Author	Moshkovitz, S. and Habib, D.
Year	1993
Journal	Micropaleontology 39-2: 167-191.
Title	Calcareous nannofossil and dinoflagellate stratigraphy of the Cretaceous-Tertiary boundary, Alabama and Georgia

Abstract Moshkovitz, S. and Habib, D., 1993; Calcareous nannofossil and dinoflagellate stratigraphy of the Cretaceous-Tertiary boundary, Alabama and Georgia. Micropaleontology 39-2: 167-191 Abstract: Calcareous nannofossils and dinocysts date the base of the Clayton Formation in south-central Alabama as Danian in age. The first occurrences of Biantholithus sparsus, Cruciplacolithus primus, Senoniasphaera inornata, Danea californica and Membranilarnacia tenella in the basal sands at Mussel Creek indicate that the Cretaceous-Tertiary (KT) boundary lies virtually at the disconformity (type 1 sequence boundary) which separates the Clayton Formation from the underlying Prairie Bluff Chalk. The presence of the latest Maestrichtian Micula prinsii nannofossil zone in the uppemnost 30-50 cm of the Prairie Bluff unit closely constrains the hiatus to within several hundred thousand years. In the Braggs roadcut, the base of the Micula prinsii zone lies well within the one-meter thick magnetically unstable interval below polarity Chron C29R. This boundary indicates that the unstable interval is equivalent in age to the earlier part of this chron. In the section from southeastern Georgia, Cretaceous nannofossil taxa disappear below the KT boundary in a shallowing upward sequence of progradation to nearshore environments. Dinoflagellate taxa are potentially valuable for distinguishing third-order cycles of coastal onlap. Species are fewest in lowstand deposits directly above the KT boundary. and then increase rapidly in number in the shelf facies transgressive tract. They then decrease in number systematically from the upper part of the transgressive tract into the next prograding highstand tract. This pattern of dinoflagellate diversity is calibrated from the sequence stratigraphy of the early Danian Pine Barren member of the Clayton Formation, and correlates with third-order cycles published for the late Campanian, early Maestrichtian and late Maestrichtian as well. Dinoflagellate species of Cretaceous origin flourished in the early Danian, at a time when the calcareous-shelled biota was still impoverished by extinction.