Organic Matter Types for Imperial Tarsuit A-25 (raw data) 131 Table B.3: Percentage Organic Matter Types for Imperial Orvilruk O-03 (raw data) 133 vii LIST OF FIGURES Figure 1.1: Location map of Beaufort-Mackenzie Basin 2 Figure 1.2: Geographic location of Beaufort-Mackenzie Basin 3 Figure 1.3: Tectonic setting of the Beaufort-Mackenzie Basin 4 Figure 1.4: Base map showing location of wells in the Beaufort-Mackenzie Basin to date (1988) 6 Figure 1.5: Map showing the location of three study wells 9 Figure 2.1: Eastward translation of northern Alaska along the Kaltag fault 13 Figure 2.2: Relationship of structure and hydrocarbon discoveries.in the Beaufort-Mackenzie Basin 14 Figure 2.3: Major structural linements in Tertiary strata in the Beaufort- Mackenzie basin 15 Figure 2.4: Example of a basement-involved, wrench-related structure from the Beaufort-Mackenzie Basin 16 Figure 2.5: Evolution of stratigraphic nomenclature used by various authors for Upper Cretaceous-Holocene strata in the Beaufort -Mackenzie Basin 18 Figure 2.6: Generalized stratigraphy of the Beaufort-Mackenzie Basin 19 Figure 2.7: Schematic representation of the temporal and stratigraphic positions of deltaic cycles in the Beaufort-Mackenzie Basin 21 Figure 2.8: Schematic drawing showing inferred depositional environments in the offshore Beaufort-Mackenzie Basin 22 Figure 2.9: Schematic structural-stratigraphic cross-section through the Beaufort-Mackenzie Basin 23 Figure 3.1: NetserkF-40 Species Range Chart 36 Figure 3.2: Tarsuit A-25 Species Range Chart „....37 Figure.3.3 Orvilruk 0-03 Species Range Chart 38 viii Figure 3.4 Provisional palynological zonation for Netserk F-40 39 Figure 3.5 Provisional palynological zonation for Tarsuit A-25 40 Figure 36 Provisional palynological zonation for Orvilruk 0-03 41 Figure 3.7 Ranges of selected species used to establish provisional zones 42 Figure 4.1: Correlation of major organic maturation indices 61 Figure 4.2: Comparison of Vitrinite Reflectance to TAI scales 64 Figure 4.3: Netserk F-40. Thermal Alteration Index versus depth 66 Figure 4.4: Tarsuit A-25. Thermal Alteration Index versus depth 67 Figure 4.5: Orvilruk 0-03. Thermal Alteration Index versus depth 68 Figure 4.6: Netserk F-40. Percentage random Vitrinite Reflectance versus depth 71 Figure 4.7: Tarsuit A-25. Percentage random Vitrinite Reflectance versus depth 72 Figure 4.8. Orvilruk 0-03. Percentage random Vitrinite Reflectance versus depth 73 Figure 4.9: Netserk F-40. Organic Matter Type analysis 79 Figure 4.10: Tarsuit A-25. Organic Matter Type analysis 80 Figure 4.11: Orvilruk O-03. Organic Matter Type analysis 81 Figure 5.1: Burial history curve for Netserk F-40 88 Figure 52: Burial history curve for Tarsuit A-25 89 Figure 53: Burial history curve for Orvilruk 0-03 90 Figure 5.4: Comparison of calculated and measured maturation gradients for Netserk F-40 93 Figure 55: Burial history curve for Netserk F-40, showing temperature distribution through time represented by the reconstruction 94 Figure 56: Burial history curve for Tarsuit A-25. showing temperature distribution through time represented by the reconstruction 95 ix Figure 5.7: Burial history curve for Orvilruk 0-03, showing temperature distribution through time represented by the reconstruction 96 x ACKNOWLEDGEMENT This thesis was supported by: Dome Petroleum Ltd., who supplied cuttings samples and information for Tarsuit A-25 and Orvilruk 0-03; Esso Resources Ltd., who supplied cuttings samples and information for Netserk F-40; Texaco Canada Ltd., who supplied financial assistance through a Texaco Geological Research Grant; and British Petroleum Canada Ltd., who provided drafting assistance. The project was also supported financially by an NSERC Grant. I would like to gratefully acknowledge my thesis supervisor, mentor, and friend, Dr. Glenn E. Rouse, whom I first met in 1980, and who has been advising me ever since. His guidance, support, and patience throughout this project are sincerely appreciated. I would like to thank Dr. Marc Bustin for his help in the vitrinite reflectance and time-temperature modelling sections, and for valuable review of these chapters. Critical review and suggestions by Dr. W.C. Barnes are much appreciated. I would also like to thank Cliff Stanley for his assistance with computer analyses, and Bruce James for patiently helping me through computer kindergarten. I am grateful to all those friends in the Geology Department who made my time there memorable: roommates Derrick Brown, Steve Juras and Cliff Stanley, for providing light entertainment and much support; Dr. W. Danner, for always having an open door and a friendly ear; Carlo Giovanella, for giving me the opportunity to teach; and Ed Montgomery, for reminding me how to play hockey again. I would also like to acknowledge Dr. Ted Bogel and Simon Brame, of B.P. Canada, for their support in the last few hectic months. Finally, I would like to thank my parents, Ellen and Earl (who wondered if I would gxex graduate), for their constant encouragement, and my wife, Cindy, for making countless grammatical corrections, and standing by me throughout it all. xi 1 CHAPTER ONE INTRODUCTION 1.1 Introductory Statement By studying the organic matter in sedimentary rocks, much can be learned about a sedimentary basin. This includes the age and geometry of the sediments through detailed correlations using microfossils, depositional environment (e.g., water depth, salinity, and temperature), paleoclimate, and hydrocarbon potential (e.g., the type and quantity of hydrocarbons to be expected, the timing of hydrocarbon generation, and in some cases, possible migration pathways). In addition, when this stratigraphic and geochemical information is incorporated into the overall geological framework of the basin, predictive models can be constructed to help elucidate the geology and hydrocarbon potential of regions where less information is available. These are particularly applicable to offshore and other remote, hostile environments, where exploration is difficult and expensive. These types of predictive models can help guide exploration strategies and reduce risk, by highlighting areas with the greatest potential for commercial hydrocarbon accumulations. An excellent example of such an area is the Beaufort-Mackenzie Basin in northern Canada. 1.2 Regional Setting The Beaufort-Mackenzie Basin is a Mesozoic-Cenozoic fluvial-deltaic sedimentary basin located in the northwestern corner of Canada (Fig. 1.1). It extends northward, from the modern Mackenzie Delta to the edge of the 2 Figure 1.1: Location map of the Beaufort-Mackenzie Basin continental shelf, in approximately 200m of water (northern boundary often arbitrarily set parallel to the 200 m bathymetric contour). The area extends eastward to Cape Bathurst and the western edge of the Canadian Arctic Islands. 3 and westward to Herschel Island (Fig 1.2). Onshore, the basin encompasses the modern Mackenzie Delta, including Richards Island, Tuktoyaktuk Peninsula, and the western edge of the Yukon coastal plain (Fig. 1.3). Offshore, it includes the sediments beneath the Beaufort Sea to the continental edge. In total, the Beaufort- Mackenzie Basin encompasses approximately 100,000 square kilometers, making it one of Canada's largest sedimentary basins. Figure 1.2: Geographic location of the Beaufort-Mackenzie Basin This basin lies at the junction of three contrasting tectonic elements (Fig. 1.3). To the southwest is the northern tip of the North American cordillera, to the southeast is the Northern Interior Plain, representing the Proterozoic Canadian Shield, and to the north is the Arctic Ocean, floored by Mesozoic oceanic crust. 4 C A N A D A BAS IN Figure 1.3: Tectonic setting of the Beaufort-Mackenzie Basin 1.3 Exploration History Petroleum exploration has continued in the Beaufort-Mackenzie Basin for almost 25 years. The main factors responsible for the early interest in the basin are its size, its deltaic nature, the thickness of the sediments (greater than 10 km), 5 past successes in similar basins (e.g., Niger, Mississippi), and recent successes in the adjacent Prudhoe Bay field in Alaska. Serious petroleum exploration in the Beaufort-Mackenzie Basin began shortly after the region was opened to exploration permits in 1961. The first well in this area (Shell-Reindeer D-27) was a dry hole drilled in 1965, on the Mackenzie delta, to a total depth of 3862m (Fig. 1.4). The first oil discovery was made in 1970 on the Tuktoyaktuk Peninsula (Atkinson H-25), in Cretaceous sandstones (Fig. 1.4). The first hydrocarbon discovery on the Mackenzie delta was gas, at Taglu G-33 in in Eocene sandstones (Dixon et al., 1985) (Fig.1.4). Offshore drilling began in 1973 with the drilling of Immerk B-48 (Fig. 1.4). in shallow water, from an artificial island. The first offshore discovery (oil/gas) was at Adgo F-28 (Fig. 1.4). In the late nineteen seventies, following the introduction of ice-strengthened drilling ships, exploration moved into deeper waters. This lead to major discoveries at Kopanoar (1978), Tarsuit (1979), and Issungnak (1980). After a lull in the early nineteen eighties, exploration began again, with significant oil/gas discoveries at Amauligak (1984) and Nipterk (1985). Following a second lull in the mid nineteen eighties, precipitated by depressed world oil prices, exploration has again cautiously resumed. This was largely spurred on by the success of the Amauligak field, which, alone, was originally reported to contain up to one billion barrels of oil. To date, nearly 250 wells have been drilled in the Beaufort-Mackenzie Basin (COGLA, 1988), resulting in 39 significant hydrocarbon discoveries (17 gas, 13 oil, 9 oil and gas) (Dixon et al., 1985). Total discovered resources, as of 1985 (Dixon et al., 6 Figure 1.4: Base map showing location of wells in the Beaufort-Mackenzie Basin to date (1988) (see sleeve in back HPublished with permission from COGLA). 7 1985), were estimated to be 360 x 106 m 3 (12.7 Tcf) of recoverable gas and 175 x l O 6 m 3 (1.1 billion barrels) of recoverable oil (Dixon et al., 1985). These figures are minimum estimates. Actual values may be much higher, considering the recent discoveries at Amauligak. 1.4 Purpose The Beaufort-Mackenzie Basin contains two distinct hydrocarbon provinces. The first is a Mesozoic-Paleozoic province, encompassing the Tuktoyaktuk Peninsula and southern delta. This consists largely of Cretaceous sandstones, and, to a lesser extent, of Devonian carbonates. The second is a Tertiary province, which includes the northern delta and offshore, and consists entirely of Tertiary elastics. The Mesozoic-Paleozoic province is reasonably well understood. In contrast, many gaps remain in the understanding of the geology and evolution of the of the Tertiary province. This is true despite the fact that 33 of the 39 hydrocarbon discoveries reported from the Beaufort-Mackenzie Basin (Dixon et al., 1985), including the recent Nipterk and Amauligak discoveries, have been in Tertiary elastics. Problems include a lack of detailed correlations, no identification of a source rock for the Tertiary oils, and undefined timing of hydrocarbon generation in relation to the formation of traps. This study was undertaken to address these concerns, with the following objectives: 1. To palynologically analyse cuttings samples from three wells from the Beaufort- Mackenzie Basin (Netserk F-40, Tarsuit A-25, Orvilruk 0-03) with the purpose of establishing detailed palynozones to be used in the dating and correlating of wells in the basin. 8 2. To investigate the effects of basin margin proximity on the palynology of the three wells which lie approximately in a South-North alignment. 3. To determine the levels of thermal maturation of the three wells using TAI and Vitrinite Reflectance methods. 4. To make visual estimates of the percentages of Kerogen types at 200m intervals for each well. 5. To combine the maturation data with the visual Kerogen results to identify those sediments within the three study wells with greatest potential for hydrocarbon generation. 6. To combine the palynological zonations with the maturation data, using a modified version of Lopatin's 1970 equation, in order to model the subsidence and thermal history of each well. 7. To delineate those zones/strata in the Tertiary hydrocarbon province with the highest probability of success as future exploration targets. 1.5 Study Area The three wells considered in this study, from south to north, are Imperial Netserk F-40, Dome-Gulf Tarsuit A-25. and Dome et al. Orvilruk 0-03 (Fig. 1.5). Netserk F-40 is located at latitude 69°40' N and longitude 135°45' W, and was drilled in 1976 from an artificial island to a total depth of 4365m. The well was drilled on the south flank of an east-west trending listric growth fault, and flowed gas at a maximum flow rate of 2.5 x 105 m 3 /d (9 MMcf/d) (Dixon et al, 1985). 9 Figure 1.5: Map showing location of the three study wells. Tarsuit A-25 is located at latitude 69°54' N and longitude 136°20' W , and was drilled from a drillship in approximately 23 m of water. The well was drilled over two seasons, 1978 and 1979, to a total depth of 4445m. It is located on the northern flank of a large east-west trending antithetic fault that cross-cuts a major, deep-seated anticline (see seismic section). The well flowed oil at a maximum rate of 270 m 3 barrels of oil per day from Oligocene sandstones, with total recoverable reserves estimated at 23 to 55 x 10 6 m 3 (150-350 million barrels) of oil (Dixon et al., 1985). 10 Orvilruk 0-03 is located at latitude 70°22' N and longitude 136°30' W, and was drilled from a drillship in approximately 60 m of water. The well was drilled over two seasons, 1980 and 1982, to a total depth of 3912m. Samples were available only from the first drilling season in which 3606m were drilled before ice conditions forced the well's suspension. The well is located on the south flank of an elongate east-west diapiric structure, and had no significant oil or gas shows. 11 CHAPTER TWO GEOLOGICAL HISTORY OF THE BEAUFORT-MACKENZIE BASIN 2.1 Tectonic Development The Beaufort-Mackenzie Basin was formed during the Cretaceous and Tertiary in response to the opening of the Canada Basin (Collot et al., 1984). The Canada Basin was formed by seafloor spreading associated with the counterclockwise rotation of northern Alaska away from the Canadian Arctic Islands, about a pivotal point near the Mackenzie delta (Carey, 1958; Tailleur, 1973;Grantzet ai., 1979; Sweeny, 1982, 1985; McWhae, 1986). The basin formed in three stages : 1. pre-rifting, (Middle Jurassic to Earliest Cretaceous) consisting of the uplift and erosion on the basin margins; 2. continental breakup (approximately 130 to 110 Ma), with associated extrusive magmatic activity, and the formation of grabens perpendicular to the basin margin; and 3. seafloor spreading (approximately 120 to 80 Ma), associated with the formation of oceanic floor (Sweeny, 1985). There is also evidence to suggest that the basin may have opened and closed at least once previously (Churkin, 1973). Evidence for a rifted origin includes bathymetric fit (Carey, 1958; Grantz et al., 1979), and geologic fit (Tailleur, 1973; Grantz et al., 1979), as well as the presence of oceanic crust flooring the basin (Oliver et al., 1955; Osteno and Wold, 1973; Baggeroer and Falconer, 1982; Sweeny, 1983). In addition, many typical geological features, commonly associated with rifted passive margins, are present. These include continental uplift and erosion of basin margin (Sweeny, 1983; McWhae, 1986), extensional faulting and graben formation (Dixon et al., 1985). extrusive tholeiitic basalts and gabbroic dykes and sills (Sweeny, 1985), breakup 12 unconformities (Sweeny, 1985; McWhae, 1986), and low amplitude magnetic lineations (Taylor et al., 1981; Vogt et al., 1982; Sweeny, 1985). The timing of the formation of the Canada Basin has been the subject of some controversy. Based on ambiguous low amplitude magnetic lineations', Taylor et al., (1981), and Vogt et al., (1982), proposed a Late Jurassic to Early Cretaceous age for its opening. Alternatively, several authors do not recognize these lineations as true magnetic anomalies caused by seafloor spreading (e.g., Grantz et al., 1979; Sweeny, 1985; McWhae, 1986). Instead, they suggest that the majority of the seafloor was formed during a Mid-Cretaceous (110-80 Ma) period of magnetic quiescence, during which the magnetic field did not reverse (Grantz et al., 1979). Evidence for a mid-Cretaceous opening of the Canada Basin includes: the dates assigned to breakup unconformities (Sweeny, 1985; McWhae, 1986); the oldest rocks present at the start of faulting and erosion during the breakup phase (Sweeny, 1985); the youngest sediments deposited during the subsidence phase (Sweeny, 1985); and the absolute age dates of tholeiitic basalts and gabbroic dykes and sills (Thorsteinsson and Tozer, 1970; Balkwill, 1978). Additional evidence includes geophysical measurements of age versus depth (Eittreim and Grantz, 1979; Baggeroer and Falconer, 1982), and age versus heat flow (Lawver and Baggeroer, 1983). For further discussion on the origin and age of the Canada Basin the reader is referred to Grantz et al., (1979), Sweeny, (1983, 1985), and McWhae, (1986). Shortly following the cessation of spreading approximately 85 -80 million years ago, the Canada Basin was severed from the North American plate by right lateral movement along the Kaltag fault system (Fig. 2.1) (Collot et al., 1984; McWhae, 1986). As a result, the Beaufort-Mackenzie Basin was subjected to a strong compressional event and underwent crustal deformation in order to 13 accommodate the eastward translation of northern Alaska (Collot et al., 1984). Displacement, estimated at 50 to 100 km, culminated in the early to middle Tertiary (Collot et al., 1984), after which the basin has been tectonically quiet (except, possibly, for small movements along the Kaltag fault) (McWhae, 1986). Figure 2.1: Eastward translation of northern Alaska along the Kaltag fault. (Collot et al., 1984). 2.2 Structure The Beaufort-Mackenzie Basin is the site of a complex structural style that has resulted in the formation of a variety of hydrocarbon traps (Fig 2.3). The degree of complexity of structures has created severe problems in correlating. The western part of the basin is dominated by a series of dense, arcuate anticlines and associated faults. The northeastern part is dominated by down-to-the- ? -JM BEAUFORT-MACKENZIE U BASIN Figure 2.2: Relationship of structure and hydrocarbon discoveries in the Beaufort- Mackenzie Basin. basement listric growth faults (Fig. 2.2). The anticlines are interpreted to be shale- cored diapirs formed by the upward movement of undercompacted shales from the underlying beds (Dixon et al., 1985). They are commonly associated with listric growth faults that may or may not sole out in the underlying sediments. The structures in the basin have traditionally been interpreted as detached, syn-sedimentary, gravity-induced features that developed in response to the rapid progradation of the thick Tertiary wedge across the continental margin (Dixon et 15 al., 1985). In contrast, Young et al., (1976) and Collot et al., (1984) proposed that the main structural style is wrench-related and basement-involved, and developed concurrently with gravity-induced tectonics. The wrench style structures are Figure 2.3: Major structural linements in Tertiary strata in the Beaufort-Mackenzie Basin (from W ilium sen and Cote, 1982, Figure4.4) postulated to be the result of crustal deformation due to the compressional event that affected the basin during the Late Cretaceous to Mid-Tertiary (Collot et al., 1984) (Figure 2.4). These dominate in the southwest part of the basin, and detached, gravity-induced structures dominate in the north, where the sediments are thicker and less stable. The stratigraphic section can be divided vertically, based on the dominant structural style (Dixon et al., 1985): 1. the Late Cretaceous to Middle-Tertiary, dominated by wrench-tectonics; 2. the Late Eocene to Late Miocene, dominated by 16 gravity-induced diapirs and listric growth faults; and 3. the Late Miocene to Pleistocene, which is largely undisturbed. Figure 2.4: Example of a basement-involved, wrench-related structure from the Beaufort-Mackenzie Basin. The scale on the right is two way travel time (Collot et al., 1984). 2.3 Stratigraphic History The stratigraphic column for the Beaufort-Mackenzie Basin can be divided into three parts: 1. Precambrian to Paleozoic basement rocks, consisting largely of carbonates, quartzites, and elastics; 2. Mesozoic sediments, deposited during the subsidence phase of the opening of the basin; and 3- a thick regressive, deltaic wedge that prograded across the continental margin during the Tertiary (Fig. 2.6). For a description of the Precambrian to Paleozoic basement rocks, the reader is referred to Lerand (1973), Grantz et al. (1979), and Norris and Yorath (1981). For a discussion of the Jurassic to Cretaceous stratigraphy, the reader is referred to Young et al. (1976), Dixon (1982), and Dixon et al. (1985). The Upper Cretaceous to 17 Holocene section is described by Young and McNeil (1984) and Deitrich et al. (1985). Characteristics of the basin's Tertiary sedimentation are described by Willumsen and Cote (1982). 2.4 Tertiary Lithostratigraphv Over 10 km of sediments have been deposited in the Beaufort-Mackenzie Basin since its formation. These sediments can be divided into five deltaic cycles separated by transgressions (Fig. 2.7) (Willumsen and Cote, 1982). They represent two main facies: pro-deltaic mudstones, and sandstone dominated delta front and delta plain deposits (Fig.2.8). Based on these broad generalizations, formal lithostratigraphic nomenclature for the area beneath the modern Mackenzie delta has been proposed (Young and McNeil, 1984). The evolution of this nomenclature is summarized in Figure 2.5. The sediments have also been divided into seismic sequences, based on reflection profiles and well data (Fig.2.9) (Deitrich et al., 1984). A sequence is defined as a genetically related package of strata divided by unconformities (or their correlative equivalents). Seismic stratigraphy has become the most common method for sub-dividing and correlating the offshore sediments in the Beaufort- Mackenzie Basin, because well control is relatively poor, and lithological units are often thick, monotonous, and diachronous. A comparison of the proposed seismic stratigraphy to the proposed lithostratigraphy is presented in Figure 2.5. The following is a brief description of the formations penetrated by the wells considered in this study. Included is a brief description of the lithologies, D a l t i l c h , O l i o n and M c N a l l 1985 W l l l u m i a n and C o l a 1 982 Young and M c N a l l I S B 2 J o n a a a l a l . 1 9 8 0 L a n a and J a c k a o n 1980 Haa a l al. 1 980 Young a l a l 1 9 7 6 3 O Co T C S H A L L O W B A Y S E Q U E N C E i i i i i i i i i i i i n i m Glac i . i l depos i t s I P E H K S E Q U E N C E T A K P A K SEC M A C K E N Z I E S E Q U E N C E K U G M A L L I T S E Q U E N C E " "V K O P » H O A R . IK 5 1 Q R I C H A R D S S E Q U E N C E R E I N D E E R S E Q U E N C E 8 JJJ>*^ F I S H R I V E R S E Q U E N C E f MILL S L QUI ru;t BEAuron t D E L T A P U L L E N D E L T A U l l M i l i M U t l E o c e n e s h a l e ) A G l . U D E L T A M065P C H A N N E L N o s w a h y r a p r n u n t l s n a m e d R e c e n l depos i t s Q U A T HERSCHEL IS FM N U K T A K F M B E A U F O R T K U G M A L L I T 1Z- M I C H A M O S I 'M R E I N D E E R F M a f * MO~OSE Q C H A N N E L t A t r | F M T E N I I S L A N D F M . B O U N D A R Y C H E E K F M DC C u U I P E R K G R O U P Unidenl i l ied P a l e o y e i i e L j i i n . i m e c l u p p e r C r e t a c e u u s s l i a i d Q U A T UJ a U E A U F O H I M A C K E N Z I E S E Q U E N C E K U u M A I 1 I I S E Q U E N C E R E I N D E E R S E Q U E N C E F l S H R I V E R S E O U f - n C E IIIIIHIIIIIIIIIII N o s 11 a I K J I a p h i c unit s n a m e d or. K G l . u i . i l J n l l i i i m i i i i i i u m U E A u F O H l F M I 'WL I .LN S A N D U i i n j i n u O i l i a l e H I . I N O E L R F M M O O S E C H A N N E L I 'M 1 L N I ISL A N D F M B O U N D A R Y C H I I K I M I I I I 111 Ti I I I 1 11 f | N u i l J t d Hi ilwM *»,inO G r e y b j n c f nnrc H E A U F O R T K M . ? UfiH A Upper ( ' . i l c o y e r i U m l U Unturned LOLCIIL' id.lit: H t t N U t . f . H f M M O O S i > T E N I i S l A N D I M B O U N I J A l n C H I 1 K I 1.1 Figure 2.5: Evolution of stratigraphic nomenclature used by various authors for Upper Cretaceous - Holocene strata in the Beaufort -Mackenzie Basin. Non - hatchered sequence boundaries imply the contact is a submarine unconformity (Deitrich et al., 1985). 19 3 E A U F 0 R T S E A r U K P E N I N S U L A t-Z-Z-Z—.J F I NE C L A S T I C 5 :~~ =1 C A R B O N A T - I S E C T I O N J M I S S I N G KiftWtom C O A R S E C L A 3 T I C S •.: • ;:.-~v • MET AMORPHICS Figure 2.6: Generalized stratigraphy of the Beaufort-Mackenzie Basin (Jones et al., 1980). distribution and thicknesses, contact relationships, and depositional environments. Because the oldest sediments encountered were middle Eocene in Tarsuit A-25, the descriptions begin with the Richards Formation. For a discussion of the entire Late Cretaceous to Holocene section, the reader is referred to Young and McNeil, (1984), and Deitrich etal., (1985). Richards Formation The Richards Formation is the lowermost formation penetrated in the study wells. It conformably overlies the Reindeer Formation (Paleocene to Middle 20 Eocene), which consists of a major deltaic, regressive wedge of sandstone and silty mudstone, with minor amounts of conglomerate (Young and McNeil, 1984). Its contact with the superjacent Kugmallit Formation is abrupt but conformable (Young and McNeil, 1984). The Richards Formation underlies all of Richards Island, the adjacent offshore area, and the outer fringe of deltaic islands to the southwest. It is a thick mudstone unit of probable prodeltaic origin, which changes facies southwesterly into the coarser elastics and coals assigned to the Reindeer Formation. The thickness of the formation increases northward from nearly 400 m in southern Richards Island, to more than 1500 m near Garry and Pelly Islands, and to greater than 2000 m near Ellice Island. These variations may be due, in part, to listric growth faults active before, during , and after deposition of the formation. The Richards Formation is composed mainly of light grey marine mudstone, and shale, with minor smectite and bentonite seams near the top. Poorly sorted and stratified pebble conglomerates are also common, suggesting deposition by subaqueous debris flows on prodeltaic sloping surfaces (Young and McNeil, 1984). Kugmallit Formation The Kugmallit Formation is a thick deltaic complex of soft, semi-consolidated, largely terrestrial, clastic sediments (Young and McNeil, 1984). It has been largely removed by erosion over the Langly High, but thickens abruptly to the north, to more than 1900m under northeast Richards Island. The formation is divided into two members: a lower Ivik unit, and an upper Arnak unit, between which the boundary varies from gradational to abrupt, but is generally conformable (Norris, 1985). 21 Epoch BEAUFORT SEA South North Deltaic Sequence Pleistocene to Miocene Oligocene Eocene Paleocene Cretaceous Beaufort Akpak Pullen Taghj Moose Channel joa O E L T A P L A I N Q D E L T A F R O N T f ~ ] P R O D E L T A S H A L E S HI T U R B I D I T E S Figure 2.7: Schematic representation of the temporal and stratigraphic positions of deltaic cycles in the Beaufort-Mackenzie Basin (Willumsen and Cote, 1982). The lower contact with the Richards Formation is also abrupt but conformable. The contact with the overlying Mackenzie Bay Formation is conformable to the north, but grades from disconformity to angular unconformity in the south (Young and McNeil, 1984). The Kugmallit Formation consists mainly of sand, mudstone, gravel, lignite, and coalified wood fragments. The Ivik Member is transitional between the prodeltaic mudstone of the Richards Formation, and the delta plain deposits of the upper Arnak Member. It consists of rhythmic alternations of mudstones and 22 sandstones, which commonly display medium scale, coarsening upward trends, typical of progradational deltas (Young and McNeil, 1984). In contrast, the Arnak g l DELTA PLAIN Q PROOELTA SHALES • DELTA FRONT H TURBIDITES Figure 2.8: Schematic drawing showing inferred depositional environments in the offshore Beaufort-Mackenzie Basin (Willumsen and Cote, 1982). Member is characterized by fining upward rhythmic cycles of gravels, sand, silt, and coal, typical of meandering stream channels on an alluvial or deltaic plain. Mackenzie Bav Formation The Mackenzie Bay Formation is a mudstone unit that lies immediately west of the outer part of the Mackenzie Basin (Young and McNeil, 1984). It varies in thickness from 330 to 600m, north and northwest of Richards Island. Towards the south, the unit becomes thinner, and intertongues with the fluvial Beaufort Formation. The formation abruptly but conformably overlies the Kugmallit 23 Formation, and is overlain abruptly by the Nuktak Formation in the south. In the north, the upper boundary is more obscure, and is marked by a limy hardground. Figure 2.9: Schematic structural-stratigraphic cross-section through the Beaufort- Mackenzie Basin. A. Distribution of sequences, I p-1 perk, Ak-Akpak; Mb-Mackenzie Bay, Kg-Kugmallit, Kp-Kopanoar, Ri-Richards, Rnd-Reindeer, Fr-Fish River, Puc-Pre- Upper Cretaceous. B. Facies distribution within the sequences (after Dietrich et al., 1985). The Mackenzie Bay Formation consists of predominantly light grey, soft mudstones with some silt or sand laminae, scattered chert and plant fragments, and pyritized burrows. Water-laid volcanic ashes and bentonites occur in its lowermost part. 24 Beaufort Formation The Beaufort Formation is a lateral facies equivalent of the Mackenzie Bay Formation (Young and McNeil, 1984). It is best developed and thickest (up to 1000m) under the northeastern part of Richards Island, and adjacent offshore areas. The formation thins and changes facies to a marine mudstone (Mackenzie Bay Formation) to the north and northwest. The lower contact with the Kugmallit Formation is largely unconformable, and there may be a hiatus to the south. To the north and northwest, where the formation is overlain by the Mackenzie Bay Formation, the contact is gradational to interbedded (as would be expected with a facies change). The formation is dominated by quartzitic and cherty sandstones with numerous thick and thin gravel beds. Minor interbedded mudstones, containing lignite and abundant plant fragments such as logs, uncompressed wood, spruce cones, and walnuts (Young and McNeil, 1984), are also present. The sediments represent alluvium and alluvial fans laid down by braided, gravely streams. The naming of the Beaufort Formation is controversial. Deitrich et al., (1984) suggest that Young and McNeil's (1984) Beaufort Formation is actually part of the uppermost section of the Kugmallit Formation. It is included in these descriptions as part of the formal lithostratigraphic nomenclature for the Beaufort-Mackenzie Basin to date, with the knowledge that it may be revised in the near future. For a further discussion of the confusion surrounding the formation and its name, the reader is referred to Deitrich et al., (1984). 25 Nuktak Formation The Nuktak Formation is a widespread unit consisting of two unnamed members: a lower gravel unit, and an upper mud unit. It is approximately 650m thick in its type section at Nuktak C-22. The gravel unit thickens from a zero edge on the Langly High and East Richards Island, to greater than 500m on northern Richards Island (Young and McNeil, 1984). It represents a gravel deltaic plain deposit, and lies disconformably, with little evidence of erosion on the Mackenzie Bay or Beaufort Formations. The mud unit is found at or near the top of the modern delta plain, northeast Richards Island, and the surrounding offshore. It is unusual in that it is slab- shaped and not wedge-shaped. It ranges from approximately 50 m depth to between 150 and 245m depth, and was likely deposited in a marine embayment (Young and McNeil, 1984). The upper contact of the Nuktak Formation is poorly known, but is likely unconformable with the overlying Late Pleistocene to Holocene gravel, sand, till, and mud of the Herschel Island Formation (Young and McNeil, 1984). 26 CHAPTER 3 PALYNOSTRATIGRAPHY 3.1. Introduction Palynology has proven to be important for age determinations and the correlation of Cenozoic strata in the Beaufort-Mackenzie Basin. While several informal preliminary zonations have been proposed, (Staplin, 1976; Doerenkamp et al., 1976; Ioannides and Mclntyre, 1980; Norris, 1986), no formal palynological zonation exists. This lack of a formal zonation is primarily due to the absence of accurate chronological control. Many factors have contributed to this, including: 1. Rapid facies changes in the basin, which can alter the apparent ranges of many fossils, because it becomes unclear whether an appearance or disappearance is due to evolution or extinction, or whether the fossil is simply responding to a facies change; 2. Unconsolidated nature of the sediments, which results in a limited number of cores, and a reliance on cuttings samples for analysis, leading to a loss of resolution, uncertainty of stratigraphic position, cavings, and contamination; and 3. Complex structures in the basin which make it difficult to obtain complete, undisturbed sections for biostratigraphic study, as well as making correlations more difficult. An additional problem with palynostratigraphic studies in the Beaufort- Mackenzie Basin is the high incidence of recycled material encountered. The Late Cretaceous and Tertiary was a period of cyclical delta building and erosion, resulting in the mixing of older with younger sediments. The reworked fossils are ' 27 often difficult to distinguish from the contemporaneous ones, resulting in the misplotting of ranges and erroneous age dating. The above difficulties might be expected in the study of any similar depositional environment, but there are additional problems in the Beaufort- Mackenzie Basin, because of its its high latitude and cool climate. These include less diverse assemblages of long ranging species (e.g. the monolete fern spore Laevigatosporites ranges from the Paleozoic to Recent), large numbers of endemic species, and a lack of standard index fossils. Consequently, the Beaufort-Mackenzie basin assemblages often do not compare well with the warmer, central-latitude assemblages, upon which the majority of age determinations are based. Furthermore, those species that do compare, may have different ranges. This is particularly evident in the Neogene, when climatic gradients are highest. Despite these limitations, paiynology remains an important tool in the exploration for hydrocarbons in the Beaufort-Mackenzie Basin. This is partially due to the paucity of pelagic foraminifers, used worldwide for correlations from the Middle Cretaceous through the Cenozoic. In this study, cuttings samples from three wells in the Beaufort Sea were examined palynologically. The wells are, from south to north, Netserk ¥-40, Tarsuit A-25, and Orvilruk 0-03 (Fig. 1.5). 3.2. Previous Work As previously discussed, only informal palynological zonations for the Beaufort-Mackenzie Basin have been proposed (Staplin. 1976; Doerenkamp et al., 1976; Ioannides and Mclntyre, 1980; Norris, 1986). These are based almost 28 exclusively on terrestrial species, as maceration techniques in the past have resulted in the destruction of many of the algal cysts , and even when intact, many are colourless, transparent, and difficult to detect. Additionally, most of the previous work has been done on terrestrial sections of outcrops, as well as onshore and nearshore wells. Currently, more emphasis is being placed on marine palynomorphs from Tertiary wells in the Beaufort Sea. In contrast, earlier work was limited to scattered Mesozoic and lowermost Cenozoic outcrops across Arctic Canada. The goal was to establish zonations which could later be used in the adjacent Beaufort- Mackenzie Basin. It was not until the analysis of the subsurface began that the Tertiary was seriously considered. The first published palynological determination for the Tertiary in northern Canada was by Rouse in Mountjoy (1967), in which a Paleocene age was assigned to sediments in the Caribou Hills. This initial work was followed by a multitude of reports of Early Tertiary in the Canadian Arctic (Hills and Wallace, 1969; Hopkins, 1971; Rouse and Srivastava, 1972; Elsik and Jansonius, 1974; Doerenkamp et al.. 1976; Rouse, 1977; Wilson. 1978; Ioannides and Mclntyre, 1980; Choi, 1983). However, only three studies reported ages younger than Paleocene. Doerenkamp et al. (1976), presented an informal zonation for Cretaceous-Tertiary sediments from Banks Island and adjacent areas, including the Mackenzie basin. Rouse (1977), presented a zonation of the Paleogene from Western and Arctic Canada. Finally. Ioannides and Mclntyre (1980), recognized four palynological zones from the Caribou Hills, ranging from Late Cretaceous to Oligocene. Rouse (1977), also demonstrated that, despite the large distances and dramatic changes in lithologic and palynologic facies, it was possible to correlate many elements of the palynological assemblages from different locations. 29 The first published biostratigraphic report on the subsurface of the Mackenzie Delta was by Chamney (1969), from the Reindeer D-27 well. Using foraminifers, Chamney was the first to recognize the thick Tertiary section (Chamney, 1969), and the first to propose a biostratigraphic zonation for the Cretaceous-Tertiary sediments (Chamney, 1971). The earliest published palynological report on the subsurface was by Hopkins, in Norford et al., (1971). This was the first in a series of reports of biostratigraphic determinations for over 80 wells in the region ( Norford et al., 1971; Norford et al., 1973; Barnes et al., 1974; Brideaux et al., 1975; Brideaux et al., 1976). The first palynological zonation proposed for the subsurface was by Brideaux and Myhr (1976), in which they described a Jurassic to Early Tertiary algal cyst succession from the Parsons N-10 well. The full potential of paiynology in explaining the stratigraphy of this region was not realized until 1976. At this time, Staplin (1976) incorporated the biostratigraphic data from four wells (Taglu G-33. Taglu C-42, Ya-Ya P-53, Reindeer D-27) to create the first complete zonation of the Tertiary of the Mackenzie Delta. It included four informal zones for the Paleogene and one for the Neogene. The zonation was based on algal cysts, pollen, spores, fungi, and foraminifers. Several key index fossils were described. Following Staplin's paper, a number of Geological Survey of Canada Open File reports were released, summarizing the palynostratigraphy of several wells from the basin (Austin and Cumming Exploration Consultants 1977, 1978a, 1978b, 1978c, 1979a, 1979b, 1979c, 1979d, 1979e). These were followed by papers on 30 the Ukalerk C-50 well (McNeil et al.. 1982). the Kopanoar M-13 well (Bujak and Davies, 1981; Dixon et al.. 1984). and the Nuktak C-22 well (Norris. 1986). The paper by Norris, on Nuktak C-22, contains the most complete palynological zonation proposed to date for the Tertiary of the Beaufort-Mackenzie Basin. In a detailed study of the taxonomy and palynostratigraphy of the well, Norris proposed eight informal palynological zones, ranging in age from the Middle Eocene to Pliocene! He was able to correlate this with other wells in the basin, and with adjacent sections from the Caribou Hills and Banks Island. The work on the Kopanoar well (Bujak and Davies, 1981; Dixon et. al, 1984) is important for two reasons. First, in contrast to previously studied wells, which represented marine shelf and terrestrial sections, much of the Kopanoar well represented sedimentation in deep, probably bathyal water (Dixon et al., 1984). Consequently, the well serves as an important reference for deeper water taxa. Second, the report marked the first time that a distinct Neogene algal cyst assemblage had been used in the zonation and correlation of a well in the Beaufort- Mackenzie Basin. Previously, contemporaneous marine palynomorphs had been considered rare in the basin (except in a few restricted sections, primarily in the Paleocene and Eocene). For example, Norris (1986), identified only 12 algal cysts (one from the Neogene) in Nuktak C-22. While the early palynological work in the basin may have concentrated on terrestrial Mesozoic-lowermost Cenozoic outcrops and nearshore wells, the future palynological work in the basin will likely focus on the Eocene and younger sediments from the offshore regions, with a much greater emphasis on algal cysts . 31 3.&Mfithodft 3.3.1. Sample preparation Unprocessed ditch cuttings from Tarsuit A-25 and Orvilruk 0-03 were supplied by Dome Petroleum Ltd., and from Netserk F-40 by Esso Resources Ltd. Fifty metre composite samples were prepared from each well. These were thoroughly washed then sieved though a lOum mesh, to eliminate as much drilling mud as possible and reduce contamination. The samples were then macerated using slightly modified standard palynological techniques. This included treatment with concentrated hydrochloric acid (45% commercial), to remove carbonate material, and hydrofluoric acid (52% commercial), to eliminate silicious material. The hydrochloric acid treatment was continued until no further reaction occurred. Because the samples were not rich in carbonate material, the reaction usually ceased within a few hours. The hydrofluoric acid treatment was monitored regularly, to insure that less-resistant, thin-walled taxa were not destroyed. Samples were not exposed to oxidizing agents. This less harsh maceration technique was used in an effort to improve the recovery of fragile palynomorphs that may have been missed in previous studies. The samples were washed and sieved a second time and mounted on slides using Flo-Tex.R No stains were applied. (Coaly material, for vitrinite reflectance analysis, was hand-picked just prior to the second filtering). Photography was done using a Leitz Ortholux microscope, with interference contrast illumination, and a Leitz Orthomat camera. 3.3.2. Analytical Techniques 32 3.3.2.1. Recognizing contemporaneous palynomorphs One of the biggest problems in studying palynology in the Beaufort- Mackenzie Basin is distinguishing the contemporaneous palynomorphs from the numerous recycled and caved palynomorphs (in many slides, recycled material accounted for greater than ninety-five percent of the residue, and cavings, while not as abundant, were consistently present). In order to make this distinction, a number of methods are available (for a complete discussion see Williams, 1986). In this study, taxonomic identification, state of preservation, and pollen and spore colour (Thermal Alteration Index) were used. In general, the most reliable technique for distinguishing recycled and caved from contemporaneous palynomorphs is taxonomic identification (Williams, 1986). Unfortunately, in the Beaufort-Mackenzie Basin this is not necessarily true, due to the difficulties in establishing accurate species ranges (see Section 3.1). In some circumstances, the state of preservation can be used to distinguish recycled and caved from contemporaneous grains (Williams, 1986 ). Older, recycled palynomorphs tend to be less well-preserved than contemporaneous ones. However, the opposite can be true, so that this method is also not always reliable. The colour of pollen and spores is useful in distinguishing contemporaneous from non-contemporaneous palynomorphs, and was used extensively in this study. Pollen and spores undergo a systematic change in colour (light-yellow, yellow, orange, orange-brown, brown, black) with increasing thermal maturation (Figure 4.2). The colour is a function of time and temperature. If a constant geothermal 33 gradient is assumed, the colour can be used as an indicator of relative ages. Generally, the older grains are darker. However, it is also important to consider wall thickness and ornamentation. Thick-walled and heavily ornamented grains are usually darker than those with thin walls and less ornamentation (Williams, 1986). Different species may also react differently to increases in thermal maturation. The colour of the pollen and spores is assigned a numerical value based on a Thermal Alteration Index (TAI). A modified Chevron TAI scale was used for this study (Fig. 4.2). In order to insure consistency. TAI's were determined using leaf cuticle, whenever possible. If not, then the thinnest portion of Laevigatosporites or PinuspolJenites-1 was used. Starting at the top of each well, TAI values were assigned to each sample. At the top, the palynomorphs are virtually colourless, allowing accurate determination of TAI values for contemporaneous material. By assuming a constant geothermal gradient, a gradual increase in the TAI with depth could be plotted, and contemporaneous palynomorphs consistently recognized. Overall, the TAI method proved to be very effective. It was, however, limited when age differences between the contemporaneous and non- contemporaneous material were small, and colour variations too subtle to detect. This is a common problem in the Beaufort-Mackenzie Basin, because much of the recycled material is derived from the Upper Cretaceous and Tertiary. In addition, due to the basins relative immaturity, the spore colour changes were minimal, with each colour change representing long periods of time. Of note is that algal cysts do not show a similar systematic colour change with increasing thermal maturation. They do, however, often exhibit a characteristic glassy luster, and this, in combination with tazonomic identification, is used to help distinguish contemporaneous from non-contemporaneous algal cysts. Unfortunately, in the Beaufort-Mackenzie Basin, because many of the algal cysts do not have established ranges, the usefulness of the taxonomic identification method is limited. 3.3.2.2. Palynological interval zones Interval zones are defined as intervals which lie between successive biostratigraphic events (North American Commission of Stratigraphic Nomenclature, 1983). In this study, they were defined by range tops or exits. Entries were not considered because of the problems with cavings. The intervals are named after the species whose highest stratigraphic occurrence is used to define the upper limit of a zone (Williams, 1986). When possible, for the sake of continuity and correlation, these were species used previously in zonations from other areas (e.g., Norris, 1986; Williams , 1986; Mathews and Rouse, 1986). The intervals extend downward to, but not including, the range top of the species defining the top of the underlying zone (Williams, 1986). Because of the difficulties with chronological control in the basin, these zones are considered informal. A total of 226 slides were examined for fossil content. A visual estimate of numbers was made using three categories: present (1), common (2-5), and abundant (>5). In general, palynomorphs were sparse, usually accounting for less than ten percent of the residues. 35 3.4. Results 3.4.1. Palynological zonation A total of 223 species of pollen grains, spores, fungi, and algal cysts were identified from the three study wells. Palynomorph range charts are presented in figures 3.1 to 3.3 (see sleeve at back). Palynological zonations for each well are presented in figures 3.4 to 3.6. Included are crude lithologic columns compiled from cuttings sample descriptions. Additional species lists, for both composite and individual wells, arranged alphabetically and taxonomically, are presented in Appendix A. Seven palynological interval zones were recognized from the three wells. These are discussed below in descending stratigraphic order. Included are the diagnostic palynomorphs which best characterize each zonal assemblage. Ranges of these zonally important species are presented in figure 3.7. 1. Laevieatosoorites Interval Zone. Pleistocene This zone is defined by the the monolete spore Laevigatosporites novus. The upper limit of the zone, and the species range tops that it contains, is considered artificial, due to its truncation in the Netserk and Tarsuit wells. The Laevigatosporites zone was not recognized in the Orvilruk well, likely due to the lack of samples available from its first 200m. The interval is marked by a low diversity, high abundance palyno-assemblage. Characteristic pollen and spores include: Laevigatosporites novus, L. ovatus, Stereisporitesminor, S. microgranuiatus., Pinuspoiienitesiabdacus, PA, Figure 3.1: Species range chart, Netserk F-40 (see sleeve in back) 37 Figure 3.1: Species range chart, Tarsuit A-25 (see sleeve in back) i Figure 3.2: Species range chart, Orvilruk 0-03 (see sleeve in back) DEPTH (m) 18 73 564 1685 3 002- 3296- INFERRED AGE Pleistocene late Pleistocene to Pliocene middle to late Miocene middle to late Oligocene early Oligocene early Oligocene to late Eocene PALYNOMORPH ZONE Laevigatosporites Chenopodipollis Pyxidiella sp.b Sigmopollts Ericipites ericius Tsugaepollenitea Tricolporitea - 1 Ty thodlseus Multiplicisphaendium - 1 Impletospnaeridium - I BatiacasDhaerica sp. Oino - 7 Selenopemphix - 1 Oblosoontes - 1 Myricipits - 1 Carpinipidites - 1 Integricorpus Alnipolleniies roouata Araliaceoipollenites Pejavis tagluensis Tetrad - 1 Juglans robuata Tillaooilenite j Calllmothallua partusa Muitlcellaeaporitea PalaoperMlnlum H>:-:-:-I 4365 1 1 Li. — J Figure 34: Provisional palynological zonation for Netserk F- INFERRED AGE PALYNOMORPH ZONE Pleistocene late Pleistocene to Pliocene late to middle Miocene early Oligocene early Oligocene to late Eocene middle Eocene Laevigatosoorites Chenopodipollis Ericipites ericius Tythodiscus Dino - 7 Tsugaepollenrtes Integricorpus Almoollenites robusta Araliaceoipollenites Pesavis tagluensis Juglans robusta Tiliapollenites Tetrad - 1 Striadisporites multistriatus Pistillipollenites mcgregorii Dyadospontes so. Ctenosporites woltei Microthyrites sp. Glaphrocysta ordinata Figure 3.5: Provisional palynological zonation for Tarsuit A-25. DEPTH (m) 200- INFERRED AGE PALYNOMORPH ZONE LITH. 450- 1200- 2400- 2650- 3606- Pliocene middle to late Miocene middle to late Oligocene early Oligocene early Oligocene to late Eocene Chenopodipollis Pyxidiella so b Ericipites ericius Tricolporitos - 1 Impletosphaeridium - 1 Tythodiscus Tsugaepollenites Oino - 7 Selenopemphix - 1 Oblosoorites - 1 Myricipites sp. Carpinipidites - 1 Integricorpus Alnipollenites robusta Araliaceoipollenites Tiliapollenites Multiceilaesporites sp. Tetrad - 1 Figure 3.6: Provisional palynological zonation for Orvilruk 0-03. 2? tSo" CM 43 Piceapollenites grandivescipites, Taxodiaceaepollenites hiatus, Keteleeria-1, Compositae-1, and Betulaceoipollenites claripites.. The zone is also characterized by a moderate algal cyst population, including: Pyxidiella sp. A, Grculodinium perforata, Pteridinium circusutum, Micrhystridium inconspicuum, Multiplicisphaeridium-X, Lejeuniahyalina, Veryhachium-l, V.-2, Caledonidinium vermiculatum, and Batiacasphaera micropapiJlata Also present are large numbers of recycled Cretaceous and Tertiary miospores and algal cysts, including Spinidinium acutus, Chytroisphaeridia-1, and Retriletes-\. The Laevigatosporites zone is assigned a Pleistocene age. based upon its stratigraphic position above the early Pleistocene to Pliocene Chenopodipollis zone. This assemblage correlates closely with an assemblage recognized in several other Beaufort Sea wells (e.g. Norris, 1986). However, it has previously been assigned a Pliocene-Miocene age. A Pleistocene age is favoured because, when present, the Laevigatosporites assemblage is always located at the top of the section. To date the assemblage as Pliocene would infer that there has been no deposition in the region during the Pleistocene, a time span of 1.6 million years. Considering the immense discharge from the modern Mackenzie River, this seems unlikely. The boundary between the Laevigatosporites and the underlying Chenopodipollis zone is marked by a large number of disappearances. This is attributed to the cooling event that would have accompanied the onset of Pleistocene glaciation in the region. 2. Chenopodipollis Interval Zone Early Pleistocene to Pliocene 44 The upper limit of this zone is defined by the range top of Chenopodipollis, and its base, by the range top of Ericipites ericius In Orvilruk, where the Laevigatosporites zone was not present, the Chenopodipollis zone extends to the top of the well. The palynological assemblage is dominated by the same species as the overlying Laevigatosporites zone. The Chenopodipollis zone is characterized by a large number of last or single occurrences. Pollen and spores making their final stratigraphic appearance in the zone include: Chenopodipollis, Vitreisporites minor, Tsugaepollenites, Deltoidspora diaphana, Graminidites, Caryapollenites, Alnipollenites, Saliipollenites, Sigmopollishispid us, Stereisporites antiquasporites, Betulaceoipollenites minor, Schizosporis-\, and Pterospermopsis sp. Algal cysts making their last stratigraphic appearance include: Paralacanieila indentata, Veryhachium^, Batiacasphaera sphaerica Micrhystridium fragile, Chiropteridium, Pyxidiellasp. B, and Dino-1. The Chenopodipollis zone is assigned an early Pleistocene to Pliocene age, based on the correlation with an assemblage recognized by Mathews and Rouse (1986), from south-central British Columbia. Mathews and Rouse were able to fix the age of the zone, using radiometric dates from adjacent lava flows. The Chenopodipollis zone also correlates with an assemblage recognized by Norris (1986), from the Nuktak C-22 well. However, at that time, it was assigned a Pliocene to Late Miocene age. The boundary between the Pliocene Chenopodipolhs and middle to late Miocene Ericipites interval zone below is marked by a large number of disappearances. These are interpreted to be the result of a Late Miocene erosional event. However, McNeil et al. (1982), based on work from Ukaierk C-50 , suggest a major cooling trend across the Late Miocene-Pliocene boundary to explain the dramatic change in the palynofloras. 3. EriciDites Interval Zone Middle to late Miocene The top of this zone is defined by the range top of Bridpites ericius and its base by the range top of SeJenopemphii-\. It is characterized by a relatively diverse and abundant mixed terrestrial-marine palyno-assemblage. Particularly numerous are triporate and tricolporate pollen grains, such as Myricipites, Carpinipites, Caryapoiienites, Betulaceoipollenites Ostryoipollenites, TricoJporites- 1, Quercoidites-\, Saiiipoiienites-\, and Fraxinoipoiienites Other characteristic pollen and spores include: Tsugaepoilenites igniculus, Tsugaepotienites viridifluminipites, Stereisporites, Deltoidospora and Vitreisporites The interval also contains many long-ranging gymnosperm pollen seen in the overlying zones. In addition, the interval is marked by several distinctive algal cysts. These include: Impletosphaeridium-\, Micrhystridium fragile, Tithodiscus, Apteodinium, Dino-1, and Chiropteridium. Also present are many long-ranging algal cysts, such as Lejeunia hyaiina, Pteridinium circumsutum, Batiacasphaera micropapillata, B. sphaerica, Paralacanielia indentata and MuJtiplicisphaeridium-\. The Ericipites zone is dated as middle to late Miocene, largely based on the abundance of Tsugaepoilenites igniculus. This grain has been used by both Norris (1986). and Williams (1986). in the Mackenzie basin and Labrador Sea. respectively, to indicate a Middle to Late Miocene age. 46 The boundary between the Ericipites and Selenopemphix zones is interpreted to be conformable at Netserk and Orvilruk, but unconformable at Tarsuit, where the upper Oligocene appears to be missing. 4. Selenopemohix-X Interval Zone Middle Oligocene to late Oligocene The upper limit of this zone is defined by the range top of a newly described algal cyst, Selenopemphii-\. The base of the zone is unusual, in that it is not defined by a species top. Instead, it is marked by a sudden drop in species diversity (especially algal cysts) across the upper-lower Oligocene boundary. The zone is recognized in the Netserk and Orvilruk wells. It appears to be missing in the Tarsuit well, likely due to a period of non-deposition. The interval is characterized by a relatively sparse but mixed terrestrial- marine paly no-assemblage. It is dominated by long-ranging species, including many triporate and periporate pollen grains such as Betulaceoipollenites, Myricipites, Carpinipites, Caryapollenites, Alnipolfenites.mA Juglanspollenites Also common are the gymnosperm pollen Piceapolienites, Pinuspollenites, Taxodiaceaepollenites, Tsugaepoiienites, and Laricoidites Characteristic algal cysts include: Selenopemphii-\, S. selenoides, Veryhachium reduction, and Micrhystridium deflandrea. These all have their final stratigraphic occurrence in this zone. Common long-ranging algal cysts include: Pteridinium circumsutum. Paraiacanieiia indentata, Pyxidiella sp.a, Pyxidiella sp.b, Lejeunia hyalina, and Micrhystridium fragile Infrequent to rare algal cysts include Deflandrea phosphoritica, Hemicystodinium zohari, Dino-27, Apteodinium and Deflandreagigantica (possibly recycled). 47 The interval is also characterized by the fungal spore Oblosporites\ which occurs throughout, and has its last stratigraphic occurrence here. Monosporonites, Multiceiiaesporites and Pluricellaesporites also have their final stratigraphic appearance in this zone. In general, fungal spores become more abundant near the base. The Selenopemphix-\ interval is tentatively assigned a middle to late Oligocene age. It is interpreted to be equivalent to the Arnak Member assemblage from Nuktak C- 22, described by Norris (1986). Both are distinct in their position above relatively depauperate lower Oligocene assemblages. The zone's stratigraphic position, below the Ericipites zone, also supports a late to middle Oligocene date. The boundary between the Selenopemphii-1 zone and the integricorpus zone is interpreted by Norris to be conformable, due to changing depositional environments. 5. Inteericorous Interval Zone Early Oligocene The top of this zone, like the bottom of Selenopempnir-i, is marked by a sharp drop in species diversity and abundance. It is named for the single occurrence of the zonally important pollen grain. Integricorpus, at the top of the interval in the Tarsuit well. The base is defined by the range top of Araiiaceoipollenites spp. This zone was recognized in all three wells. The zone is characterized by a relatively depauperate, predominantly terrestrial, palyno-assemblage. It is dominated by long -ranging species. Common pollen and spores include: PiceapoJJenites, Pinuspollenites, Caryapollenites, 48 Alnipollenites and Juglans. As mentioned above, there is a single occurrence of Integricorpus. A gradual increase in the amount of fungal material occurs towards the base. Although the assemblage is predominantly terrestrial, it does contain a small number of algal cysts, including: Selenopemphix-\, Deflandreaphosphoritica, and Grculodmium granulosum perforatum. The integricorpus interval is assigned an early Oligocene age, and is interpreted to be equivalent to the Ivik Member assemblage from Nuktak C-22. described by Norris (1986). It is distinguished from the Arnak Member by its relatively low species diversity. An early Oligocene age is also supported by the occurrence of integricorpus, a widespread early Oligocene index fossil that has been used in Arctic Canada (Rouse, 1977), the Beaufort-Mackenzie Basin (Norris, 1986), and the Labrador Sea (Williams, 1986). Despite the large number of extinctions, and the overall increase in species diversity, the boundary between the integricorpus and AraiiaceoipoiJenites zones is interpreted to be conformable. 6. AraiiaceoipoiJenites Interval Zone Early Oligocene to late Eocene The upper limit of this zone is defined by the range top of Araliaceoipollenites spp., and the base, by the range top of Pistiliipoiienites mcgregorii. It was the last zone to be recognized in Netserk and Orvilruk. It is clearly distinguished from the overlying integricorpus interval by a distinctive, abundant, relatively low diversity palyno-assemblage. Dominant pollen grains are Araliaceoipollenites spp, Juglans robusta, and Alnipollenites robusta. Also characteristic, but less frequent, are Tetrad - 1 , Tiliapollenites vescipites, Tiliapollenites crassipites and Osmundacidites In addition, the zone contains many long-ranging pollen and spores, including Pinuspollenites, Piceapoilenites, Taiodiaceaepollenites, Tsugaepoilenites, Laricoidites, Myricipites, and Carpinipites. An abundance of fungal material, including spores, hyphae, and fruiting bodies, is present. This include: Monosporonites, Diceilaesporites, Diporicellaesporites, MulticelJaesporites, Pleuricellaesporites, and Callimothallus pertusa. The interval is predominantly terrestrial in Tarsuit and Orvilruk, and mixed terrestrial-marine in Netserk. It contains several characteristic algal cysts, including Selenopemphir-l, Paleoperidinium adridnae, Micrhystridium fragile^, and Dioiya-\. Abundant recycled Cretaceous and Paleocene miospores and algal cysts are also present. The zone is dated as early Oligocene to late Eocene, based on the disappearance of Araliaceoipollenites spp. Williams (1986), and Rouse and Mathews (In press), have both recently used this species to mark the Eocene- Oligocene boundary in the Labrador Sea and central British Columbia, respectively. Other characteristic late Eocene palynomorphs in the zone include Tetrad-1, Tiliapollenites, Pesavis tagluensis, Diozya,, and Callimothallus The abundance of fungal material is also characteristic of the Eocene. The boundary between the Araliaceoipollenites and Pistillipolienites zones is interpreted to be conformable. 7. Pistillipollenites mcereeorii Interval Zone Middle Eocene 50 The top of this zone is defined by the range top of Pistillipollenites mcgregorii. The base is undefined, because this is the last interval zone encountered. The palyno-assemblage is dominated by the same species as in the overlying AraiiaceoipoiJenites interval. However, the zone also contains the final, or only, stratigraphic occurrence of several zonally important species. These include: Pistillipollenites mcgregorii, Pesavis juvinilis, Verrutricolporites -1, Triporopollenites muilensis, Q'catricosisporites intersectus, Microthyrites sp A, Striadiporites multistriatus, Ctenosporites wolfei, Bracnysporisporites sp, Dyadosporitessp.k, Thalissiophorapelagica, Aereosphaeridium,2&A Glapnyrocysta ordinata. Also present are a large number of recycled Cretaceous and Paleocene miospores and algal cysts. The Pistillipollenites interval is assigned a middle Eocene age, based on the range top of Pistillipollenites mcgregorii which is not believed to occur above the midpoint in the Middle Eocene (Rouse, 1977). The assemblage closely correlates with other Middle Eocene assemblages from the Labrador Sea (Williams, 1986), south-central British Columbia (Mathews and Rouse, 1984), and the Mackenzie basin (Norris, 1986; Ionnides and Mclntyre, 1980). 3.4.2. Correlations between the three study wells Results from the three study wells correlate closely, and suggest that the recognized palynological assemblages may be continuous across the basin. Despite the large distances and complex structures between the wells, the results also provide some broad geological information. For example, the missing upper Oligocene in Tarsuit suggests that this was either a site of non-deposition or erosion during that time, and may have been uplifted into a topographic high during the early Oligocene. The relatively thin lower Oligocene intervals, in all three wells, suggest a regional slowing of deposition during this period. In addition, the thick middle-upper Oligocene sections in Netserk and Orvilruk support the theory that the Middle to Late Oligocene was the basin's prolific delta-building period within the Tertiary (Willumsen and Cote, 1982). Relatively complete sections at Netserk and Orvilruk suggest more continuous deposition at these wells, than at Tarsuit. A further observation is the absence of a thickening, prograding wedge, which might have been expected, since the wells are in a S-N alignment. 3.4.3. Correlations with other Tertiary zonations in northern, western and eastern Canada Many elements of the seven palynological interval zones proposed in this study can be recognized in other zonations from northern, western, and eastern Canada. The correlations within the basin demonstrate that it is possible to develop a locally useful palynological zonation for the Tertiary. The correlations beyond the basin suggest that the palyno-assemblages from the region may not be as isolated and endemic as once thought. The informal zonation proposed in this study correlates closely with that proposed by Norris (1986), for the Imperial Nuktak C-22 well in the Beaufort Sea. 52 It also correlates, in part, to zonations from other wells in: 1. the Beaufort Sea (e.g., Ivik, Austin Cumming Exploration Consultants, 1979a; Adgo, Austin Cumming Exploration Consultants, 1977); 2. the Caribou Hills (Ionnides and Mclntyre, 1980); 3. Banks Island (Doerenkamp et al., 1976); 4. the Mackenzie basin, the Eureka Sound Formation and equivalent beds in the Canadian Arctic (Rouse, 1977); 5. south-central British Columbia (Piel, 1977; Mathews and Rouse, 1984; 1986); 6. the Labrador Sea (Williams, 1986). The Pleistocene Laevigatosporites and early Pleistocene to Pliocene Chenopodipollis palyno-assemblages are amongst the most distinct and consistent in the region, and correlate closely to similar assemblages from across the Beaufort-Mackenzie Basin (e.g., Nuktak (Norris, 1986); Adgo.Ivik, Kugpik, Tingmiark, Uvilruk (Austin and Cumming Exploration Consultants 1977, 1978a, 1978b. 1978c, 1979a, 1979b, 1979c. 1979d, 1979e)l. The Chenopodipollis assemblage also correlates with an assemblage recognized by Mathews and Rouse (1986) from south-central British Columbia. The middle to late Miocene Ericipites palyno-assemblage is characterized by an abundance of bladdered conifer pollen, including the zonally important species Tsugaepoilenites igniculus \\ correlates with other Middle-Late Miocene assemblages from the Beaufort-Mackenzie Basin (e.g., Norris, 1986; Austin and Cumming Exploration Consultants 1977,1978a, 1978b, 1978c, 1979a, 1979b, 1979c, 1979d, 1979e), and from the Labrador Sea (Williams, 1986). In contrast to other zones, the late to middle Oligocene Selenopemphix-1 palyno-assemblage does not correlate well outside the basin. It is interpreted to be approximately equivalent to the Upper Oligocene Arnak Member assemblage described by Norris (1986) from Nuktak C-22. The correlation is based more on 53 relative species diversity (compared to the underlying depauperate Integricorpus assemblage), than on specific species and range tops. The early Oligocene Integricorpus assemblage tentatively correlates with assemblages from the Beaufort Sea (e.g., Norris. 1986; Austin and Cumming Exploration Consultants 1977, 1978a, 1978b, 1978c, 1979a, 1979b, 1979c, 1979d, 1979e; Staplin, 1976); the Caribou Hills (Interval D of Ionnides and Mclntyre, 1980); south-central British Columbia (Piel, 1971, 1977; Rouse, 1977; Mathews and Rouse, 1984; 1986 ); and the Labrador Sea (Williams, 1986). This correlation is tentative, because of the single occurrence of Integricorpus in the Tarsuit well, and because of the absence of several other key lower Oligocene marker fossils, such as Boisduvaiia ciavatites, Jussiaea sp.. and Diervilla ecninata It is based largely on the presence of a relatively depauperate, predominantly terrestrial palyno- assemblage, dominated by triporate and periporate pollen grains. This roughly correlates to the lower Oligocene Ivik Member assemblage described by Norris (1986) from Nuktak C-22. If this is true, then the Integricorpus zone (this study) is also equivalent to the Retriletes, Osmundacidites, and the uppermost portion of the Integricorpus zones proposed by Norris (1986). The early Oligocene-late Eocene Araliaceoipoilenites palyno -assemblage correlates closely with assemblages from the Labrador Sea (Williams, 1986), and south-central British Columbia (Mathews and Rouse, in press). Of note is that the assemblage does not correlate as well with others in the Beaufort-Mackenzie Basin. Based on age determinations, it correlates roughly to the middle to lower portion of the Integricorpus zone described by Norris (1986) from Nuktak C-22 . The middle Eocene Pistillipoilenites assemblage is widespread and correlates closely with assemblages from the Mackenzie basin (Norris 1986); the Caribou Hills (Ioannides and Mclntyre, 1980); the Eureka Sound Formation and equivalent beds in Arctic Canada (Rouse, 1977); south central British Columbia (Mathews and Rouse, 1984); and the Labrador Sea (Williams, 1986). It also correlates with the Pesavis zone described by Norris (1986), from Nuktak C-22 . The correlations discussed above are based almost exclusively on terrestrial species. This is largely due to the lack of recognition, until recently, of marine species in the basin. However, many of the algal cysts recognized from the three study wells show similarities to assemblages from as far away as Antarctica (Kemp et al., 1976), and the English Isles (Reid, 1974, 1977). This emphasizes, again, that the palyno-assemblages from the Beaufort-Mackenzie Basin are not as isolated and endemic as once thought. 3.4.4 Comparison with previous palynological zonations from the Beaufort- Mackenzie basin There are two major differences between previous zonations from the Beaufort-Mackenzie Basin and those presented here. First, the Tertiary sediments encountered in these study wells have been assigned younger ages than those in many previous zonations. The oldest sediments encountered in this study are middle Eocene, in the Tarsuit A-25 well, and early Oligocene to late Eocene, in the Netserk F-40 and Orvilruk 0-03 wells. This is in contrast to the Paleocene ages assigned to the bottommost sediments of several other wells in the basin, including the adjacent Netserk B-44 well (Austin and Cumming Exploration Consultants, 1979b). Even when the ages of the bottom sediments are similar, the ages of the overlying sedimentary columns are generally younger (with lower stage boundaries) in the current study. This is particularly true in the Neogene. This discrepancy may be due, in part, to the fact that many of the previously analysed wells were onshore or nearshore, with resultant thinner Neogene sections. The differences in assigned ages may also be attributed to more precise charting, allowing the exclusion of many recycled fossils from the present analysis. The second major difference between previous zonations and that presented here is a larger recovery of contemporaneous algal cysts reported in this study. This is attributed to less harsh maceration techniques used for sample preparation (see Section 331). Past methods, involving long exposures to Schultzes solution, likely destroyed the often transparent pollen, spores, and algal cysts, giving the false impression that they were scarce. Dinoflagellates and other algal cysts have been described from the Beaufort- Mackenzie Basin since the early seventies [several are regarded as key marker fossils, for example, Dino-J-7 (D/oiya), Wetzeliellahampdenensis\ (Staplin, 1976)1, but they were generally regarded as rare to absent, especially in the Neogene. As a result, there have been relatively few papers published (Harland et al., 1980; Bujak and Davies, 1981; Bujak, 1984; Dixon et al., 1984) dealing with algal cysts as important constituents of the palynofloras of the region. Consequently, the stratigraphic application of algal cysts in this study is largely restricted to local correlations and broad paleo-environmental interpretations. With little to compare with, most of the algal cysts identified here are categorized as new, new to the basin, or endemic to the basin. Their stratigraphic ranges are often unknown, and therefore are of little use for correlations beyond the study wells. 3.4.5.Nearshore-offshore effects on oalvnologv 56 In this study, the effect of basin margin proximity on the paiynology of the Beaufort-Mackenzie Basin was investigated. To facilitate this, wells were selected in a south-north alignment, assuming that this transect would be approximately perpendicular to the basin margin. Environments both proximal and distal to the margin could then be sampled. In studying the effect of basin margin proximity, the ratio of terrestrial (pollen, spores, and fungal material) to marine (algal cysts) paiynomorph species was calculated for each well (Table 3.1). The ratio considers only species diversity, and does not take into account the relative abundances of the fossils. With increasing distance from shore, the terrestrial:marine ratio would be expected to drop, due to increasing water depth, salinity, and transport distance for terrestrial material. However, the palynological data did not exhibit this trend. Instead, each well showed a relatively strong terrestrial influence throughout, regardless of its proximity to the basin margin. One explanation for this is that a large terrestrial discharge from the Mackenzie River has affected the region throughout the time represented by the wells. The most terrestrial' well is Tarsuit, with a terrestrial:marine ratio nearly double that of Netserk and Orvilruk (Table 3.1). The higher ratios for Tarsuit suggest that it was either located near the mouth of a channel, or that it was a topographic high with limited marine influence. The relatively high ratios for all three wells during the lower Oligocene suggest a broad uplift of the basin during this time, and supports the latter explanation. The missing middle to upper 57 PLEISTOCENE PLIOCENE MIOCENE UPPER OLIGOCENE LOVER OLIGOCENE UPPER EOCENE MIDDLE EOCENE TOTAL OrvirukO-03 - 30:18 (I 67) 48:44 (1 09) 29:24 (2.27) 25:11 (6.20) 31:5 (6 20) - 153 102 (1 59) Tu-suit A-25 17:7 (2.40) 23 16 (1 44) 33 15 (2 20) (4.75) 33.8 45 5 (9 00) 35:16 (5 31) 241 67 (3 59) N o u e r i f-40 12:6 (2 00) 34:37 (0 92) 46:33 (I 39) 40:23 11.74) 24:3 (8.00) 39:21 (1.86) - 195 123 i 1 58) Table 3.1: Ratio of terrestrial species (pollen grains, spores and fungi) versus marine species (algal cysts) Ratio considers total number of species recorded for each interval. The first ratio is the actual number of species recorded, the second is the fraction. Oligocene in Tarsuit suggests non-deposition or erosion, also supporting the topographic high explanation. The values for Netserk and Orvilruk are similar to each other and suggest that the offshore conditions in the basin may not have varied substantially across the shallowly dipping continental shelf of the Beaufort Sea. Perhaps a higher gradient might have been observed if one of the wells in the study had been located onshore. In summary, the paiynology does not exhibit a marked increase in marine influence along the south to north transect. Possible explanations for this are that the large discharge from the Mackenzie River masked the effects of basin proximity, or that the transect was not perpendicular to the basin margin. Willumsen and Cote (1982), proposed that the delta front shifted counter-clockwise several times during the Tertiary. This rotation of the basin margin could explain why no consistent pattern in the paiynology, in relation to basin margin proximity, is observed. 58 3.5. Summary and Conclusions 1. A total of 226 slides from 50m composite samples, from Netserk F-40, Tarsuit A-25, and Orvilruk 0-03 were examined for fossil content. In total, 223 species of pollen, spores, fungi, and algal cysts were identified. 2. Seven informal palynological interval zones from the three study wells were proposed. 3. Correlations within the basin indicate that the proposed zonation may be useful for local correlations. 4. Correlations outside the basin indicate that the palynological assemblages from the Beaufort-Mackenzie Basin may not be as isolated and endemic as first thought. 5. The recognition of greater than 100 species of algal cysts is the largest recovery of cysts from the Beaufort-Mackenzie Basin to date, and is attributed to less harsh maceration techniques used in sample preparation. 6. The high recovery of algal cysts confirms a substantial population from a region that, until recently, had been regarded as virtually barren of these . 7. The recognition of many algal cysts from previous reports indicates that they may also be useful for future regional correlations. 59 8. The paiynology does not exhibit an increase in marine influence with decreasing proximity to the basin margin. Instead it shows a consistent, strong terrestrial influence throughout each well. The large terrestrial discharge from the Mackenzie River is interpreted to have masked the effect of basin proximity on the paiynology of the area. 60 CHAPTER 4 ORGANIC GEOCHEMISTRY 4.1 Thermal maturation 4.1.1. Introduction Oil and gas are formed by the progressive diagenesis of organic matter in response to increasing temperature and time (Fig. 4.1). The level of diagenesis in relation to the ability of organic matter to generate hydrocarbons is referred to as its thermal maturation. Organic matter that has not reached the threshold for oil and gas formation is considered immature. Organic matter that has reached the threshold is considered mature. Finally, organic matter that has been heated above the oil/gas threshold is considered inert, and only gas can be generated. Because of the close relationship between petroleum generation and temperature, it is important to determine the thermal maturity of organic matter in potential source rocks. There are a variety of methods available for this. For a complete discussion of these, see Waples (1984a), Tissot and Welte (1984), and Hunt (1979). In the present study, pollen and spore colouration (TAD, as well as vitrinite reflectance, are used to estimate the levels of thermal maturation. The Thermal Alteration Index method is based on the systematic colour changes that pollen and spores undergo when exposed to increasing temperature (Fig. 4.2). These changes are due to the increasing carbonization of the organic 61 o u 2 i o > 3 2 Z o z 03 O si O P T I C A L . P A R A M E T E R S O S Q A N I C Q E O C M E u i s O F K E R O Q E N S o Ui CC 5 a? o o ~ cc z o 5 3 10 II) 01 CO UJ z UJ < < z U l o < w U l 2 7 0 P e a t L i g n i t e ? -10 5 « 6 Low vol. bltum. - 5 U e l e - a n t T w a . Oae - 0.40 0.50 0.80 0.70 0.80 O.flO 1.0 1.3 1.35 2 . 0 3.0 4.0 &.0 y e l l o w - 2.5 o r a n g e o r a n g e - b r o w n 3.0 red- brown 3.7-1 3 , i t 435"C 4 70°C 4 8 8 C jo 'o* Figure 4.1: Correlation of major organic maturation indices (from Bustin et al., 1985; p. 5). The correlations shown are based on vitrinite reflectance. Modified from (1) Barnes et al., (1984); (2, 3. 4, 5.7) Teichmuller and Teichmuller in Stach et al., (1982; p 45, 47); (6) Dow (1977); (8,9) van Gijzei (1979) and Teichmuller and Durand (1983); (10) Jones and Edison (1978); (11) Epstein et al., (1977); (12) Durand and Monin (1980); (13) Espatalie et al., (1977b); (14) Allan and Douglas (1977). matter. The grains begin colourless, and change from yellow, to yellow-brown, to brown, to black. Because the colour changes are irreversible, the TAI method is a reliable indicator of maximum attained temperature. The vitrinite reflectance method is based on the systematic increase in reflectivity of the coal maceral, vitrinite, with increasing thermal maturation. This occurs because of alterations in the molecular structure of the maceral (Bustin, 1983). Because these changes are irreversible, the method is not affected by retrograde metamorphism, and can therefore be considered an accurate index of maximum attained maturation. For a complete discussion of the method (theory- techniques-anaiysis) see Bustin et al.,(1983). In vitrinite reflectance, values are recorded as percentage of incident light reflected off individual vitrinite particles (%Ro). Oil generation occurs at values between 0.6 and 1.5, with peak oil generation occurring at 1.0 (Fig.4.1). These values are for oil prone Type I kerogen, and, like all maturation parameters, will vary according to the original organic matter present. For a discussion of this variability, see Tissot and Welte, (1985). For a comparison of TAI and vitrinite scales, see Table 4.1. A frequently cited advantage of the vitrinite reflectance method (over other maturation parameters) is the objective manner in which the data is gathered, with computer-aided instruments. However, the vitrinite is chosen subjectively, and, depending on the type of sample, it can be difficult to differentiate vitrinite from other macerals. Another problem, particularly when working with cuttings samples, is the recognition of indigenous vitrinite. Up to four distinct populations (of vitrinite) can be present: indigenous, recycled, caved, and additive contaminants. In addition, the relative preservation of the vitrinite can also affect 63 its reflectance. That which has undergone various degrees of oxidation will show higher reflectance values than fresh, non- oxidized vitrinite. %Ro TAI %Ro TAI 0.03 2.0 1.26 3.15 0.34 2.1 1.30 3.2 0.38 2.2 1.33 3.25 0.40 2.25 1.36 3.3 0.42 2.3 1.39 3.35 0.44 2.35 1.42 3.4 0.46 2.4 1.46 3.45 0.48 2.45 1.50 2.5 0.50 2.5 1.62 3.55 0.55 2.55 1.75 3.6 0.60 2.6 1.87 3.65 0.65 2.65 2.0 3.7 0.70 2.7 2.25 3.75 0.77 2.75 2.5 3.8 0.85 2.8 2.75 3.85 0.93 2.85 3.0 3.9 1.00 2.9 3.25 3.95 1.07 2.95 3.5 4.0 1.15 3.0 4.0 4.0 1.19 3.05 4.5 4.0 1.22 3.1 5.0 4.0 Table 4.1: Comparison of TAI and Vitrinite Reflectance scales (after Waples. 1980). 4.1.2. Methods 4.1.2.1. Thermal Alteration Index (TAI) The TAI method is described in Section 3.3.2.1. Each sample was assigned a numerical value on a Thermal Alteration Index, based on the colour of the pollen MATURATION %Ro COLOR CHEVRON STAPLIN LEVEL (1978) (1969) Immature < 0.3 colorless 0.5 0.3 yellow 1.0 0.4 2.0 ± 2 . 0 0.5 yellow - orange 2.5 ± 2 . 5 . - — — 0.6 2.6 — • — 0.7 orange - brown 2.7 0.85 2.8 Mature 0.93 2.85 1.0 reddish - brown 2.9 1.15 3 0 1.22 3.1 1.30 3.2 ± 3 . 0 . — — • 1.5 brown 3.5 2.0 3.7 2.25 black 3.75 2.5 3.8 Metamorphosed 3.0 3 9 ± 4 . 0 3.5 4.0 4.0 4.0 >4.0 4.0 ± 5 . 0 Figure 4.2: Comparison of Vitrinite Reflectance to TAI scales developed by Chevron (1978) (used in this study) and Staplin (1969). and spores. In this study, a four-point system, developed by Chevron (1978), was used (Fig. 4.2). On this scale, oil generation begins at 2.6, peaks at 2.9, and ceases at 3.2. Again, these numbers are estimates based on oil prone Type 1 kerogen. The measurements are considered accurate to plus or minus 0.25. TAI values were recorded for each slide at 50 m intervals, to the total depth of each well, and plotted against depth (Fig. 4.3-4.5). 4.1.2.2. Vitrinite Reflectance 4.1.2.2.1. Sample Preparation Material for vitrinite reflectance analysis was hand-picked from 226 macerated kerogen residues (see Section 3.3.1). Dark, coaly' material, floating on top of the residues, was selected. However, only small amounts of material were recovered from each sample, and this became a limiting factor in the selection of samples for analysis. Seventy samples were eventually analysed for random vitrinite reflectance: thirty from Netserk F-40 , twenty-eight from Tarsuit A-25, and twelve from Orvilruk O-03- Samples were pulverized with a mortar and pestle, mixed with Strover's Epofix epoxy R , and placed in small holes (3mm x 2mm) which were drilled into transoptic plugs (six samples per plug). These were allowed to harden, and were then polished just prior to analysis. 4.1.2.2.2. Analytical Techniques Seventy samples were analysed for random vitrinite reflectance. Polished samples were analysed under oil immersion (n-1.515) on a Leitz MPV2 Thermal Alteration Index p p p p p p p NJ NJ NJ Figure 4.3: Netserk F-40. Thermal Alteration Indei versus depth. 67 Therrnal Alteration Index Figure 4.4: Tarsuit A-25. Thermal Alteration Index versus depth. Thermal Alteration Index * -i — Figure 4.5: Orvilruk 0-03. Thermal Alteration Index versus depth. microscope, equipped with a 50X objective, 10X ocular, stable voltage supply, photomultiplier, and a computer-assisted data collector. The size of the measuring aperture was 8mm. Each sample was manually scanned until 50 measurements had been taken, or until the entire polished surface had been examined. If the sample quality was high enough, samples with fewer than 50 measurements were repolished and re-examined, in order to satisfy the minimum sample number. The apparatus was calibrated against a known standard and checked every 25 readings. If the calibration was out by more than 0.02% at the end of a run, the run was discarded and repeated. The resolution of populations was accomplished using a model that fits mixtures of log and log normal populations (Prob plot.. Stanley, 1987 ). Plots of %Ro and Log%Ro versus depth were constructed for each well. The data plotted equally as well arithmetically and log-linearly. This occured because of the low values present, in which the relationship between Ro and depth is assumed to be arithmetic (Stach, 1983). The arithmetic plots are presented in figures 4.6- 4.8. 4.1.3. Results 4.1.3.1. Thermal Alteration Index (TAI) The TAI profiles for the three wells show a gradual increase with depth, indicating an increase in thermal maturation (Fig. 4.3- 4.5). However, none of the sediments penetrated in the three wells have reached the oil window (TAI = 2.6) (Table 4.2). Because no commercial quantities of hydrocarbons can be expected from source rocks that have not attained the peak level of thermal maturation for oil generation (TAI - 2.9), none of the sediments in this study can be considered a source for the Tertiary (offshore) oils of the Beaufort-Mackenzie Basin. The data supports a cool basin' interpretation for the Beaufort- Mackenzie Basin (discussed in Chapter 5). The TAI profiles for Orvilruk 0-03 and Netserk F-40 show no evidence of unconformities. The TAI profile for Tarsuit A-25, however, does show a change in slope at approximately 1500m, possibly suggesting some missing section. WELL TOTAL DEPTH (m) MAXIMUM TAI Netserk F-40 4365 2.2 Tarsuit A-25 4445 2.4 Orvilruk 0-03 3606 2.0 Table 4.2: Total depth versus maximum attained TAI values from modified Chevron TAI scale (see figure 4.2), in which oil window - 2.6, and peak oil generation - 2.9. 4.1.3.2. Vitrinite Reflectance Values from the vitrinite reflectance analysis of the samples from Netserk F- 40 show a direct relationship between Ro and depth (Fig. 4.6). The vitrinite profiles for Tarsuit A-25 and Orvilruk 0-03 (Fig. 4.7, 4.8), however, do not demonstrate a significant relationship between these two variables. In Netserk F-40, a gradual increase in Ro with depth, indicating an increase in thermal maturation, is observed. The Ro at total depth (4365m) was extrapolated as 0.44%, clearly short of the oil window (0.6 %Ro). This is in agreement with the TAI analysis, which suggests that the well is immature to its total depth. R«f1«etanc« p p p o o Q o -» N u j> cn 01 R2 " 0.76 n - 26 Figure 4.6: Netserk F-40. Percentage random vitrinite reflectance versus depth. Error bars represent one standard deviation. R«fl«ctone« Figure 4.7: Tarsuit A-25. Percentage random vitrinite reflectance versus depth. Error bars represent one standard deviation. R«f1«ctanc« «-»• u - Figure 4.8. Orvilruk 0-03: Percentage random vitrinite reflectance versus depth. Error bars represent one standard deviation. The measured maturation gradient for the Netserk F-40 well is 0.07 Ro/km (0.11 logRo/km). Sedimentation rates need to be less than lOm/Ma (O.Olmm/yr) to maintain thermal equilibrium (Stach et.al., 1982). However, estimated sedimentation rate for Netserk F-40 is 100 m/Ma (O.lOmm/yr) (calculated as total depth divided by maximum absolute age of the well). Rapid sedimentation can retard the maturation gradient when the sediments are prevented from reaching an equilibrium geothermal gradient (Stach et.al., 1982). The low value of the measured maturation gradient for the Netserk F-40 well is therefore attributed to the rapid sedimentation in the basin during the Late Cretaceous and Tertiary. The measured maturation gradient is consistent with values reported from other similar basins. Shibaoka and Bennett (1977) reported gradients of 0.08 to 0.15 logRo/km for the Gippsland basin in Australia; Bostick et al (1978) reported gradients of 0.02 logRo/km for the Ventura and Los Angeles basins; England and Bustin (1986) reported gradients of 0.07 to 0.15 logRo/km for the Western Canada Sedimentary Basin; and Bustin (1986) reported gradients of 0.10 to 0.37 logRo/km from the western Sverdrup Basin, east of the present study area. In each case, the low maturation gradients were attributed to rapid sedimentation. In Orvilruk 0-03. the poor vitrinite reflectance results are due to insufficient vitrinite. Only 12 samples had enough material to analyse. Of these, only 10 contained measurable vitrinite, and only 6 had enough particles to satisfy the optimal 50 measurements required for consistant statistical analysis. Three samples had 10 or less measurements. In addition, the vitrinite was of generally poor quality. This lack of vitrinite is most likely due to the deep water, marine depositional environment of the Orvilruk well. In Tarsuit A-25, the poor results are probably due to the difficulty in identifying the indigenous vitrinite populations, a common problem when working with cuttings samples. 4.1.4. Summary and Conclusions 1. The sediments in each of the three study wells are immature to total depth, and could not be the source of Tertiary oils in the Beaufort-Mackenzie Basin. 2. The levels of maturity in the wells, combined with the low maturation gradient calculated for Netserk F-40 , suggest that thermal maturation will only be achieved at much greater depths. 3. The low maturation gradient for Netserk F-40 (0.07 Ro/km) is attributed to rapid sedimentation in the basin during the Late Cretaceous and Tertiary, and is in good agreement with reported gradients from similar basins. 4. The unsuccessful vitrinite reflectance analyses of Tarsuit and Orvilruk demonstrate some of the problems associated with this type of analysis in the Beaufort-Mackenzie Basin. 4.2. Organic Matter Type (OMT) 4.2.1. Introduction The nature, and proportions, of the original organic matter types present in sedimentary rocks control both the level of thermal maturation necessary for hydrocarbon generation, and the ultimate product generated (gas, oil, condensate; Fig. 4.1; Snowden and Powell, 1982). For example, resinite may generate oil at a 76 thermal maturity of 0.4 %Ro (Snowden and Powell, 1982.).It is therefore important to be able to identify the various types of organic matter present. There are a number of techniques and classification schemes available for this purpose. For a complete discussion of these methods, the reader is referred to Tissot and Welte (1984), Waples (1981), Bostick (1979), and Hunt (1977). In this study, the organic matter was classified based on its appearance under transmitted light, and divided into the following categories: 1. Amorphous: organic matter that lacks form, without clear outlines, due to microbial reworking. Usually translucent. Derived mainly from algae or a combination of algal lipids and waxes from higher plants (Barnes et al., 1984). Has high initial H/C and low O/C ratios and a high potential for generating oil. (Type 1 organic matter, alginite) 2. Lipinite : organic matter derived from the decomposition and polymerization of fatty organic materials. Has intermediate initial H/C and O/C ratios. Includes algae, pollen grains, spores, resin, and leaf cuticle. Mainly found in reduced marine strata. Has a high potential for generating oil and some gas. (Type II organic matter, exinite) 3. Vitrinite : organic matter derived from terrestrial plants and contains much identifiable woody material (e.g., xylem, fibres). Composed largely of aromatics derived from lignins and cellulose. Has an initial H/C ratio of less than 1, and an initial O/C ratio of 0.2 to 0.3 (Barnes et al., 1984). Deposition is mainly in deltaic and other thick, rapidly accumulating continental margin sediments. Has a high potential for generating gas and possibly some oil. (Type III organic matter) 77 4. Inertinite : opaque organic matter that has undergone excessive oxidation prior to deposition, due to such factors as forest fires or air/bacterial degradation. Often recycled. Not possible to distinguish between contemporaneous and recycled inertinite. Has no potential to generate oil and a low potential to generate gas. 4.2.2. Methods A total of ninety-one slides from the three wells were examined visually, under transmitted light, to determine organic matter type (OMT). These included 38 samples from Netserk, 29 from Tarsuit, and 24 from Orvilruk, at approximately 200m intervals. The results are presented as percentage of total organic matter up to 100 %, and percentage of contemporaneous material up to 100 % ( fig. 4.9 to 4.11, Appendix B). 4.2.3. Results and Discussion The most striking result of the OMT analysis is the predominance of recycled and terrestrial inert material (Fig 4.9a- 4.1 la). This is, however, what would be expected, given the depositional environment of the region (Tertiary was a period of cyclical delta building and erosion), and is in agreement with previous reports (Deitrich et al, 1985). Perhaps more interesting is the small but consistant presence of potential oil- generating organic matter types (amorphous, lipinite) throughout each of the wells (fig 4.9b- 4.1 lb). The lipinite is dominated by terrestrial material, including pollen grains, spores, and leaf cuticle. Algal cysts are present but less abundant. This is in agreement with the 'terrestrial source theory' for the offshore oils in the Beaufort- 78 Figures 4.9- 4-11: Proportion of Organic Matter Types for Netserk F-40 (Fig. 4.9), Tarsuit A-25 (Fig. 4.10), and Orvilruk 0-03 (Fig. 4.11) (a) The percentages of contemporaneous ! | § ; recycled Q ; and inertinite n material up to 100X of the total slide, (b) The percentage of the components of the contemporaneous fraction (excluding inertinite ): amorphous j | | ; lipinite [J| ; and vitrinite. . %Total Slide % Contemporaneous Depth (m) I 1 ' I I I I I I I I I I | I | | 10 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 I 1 I 10 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 Figure 4.9: Organic Matter Type analysis - b. Netserk F-40 a. b. Figure 4.10: Organic Matter Type analysis - Tarsuit A-25 Figure 4.11: Organic Matter Type analysis - Orvilruk 0-03 82 Mackenzie Basin (Lane and Jackson, 1980; Snowden, 1980). The contribution of marine fauna, however, should not be underestimated. As stated earlier, it was not until recently that a significant algal cyst population was recognized from the basin. The hydrocarbon generating potential of the sediments is limited, due to the abundance of recycled and inertinite material (this constitutes 95 % or more of the total organic matter in many slides). The zones with the greatest potential for generating oil are those with the highest amounts of contemporaneous material (Fig. 4.9a to 4.1 la) (assumes recylced material has no potential to generate hydrocarbons). Amorphous and lipinite material is consistantly present throughout the wells. This increases near the bottom of each well, and suggests that this trend may continue to a much greater depth. If the necessary level of thermal maturation is attained, these sediments could act as source rocks for hydrocarbons. The source of the Tertiary hydrocarbons in the Beaufort-Mackenzie Basin is controversial. The most popular theory is that they are derived from resinite at low levels of maturation (< 0.6 %Ro)(Lane and Jackson, 1980; Snowden, 1980; Snowden and Powell, 1982). However, this idea has recently been disputed by Lewan and Williams (1987) who, based on hydrous pyrolysis analysis of several resinites, proposed that resinite could not generate commercially produced oils, and that the maturation of resinite does not occur at abnormally low levels of thermal maturation. Even if it can be shown that resinite matures at low levels of thermal ._ maturation, unless resinite constitutes a major proportion of the amorphous 83 fraction seen in the present study, its sporadic and rare occurrence make it, at best, a questionable source for the Tertiary oils in the basin. 84 CHAPTER 5 TIME-TEMPERATURE MODELLING 5.1. Introduction The thermal maturation of organic matter is a function of time and temperature. The relationship is derived from the Arrhenius equation(eq. 5.1). in which the reaction rate is dependent on the temperature and activation energies. Eq.5.1 k - A e - y R T where k - rate constant T - temperature (K) Ea = activation energy R = universal gas constant A - frequency factor Based on this chemical premise, many numerical models have been proposed to predict thermal maturity (e.g., Karweil, 1956; Lopatin, 1971; Bostick, 1973; Connan, 1974; Hood et al., 1975; Waples, 1980; Mackenzie, 1981; Middleton. 1982). For a complete discussion of thermal alteration models, the reader is referred to Waples (1980), and Bustin et al., (1985). The equation used in this study is an integral form of Lopatin's 1971 equation (Bustin, 1984). Lopatin's model calculates interval maturations by integrating the length of time spent by the strata in each 10 degree (Celsius) interval. The total maturation (TTI - Time-Temperature Index) is the sum of the interval maturations (eq. 5.2), (Bustin et al., 1985). For a comparison of Lopatin's Time-Temperature Index with other maturation parameters, see Table 5.1. 85 nmax Eq.5.2. TTI - £ (DTnMrn) nmin where TTI - Time temperature index nmax - highest 10° interval nmin - lowest 10° interval AT - Time spent in each 10° temperature interval r - 2 (assuming rank doubles for each 10° degree rise in temperature ) Stage TTI Ro TAI Onset of oil generation 15 0.65 2.65 Peak oil generation 75 1.00 2.9 End of oil generation 160 1.30 3.2 Upper TTI limit for occurrence of oil with API gravity 40 500 1.75 3.6 Upper TTI limit for occurrence of oil with API gravity 50 1000 2.0 3.7 Upper TTI limit for occurrence of wet gas 1500 2.2 3.75 Last known occurrence of dry gas 65,000 ~ ~ Table 51 Correlation of TTI, Ro, and TAI with several important stages of oil generation and preservation (after Waples, 1980). The length of time spent in each temperature interval by the strata is determined from a burial history curve which plots depth of burial against absolute time. The confidence in the model is largely dependent on how accurately the burial history can be reconstructed. Several assumptions are necessary and how effectively these can be constrained affects the applicability of the model to the actual situation. The model assumes a linear relationship between time and maturation (ie., if the residency time at a constant temperature is doubled, so is the thermal maturation), and an exponential relationship between temperature and maturation (ie., for every 10 °C rise in temperature, thermal maturation is doubled). The equation used in this study calculates maturity for every 1 °C of the strata's thermal history (eq. 53). The model has two options. If the temperature history of the strata is known, but the thermal maturity is not, the maturity at any time or depth can be predicted. Conversely, if the thermal maturity is known, but the temperature history is not, the temperature history can be predicted. Because the thermal maturity of the three study wells was measured (see Chapter 4), this second option was used. to Eq.5.3. TTI - J 2<T(t)-105/10)dt lP where T(t) - Temperature (°C) as a function of Time (t) to - Time of original deposition tp - Present time The model was used to graphically illustrate the thermal history of the study wells, to estimate the paleogeothermal gradient that would account for the observed maturities in Chapter 4, and to estimate the timing of maturation in relation to the timing of the formation of traps. Those zones/strata with the greatest hydrocarbon potential could then be delineated. 5.2. Mfiihfidj. The first step in the Lopatin method is the construction of burial history curves. These were constructed for each well by combining the palynologic zonations (see Chapter 3) with an absolute time scale (DNAG, 1983), (Fig. 5.1-5.3). The curves do not take into account the effects of compaction. The curves for Netserk and Orvilruk have been constructed assuming continuous subsidence and deposition over the time represented by the reconstruction. Unconformities have been reported from the basin (Willumsen and Cote, 1982; Dixon et al., 1984), but were excluded from the model used for these two wells. This was done because of a lack of evidence for significant missing section from either the palynological or thermal maturation analyses, and because of inconsistencies in the literature regarding the age and extent of the unconformities. In Tarsuit, however, deposition does not appear to have been continuous and it is assumed that the Middle to Late Oligocene was an interval of non-deposition. Because the absolute age at the bottom of the wells is uncertain, an age corresponding to the base of the last time-unit' encountered was assigned. For example, in Netserk F-40, the bottom of the well was identified as upper Eocene, and the bottommost sediments were assigned a corresponding absolute age of 43 million years. The approximations had little effect on total maturation, due to the shallow depths and low temperatures involved. The following factors were assumed to be constant during the time represented by the reconstructions: geothermal gradient, heat flow and conductivities, activation energy, and a surface temperature of 10 °C. In order to estimate their temperature history, each well was modelled using geothermal gradients of 10, 15, 20, 25, and 30 °C/km. The calculated maturities (TTI), were compared to the observed maturities from the TAI analysis. Because the model does not calculate TAI directly, the maturities were converted using a conversion table from Waples, (1980) (Table 4.1). The paleo - geothermal gradients determined in this manner are presented in Table 52. Age (mm) Figure 51: Burial history curve for Netserk F-40. Curve assumes continuous deposition during the time represented by the reconstruction. Ate (••) Depth (m) Figure 52: Burial history curve for Tarsuit A-25. during the Late Oligocene. *• 5000 Curve assumes a period of non - deposition Ate (••) Depth (m) 4000 Figure 53: Burial history curve for Orvilruk 0-03. the time represented by the reconstruction. Curve assumes continuous deposition during 91 WELL PALEOGEOTHERMAL PRESENT DAY GRADIENT GEOTHERMAL GRADIENT °C/km From Well Regional *....Hi. i . in.ii.il i — , M| i .. I|||.IIM|...T—W—̂ .1.1.11. i — . „ — I ..--i.n.n..- i i •• II n •• Netserk F-40 15 25 29 Tarsuit A-25 15 26 >40 Orvilruk 0-03 15 29 >40 Table 5.2. Comparison of paleogeothermal gradient calculated by Lopatins method, those calculated from present day down hole temperatures (from the wells), and those reported by Judge and Bawden (1987), and the ASPG (1976) (regional). The thermal history of the Netserk F-40 well was additionally modelled using the coalification gradient generated by vitrinite reflectance analysis (Bustin, 1986). The advantage of this method is that the maturation gradient is calculated independently of absolute maturities. The model calculates Ro directly, so that coalification gradients can be derived for each geothermal gradient, and matched to the observed gradient (fig.5.4). Gradients of 10, 13, 15, 17, 20, 25, and 30 °C/km were used (Table 5.3). For a comparison of the paleogeothermal gradients calculated for Netserk by the different methods, see Table 5.4. G Slope (°C/km) (% Ro/km) 10 0.4823 13 0.6179 measured 0.6756 15 0.7150 17 0.8318 20 1.0634 25 1.4833 30 2.0162 Table 5-3. Geothermal gradient (G) versus slope for:l. calculated geothermal gradients (Lopatin model), and 2. the measured gradient from vitrinite analysis for Netserk F-40 (see Fig. 5.4). 92 Tarsuit A-25 and Orvilruk 0-03 could not be modelled in this manner because of their anomalous vitrinite results (Section 4.1.3-2). Table 5.4. Comparison of paleogeothermal gradients for Netserk F-40 derived by four different methods. 5.3. Results and Discussion For each of the three wells, the paleogeothermal gradient that best accounted for the measured maturities was 15 °C/km (Table 52). This is approximately one-half of the present day gradient at Netserk, and one third of the gradients at Tarsuit and Orvilruk (Judge and Bawden, 1987; ASPG, 1976). The low gradient is consistent with the general geologic setting of the region, and is comparable to that calculated by Bustin (1986) for the western Sverdrup Basin, east of the Beaufort-Mackenzie Basin. It is also similar to gradients reported from the Western Sedimentary Basin (England and Bustin, 1986), and the Gippsland Basin (Shibaoka and Bennett, 1977). The low gradients in these studies were attributed to rapid sedimentation, causing the retardation of maturation gradients (Stach et. al, 1982). This suggests that the sediments never reached an equilibrium geothermal gradient. The rapid sedimentation in the Beaufort Mackenzie Basin during the Late Cretaceous and Tertiary (estimated at lOOm/Ma for Netserk) supports a similar interpretation for this basin. Source Paleogeothermal gradient (°C/km) Comparison to TAI Fitting coalification gradients Maximum downhole temp. AAPG Map-modern gradients 15 14 25 29 93 Figure 5.4. Comparison of calculated and measured maturation gradients for Netserk F-40. The gradients have been plotted through the origin (0.15 % Ro) to facilitate comparison of the slopes. G: Geothermal gradient (°C /km). Reflectance: XRo. For a list of the slopes see Table 53. Age <••) 85°C * 5000 Figure 5-5: Burial history curve for Netserk F-40, showing temperature distribution through time represented by the reconstruction (assumes constant geothermal gradient) Age (•«) Depth (m) 85°C 5000 Figure 5.6: Burial history curve for Tarsuit A-25, showing temperature distribution through time represented by the reconstruction (assumes constant geothermal gradient) Age <•») S5°C 5000 Figure 5.7: Burial history curve for Orvilruk 0-03, showing temperature distribution through time represented by the reconstruction (assumes constant geothermal gradient) Based on a calculated paleogeothermal gradient of 15 °C/km, the maximum paleo-temperatures attained by the three wells are: Netserk. 75 °C; Tarsuit. 76 °C; and Orvilruk. 64 °C (Fig. 55 - 5.7). This, in addition to cumulative TTI values, suggests that the sediments encountered in the study wells have not reached the time - temperature threshold for oil generation (Table 5.5). This is in close agreement with the maturation analysis in Chapter 4. Well Calculated Cumulative TTI Maximum Geothermal Gradient Paleo - Temperature °C/km °C Netserk F-40 15 1.5 75 Tarsuit A-25 15 1.8 76 Orvilruk 0-03 15 0.8 64 Table 5.5: Cumulative TTI and maximum paleo - temperatures, assuming a paleogeothermal gradient of 15 °C/km. It should be noted that the three study wells were drilled on structural highs. It is possible that equivalent sediments, located off the highs and buried more deeply, could have achieved the level of thermal maturation necessary to generate hydrocarbons. 98 SUMMARY AND CONCLUSIONS 1. A total of 226 slides from 50m composite samples from Netserk F-40, Tarsuit A-25, and Orvilruk O-03 in the Beaufort - Mackenzie Basin were examined palynologically. A total of 223 species of pollen, spores, fungi, and algal cysts were identified. 2. Each well was examined palynologically and zoned based on the species ranges of pollen, spores, fungi, and algal cysts present. Using local extinction events of zonally diagnostic species to define the tops of intervals, seven informal palynozones are presented: Laevigatosporites (Pleistocene); Chenopodipollis (Pliocene to early Pleistocene); Ericipites (middle to late Miocene); Selenopemphix - 1 (middle to late Oligocene); Integricorpus (early Oligocene); Araliaceoipoiienites (late Eocene to early Oligocene); and Pistillipollenites (middle Eocene). 3. Correlations within the basin indicate that the proposed zonation may be useful for local correlations. Correlations outside the basin indicate that the palynological assemblages from the Beaufort - Mackenzie Basin may not be as isolated and endemic as first thought. 4. A high recovery of algal cysts is attributed to less harsh maceration techniques, and confirms a significant population of cysts from a region in which they were formerly believed to be relatively scarce. A more important role for algal cysts in future biostratigraphic zonations of the basin is anticipated. 99 5. The palynology does not exhibit an increase in marine influence with decreasing proximity to the basin margin, but instead shows a consistent, strong terrestrial influence throughout each well. The large terrestrial discharge from the Mackenzie River is interpreted to have masked the effect of basin proximity on the palynology of the area. 6. The study wells are dominated by terrestrial Type III organic matter. Recycled and terrestrial inert material often make up over 95 % of the residues. These results support a terrestrial source for the offshore oils in the Beaufort - Mackenzie Basin. 7. There is a small but consistent presence of potential oil-generating material throughout each well (amorphous and lipinite). The lipinite is largely composed of pollen grains, spores, and leaf cuticle. Algal cysts are present but less abundant. The contribution of this marine material should not be underestimated, as it was not until recently that a significant algal cyst population was recognized from the basin. If the amount of amorphous and liptinite material continues to some depth, where a sufficient level of thermal maturation might be reached, these sediments could act as a source of hydrocarbons. 8. The sporadic occurrence of resinite in the residues from the study wells questions the resinite source theory for hydrocarbons in the basin (unless it can be demonstrated that resinite makes up a major portion of the amorphous material). 100 9. The sediments in each of the three study wells are immature to total depth, and could not be the source of Tertiary oils in the Beaufort-Mackenzie Basin. The levels of maturity in the wells, and the low maturation gradient calculated for Netserk F-40 (0.07 Ro/km), suggest that thermal maturation will only be achieved at much greater depths. 10. The low maturation gradient for Netserk F-40 is attributed to rapid sedimentation in the basin during the Late Cretaceous and Tertiary, and is in agreement with previously reported gradients from similar basins. 11. By combining the zonations from Chapter 3 with the maturation data from Chapter 4, the burial and thermal history of each study well was reconstructed. Using a modified version of Lopatin's method, paleo- geothermal gradients were calculated for each well. In each case, the gradient that best accounted for the measured maturities was 15 °C/km. 12. The calculated gradient is approximately 1/2 to 1/3 of the present geothermal gradients for the wells. 13. The low paleo-geothermal gradient is considered responsible for the failure to encounter effective source rocks in any of the study wells. The source of the Tertiary hydrocarbons in the Beaufort-Mackenzie Basin is likely located at greater depths than those reached in this study. Prospective targets may therefore be located adjacent to sites where vertical migration of hydrocarbons is likely, such as steeply-dipping faults. BIBLIOGRAPHY Allan, J. and Douglas, A. G., 1977, Variations in the content and distribution of n-alkanes in a series of Carboniferous vitrinites and sporonites of bituminous rank: Geochemica et Cosmochimica Acta, v. 58, p. 2284- 2294. American Society of Petroleum Geologists, 1976, Geothermal gradient map of North America, 1: 5.000,000: Am. Assoc. Petrol. Geol. and U.S. Geol. Surv. 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L., 1981, Detailed Aeromagnetic Investigation of the Arctic Basin, 2: Journal of Geophysical Research, v. 86, p. 6323-6333. Thorsteisnsson, R. and Tozer, E. T„ 1970, Geology of the Arctic Archipelago, Geol. Surv. Can.. Econ. Geo. Ret., p. 548-590. 113 Tissot B. P., 1984, Recent Advances in Petroleum Geochemistry Applied to Hydrocarbon Exploration: AAPG Bull., v. 68, p. 545-563 Tissot, B. P. and Welte, D. H., 1984, Petroleum Formation and Occurrence: Berlin, Springer-Verlag, 699 p. Tschudy, R. H., 1973, Stratigraphic distribution of significant Eocene palynomorphs of the Mississippi etnbayment: U.S. Geological Survey, Prof. Paper 743-B, 24 p. Vogt, P. R., Taylor, L. C. Kovacs, and Johnson, G. L., 1982, The Canada Basin: Aeromagnetic Constraints on Struture and Evolution: Tectonophysics, 89, p. 295-336. Waples, D W., 1984a, Modern Approaches in Source-Rock Evaluation: in: J- Woodward, F. F. Meissner, and J. L. Clayton, eds.: Source rocks of hydrocarbon of the Greater Rocky Mountain region, Denver, 1985: Rocky Mountain Association of Geologists, p. 35-50. Waples, D. W., 1984b, Thermal Models for Oil Generation: ia: J. Brooks and D. Welte, eds., Advances in Petroleum Geochemistry, Academic Press, p. 7-68. Waples, D. W., 1981, Organic geochemistry for Exploration Geologists: Minneapolis, CEPCO, 144 p. Waples, D. W., 1980, Time and Temperature in Petroleum Formation: Application of Lopatin's Method to Petroleum Exploration: Am. Assoc. Petrol. Geol. Bull., v. 64, 916-926. Williams, G. L. and Brideaux, 1975, Palynological analyses of Upper Mesozoic and Cenozoic rocks of the Grand Banks, Atlantic continental margin: Geol. Surv. Can. Bull. 236, 236 p. Williams, G. L. and Bujak, J. P., 1977, Distribution patterns of some north Atlantic Cenozoic Dinoflagellate cysts: Marine Micropaleontology, 2, p. 223-233. Williams, G. L. and Bujak, J. P., 1977, Cenozoic palynostratigraphy of offshore eastern Canada: in W. C. Elisk, ed., Contributions of Stratigraphic Paiynology, v. 1, Cenozoic paiynology, Amer. Assoc. Stratigraphic Palynologists, Contr. Ser., No. 5A, p. 14-44. Williams, V. E., 1986, Palynological study of the continental shelf sediments of the Labrador Sea: Unpublished PhD dissertation, University of British Columbia, May, 1986, 214 p. Willumsen, P. S. and Cote, R. P., 1982, Tertiary Sedimentation in the southern Beaufort Sea, Canada: ia: A. F. Embry and H. R. Balkwill, eds., Arctic Geology and Geophysics: Can Soc. Petrol. Geol., Memoir 8, p. 43-53. Wilson, M. A., 1978, Paiynology of three sections across the uppermost Cretaceous/Paleocene boundary in the Yukon Territory and District of Mackenzie, Canada: Palaeontographica Abt. B., v. 166, p. 83-183. Young, F. G. and McNeil, D. H., 1984. Cenozoic Stratigraphy of the Mackenzie Delta, Northwest Territories: Geol. Surv. Can. Bull., 336, p. 63. Young, F. G., Myhr, D. W., and Yorath, C. J., 1976, Geology of the Beaufort- Mackenzie Basin: Geol. Surv. Can., Paper 76-11, p. 65 Yukler, A. M., Kokesh, F., 1984, A Review of Models Used in Petroleum Resource Estimation and Organic Geochemistry: ia: J. Brooks and D. Welte, eds., Advances in Petroleum Geochemistry, Academic Press, p. 69-113. APPENDIX A Species lists: Composite soecies list - Alphabetical Composite species list - Taxonomic 116 A. l .Composite species list (Alphabetical) Achomosphaera - 1 Adnatosphaeridium - 1 AJnipoIJenites robusta Alnipollenites rugosa AJnipoIJenites verus (Potonie) ex. Potonie Alternaria - 1 Apteodinium - A Apteodinium - B Apteodinium - C AraJiaceoipoUenites granulatus Potononie (Frederickson) 1980 AraliaceoipoUenites megaporifer Frederickson 1980 AraJiaceoipoUenites profundus Frederickson 1980 Areoiigera senonensis Lejeune Carpentier Areosphaeridium - 1 Astrocysta cretacea Pocock,1962 (Davey, 1970) AzoJJa - 1 BacuJatisporites quintus Thompson and Pflug (Krutzsh) BaJtisphaeridium - 1 BaJtisphaeridium - 2 BaJtispnaeridium - 3 BaJtispnaeridium -4 Batiacasphaera granulatus Batiacasphaera micropapiilata Batiacaspnaera spnaerica Stover, 1977 BetuJaceoipoJJenites ciaripites Wodehouse, 1933 BetuJaceoipoBenites minor Brachysporisporites cf. cotaJis Elisk and Jansonius Brigantedinium -1 CaJedonidinium -1 CaJedonidinium granulatus CaJedonidinium vermicuiatum Reid, 1977 CaJIimothaJIus pertusus Dilcher Carpinipites - 1 CaryapoJJenites viridifJuminipites Wodehouse CaryapoJJenites vescipites cf. Pthanopteridinium cf. Wailodinium Chenopodipollis - 1 Chenopodipollis - 2 Chenopodipollis nuktakensis Chiropteridium partispinatum Gerlach (Brosius, 1963) Chiropteridium aspenatum Gerlach 117 ChJropteridium dispersum Gocht, 1960 Chiropteridium lobospinosum Gocht, 1960 Chytroeisphaeridia - 1 Gcatricosisporites ntersectus Rouse Circulodinium perforatum Circulodinium perforatum granulata Circulodinium phaeropsis Compositae - 1 Cribroperidinium intricatum Davey, 1969 Ctenoperis elsikii Ctenosporites woifei Elisk and Jansonius Cupuliferoipolienites - 1 Cupuiiferoipoilenites liblarensis Cycadopites ovatus CycionepheJium -1 Cycionephelium -2 Cycionephelium ordinatum Williams and Downie, 1966 Cyclopsiella - 1 Cyclopsiella circuloides Cyclopsiella circuloides minutus Cyclopsiella elliptica Drugg and Loeblich, 1967 Deflandrea phosphoritica Eisenack, 1938 (Cookson and Eisenack, 1961) DeJtoidspora granuiatus Deltoidosporo diaphana Wilson and Webster Dicellaesporites -1 Dicellaesporites -2 Dicellaesporites 1 evis Dictyophylophitis -1 Dino - A Dino -7 Dioxya -1 Norris, 1985 DiporoceJlaesporites - 1 Diporocellaesporites beilulus Ke et Shi ex. sung et. al. Dyadosporonites - 1 Ephedra - 1 Ericipites ericius Faguspollenites sp. Fractisporites ordinatus Fraiinoipollenites medius Frederiksen Fraiinoipollenites variabeles Stanely Fungulhyphae - A Fungulhyphae -B Fungulhyphae -C Fungulhyphae -D Gonyaulacysta - 1 118 Graminidites - 1 Grapes-1 Hemicystodinium - 2 Hemicystodinium zohari Rossignol, 1962, Wall, 1967 Hystrichosphaeridium obscurum Deflandrea, 1973, emend Davey andWilliams, 1969 Hystrichosphaeridium tubiferum Ehrenberg (Williams, 1966) JieipoJlenites iiiacus fmpletosphaeridium - 1 Morgenroth, 1966 inapertisporites subcapularis Sheffy and Dilcher inapertisporites circularis Sheffy and Dilcher Inaperturopollenites -1 inaperturopoiienites coiumelius Juglans - 1 Juglans robusta Keteiiaria - 1 Laevigatosporites minutus Laevigatosporites novus Norris, 1985 Laevigatosporites ovatus Wilson and Webster Laricoidites - 1 Le/eunecysta - 1 Lejeunia - 1 Lejeunia - 2 Le/eunia faiiax Morgenroth, 1966 Artzner and Dorhofer, 1978 emend. Biffiand Grigani Lejeunia hyaiina Gerlach, 1961 Artzner and Dorhofer, 1973 Le/eunia minutus Lejeunia parateneiia Benedek, 1972 Lejeunia tricuspata Lingulodinium machaerophorumWall, 1967 Magnosporites - 1 Micrhystridium deflandrea Deflandre, 1937 Micrhystridium fragile - 2 Micrhystridium fragile Deflandre Micrhystridium inconspicuum Deflandre Micrhystridium stellatum Deflandre Microthyriadtes - 1 Momipites rotundus Leffingweil, (Nichols, 1973) Monosporites -1 Monosporonites singularis Sheffy and Dilcher Monosulcites - 1 Monosulcites gran ula tus Multicellaesporites - 1 Multicellaesporites - 2 Multicellaesporites conicus Ke et shi ex. Sung et. al. 119 Multicellaesporites ellipitus Sheffy and Dilcher, 1971 Multicellaesporites irregularis Sheffy and Dilcher, 1971 Multicellaesporites leptalus Ke et shi ex. Sung et. al. MultipUcisphaeridium -1 Multispinula minutus Bradford, 1975 Myricipites - 1 Oblosporites - 1 OUgosphaeridium complex White, 1842, (Davey and Williams, 1966) Osmundacidites regalites Martin and Rouse Osmundacidites wellmanii Couper Ostryoipollenites levis Paleoperidinium ariadnae Deflandre Paraalnipollenites - 1 Paralandella indent a ta Peridinium - 1 Peridittium - 2 Peridinium - 4 Periporate - 1 Pesavis /uviniles Elisk and Jansonius Pesavis tagluensis Elisk and Jansonius Piceapollenites grandivesdpites Wodehouse Pinuspollenites - 1 Pinuspollenites contorta Pinuspollenites haploxyon Pinuspollenites labdacus Potonie, (Raatz and Potonie) PistiWpollenites mcgregoru 1968) Pluricellaesporites - 1 Pluricellaesporites serratus Sheffy and Dilcher, 1971 Podocarpus - 1 Polypodiasporites - 1 Polypodiasporites alien us Pterocaryapollenites -1 Pterocaryapollenites levis Pterodinium circusutum Morgenroth Pterospermopsis. - 1 Pterospermopsis - 2 Pterospermopsis - 3 Pterospermopsis - 4 Pterospermopsis - 5 Pyxidiella sp. A Pyxidiella sp. B Quercoidites - 1 Quercoidites isleyanus Quercoidites microhenrici Potonie Potonie Reduviasporonites -1 Retitricolporites - 4 Retitrilites - 1 Saliipollenites - 1 Saliipollenites dlscoioripites Wodehouse (Srivastava) Schizosporis - 1 Selenopemphii - 1 Selenopemphii - 2 Selenopemphii selenoides Benedek, 1972 emend., 1981 Selenopemphii nephroides Benedek, 1972 emend., 1981 Senoniasphaerica - 1 Sigmopollis hispidus Piel Spinidinium - 1 Spinidinium - 2. Spinidinium acutus Spinifirites - 1 Spinifirites belerius Reid, 1977 Spinifirites ramosus Ehrenberg Staphlosporonites concoides Sheffy and Dilcher Staphlosporonites ovalis Sheffy and Dilcher Stereisporites antiquasporites Wilson and Webster Stereisporites microgranulatus Krutzsh Stereisporites microgranulatus minutus Stereisporites minor Raatz (Krutzsh) Stereisporites steroides Potonie andVenitz Stereisporites stictus Striadiporites multistriatus Ke et Shi ex. Sung et. al. Taiodiaceaepollenites hiatus Potonie (Kemp, 1949) Tetrad - 1 Thalassiophoro pelagica Eisenak Tiliapollenites crassipites Wodehouse, 1933 Tiliapollenites vescipites Wodehouse Tythodiscus - 1 Norem, 1955 Tricolporites - 1 Triporopollenites mullensis Simpson (Rouse and Srivastava) Tsugaepoilenites heterophyila Tsugaepoilenites igniculus Potonie (Potonie and Venitz, 1934) Tsugaepoilenites viridifluminipites Wodehouse, 1933 Ulmipollenites undulosa Undulatisporites - 1 Verrutricolporites - 1 Veryhachium - 1 Veryhachium - 2 Veryhachium - 3 Veryhachium reductum Deunff, 1958 (Jekhowsky) Vitreisporites - 1 121 Vitreisporites au'nor > 122 A.2.Composite species list (Taxonomic) AogiQs perms Alnipollenites robusta Alnipollenites rugosa Alnipollenites verus Araliaceoipollenites gran ulatus Araliaceoipollenites microporites2 Araliaceoipollenites profundus Betulaceoipollenites claripites Betulaceoipollenites minor Carpinipites - 1 Caryapollenites viridifluminipites Caryapollenites vescipites Chenopodopollis - 1 Cbenopodopollis - 2 Chenopodopollis nuktakensis Compositae -1 CupuJiferoipollenites - 1 Cupuliferoipollenites liblarensis Ephedra -1 Ericipites ericius Faguspollenites - 1 Fraiinoipollenites medius Fraiinoipollenites variables Graminidites - 1 Ileipollenites iliacus Inaperturopolienites - 1 Inaperturopollenites coJumellus Juglans - 1 Juglans robusta Momipites rotundus Myridpites - 1 Ostryoipollenites - 1 Ostryoipollenites levis Paraalnipollenites -1 Periporate -1 Pistillipollenites mcgregorii Pterocaryapollenites -1 Pterocaryapollenites levis Quercoidites - 1 Quercoidites isleyanus Quercoidites micrhenru Quercoidites micrhenri Saiizpoilenites - 1 Salixpollenites discoloripites Sigmopoilis - 1 Sigmopoiiis hispid us Tetrad - 1 Tiliapollenites crassipites Tiliapollenites vescipites Tricolporites -1 Triporopollenites mullensis Ulmipollenites undulosa Undulatisporites - 1 Verrutricolporites - 1 Brvophvtes Stereisporites antiquasporites Stereisporites microgranulatus minutus Stereisporites microgranulatus Stereisporites minor Stereisporites steroides Stereisporites stictus Fungi Alternaria -1 Brachysporisporites cf. c otalis Callimothallus pertusus Ctenosporites wolfei Dicellaesporites -1 Dicellaesporites - 2 Dicellaesporites levis Diporicellaesporites - 1 Diporocellaesporites bellulus Dyadosporonites - 1 Fractisporites ordinatus Fungul hyphae - C Fungul hyphae - A Fungul hyphae - B Fungul hyphae - D Grapes -1 Inapertisporites circularis Inapertisporites subcapularis Integricorpus - 1 Microthyriacites - 1 Monosporites - 1 Monosporonites singularis Multicellaesporites -1 Multicellaesporites - 2 Multicellaesporites conicus Multicellaesporites ellipitus Multicellaesporites irregularis Multicellaesporites lep talus Oblosporites -1 Pesavis tagluensis Pesvais Juviniles Pluricellaesporites - 1 Pluricellaesporites serratus Reduviasporonites -1 Staphlosporonites concoides Staphlosporonites ovalis Striadiporites multistriatus Gvmnosoerms Ctenoperis elsikii Cycadopites ovatus Ketellaria -1 Laricoidites - 1 Piceapollenites grandivesdpites Pinuspollenites - 1 Pinuspollenites contorta Pinuspollenites naploiyon Pinuspollenites labdacus Podocarpus - 1 Taiodiaceaepollenites hiatus Tsugaepoilenites heterophylla Tsugaepollenites igniculus Tsugaepoilenites viridifluminipites Vitreisporites -1 Vitreisporites minor Pteridophytes AzoJJa - 1 BacuJaUsporites quintus Q'catricosisporites intersectus Deltoidspora granulatus Deltoldosporo diaphana Dlctyophylophltls - 1 Laevigatosporites minutus Laevigatosporites novus Laevigatosporites ovatus Magnosporites - 1 Monosulcites -1 Monosulcites granulatus Osmundacidites regalites Osmundacidites wellmanii Polypodiasporites - 1 Polypodiasporites alien us Betitricolporites - 4 Retitrilites - 1 Dinc-flagellates Acnomospora - 1 Adnatosphaeridium - 1 Apteodinium - A Apteodinium - B Apteodinium - C Apteodinium - D Areolegria senonensis Areosphaeridium - 1 Astrocysta retacea Baltishaeridium - 1 BaJtisphaeridium - 4 BaJtisphaeridium - 2 BaJtisphaeridium - 3 Batiacasphaera granulatus Batiacasphaera micropapillata Batiacasphaera sphaeropsis Brigantedinium - 1 Caledonidinium - 1 CaJedonidinium granulatus Caledonidinium vermiculatum cf. Deflandrea wardensis cf. Pthanopteridinium cf. WaJJodJnJum Chiropteridium partispinum Chjropteridwm aspenatum Chiropteridium dispersum ChJropteridium Jobospinosum Chytroeisphaeridia - 1 Circulodinium perforatum granulata Circulodinium perforatum Circulodinium sphaeropsis Cribroperidinium ntricatum Cycionephelium - 1 Cycionephelium ordinatum Cycionephelium - 2 Cyclopsiella circuloides minutus Cyclopsiella circuloides Cyclopsiella elliptica Cyclopsiella - 1 Deflandrea phosphoritica Dino - 7 Dino - A Dioiya - 1 Gonyaulacysta - 1 Hemicystodinium zohari Hystrichosphaeridium tubiferum Hysytrichosphaeridium obscurum impletosphaeridium - 1 Lejeunecysta - 1 Lejeunia - 1 Lejeunia - 2 Lejeunia fallai Lejeunia hyalina Lejeunia minutus Lejeunia paratella Lejeunia tricuspata Linguiodinium machaerophorum Micrhystridium deflandrea Micrhystridium fragile -2 Micrhystridium fragile Micrhystridium inconspicuum Micrhystridium steilatum Multiplicisphaeridium -1 Multispinula minutus Oligosphaeridium complex Paleoperidinium ariadnae Paralanciella indentata Peridinium - 1 Peridinium - 2 Peridinium - 4 Pterodinium circusuturn Pterospermopsis - 1 Pterospermopsis - 2 Pterospermopsis - 3 Pterospermopsis - 4 Pterospermopsis. - 5 Pyxidiella - 1 Pyxidiella - 2 Schizosporis - 1 Selenopemphix - 1 Selenopemphix - 2 Selenopemphix selenoides Selenopemphix nephroides Senoniasphaerica - 1 Spinidinium - 1 Spinidinium acutus Spinidinium - 2 Spinifirites - 1 Spinifirites belerius Spinifirites ramosus Thalassiophoro pellagica Tythodiscus - 1 Veryhachium - 1 Veryhachium - 2 Veryhachium - 3 Veryhachium reductum APPENDIX B Raw Organic Matter Type Analysis Data %TOTAL SLIDE SAMPLE CONTEMPORANEOUS REWORKED INERTINITE Depth (m) % Total % Amorphous % Lipinite % Vitrinite 18.3-73.2 0-5 10-20 40-50 40-50 30-40 60-70 128.3- 182.9 20-30 10-20 80-90 0-10 30-40 30-40 238 0 - 292.6 5-10 0-10 50-60 40-50 20-30 70-80 402.6 - 457.2 0-5 40-50 50-60 0-10 50-60 40-50 512.4-563 9 5-10 10-20 60-70 20-30 70-80 10-20 661.7-710.2 0-5 50-60 40-50 0-10 60-70 30-40 759.3 - 807.7 5-10 10-20 60-70 20-30 80-90 10-20 905 6 - 954.0 < 1 20-30 60-70 10-20 80-90 10-20 1003.1 - 1051 6 < 1 10-20 80-90 0-10 60-70 30-40 1198.1 - 1246.6 0-5 20-30 60-70 0-10 80-90 10-20 1295 7- 1344.1 0-5 10-20 10-20 60-70 80-90 10-20 1490.8 - 1539.2 < 1 40-50 50-60 0-10 80-90 10-20 1588.3- 1636.8 < 1 30-40 10-20 50-60 60-70 30-40 1685 8 - 1734.3 0-5 60-70 30-40 0-10 90-95 5-10 17346- 1783.1 < 1 80-90 0-10 0-10 70-80 20-30 1832.1 - 1880.6 < 1 70-80 20-30 0-10 80-90 10-20 2027.2 - 2075.7 10-20 60-70 10-20 20-30 70-80 10 -20 2124.8-2173 2 0-5 10-20 60-70 10-20 70-80 20-30 2222.9 - 2270.8 0-5 0-10 10-20 70-80 70-80 20-30 2417.4 - 2465 8 < 1 30-40 50-60 0-10 90-95 5-10 2514.9-2563 4 < 1 0-10 10-20 70-80 60-70 30-40 2612.4-2660.9 <1 40-50 50-60 0-10 50 - 60 40-50 TABLE Bl: Percentage Organic Matter Types for Imperial Netserk F-40 (raw data). For definitions of organic matter types see Section 4.2. TABLE B l (Continued) % TOTAL SLIDE SAMPLE NO. CONTEMPORANEOUS REWORKED INERTINITE Depth (m) Total % Amorphous % Lipinite % Vitrinite 2758.7-2807.2 0-5 70-80 10 - 20 0-10 70-80 20- 30 2807.5 - 2856.0 <1 30-40 50-60 10-20 70-80 20- 30 3002.6- 3051 0 < 1 60-70 20-30 10-20 60-70 30- 40 3148.9 - 3197.4 < 1 40-50 50-60 0-10 40-50 50- 60 3295 2- 3343 7 <1 0-5 70-80 20-30 80-90 10- 20 3441.2- 3489.9 0-5 40-50 50-60 0-10 70-80 20- 30 3539.0- 3587.5 0-5 60-70 20-30 0-10 60-70 30- 40 3685 3- 37338 10-20 30-40 40-50 10-20 70-80 10- 20 3782.9- 3831.3 10-20 10-20 60-70 10 -20 30-40 40- 50 3929.2- 3977.6 10-20 30-40 40-50 10-20 30-40 40- 50 4026.7 - 4075 2 5-10 50-60 30-40 10-20 60-70 20- 30 4173 0 - 4221 5 10-20 40-50 50-60 0-10 60 - 70 20- 30 4270.6 - 4319.0 10-20 60-70 20-30 0-10 50-60 30- 40 4319.3-4367.8 20-30 80-90 0-10 0- 10 60-70 10- 20 % TOTAL SLIDE SAMPLE CONTEMPORANEOUS REWORKED INERTINITE % % % % Depth (m) Total Amorphous Lipinite Vitrinite 450 - 495 10 - 20 10-20 70-80 10-20 30-40 40-50 600 - 645 < l 10-20 80-90 0-10 20-30 70-80 700 - 745 0-5 0-10 80-90 0-10 20-30 70-80 900 - 945 < l 0-10 80-90 0-10 10-20 80-90 1050 - 1095 0-5 0-10 80-90 0-10 20-30 70-80 1200 - 1245 < 1 20-30 70-80 0-10 30-40 60-70 1350- 1395 < 1 0-10 80-90 0-10 20-30 70-80 1500 - 1545 0-5 20-30 70-80 0-10 60-70 30-40 1650 - 1645 < 1 0-10 80-90 0-10 30-40 60-70 1800 - 1845 < 1 20-30 70-80 0-10 10-20 80-90 1950 - 1995 < 1 70-80 10-20 0-10 10-20 80-90 2100- -2145 < 1 70-80 20-30 0-10 30-40 60-70 2250 - 2295 < 1 30-40 60-70 0-10 30-40 60-70 2400 - 2445 < 1 70-80 20-30 0-10 30-40 60-70 2550 - 2595 < 1 70-80 20-30 0-10 30-40 60-70 2700 - 2745 < 1 10-20 80-90 0-10 10-20 80-90 2800 - 2845 < 1 70-80 20-30 0-10 10-20 80-90 2850 - 2895 < 1 20-30 70-80 0-10 40-50 50-60 3000 - 3045 < 1 10-20 70-80 10-20 20-30 70-80 3150-3195 < 1 20-30 70-80 0-10 30-40 60-70 3300-3345 < 1 10-20 70-80 0-10 20-30 70-80 3450 - 3495 < 1 20-30 70-80 0-10 20 - 30 70-80 Table 8.2: Percentage Organic Matter Types for Tarsuit A-25 (raw data). For definition of different types of organic see Section 4.2. TABLE B 2 (Continued) % TOTAL SLIDE SAMPLE NO. CONTEMPORANEOUS REWORKED INERTINITE % % % % Total Amorphous Lipinite Vitrinite 3600 - 3645 10-20 10-20 70-80 10-20 30-40 50-60 3750 - 3795 5-10 50-60 30-40 0-10 60-70 30-40 3900 - 3945 5-10 10-20 70-80 0-10 50-60 40-50 4050- -4095 5-10 20-30 70-80 0- 10 50-60 40-50 4200 - 4245 0-5 60-70 30-40 0-10 50-60 50-60 4350 - 4395 5-10 20-30 70-80 0-10 20-30 70-80 4400 - 4445 0-5 70-80 20-30 0-10 50-60 40-50 %TOTALSLIDE SAMPLE CONTEMPORANEOUS REWORKED INERTINITE % % % % Depth (m) Total Amorphous Lipinite Vitrinite 205 - 250 0-5 5-10 60-70 20-30 15-20 80-85 405 - 450 0-5 20-30 70-80 0-10 20-30 70 - 80 505 - 550 10-20 0-5 70-80 20 - 30 30 -40 40-50 705 - 750 0-5 20-30 60-70 0-10 40-50 50 -.60 805 - 850 0-5 0-5 70-80 20-30 40-50 50-60 1005 - 1050 5-10 10-20 70-80 10-20 20-30 70-80 1104-1150 < 1 0-5 80-90 10-20 10-20 80 - 90 1305- 1350 < 1 10-20 80-90 0-10 20 - 30 70-80 1405 - 1450 < 1 50-60 20-30 20-30 20-30 70-80 1605 - 1650 < 1 0-10 70-80 20-30 20 - 30 70-80 1705 - 1750 0-5 0-5 60-70 30 -40 10-20 80 - 90 1905 - 1950 0-5 20-30 70-80 0-10 20-30 60-70 2005 - 2050 < 1 0-5 70-80 20-30 5-10 90-95 2205 - 2250 < 1 10-20 80-90 0-10 10-20 80-90 2305 - 2350 0-5 0-5 70-80 20-30 20-30 70-80 2505 - 2350 < 1 10-20 80-90 0-10 10-20 80-90 2605 - 2650 < 1 0-5 70-80 20-30 20 - 30 70-80 2805 - 2850 < 1 0-10 70-80 20-30 30-40 60-70 2905 - 2950 0-5 0-5 70-80 20-30 30-40 60-70 3105-3150 0-5 40-50 50-60 0-10 30-40 60-70 3205 - 3250 0-5 0-5 70-80 20 -30 20-30 70-80 3405 - 3450 < 1 10-20 80-90 0-10 30-40 60-70 3505 - 3500 0-5 0-5 70-80 20-30 30-40 60 - 70 3555-3600 0-5 0-5 50-60 40-50 40-50 50-60 TABLE B 3: Percentage Organic Matter Types for Orvilruk 0-03. For definition of organic matter types see Section 4.2. 134 APPENDIX C PLATES PLATE 1 All figures x 1000 1.0. Laevigatosporites minutus 2.0. Laevigatosporites novus 3.0. Laevigatosporites novus 4.0. Brigantedinium- 1 5.0. Compositae - 1 6.0. Caledonidinium granuJosua 7.0. Stereisporites minor 8.0. Deltoidospora diaphana 9.0. Stereisporites antiquasporites 10.0. Stereisporites antiquasporites 11.0. Deltoidospora diaphana 12.0. PinuspoJlenites Jabdacus 13.0. Piceapollenitesgrandevescipites 14.0. Betualaceoipolienires ciaripites 15.0. Chenopodipollis -1 16.0. Stereisporites microgranulatus /36 Plate 1 137 PLATE 2 All figures x 1000 Figure 17.0. Laevigatosporites ovatus 18.0. Pinuspollenites labdacus 19.0. Betulaceoipollenites claripites 20.0. Betulaceoipollenites minor 21.0. Betulaceoipollenites claripites 22.0. Betulaceoipollenites claripites 23.0. Laricoiditesplicata 24.0. Cyclopsiella circuloides minutus 25 0. Vitreisporites minutus 26.0. Vitreisporites -1 27.0. Sigmopollishispidus 28.0. Cyclopseilla ellipitica 29.0. Pterospermopsis -1 30.0. Tricolporites -1 31.0. Tricolporites -1 32.0. Quercoidites miorohenrici Plate 2 PLATE 3 All figures x 1000 Figure 33.0. PyiMeJJa sp.a 34.0. Pyxidiella sp.a 350. Pyxidiella sp.a 36.0. Pyxidiella sp.b 37.0. Pyxidiella sp.b 38.0. Peridinium- 1 39.0. Orculodinium perforata 40.0. Circulodinium sphaeropsis 41.0. Batiacasphaera micropapillata 42.0. Batiacaspheara micropapillata 430. Paralacaniellaindentata /4-0 Plate 3 141 PLATE 4 All figures xlOOO Figure 44.0. Qrculodinium sphaeropsis 450. Batiacasphaera micropapillata 46.0. Multiplicisphaeridium - 1 47.0. Veryhachium - 1 48.0. Batiacasphaera micropapiiiata 49.0. Micrhystridium deflandrea 50.0. Spinidinum acutus 51.0. Spinidinium - 1 52.0. Tythodiscus - 1 53.0. Dino - 7 54.0. Selenopemphii nephroides 550. Tythodiscis - 1 56.0. Multicellaesporites leptalus 57.0. Multicellaesporites conicus 58.0. Dicellaesporites - 1 Plate 4 PLATE 5 All figures x 1000 Figure 59.0. Ericipites ericius 60.0. Myricipites - 1 61.0. Myricipites.- 1 62.0. Carpinipites.-A 630. OstryoipoJJenenites - 1 64.0. Alnipollenites - 1 650. Oblosporites- 1 66.0. Oblorsporites - 1 67.0. Oblosporites - 1 68.0. Fraziniopollenites medius 69.0. Quercoidites - 1 70.0. Quercoidites - 1 71.0. Multicellaesporites - 1 72.0. Multicellaesporites irregularis Plate 5 PLATE 6 All figures zlOOO Figure 73.0. Selenopemphix -1 74.0. Integricorpus- 1 75.0. Jugians robusta 76.0. Jugians robusta 77.0. Jugians robusta 78.0. Pterocarya levis 79.0. Triporopollenites sp. 80.0. Taxoidiaceoipollenites hiatus 81.0. Osmundaciditesregalites 82.0. Tetrad - 1 83.0. Tetrad - 1 84.0. Selenopemphix- 1  PLATE 7 All figures x 1000 Figure 85.0. Araliaceoipollenites megaporifer 86.0. AraiiaceoipoiJenites megaporifer 87.0. Verrutricolporites -1 88.0. Araliaceoipollenites profundus 89.0. Araliaceoipollenites profundus. 90.0. Araliaceoipollenites granulatus. 91.0. Araliaceoipollenites granulatus 92.0. Tiliapollenites vescipites 93.0. Tiliapollenites crassipites 94.0. Thalassiphora peiagica 950. Micrhystridium fragile - 2 96.0. Dioxya - 1 97.0. Micrhystridium fragile- 2 98.0. Tiliapollenites crassipites 99.0. Taioidiapollenites hiatus Plate 7 149 PLATE 8 All figures xlOOO Figure 100.0. Pesavis tagluensis 101.0. Striadisporites multistriatus 102.0. Retitriletes - 1 103.0. Cicatricosporites intersectus 104.0. Reduviasporonites - 1 105.0. Ctenosporites woifei 106.0. Ctenosporites sp. 107.0. Caliimothallus pertusa 108.0. Pluricellaesporites - 1 109.0. Baculatisporites quintus 110.0. Microththyriacites - 1 /so Plate 8

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