Abstract: Comparison of Upper Cretaceous and Paleogene Depositional Sequences in the Eastern Gulf Coastal Plain

Ernest A. Mancini, Berry H. Tew, T. Markham Puckett

Genetic depositional sequences of 0.5 to 11 million years' duration, their component systems tracts, and associated physical surfaces have been mapped in Upper Cretaceous and Paleogene strata of the eastern Gulf Coastal Plain. The time duration in which these sequences were deposited appears to have little impact on sequence development in that the component systems tracts can be recognized in all of the sequences. However, the Upper Cretaceous sequences span longer periods of time, resulted from lower sedimentation rates, experienced lower subsidence rates, and reflect more marine paleoenvironmental conditions. In the eastern Gulf Coastal Plain, the Late Cretaceous is characterized as a time when climate was warm, relative sea level was high, and stable depositional cond tions prevailed. Conversely, Paleogene cycles were of shorter durations, were greatly affected by differential rates of sedimentation and subsidence, and generally, only the transgressive systems tracts were characterized by marine depositional conditions. In the eastern Gulf Coastal Plain, the Paleogene is characterized by rapidly fluctuating climates and dynamic depositional conditions. Upper Cretaceous sequences, therefore, generally span more than one biozone, whereas Paleogene cycles usually are restricted to a single biozone. Thus, the diachroneity of sequence boundaries and first transgressive surfaces and the synchroneity of maximum flooding surfaces are more easily discerned by mapping Upper Cretaceous systems tracts and associated physical surfaces.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas