Depositional Cycle Chart for Gulf of Mexico Plio-Pleistocene Strata: Documentation of Regionally Significant Events

ARMENTROUT, JOHN M., Mobil Research and Development Corporation, Dallas, TX, and J. FRED CLEMENT, Micropaleontology/Biostratigraphy Consultant, Dallas, TX

Correlations from biostratigraphic checklists of foraminifera and calcareous nannoplankton have been integrated with correlations based on wireline logs and seismic studies to construct a Plio-Pleistocene depositional-cycle chart for the eastern offshore Texas area. The biostratigraphic data defining the sequence boundary and condensed section framework is presented in the form of two cross sections that record the stratigraphic position of all identified faunal discontinuities and pertinent biofacies information.

High faunal abundance values define ten regionally significant condensed sections coincident with maximum flooding surfaces. Patterns of rapid change in biofacies distribution and low faunal abundance values define faunal discontinuities, interpreted as depositional sequence boundaries. Ages assigned to condensed sections using key index fossils help correlate these faunal discontinuities and result in recognition of seven demonstrable and four probable regionally significant sequence boundaries, bounding ten depositional cycles.

These local depositional cycles are compared with the depositional sequences of Beard et al. (1982), Lamb et al. (1987), Haq et al. (1988), Pacht et al. (1990), and Wornardt and Vail (1990). The general age agreement for sequence boundaries, by both the above authors and this study, suggests we have a reproducible technique that permits regional Plio-Pleistocene sequence stratigraphic analysis with resolution of approximately 100,000 years in the Gulf of Mexico. Tentative correlations of the biostratigraphic framework and depositional cycles with the oxygen isotope cycles of Trainor and Williams (1987) suggests that the observed depositional cycles are glacio-eustatic.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)