TERTIARY MOLLUSKS OF THE SCOTIAN SHELF, ATLANTIC CANADA

Cuttings from the Cenozoic section of LASMO/NSRL Cohasset Producer CP1 P-51, a production well on the Scotian Shelf, offshore Atlantic Canad a, contain relatively large numbers of small molluscs and other microi nvertebrates. The stratigraphic distributions of these tars have been compared with the previously established foraminiferal zonation for th is site. Over 50 species of these fossils are recognized, and many rep resent extant forms now found in much warmer conditions than presently exist on the Scotian Shelf. Occurrences of most of these warm-water f orms are concentrated in the upper portion of the Lower Eocene and low er Middle Eocene, in the lower part of the Oligocene section and, to a lesser extent, in the Lower Miocene, supporting claims for climatic w arming trends during these intervals in the foraminiferal literature. There is some suggestion that at least part of the molluscan assemblag e is allochthonous, having been transported into deeper waters from it s nearshore origin. If true, this does not affect paleoclimatic interp retations. If the molluscs are in place, fluctuating numbers of these tars with respect to foraminiferal numbers may suggest differences in the parameters affecting the productivity of the two groups. The restr icted stratigraphic ranges of some of these forms may prove useful in correlations with other Atlantic Canada sites where foraminiferal asse mblages are impoverished. In one of the Cohasset species, the serpulid worm Paliurus, the known stratigraphic range appears to be extended f rom the Eocene up to the Oligocene. A second species, ''Coleolus'', pr esent in Paleocene to Oligocene horizons, appears to be a homeomorph o f a little-known Palaeozoic form. The absent or very condensed Upper E ocene section of CP1 P-51 may be related to increased deep-ocean circu lation in the Early Oligocene, as suggested in some foraminiferal lite rature.