Paleogene sea levels and climates: U.S.A. eastern Gulf Coastal Plain

Abstract

Biostratigraphic zonation of the Paleogene formations in the eastern Gulf Coastal Plain of the U.S.A., based on calcareous nannoplankton, allows a reassessment of the timing and pattern of changing sea levels and climates in the region. General similarity is recognizable between the gross pattern of Paleogene transgressions/regressions in the eastern Gulf Coastal Plain and the recently published (Vail et al., 1977) scheme of eustatic sea-level changes. Local tectonism and sedimentation have, however, overprinted intra-cycle shoreline fluctuations on the eustatic pattern. A hiatus, spanning at least calcareous nannoplankton Zone NP 11 exists between the early Eocene Hatchetigbee and Tallahatta Formations. Another significant hiatus representing most or all of NP 23 exists between the early Oligocene Bucatunna Clay and the late Oligocene Chickasawhay Limestone. Nannoplankton assemblages suggest temperate sea-surface waters during the early and early late Paleocene, followed by subtropical sea-surface conditions from latest Paleocene to earliest Oligocene. Climatic conditions were cooler during the remainder of the early Oligocene.