Abstract: Neogene Comparative Sequence Stratigraphy, Offshore Louisiana and Mississippi, Gulf of Mexico

Jie Zhang, Joel S. Watkinssu Y. Yang, Don Sunwoo

In this paper we compare characteristics of depositional sequences and their controlling factors in three areas of the Gulf of Mexico: western offshore Louisiana, central offshore Louisiana, and offshore Mississippi. Our work is based on detailed nannofossil counts from over 20 wells. These have been analyzed and reliably documented. Condensed sections and sea level cycles were refined based on these data. Integrating nannofossil, oxygen stable isotope, well log and seismic data, we have investigated depositional sequences produced by rapid deposition during short 4th order cycles (~100 k.y.) and by slow deposition during longer 3rd order cycles (0.5 ~ 1.5 m.y.) during the Plio-Pleistocene and Miocene, respectively. We observed that rate of accommodation creation (A) and ediment flux (S) vary significantly from western offshore to offshore Mississippi to central offshore Louisiana and from Early-Miocene to Late Miocene to Plio-Pleistocene. Early-Mid Miocene deltas in western offshore Louisiana built out over shelves mainly during highstands where S<A. Late-Miocene-Early Pliocene deltas in offshore Mississippi built out over shelves and slopes during both high- and lowstands where S approx. equals A. Plio-Pleistocene deltas in central offshore Louisiana built out onto the upper slopes mainly during lowstands where S>A. We propose three depositional models, i.e., faulted deep-water ramp, deep-water shelf-margin, growth fault-salt-withdrawal-basin to explain the interaction of sequence development and structural styles in western offshore Louisiana, o fshore Mississippi, and central offshore Louisiana, respectively.

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