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THE GEOLOGY OF THE ST. DOMINIQUE RIDGE, BAGOT COUNTY, QUEBEC A Thesis Submitted to the Faculty of Graduate Studies and Research in Partial Fulfilment of the Requirements for the Degree of Master of Science in the Department of Geological Sciences McGill University by John L. Usher MONTREAL April, 1947 TABLE OF CONTENTS Page Introduction 1 Location 1 Physical Features 2 Culture 3 Transportation 4 Previous work and the Present Study 4 General Geology 10 Formations of the St. Dominique Ridge 15 Beldens Formation 15 Fauna and Correlation 22 St. Dominique Formation • 24 Fauna and Correlation •• 32 Formations of the Black River Group 41 Formations of the Trenton Group ••••• 46 The Cryptolithus Beds 47 The Rosemount Formation • 43 The Higher Trenton Beds 49 Utica-Lorraine Shales ..... 50 Structure 54 Folds and Faults 54 Cleavage • 61 Gash Veining ..... 62 Geologic History of the St. Dominique Ridge 64 Summary and Conclusions •• • 77 Bibliography of References Cited 81 FIGURES AND CHARTS Page Table of Formations 14 Correlation Chart of the St. Dominique Limestone F&una. 38 Follows Page Figure 1 - Location of St. Hyacinthe Map-Area 2 Figure 2 - Western Half of the St. Hyacinthe Map-Area . 9 Figure 3 - Map of St. Dominique Ridge 13 Figure 4 - St. Pie Hill 19 Figure 5 - Map of Abandoned Quarry South of La Carriere 40 Figure 6 - Quarries at La Carriere 44 Figure 7 - Paleogeographic Maps of the Positions of the Chazy Bnbayment 63 THE GEOLOGY OF THE ST. DOMINIQUE RIDGE, BAGOT COUNTY, QUEBEC INTRODUCTION The ridge of Ordovician rocks at St. Dominique, Quebec, abounds in problems of stratigraphical, paleontological and structural importance, yet, in spite of its nearness to Montreal, it has so far received only cursory attention from geologists. Because of these features the present writer considers himself fortunate to be able to devote himself to this nearby though practically untouched field. LOCATION The St. Dominique Ridge, so named after the village of St. Dominique, Bagot County, Quebec, is located in the western half of the St. Hyacinthe map-area (Department of National Defence, sheet 31H, 1940, delimited on the north and south by latitudes 45°50f and 45°30f respectively and on the east and west by 72°45f and 73° respectively). It stretches from near the village of St. Pie - 2 - for almost eight miles towards the north-northeast and constitutes the first rise of land separating the nearly flat plain of the St. Lawrence Lowlands to the west from the hilly country of the eastern half of the map-area. St. Pie is situated on the north bank of tne Black River about a mile south of the southern tip of the ridge. The road from St. Dominique to St. Hyacinthe, running northwest-southeast cuts across the middle of the ridge. Along this road, at the junction of the plain and ridge, is the village of La Carriere. The accompanying index map (Fig. 1) indicates the position of the ridge in the St. Hyacinthe map-area, PHYSICAL FEATURES As mentioned above, the western margin of the ridge is the dividing line which separates the almost featureless plain of the St. Lawrence Lowlands to the west from the hilly rolling country to the east. From an elevation of 125 feet at the base of the ridge, the Lowlands slope down gently towards the west. Beginning as a hill nearly 100 feet high above the plain near St. Pie, the ridge stretches north, widening to the extent of one mile some 3 miles from its southern extremity. It disappears as a prominent feature south of the stream which flows through St. Rosalie. It is steepest on the west, being almost precipitous J ~ ^ - ** 5 i c I o k 0 0 ^J K - 3 - in places, while its eastern side grades down imperceptibly into the St. Dominique plain which continues as far as the Granby thrust. Along the road from St. Hyacinthe to St. Dominique the ridge rises to its greatest height, more than 200 feet above sea level. Other than the Yamaska River, which drains northward past St. Hyacinthe, and its tributary, the Black River whose headwaters are to the east and which circum­ vents the southern tip of the ridge at St. Pie, there are no waterways of any consequence. CULTURE Most of the population outside of the to?/ns are engaged in mixed farming, for the country is but sparsely wooded. St. Hyacinthe is a thriving city of 15,000, owing its location to rapids across the Yamaska River. St. Pie, the largest village in the area, is also situated beside rapids, this time in the Black River. St. Dominique is a limestone producing centre. Quarrying has been carried on for more than a hundred years and the numerous quarries still in operation point to the importance of the area as a limestone producer. Most of the quarries are close to the highway between St. Dominique and St. Hyacinthe. Whereas formerly the stone was used for building purposes and engineering construction in the neighboring towns, the present day products are largely crushed stone, flux and stone for lime - 4 - burning. All but one of the quarries are worked on a small scale. Gravel deposits in the eastern part of the area have been found suitable for road construction and cement making and are being used for that purpose. TRANSPORTATION Access to the area is gained by a system of good roads, few of which are paved. The new Sir Wilfred Laurier highway passes through St. Hyacinthe as does the main line of the Canadian National Railways from Montreal to Halifax. Transportation along the above mentioned rivers is prohibited by fluctuating waters and the presence of boulder-strewn rapids during the low water seasons of the year. PREVIOUS WORK AND THE PRESENT STUDY Despite the fact that the St. Dominique ridge is not identified by name on the present topographic map, it is an out­ standing physiographic feature. For this reason and also because parts of the St. Dominique ridge are well settled and because it has been of economic interest as far as stone for building purposes is concerned, it is amazing that no detailed geological work has been done upon it. Nonetheless, rocks in the area have not hitherto been described in detail nor have any extensive collections of fossils been made. - 5 - Logan's Geology of Canada, 1863, contains the first reference to the rocks around St. Dominique and St. Pie. His brief resume of the section includes all formations from the Chazy to and including the Trenton. A small number of fossils are listed from the Chazy rocks. The Trenton limestones, which make up the bulk of the ridge, were evidently no better collecting grounds at that time than they are to-day. Presumably the identification of these few remains was made by Billings. Logan considered the ridge to be anticlinal in structure and correlated this with the Deschambault anticline which he traced from north of the St. Lawrence to Lake Champlain. The economic resources and possibilities of the district were also discussed. In 1896, Ells1 report of the south-west sheet of the Eastern Townships included a brief description of Trenton rocks at St. Pie and of the Chazy, Black River and Trenton series, with some mention of fossils at St. Dominique. In the appendix of this same report Ami published four lists of Chazy fossils from the St. Dominique area, three of which embodied the results of his own work, and the fourth contained species previously identified by Billings. Ten years later, Raymond published one of the first of a series of paleontological and stratigraphical papers on the Chazy formation and its fauna. This paper dealt with the formation in - 6 - its generally wide extent throughout the Ottawa-St. Lawrence Lowlands and compared the faunas and lithology of various well known sections in Canada and north-east United States. In that portion of his paper in which he described Chazy rocks in Canada, Raymond included a revised list of the fossils from St. Dominique. Raymondfs paper was the most valuable contribution to the geology of the area since Logan's Geology of Canada. There still was, however, no stratigraphic section or detailed measuring of the rocks. It was in 1914 that Parks1 "Report of the Building and Ornamental Stones of Canada", Volume III, was published by the Canadian Department of Mines. Excellent descriptions of the stone quarrying industry near St. Dominique with accompanying descriptions of the lithology of the rocks were included in this work, but scarcely a word that would help in establishing a stratigraphic section. Twenty-one years later, Goudge published Part III of his "Limestones of Canada", and gave more detailed descriptions of the rocks than had his predecessor Parks. The lithologic descriptions given by Parks and by Goudge are splendid. The stratigraphic sequence and thickness of the formations are barely mentioned, they being frankly beyond the purpose of the reports. The most recent reference to the rocks of the St. Dominique ridge is by G.M. Kay (1945) in an abstract of the geology of north-west Vermont in the Bulletin of the Geological Society of America. Kay - 7 - measured and named a series of Middle and Upper Ordovician rocks near Highgate Springs, Vermont, and correlated them with the section at St. Dominique. In Vermont, the Beldens limestone (500 feet thick) is overlain by the Carman sandstone (135 feet thick) in turn followed by the Youngman limestone (300 feet thick). These three are all of Chazy age, and in Kay's article have been correlated respectively with the Beldens limestone, and the St.

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