Fossils found in the Pre-Cambrian Conception Group of South-eastern Newfoundland

Abstract

THE Biscay Bay–Cape Race area of the southern end of the Avalon Peninsula, south-eastern Newfoundland (Figs. 1 and 2), was mapped by one of us (S. B. M.) during the summer of 1967; it was found to be underlain by rocks belonging to the Conception Group and the overlying St John's Formation of the Cabot Group, largely hidden beneath a cover of glacial drift except along the coast where the strata are well exposed in cliff sections. It has been found possible on a lithological basis to subdivide locally that part of the Conception Group which is present in this area into lower, middle and upper divisions. The lower division is chiefly cherts, the middle dominantly siliceous mudstones occasionally interbedded with sandstones, and the upper of green and red shaly mudstones, more massive siliceous mudstones and graded sandstones (turbidites). These strata have a combined thickness of some 5,000 feet which is less than Rose's¹ estimate of 7,000 feet for the thickness of the Group as a whole (a figure which Brueckner, personal communication, regards as probably an underestimate). The beds of the Conception Group and of the conformable St John's Formation are thrown into folds which trend north-east. Although the basal part of the Conception Group is apparently absent from the sequence in this area, the local upper division, which is the one that particularly concerns us here, undoubtedly lies within the actual upper part of the Conception Group as a whole, for the transition from Conception to Cabot Group takes place, only a little higher stratigraphically in the sequence, between Mistaken Point and Cape Race.