Northwestern Atlantic Mesozoic biostratigraphy

Abstract The marine Mesozoic sedimentary and paleoceanographic history of the western North Atlantic region is buried in the 0.5–2 km thick sediments of the ocean basin and in the 2–15 km thick sedimentary wedges forming the Atlantic continental margin and the Atlantic Coastal Plain. In the Atlantic Coastal Plain itself there are outcrops of shallow marine Upper Cretaceous strata for which Olsson (1978) has provided a good biostratigraphic sum- mary. North of New Jersey, Paleozoic strata in the Appalachian orogenic belt are present along the shoreline. These Paleozoic strata form part or all of the basement beneath the shelf as far north as the Grenville Front between Newfoundland and Labra- dor (Wynne-Edwards, 1972). In a general sense, the present east- ern coastline of Newfoundland, Nova Scotia, and the New England states matches that of the late Jurassic and late Cretace- ous. This study surveys the types and distribution of Mesozoic microfossils to further our understanding of Atlantic Mesozoic stratigraphy. Micropaleontology, the microscopic study of fossils from about 0.001 to several millimeters in longest dimension, plays an important part in the reconstruction of the geological history of ocean basins. These small fossils are recovered, unbroken, in large numbers in core samples. The types and distribution in time and space of these fossils help the micropaleontologists to determine the relative age and original environment of the rocks in which they are found, as well as to reconstruct paleoceanographic conditions. Different types of microfossils found in the marine Mesozoic strata offshore are nannofossils