Abstract:
Detailed biostratigraphic analyses of nine cores from the Atlantic Coastal Plain and two cores from the Blake Nose, western Atlantic Ocean, provide the basis for subdivision and correlation of upper Maastrichtian sediments along a shallow-to deep-water transect. The calcareous nannofossil record from these sites shows distinct differences between the middle to outer neritic Coastal Plain sediments and the lower to upper bathyal Blake Nose sediments. Micula murus, a reliable marker species for low-to mid-latitude sites, is shown herein to respond to differing palaeoenvironmental conditions of nearshore v. open-ocean sites. Its usefulness as a biostratigraphic marker for neritic sediments is called into question. The last appearance datum of Ceratolithoides kamptneri is documented as a reliable biozone marker for latest Maastrichtian time (within CC26b) in this region. The evolutionary radiation and resulting biostratigraphic utility of species of Ceratolithoides, Lithraphidites and Micula is discussed in detail, and their first and last occurrences are tied to magneto-stratigraphic chrons where possible. Ceratolithoides amplector, Ceratolithoides indiensis and Ceratolithoides pricei are shown to be useful, biostratigraphically, in sediments deposited under bathyal conditions. Several species of Lithraphidites (Lithraphidites? charactozorro, Lithraphidites kennethii and Lithraphidites grossopectinatus) can be used to further subdivide upper Maastrichtian sediments at both neritic and bathyal localities. The first and last occurrence of Micula praemurus in Zones CC25a and CC26a, respectively, are shown to be useful biostratigraphic datum points.