DEPOSITIONAL ENVIRONMENT OF THE LOWER PALEOZOIC SEDIMENTS ON THE GRAND BANKS OF NEWFOUNDLAND

Abstract

Lower Paleozoic platformal sediments on the Avalon Peninsula continue offshore in the area between the Avalon Peninsula and the Virgin Rocks. Dating of ten drilled cores from the offshore area and continuous seismic profiles show that conformable deposition occurred from Cambrian to post-Silurian (?Devonian) time accumulating a stratigraphic thickness of some 8,000 m of fine grained sediments. This study undertakes to examine the sedimentological and ichnological aspects of the ten bedrock cores of 80 cm average length with an aim to establishing their depositional environment.

The cores are thought to represent three general environments; Ordovician black shales representing restricted shallow marine conditions appear to have predominated over a vast area; Late Ordovician and Silurian siltstones have evidence of deposition in more dynamic and well oxygenated conditions and probably represent a predominance of a normal shallow marine environment.

There is some evidence to suggest a cycling between normal marine and more restricted conditions in Silurian times. Red siltstones and sandstones of probable Devonian age indicate a shallowing of the basin and deposition probably under terrestrial conditions.

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