L £ 5 * 7 if-i 1 R 7 Car STRATIGRAPHY AMD STRUCTURE OF A PORTION OF THE SHIGKSHOCK MOUNTAINS, GASPB _P gNimULA. A thesis submitted in pa r t i a l f u l -filment of the requirements for the course leading to the degree of Master of Applied Science In Geological Engineering at the University of B r i t i s h Columbia. Come Garbonneau University of B r i t i s h Columbia. A p r i l , 1949 • CONTENTS. Page. Foreword 1 Abstract I l l INTRODUCTION 1 Location of area 2 Means of access 2 Previous work 3 PHYSICAL FEATURES 5 Topography 5 Drainage 8 Geomorphic History 10 Glaciation 10 STRATIGRAPHY 20 Ordovician 20 Sedimentary rocks 20 Shickshock series 24 Silur ian 33 LIthology 33 Paleontology 38 Correlation 44 Devonian 47 Gaspe limestone series 477 Gaspe sandstone series 50 Basic volcanics and basic dykes 53 INTRUSIVE ROCKS 55 Serpentine 55 Granite 60 Diori te 61 STRUCTURE 61 Structure north of the Shickshock ser ies . . . 61 Structure in the Shickshock series 63 St ru^ t re south of the Shickshock se r i e s . . . 64. BIBLIOGRAPHY 66 MAPS. . . . . i n pocket. PIATES (After page 71) Frontispiece: Mount Albert . View from the west. Recently upl i f ted, peneplarted surface and g l ac i a l cirque. Contents (continued) PLATS 1 View looking southeast from a high point in the Shickshock mountains. Foreground: South Mountain. Center: Squaw Gap and Barn-shaped mountains. Background: level-crested surface of the lower plateau. PLATE 11 A view from the Shlckshock to the northern plateau. Background: St. Lawrence r i ve r . PLATE 111 Ground moraine along the Bathurst road in the eastern part of the area. PLATE IV On top of Mount Albert, angular debris or felsenmeer. PLATE V Jointing in the serpentine of South Mountain. PLATE VI Interior of a g l a c i a l cirque on the south flank of Mount Albert . PLATE V l l An exposure of competent, S i lur ian limestone beds dipping north. Seventeen-Mile brook. (South branch) PLATE V l l l North-dipping beds of S i lu r ian doldn-ite exposed along the Salmon Branch of the Cascapedia r i ve r . PLATE IX Slickensides in Devonian rocks exposed along Seventeen-Mile brook (South branch). 1 FOREWORD. This thesis i s the result of information obtained during the f i e l d seasons of 1947 and 1 9 4 8 . The writer was an assistant on a geological survey party for the Quebec Bureau of Mines, working in the area. The thesis contains a description of the rock formations and an Inter-pretation of the regional structures. Much of the Information had to be obtained from the l i tera ture previously published on the d i s t r i c t . The geological sketch-map accompanying this paper is drawn at the scale of one mile to the Inch. It i s a compilation of the previous geological work In Gaspe completed and modified with the aid of personal notes. In order to give a better picture of the structures, a portion of this map waa drawn at a acale of ha l f a mile to the Inch. A l l the important exposures of rocks situated aouth of the Shickshook series were via i ted, but only two weeks were spent on the northern contact of this series with the North Coaat sediments. Consequently more attention w i l l be given to the Geology aouth of the Shickahocka than can be given to the northern part of the area. The writer i s much indebted to Dr. H.W. /fc Gerrigle, under whom he has worked, for the advice received, for the opportunity to v i s i t the exposures In the f i e l d and for the use of notes and map a of the previous years. The present paper could not have been written without Dr. /Ac Gerrigle 'a a id . The writer i s also deeply grateful to 11 Dr. V . J . Okulltch for his suggestions and cri t icisms during the preparation of this thesis and for his very-great helir in the ident i f icat ion of the f o s s i l s . Sincere thanks are extended also to Dr. H.O. Gunning and Dr. K. Watson for their suggestions in the study of the t h i n-3sctions. I l l ABSTRACT. The Shickahook mountains form a belt of highlands extending para l le l to the axis of the Gaspe Peninsula in South-eastern Quebec. They represent remnants of a peneplain completed by late-Tertiary time and greatly modified by stream erosion in recent geological time. Local glaciers developed in the summit areas during the Pleistocene Epoch. A short review of the controversy on the possible continental glaciation i s given. New findings are added to the evidence for continental glaciat ion. The area under consideration l i e s a few miles north-west of the geographic center of the Peninsula. The rocks range in age from possibly Cambrian to Middle Devonian. They consist mainly of sedimentary rocks intruded by granite, d ior i te and serpentine. Two major volcanic flows are inter-bedded with the sedimentary rocks. A description of the various types of rocks is given and a correlation is made with belts of similar rocks exposed elsewhere In Gaspe. A small f o s s i l fauna collected in the Si lur ian limestone is described. As a result of the present geological work, the age of a serpentine, previously thought to be Ordovician, ia questioned. No data can be added for the determination of the age of a volcanic series apparently overlying Ordovician limestones and slates. IV The structure, where i t could be determined, is one of repeated small anticlines and synclines with possible development of high-angle thrust faults near the crests of the folds. -1-INTRODUGTION . Gaspe Peninsula is located in the south-eastern part of the Province of Quebec. The Peninsula forms a tongue of land/ which extends into the Gulf of St. Lawrence. From i t s western boundary, the valley of the Matapedia r ive r , to the Bay of Gaspe, i t has a length of approximately 150 miles; i t s width between the St . Lawrence estuary and the.Bay of Chaleurs varies between 70 and 90 miles. 2-Location of Area. Means of acceaa. The region dealt with in this paper i s situated west of the Mont-Albert Map-area, approximately in the center of the Peninsula, between latitudes 66° 15' and 66° 30' and paral lels 48° 40' and 49°. The northern half of the area includes part of the national park of Gaspe. The southern l imi t of the area roughly follows the Lake Branch of the same r iver , whereas the St . Anne r iver i n part of i t s course marks almost i t s northern boundary. The southeast corner of the map-area is easi ly reached by a motor road from Grand Cascapedia on the Bay of Chaleurs. This road runs north along the Cascapedia r iver and leads to the Federal Mine Camp, pasaing within three miles of the area. From the Mining Camp a new motor road, bui l t by the Bathurst Pulp Company, runs north almost to Mount Albert , then turns west and crosses the whole width of the area in i t s central part. The southern half of the area is reaaonably well provided with old paths and t r a i l s associated with the former lumber exploitat ion, but north of the Bathurst road auch t r a i l a are completely lacking except for a few miles along the Salmon Branch. This lack of t r a i l s and the heavily wooded condition of the region render3 back-packing t rave l l ing par t icular ly arduous. Another, much shorter road may be uaed to enter the area from St. Anne des Monta, a v i l lage aituated on the n o r t h c o a s t . T h i s motor r o a d runs s o u t h e r l y f o r 10 m i l e s and t h e n t u r n s e a s t I n t o t h e v a l l e y of the S t . Anne r i v e r I n t h e n o r t h e r n p a r t o f the a r e a . However, from t h e r e t h e a s c e n t t o the t o p of t h e S h i c k s h o c k brow i s so s t e e p t h a t t h i s approach t o t h e r e g i o n i s v e r y l i t t l e u s e d . P r e v i o u s Vifork. S e v e r a l g e o l o g i s t s worked i n t h e v i c i n i t y of t h e a r e a under c o n s i d e r a t i o n . I n 1843, S i r ls) X Favosites favosus ?(Goldfuj X F. sps. X X Fenestella cf parvulipora X Gypidula sp. X Halysites §atenulatus (Limiaeus) X Nr. H. compactus. Bominger X Hel io l i t es subtubuletus McC oy X H in del l a congregata pus i l i t I Swartz? X Leptaena rhomboidalls (?filckens) X X X Leptostrophia b ipar t i t a (Hall) X Meristella? n.sp. X Nuclospira? sp. X X Orthis davidsoni X 0. sp. X Parmorthis cf elegantula (Dalman) X X Pentamerus cf oblongus. Sowerby X cf Pentamerus pesovis Withfield. X Pholipods sp. X 46-Loca l i t i ea . Dart- Bonne Table Mount Head mouth camp top Albert watera r iver area. area. area. of area. Cap Chat River. Platyoatoma? sp X Proetus sp. X Retlcularia bicostata (Hall) X Rhipidomella hydrlda (Sowerby) X X Rhynchospira cf globosa Ha l l X Schuchertella pecten X S. sp. X ? Sieverella sp. X Streptelasma cf latusculum B i l l i n g s X Stricklandia brevis X S. ap. X S. lens (? S. davidsoni) X Stromatopora damilensis Parks X S. sp X S ? aporita Parks X Strophomena antiquata X Strophonella sp/ X X Strophoatylus sp. X Whitf ieldel la cf n i t ida X cf. Wilsonia sp. X Zaphrentis sp. X It can be aeen that most of the foss i l s found in the present area are included i n this table. Cyr t la cf exporrecta and Sowerbyella ap. occur in the St. Leon formation (Middle Silurian) of the Matapedia Valley (Crickmay 1932). Proetua turgidus and Rhyncotreta cuneata americana are both found in the West Point formation of the chaleur series (Northrop 1939). P. turgldua ia reatr icted to the Weat Point formation while R. cuneata americana i s also found in the La V i e i l l e and Bouleaux formationa. -47-Mori ogr apt us clintoneusis was collected at various loca l i t i e s In the present area. The presence of this species indicates def ini te ly a Si lur ian age. The faunule described above may'not be sa t i s fac tor i ly diagnostic by i t s e l f . With the aid of the l i thology, however, i t gives enough information to correlate the beds with the northernmost belt of S i lur ian rocks. No lower Si lur ian i s known to occur in Gaspe. The upper S i lur ian may be present at the eastern end of the Si lur ian belt in Dartmouth r iver area but this i s not known def in i te ly . On the other hand, a great thickness of Middle S i l u r i a n strata occurs in Fart-Daniel and Black-Cape areas on the Bay of Chaleur. U n t i l further evidence, therefore, the present group of rocks i s belfared to bei*Middle S i lur ian age. DEVONIAN. The Devonian rocks in the present area cover the southern half of the map-sheet. Exposures are f a i r l y abundant near the center of the area but are very scarce in the southern part. As usual i n the areas underlain by sedi-mentary rocks in Gaspe, outcrops are to be found along the courses of the streams. A few c l i f f exposures occur in the limestone series. Gaspe Limestone series. An attempt has been made in the f i e l d to -48-correlate the Lower Devonian rocks of the present area with the type section e&po3ed at the P l o r i l l o n Peninsula, at the eastern end of Gaspe. In the coastal section, the so-called Gaspe limestone series has been divided by Clarke (1Q08) into three formations, namely: the St. Alban, Cape Bon Ami and Grande Greve formations. Recently, Russel (1946) has been doing very detailed work along the same section i n order to f a c i l i t a t e the correlation in the in ter ior be l t . Russel favours the early Logan's subdivisions into eight members but retains Clarke's terminology since i t is well established in the l i te ra ture . The lower St. Alban formation could not be conclusively recognised in the present area. Aa described in the coastal section, i t contains some aoft, argillaceoua, grey and greenish' grey limestonea somwwhat airoilar to some of the Si lur ian beds described above. The formation aeems to pinch out (Mc" Garrigte 1946) west of Dartmouth r iver area. It i s probable that i t does not occur i n the present area except, possibly, for a small lena which w i l l be diacuased la ter . The Bon Ami formation occurs in the present area as a diarupted belt of i r regular ly jointed, gently dipping beds overlying the Si lur ian rocka apparently conformably. It consists of dark grey to almost black, aoft, shaly to f inely sandy limestone weathering pale chocolate-brown. Some beds are magnesian. A rough colour banding was found in some of the arenaceoua limeatones. The beds range -49-in thickness from 2 inches to 2 ffiet. The formation differs from the overlying Grande Greve by i t s colour and i t s characteristic softness. Some beds contain poor plant fragments much comminuted and carbonized. Poorly preserved corals, bracirfrspods, pelecypods and cephalopods are found in this formation. Conularla sp. and Atrypa re t icu la r i s were identif ied in the f i e l d . One species was available for description: Leptocoella f l abe l l i t e s (Conrad) Leptocoelia f l a b e l l i t e s . B i l l i n g s . Geol. Canada. 1863. P. 369. f i g . 382; Pa l . Fossils 11, 1874, p. 42. p i . 3, f i g s . 5, 6. Ha l l and Clarke, Pa l . New York, V l l l , Pt 11, 1893, p. 137, p l 53, f i g s . 40 - 46, 53. Small, subcircular to squarish, plano-convex she l l . Exterior coarsely costate, Two or three prominent, concentric growth lines i n the older stages of the organism. Faint, shallow, poorly developed, dorsal sinus. The sinus vanishes before the anterior margin is reached. Structure at the cardinal margin and in ter ior of the valv© are not preserved. Loo a l i t y ; lef t bank of Bridge brook, 500 feet upstream from the Salmon Branch of the Grand Cascapedia r ive r . Age; Lower Devonian. -50-The overlying Grande Greve formation consists of grey to brownish-grey, hard, sil iceous limestones and s i l t -stones weathering pale brown. These limestones and siltstones are usually f a i r l y well bedded but parts of them show poor bedding, the rock breaking in f la t irregular slabs. A common feature of the formation i s the occurrence of f la t "warm t r a i l s " . Similar "worm t r a i l s " , however, occur near the top of the Bon Ami formation. Unfortunately, not enough information i s presently available to give the thickness of the Grande Greve formation i n the area. McGerrigle (1946) found the thickness of the formation to range from 3000 to 4000 feet for the region between the Salmon Brancfe of the Cascapedia r iver and the Matapedia r ive r . The Bon Ami formation appears to be thick approximately 2000 feet''for the section along the Salmon Branch. Gaspe sandstone series. The term 'Gaspe sandstone' Is a descriptive term given by Logan for the section along the shore of the Bay of Gaspe. These Middle Devonian sandstones have been further subdivided into the Malbr'ale, Battery Point, York River and York Lake formations. In the area, only the York River and Battery Point formations are present. Both are very poorly exposed, especially the Battery Point. The York River formation overlies the Lower Devonian Grande Greve limestone. It consists of greenish to brownish grey, medium to fine-grained, sometimes argillaceous sandstones, containing a small amount of grey feldspars. Some fine-grained variet ies -51-grade rapidly to thinly bedded greenish-grey shale. In the Battery Point formation, on the other hand, the sandstones are generally finer-grained but some medium-grained beds are present. The formation is composed of chocolate-brown to brownish red sandstones and shales. Near the southern boundary of the area, on the Lake Branch of the Cascapedia r ive r , some deep red beds can also be found. As a general rule, these red variet ies are more abundant in the southern part of the bel t . Ripple-marks and cross bedding are common features. In the area immediately to the east, Jones (1929) observed ^ut icular structures, mud-crracks, worm borings and rain imprints in these rocks. Jones notes that these features are probably the resuHtts of freshwater and subaerial deposition. In both formations, plant fragments can be found. The same series of sandstones and shales continues sexk south of the present area. The whole sequence of rocks form "a major fo ld , somewhat basin-shaped, and referred to as the Berry Mountain synclive" (McGerrigle, 1946, p.50). Only the northern flank of this fold underlies the present area. Not enough information i s available to give an accurate idea of the thickness of the series in Richard town-ship. The formations, however, have certainly a much larger surface extent than in the area along the Bay of Gaspe. There i s no reason to believe that r ep i t i t i on of strata due to folding occurs. On the east, Jones (1929) suggested a thickness of 7,700 feet. -52-Aside from the limestone and sandstone series, a group of Lower Devonian rocks was found at an unexpected loca l i t y , along the South Branch of Seventeen-Mile brook. The rocks are squeezed between the Shickshock series on the north and the S i lur ian beds on the south. Psilophyton princeps. Dawson ( 1 ) was collected in these beds. In Gaspe, this plant is known to occur in the Lower Devonian. The beds were seen to consist of the following variet ies of rocks: 1 . Greenish grey, medium-grained sandstone with abundant Interbeds of very soft, unaltered, greenish shale. 2. Interbedded greenish shaly g r i t s , greenish drab and brownish shales. 3. Lensy bands of reddish shales. 4. Well-bedded, dark, arenaceous limestone weathering brown. 5. Dark grey, soft, slaty shale. 6. Lenses of Basal (?) conglomerate. The conglomerate, just mentioned, i s made of subrounded pebbles, generally under half an inch in diameter, embedded in a greenish g r i t ty shale. The pebbles consist of the following rock types or minerals: quartz very common; s e r i c l t i c , schisted quartzite common; in smaller amount; dark, calcareous sandstone, quartzite, greenstone and diabase. Except for Psilophyton princeps, no fossi ls were found i n these rocks. However, carbonaceous material occurs commonly in various layers of the greenish, soft, ( 1 ) This plant was ident i f ied as such by Dr. J .H. Clark, McGil l Universi ty. -53-unaltered shale. These rocks are located along a fault zone. Consequently they are much disturbed and sheared. Slickensided surfaces occur frequently (Plate IX) . However, no definite fault plane could be seen. The general character of these sedimentary rocks and the pebbles of the conglomerate suggest that the group is basal on the old erosion surface of the Shickshock series. As to the stratigraphic position of these rocks In the standard section of the P l o r i l l o n peninsula, no statement can be made. The rocks do not occur In the proper s t r a t i -lenses graphic sequence. However, red and green shaly ba-s-e-s occur commonly i n the typ ica l St. Alban formation. Nevertheless, a correlation based on such l i t h o l o g i c a l characteristics over such a distance is certainly subject to much uncertainty. Basic volcanics and basic dykes. A band of basic volcanics runs acrossthe southern part of the area. These volcanice rocks are inter-bedded with the Gaspe limest-one series. Occasional flows occur in the Grand Greve formation but none were observed in the Cape Bon Ami limestone. Owing to i t s hardness and res is t -ance to erosion, this volcanic complex i s r e l a t ive ly we l l -exposed along the stream courses and in mountain c l i f f s . However, outcrops are scarce in the south-western part of the bel t . Alcock (1926) and Mailhot (1918) have made a very detailed study of these rocks which cover an extensive -54-area, south of Mount Albert . When freshly broken, the rock is dense, fine-grained, steel grey to black coloured. Some phases are medium grained. A porphyritic texture occurs in some flows; the phenocrysts consist of grey feldspar. Amygdulfcs can be found but do not constitute a common feature In the present area. The amygdules are f i l l e d with ca lc i te or less commonly quartz. Alcock(1926) and Jones (1929) observed a l ight green f i lm of dele^ite surrounding the ca lc i te f i l l i n g s in the volcanics of Mount Albert area. A s imilar coating was observed in the amygdules, in the present area. Occasional small cubes of pyrite occur i n the ca lc i te f i l l i n g s . Crystals and globular aggregates of the sane mineral are sparingly scattered throughout the rock. A similar faint mineralization was observed in the volcanics south of the Federal Mine, i n the Mount Albert area (Jones 1929). At the Federal Mine deposit, however, the ore-bearing solutions were not associated with basic volcanics, but with the granit ic intrusive of the Tabletop mountains. The occurrence of pi l low lavas (Jones 1929) and amygdules i n Berry Mountain area, shows that, in the main at least, these rocks represent lava flowa Some parts of this complex, however, may be of an intrusive type since dykes of similar material were seen cutting the Devonian and S i lu r i an rocks in the area. These dykes consist of a dark-grey, fine to medium grained diabasic rock. Some phases are porphyritic; the phenocrysts are lath-shaped, grey feldspar. Some dykes even contain amygdules f i l l e d with calci te and l ined with a f i lm of delessite. Occasional cubes of pyrite can also be -55-found. Some of these Intrusives may be s i l l s but the majority of them are dykes. Several of the dykes have a trend of north 45° west. As a general rule , the dykes invade the country rock without producing much al terat ion. In places, a narrow zone of s l i gh t ly baked and s i l i c i f i e d limy material Is developed at the contact; when this occurs calc i te venllets are abundant both i n the country rock and i n the border of the dyke. Acid Volcanics. An acid, l ight-grey to light-brown, rhyo l i t i c rock outcrops along the brooks and valley sides, located south of squaw Cap Mountain. Similar rock was observed by Alcock (1926) "northwest of Indian brook". This may correspond to the present l o c a l i t y . Alcock noted the presence of a banded variety which, in thin-section, he saw to be "evidently a result of f luxion" . This variety was not observed In place. However, about one mile westward from the l o c a i l i t y mentioned above, a breccia was found with fragments consisting of f ine ly banded rhyol i te . These l i gh brown, angular fragments stand out from the greyiwh brown to dark green weathered surface of the basic matrix. The relations of the acid rocks to the basic volcanics or to the granite Intrusive of Squaw Cap are not f u l l y understood. The breccia, however, shows that at least in part the acid volcanics antfdate the basic flows. INTRUSIVE ROCKS. Serpentine. Two small, elongated, Intrusive bodies of -56-serpentine are exposed In the central part of the area, approximately three miles north of the Bathurst road. The summit part of the eastern mass - South Mountain - forms a continuous outcrop extending for two miles, roughly east and weat(oPlate 1). The unnaed western body Is not so wel l exposed, but good outcrops can be found along the neighbouring streams. These two masses are undoubtedly connected In depth with the serpentine intrusive of Mount Albert , exposed four miles to the east. The rock was very f u l l y described by Alcock (1926) in his report on Mount Albert area. Hence no attempt has been made to give a new petrographic description. Only one thin-aection was examined. It was seen t6 consist of the following minerals: 1. Olivine: 45 percent. Anhedral cry3tals i r regular ly fractured. Stain of magnetite f i l l i n g the fracture. The magnetite ataining aid the opt ical character of the mineral (negative) indicate an i ron-r ich o l iv ine . 2. Baatite: 35 percent. Occur as large, fibrous, lamellar aggregatea leaving l i t t l e of the original enatatite. Cleavage at 90° a t l l l preaerved in places. Carbonates accompany the tranaformation of enatatite into baatite. Theae fibrous aggregates are aheared and twiated. 3. Antigori te: 5 percent. Beside i t a occurrence aa a product of alteration, of the enatatite, fibers of thia mineral f i l l the fractures in the o l iv ine . -57-4. Chrysotile: 3 percent. Short fibers growing perpendicular to the fractures and crystal boundaries In the o l iv ine . 5. Chlori te; 5 percent. Distributed as large, i r regular i crystals throughout the section. b 6. Caronates; 5 percent. Seems to enter in the process of alteration of enstatlte. Distributed also sparingly throughout the section. 7. Magnetite: 3 percent. The processes of weathering gave a character-i s t i c pit ted appearance to the surface of the rock. Two sets of joints is developed in the rock, at the eastern end of South Mountain (Plate V ) . These sets of joints , however, have no prevalent direction and cannot be worked out system-a t i c a l l y . A coarse-grained, greenish-black amphibolite was found associated with the serpentine. I t i s made wholly, of large, dark, shining crystals of hornblende. It i s exposed at the south-east end of South Mountain and along Barren Brook. Alcock(1926) records the presence of a hornblendic fringe, bordering the serpentine mass of Mount Alber t . In the present area, the amphibolite does not seem to be continuous so as to form a ring around South Mountain. However, the lack of exposures renders this conclusion uncertain. Age of the serpentine. In the Mount Albert area, the serpentine -58-\h intrude,,Into the volcanic complex of the Shickshock series. It was not seen by Alcock (1926) to cut any rock younger than Ordovician. In order to find more data on the age of the serpentine, Alcock (1924c) v is i ted Mount Serpentine, located near Dartmouth r ive r , about 65 miles east of Mount ATlbert. The serpentine was found to intrude a volcanic complex similar to that surrounding Mount Albert . I t was not aeen to cut the Gaape limeatone which overliea unconformably the igneous complex in the south-east. And the contact, notes Alcock, i s not a fault contact. On the north east aide of Mount Serpentine, the Gaape aandstone ia brought in contact with the achistose volcanics by a thrust faul t . Since the serpentine was not seen to Intrude the Gaape limestone, Alcock concluded quite reasonably that the intruaive body waa pre-Dsvonian, probably Ordovician, aa the Taconic diaturbance took place i n Gaape at the end of the Ordovician Period. In the Saatern townahips, where aimilar ultrabaaic rocks occur, Cooke(1937) found evidence that "aeema to place the peridotite Injection at or near the very end of the Post-Ordovician folding movement". He states: "Aa the peridotites were injected after one folding movement, and are themaelvea folded, i t i s evident that they must have been introduced during or ahortly after the f i r s t folding" (Cooke 1937 p. 71) In the composite volume on the Geology of Quebec (1944 p.426), Dresser notes for the same belt of rocks -59-that " nowhere have any of the rock types been observed cutt'ing Devonian or younger strata". After a review of the different reports concerning the serpentine, he concluded: "It Is known that, in the northern Appalachian region, the Devonian was a period of folding, deformation, and igneous ac t i v i t y , and i t appears most probable that, i n the main at least, the rocks of the serpentine belt were intruded at that time". In the Lake Matapedia region, Aubert de l a Rue (1941) found a small body of peridoti te, serpentine and gabbro intruding Si lur ian rocks. In the Mount Serpentine region, Jones (1935) saw " tongues of serpentine" cutting through Lower Devonian limestone. In the present area, dykes or tongues of serpen-tine were seen intruding rocks believed to be S i l u r i an . The relationship between ttee S i lur ian dolomite aid the serpentine have been mentioned previously. It must be confessed that the sedimentary rocks invaded by the serpentine, were f i r s t thought to be Ordovlcian. It was shown why they are placed in the S i lu r i an . Moreover, the serpentine intrusive of South Moun-tain appears to be injected between the Shickshock series and the Si lur ian rocks. Exposures are scarce on the south side of South Mountain, but there is no reason to believe that Ordovlcian rocks occur along this contact. East and west of the present area, no definite Ordovician rocks have ever been found overlying the Shickshock series. On the contrary, i t appears that basal Devonian overlies the Shickshock series along the south branch of Seventeen-Mile brook. - 6 0 -The result of this discussion is that, in the present area, the evidence is i n favour of a Post-Silurian age for the serpentine. This would agree with the age relationships found by Jones (1935) and de l a Rue (1941) but does not conform to the opinion expressed by Alcock (1926) and Cooke ( 1 9 3 7 ) , and conversely adds support to Dresser's suggestion, namely that these rocks were .probably intruded in Devonian time. Granite. In the eastern central part of the area, a granit ic body intrudes the Lower Devonian Gaspe limestone series. This body i s the western extension of a granite belt which forms a continuous series of ridges in the central part of Mount Albert area.(l) In the present area, such topographical features as Barren, Squaw Cap and Barn-shaped mountains are due to the more resistant character of the granite. (Plate 1) The rock i s a l ight grey to greyish pink, coarse to medium-grained granite. The phenocrysts of feldspar and quartz are lying in a fine to medium-grained, dense matrix. A phase exposed on the ridge east of Barren Mountain was seen to consist of a grey, s l i gh t ly porphyritic syenite. Dykes of porphyritic granite cut the Devonian limestone on the north-west slope of Barren Mountain. (1) A petrographic study of this Intrusive can be found in the report on Mount Albert area. Alcock (1926) pp. 4 7 - 4 8 . -61-Dlor l t e . A r e l a t i v e l y small s i l l of d ior i te i s injected into the Gape Bon Ami formation, near the mouth of Seventeen-Mile hrook on the Salmon Branch of the Cascapedia r i ve r . The d ior i te i s well-exposed along the Salmon Branch but outcrops which could be used to mark the la te ra l extent of the s i l l are lacking. The rock i s course-grained to medium-grained and contains about 50 percent of grey feldspar. Near the contact with the Cape Bon Ami formation, debris of s i l i c i f i e d , baked, hard, l ight-yellow rock were found. This zone of metamorphism, however, does not appear to extend far from the contact with the d io r i t e . STRUCTURE. Structure north of the Shickshock series. The structure in the sedimentary rocks lying north of the Shickshock series i s complex. The limestone and slate beds were involved in at least two periods of orogeny, the Taconic disturbance at the end of the Ordovlcian and the Acadian revolution in Middle Devonian time. The beds are highly contorted, drag-folded, and in places, fractured. The bedding, where i t could be detected, runs generally east-west and dips steeply to the south. No definite faults could be observed. The present map area is too small to suggest any type of major structure. Since some beds were found to be overturned, north of the St. Anne -62-r iver , high-angle, repeated, overthrust ^©ieVfcfig may occur. In the Marsohl map area, Jones (1933 p. 46) found the structure "to he one of repeated folds which apparently form a major anticlinorium whose easterly-trending axis i s about twelve miles from the St . Lawrence shore". In the Marsonl area, however, no repeated folds were observed on the south limb of the anticlinorium. To the south, the Shickshock series apparently overlies the sedimentary rocks. The writer v i s i t ed the section along du Gros Volume brook. Along this stream, there i s no observable strat igraphical break between the Ordovician limestones and slates and the Shickshock series. The contact there is not exposed but there Is no evidence of faulting either in the volcanics or the sedimentary rocks on either side of the contact. I t i s unknown whether the beds are overturned or not. The fact that the volcanics appear to l i e s trat igraphical ly above the sedimentary series, has led Alcock (1924c) to place the volcanic complex In the Ordovician. On the other hand, i f metamorphism is to be considered alone, the Shickshock Series appears to be older than the sedimentary complex. Some basic volcanics are interbedded with the typ ica l Ordovician beds of the north coast, i n the region between the Matapedia Valley and Cap Chat. According to HcGerrigle,(1) these volcanics are not as altered as the Shickshock volcanics. Aubert de l a Rue (1941) records the presence of basic volcanics Interbedded with the S i l l e r y (1) Personal communication. - 6 3 -(Lower Ordovician) and the Pohenegamook (Middle Ordosxician) formations, in the Lake Matapedia region. According to the description given, these rocks seem to he as altered as the Shickshock series: the pyroxenes have undergone u ra l i t i sa t ion and secondary epidote and chlori te are developed. In the Marsoni and Tabletop mountain areas, Jones ( 1 9 3 3 , 1 9 3 4 ) found some basic volcanics interbedded with the Ordovician limestone and s la te . These, volcanics are not described as being as metamorphosed as the Shickshock volcanics. I f the degree of metamorphism Is considered, therefore, the Shickshock series may antedate the Ordovician sedimentary complex. In such a case, they would most l i k e l y be precambrian. However, a structural d i f f i cu l t y s t i l l remains: the volcanics appear to overlie the limestone and s la te . Structure in the Shickshock series. The Shickshock series covers a belt approx-imately eight miles wide in the present area. The sbhistosity planes, developed i n this series, strike south-west and dip steeply south. The succession of flows was not seen to be different from the schistosi ty. The series has probably not the thickness suggested by i t s width. Folding and e faul t ing, therefore, are probably responsible for repetition of the flows. Unfortunately, the rocks are too much metam-orphosed to give information as to the exact nature of the se folds and faul ts . -64-Structure south of the Shickshock series. Th© Si lur ian beds south of the Shickshock series are not as intensely folded as the Ordovician rocks of the North coast. Drag-folding occurs but i t is not common. Fault zones trending east-west were observed in various l oca l i t i e s in the belt of rocks exposed along Seventeen-Mile brook. The rocks appear to be thrown in a succession of small an t i c l i na l and synclinal folds, running to the. roughly east-west and, in places, s l i gh t l y overturned vnorth. Lack of exposures makes i t impossible to trace the axis of these folds . The pressure apparently came from the south-east. The fault zone exposed along Seventeen-Mile brook appears to be developed near the crest of an an t ic l ine . Some beds are probably overturned In this region. The faults are probably high-angle reverse faults arranged somewhat in echelon. The throw along these faults could not be determined because of the lack of horizon markers. It does not have to be large to explain the present succession of rocks. This type of fault ing and folding decreases in intensity in the western part of the present area. A fault running east-west, had to be inferred to account for the missing Cape Bon Ami formation north-west of Barren moun-ta in . A system of ve r t i ca l faults trending north-south i s also developed throughout the area. I t follows from these different systems of faults that the Si lur ian complex of Seventeen-Mile brook was l i f t e d as a block between the G-rande -65-Greve formation on the south and the basal Devonian on the north. The Cape Bon Ami formation yielded differently under the stresses. I t forms a belt of gentle warping with beds dipping in every possible d i rect ion. The dior i te intrusive may also have caused a local structure to develop. The Cape Bon Ami formation appears to overly the Si lur ian series conformably. Identical strikes were found within 1000 feet between the two groups of rocks. The same relations were recorded between the Cape Bon Ami and the Grande Greve formations. Lack of information makes i t impossible to form an adequate idea of the structure in the Grande Greve limestone. As mentioned previously, the Gaspe sandstone beds form the northern flank of a major, basin-l ike fold which extends south of the present area. -66-BIBLIOG-RAPHY. Alcock, P.V. (1921) Geology of Lemieux Township, Baspe County, Quebec. C.G.S. Sum. Rapt. pp. 71 - 96. (1924) Across Gaspe. Geo. Rev. 14, 2, pp. 197 - 214. (1924) Shickshock Mountains, Central Gaspe. C.G.S. Sum. Rept. pp. 127 - 133. (I924) Geology of Mount Serpentine, Gaspe, Quebec. C.G. S. Sum. Rept. pp. 134 - 141. (1926) Mount Albert Map-area, Quebec. C.G.S. Mem. 144. 75 pp. (1928) Rivers of Gaspe. Geol. Soc. Am. B u l l . , 39, 2, 403 - 420. (1931) Relationships of the Devonian and the Si lur ian in the Gaspe Peninsula and Northern New Brunswick. Roy. Soc. Can. Trans. 3rd ser. 25, IV, 113 - 117. (1931b) Geology, New Brunswick - Gaspe sheet (map: scale equals 1 inch to 8 miles) C.G.S. Map 259A, P u l l . No. 2254. (1932) The Geology of New Brunswick and Gaspe. Can. Min. Journ., 53, 3, 120 - 122. (1935) Geology of Chaleur Bay Region. C.G.S. Mem. 103, 246 pp. (1942) Further information on Glaciation In Gaspe. Trans. Roy. Soc. Can., 3rd ser. , 38, IV, pp. 1 5 - 2 2 . Alcock, F . J . (1932) Plumb-line deflections and Gravity and Anomalies in Gaspe Peninsula and the i r s ignif-M i l i s r , A .H . icance. Trans. Roy. Soc. Can., 3rd ser., 26, IV, pp. 321 -333. Ashley, G.H. (1930) Age of the Appalachians Peneplains. Geol. Soc. Am. B e l l . , 41, 4, 695 - 700. (1933) Studies in Appalachian Mountain Structure. Geol. Soc. Am. P r o c , 6 1 - 6 2 . -67-Aubert de l a Rue, E, B i l l i n g s , E . Brown, R.A. Chalmefrs, R. Clark, T.H, Clarke, J .M. _G.o l e m a n , A . P (1941) Region du Sac Matapedia. Serv. des Min . , Quebec. Rap. Geol. 9 . (1862) Palaeozvic Foss i l s . V o l . 1. Can. Geol. Surv. (1874) Palaeozvic Foss i l s . V o l . 11. Can Geol. Surv. (1938) North Shore of Gaspe Bay. Adv. Rept. Que. Bur. Min. No. 125. 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B u l l . No. 34. 52 pp. -68-Cooke, H.C. Crickmay, G.W, Dresser J .A. and Denis T.C. (1937) Thetford, Dis rae l i s , and eastern half of Warwick map-area. Quebec. C.G.S. Mem 211, p. 71. (1948) Age of the Bolton Lavas, Memphremagog D i s t r i c t , Quebec. Trans. Roc. Soc. Can., 3rd ser. , V o l . XL11, IV, pp. 17 - 29. (1930) Structure and Stratigtaphy of the Matapedia Valley, Gaspe, Que. (Abst) Geol. Soc. Am. B a l l , 41, 1, 116 - 117. (1932) Evidence of Taconic Orogeny in Matapedia Val ley. Am. Jour. S c i . , 5th ser. 24, 368 - 386. (1944) Geology of Quebec. Vol 11, Geol Rep. No. 20. Que. Bur. Min. E l l s , R.W. Paessler, C. F l i n t , R.F. F l i n t , R .F . Desmorest, M. Washburn, A. 'L. (1883) Report on Explorations and Surveys in the Interior of the Gaspe Peninsula. Rept. of Prog., 1882 - 83 - 84, Pt E . (1940) North Shore of the Saint-Lawrence from des Rapids to Matamec r ive r , Saguenay county. Que. Bur. Min. P.R. 144. (1947) Glac ia l Geology and the Pleisocene Epoch. John Wiley, p. 82. (1942) Glaciation of the Shickshock Mountains, Gaspe Peninsula. Geol. Soc. Am. B u l l . , 53, 1211 - 1230. Goldthwait,J.W.( 1915) The Occurrence of the Glac ia l Drif t on the Magdalen Islands. C.G.S. Mus. B e l l . 14. H a l l , James and Clark, J .M. Jones, I.W. (1892) An Introduction to the study of the genera of Palaeozoic Brachlopoda. Paleout. N.Y. Vo l . 8, pt 1. (1893) Ib id , pt 2. (1929) The Berry Mountain Map area. Que. Bur. Min. An. Rept. pt D. (1930) The Lesseps Area. Ib id . (1931) The Borinecamp Map area. Que. Bur. Min. An. Rept. pt C. - 6 9 -( 1 9 3 2 ) The Tabletop Map area. Que. Bur. Min. An. Rept. pt D. ( 1 9 3 3 ) Marsoni Map area, Gaspe Peninsula. Ib id . ( 1 9 3 3 ) Summary report of North Central Gaspe. Ib id . ( 1 9 3 4 ) Dartmouth r iver Map area, Gaspe Peninsula. Ib id . ( 1 9 3 5 ) Geology of North Central Gaspe. (Ab3t) Geol. Soc. Am. Proc. 4 4 7 - 4 4 8 . ( 1 9 3 5 ) Upper York River Map area, Gaspe Peninsula. Que. Bur. Min. An. Rept. 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Quebec, MInistere des Terres et For§ts (1930) Peninsula de Gaspe, Bonawenture, Matane, (map:scale equala 1 inch to 3 milea) Leve aerien, Fejsillet No. 1 Rosett i , F, Richardson,J. Russel, L . S . (1945) Paunes cambrienn^ia des conglomerate, de la "Formation de S i l l e ry" • Le Nat. Can. V o l . 72 pp. 53 - 67. (1946) Early Upper Cambrian Tr ibo l i t e from Weatern Gaspe. Journ. of Pale on. V o l . 20, No. 5. (1946) Canadian and Early Ordovician Stratigraphy of the Lower St. Lawrence Val ley. Geol. Soc. Am. B u l l . , 57, 687-706. (1857) Report for the Year 1857, Gaape Peninsula. C.G.S. Rept. Prog. 105-169. (1946) On the Stratigraphy of the Gaspe Limestone -71-Schuchert, C. Schuchert, C. and Dart, J .D. Swans on, C O . T e r r i e r , P. Twenhof e l , W.H. Williams. ^ . Y . Series, P l o r i l l o n Peninsula, Gap des Rosiers township, County of Gaspe-South. Que. Bur. Min. P.R. No. 195. (1897) A synopsis of American f o s s i l Brachiopoda including Bibliography and Synonymy. U.C.G.S. B u l l . 87. (1925) Significance of Taconic Orogeny. Geol. Soc. Am. B u l l . 36, 341, 350. (1930) Orogenic Times of the Northern Appalachians. Geol. Soc. Am. B u l l . , 41, 4, 701-724. (1926) Stratigraphy of the Port-Daniel-Gascons area of Southeastern Quebec. C.G.S. B u l l . 44, 35-58. (1928) Isostasy and Mountain Building. Jour. Geol. V o l . 36. 411-433. p.415 (1914) La re'gion appalachianne du Canada. N.Y. State Mus. B u l l . , 173, 75-79. (Translation). (1914) The Ant icost i Island faunas. C.G.S. Mus. B u l l . 3 . (1928) Geology of Ant icost i Island. C.G.S. Mem. 154. (1919) The Si lur ian Geology and faunas of Ontario Peninsula, and Manitoulin and adjacent Islands. C.G.S. Mem. 111. PLATE 1 View looking southeast from a high point i n the Shickshock mountains. Foreground: South Mountain. Center: Squaw Cap and Barn-shaped mountains. Background: level-crested surface of the lower plateau. PLATS 11 A view from the Shickshock to the northern plateau Background: St. Lawrence r i v e r . PLATE 111 Ground moraine a l o n g the B a t h u r s t r o a d i n t h e e a s t e r n p a r t of the a r e a . PLATE IV On t o p of Mount A l b e r t , angular d e b r i s or felaenmeer PLATE V J o i n t i n g i n tne serpentine or South Mountiaini PLATS VI Interior of a g l ac i a l cirque on the south flank of Mount Alber t . PIAT3 V l l An exposure of competent, S i lu r ian limestone beds dipping nortn. seventeen-mile tirook (Soutn orancn)* PLATE V l l l North-dipping bods of S i lur ian dolomite exposed along the Salmon Branch of the Cascapedia r i ve r . PLATS IX Slickensides in Devonian rocks exposed along Seventeen-Mile brook (South branch). C A R B O N I F E R O U S S ILURIAN o o o o o O O o E A R L Y - P A L E O Z OIC O R - O L D E R D E V O N I A N [77771 E s r - u m m a c //// S c r i e s I G N E O U S R O C K S 1/ 1' 1 •' 1/ 1/ 1/ 1/ 1/ "V&lcemics * a ^ « s o f Granitic mtrusiyes A A A ti A A A A A Perpepiine , etc ; Orc iDvic icHi ; F o r i i of * bot» T t> j-iRy. & A 5 I C V O L C A N I C S G A S P E 5 A (M D-STO M E 6 E R I E S L O W E R D E V O N I A N G A S P E L I M E S T O N E - S E R I E S 3 I L U R I A N LIMESTONE, SHALE , CONGLOMERATE OROOVIClAN SER PEN T/N£ SHICKSHOCK VOLCANfCS J SLATE, SHALE, LIME ST ON E Geolotji < a / b o u n d a r y a s s u m e . c l To wn & h i/> fine. fee0 ©4* St L a w r« r\ C « •49 6m" L o c u t i o n a r e * 66/3 A P R \ L sSca / e of A/Wej C . C A R B O M ^ E A U