A geophysical investigation of the nova scotian continental shelf

Abstract

A major east-west structural discontinuity, termed the Minas Basin - Chedabucto Bay - Orpheus fault zone, transects Nova Scotia and the adjacent Nova Scotian continental shelf. To the north of this discontinuity, the geophysical evidence indicates structural continuity between the late Precambrian basement rocks of south-eastern newfound lane and Eastern Cape Breton Island. The generally dense basement rocks of the northern Scotian Shelf are pierced by intrusions of magnetic granite and traversed by linear belts of volcanic rocks. The basement is depressed into a regional east-west trough which is filled by Palaeozoic and younger sedimentary rocks. To the south of the major east-west discontinuity, the southern Scotian Shelf consists of a south easterly dipping early Palaeozoic basement complex intruded by granite and overlain by a wedge of late Palaeozoic and younger sedimentary rocks which reach their maximum thickness east of Sable Island. The most notable feature on the Nova Scotian continental shelf is the Orpheus Graben which lies along the Minas Basin - Chedabucto Bay - Orpheus fault zone and which is filled with Mesozoic sedimentary rocks. Many of the basement structural features on the Nova Scotian continental shelf appear to be products of continental collisions during the early Palaeozoic Era while other features are probably due to continental separation in the late Palaeozoic and Mesozoic Eras. In particular, the Minas Basin - Chedabucto Bay - Orpheus fault zone was probably initiated in Siluro-Devonian times as the result of the thrusting of the north-western portion of Africa into the late Precambrian rocks of the Avalon (Acado-Baltic) Platform of south-eastern New Brunswick, eastern Cape Breton Island and south-eastern, Newfoundland. Later on, the Orpheus Graben was formed along the existing zone of weakness probably in Triassic or Jurassic time as a result of continental break-up and the formation of the present-day Atlantic Ocean.