Regional geology of the Topsail-Foxtrap area

• Main Author: Dawson, James M.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1963
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/6894/; https://research.library.mun.ca/6894/1/JamesMDawson.pdf; https://research.library.mun.ca/6894/3/JamesMDawson.pdf

This thesis is concerned with an area of Precambrian volcanic, sedimentary and intrusive rocks located south of the east side of Conception Bay in the north-central part of the Avalon Peninsula, Newfoundland. Physiographically the region can be divided into a southeastern, gently rolling, plateau-like surface about 600 feet above sea level, and a northwestern sector in which the dominant features are north- northwest-trending ridges and valleys apparently carved by glaciers travelling in this direction. -- The oldest major rock group occurring here is the Harbour Main group which is mid-Proterozoic or older in age. The base of this group is not exposed, however, the visible portion comprises a lower, rhyolitic division and an upper andesitic division, both of which consist of lavas and pyroclasics. To the east of the volcanic rocks lie greenish sandstone, siltstones and cherty sediments of the Conception group, part of which is intertongued with the andesitic rocks of the Harbour Main group. -- The Harbour Main and Conception rocks are intruded by small podlike bodies of felsite, which are particularly prevalent in the zone where andesitic and sedimentary rocks are intertongued. The two main groups mentioned above are intruded by the Holyrood "granite" batholith which consists mainly of adamellite but contains smaller bodies of quartz- feldspar porphyry and aplite. Within the granite an isolated roof pendant of meta-diorite is found. This may be related to the andesites of the Harbour Main group or may represent an older or younger intrusive mass. A small number of basic dikes invade the granite and the Harbour Main group. However, in the rhyolites several sheared basic dikes are found which are possibly older than the granite. -- Lying unconformably upon the granite and volcanic rocks are small, isolated, remnants of interbedded graywacke and slate or shale, herein called the Black Hill sequence. -- Shortly before the emplacement of the batholith, the Harbour Main rocks and intertongued sediments were deformed ...