Geology of the Trepassey area, Avalon Peninsula, Newfoundland
This thesis presents the results of the first detailed study of the geology of the Trepassey area on the south coast of the Avalon Peninsula, southeastern Newfoundland, and includes a geological map on a scale of 1:8,000. -- The area is underlain by a thick sequence of late-Precambrian rocks, belong...
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| Format: | Thesis |
| Language: | English |
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Memorial University of Newfoundland
1969
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| Online Access: | https://research.library.mun.ca/6847/ https://research.library.mun.ca/6847/1/InSeokKoh.pdf https://research.library.mun.ca/6847/3/InSeokKoh.pdf |
| Summary: | This thesis presents the results of the first detailed study of the geology of the Trepassey area on the south coast of the Avalon Peninsula, southeastern Newfoundland, and includes a geological map on a scale of 1:8,000. -- The area is underlain by a thick sequence of late-Precambrian rocks, belonging to the Conception Group and to the St. John's Formation of the Cabot Group, and at least one bed of tuff indicating contemporaneous volcanic activity. Although these rocks are well exposed along the coast, inland they are largely hidden beneath ground moraine of late Pleistocene age. -- The main structural features of the area are a synclinorium and a major fault cutting its western flank. Most of the subsidiary folds of the synclinorium, the associated fracture cleavage, and many of the faults have a north-northeasterly trend although some folds and faults are cross-cutting; folds generally plunge gently to the south-southwest. An analysis of the joint pattern in the area shows its tectonic origin. -- The Conception Group consists mainly of graded beds in which the coarser element is lithic or feldspathic greywacke, containing many volcanic rock fragments, and the finer-grained element is mudstone similar in composition to the greywacke. The succession also includes fine-grained very siliceous rocks, mudstones and colour-banded cherts. Conception beds are grey to green or purple; the colouring agents are dark rock fragments, iron sulphide, chlorite and hematite. -- The rocks of the St. John's Formation are predominantly fine-grained and although the succession includes, in its lower part, thin graded beds resembling those of the uppermost part of the Conception sequence, it consists mainly of mudstone (shales) interbedded with laminae of siltstone forming a repetitive sequence thousands of feet thick; the silty beds are subgreywackes. Slump zones are characteristic of the succession. Pyrites is universally present and probably responsible for the grey colour of these beds; also noteworthy is the common occurrence ... |
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