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Abstract: Tertiary Sequence Stratigraphy in the Offshore Mississippi Delta Region

Don Sunwoo, Joel S. Watkins

Paleogene and Neogene strata beneath the continental shelf of the offshore Mississippi delta region are distinguished by different depositional histories and stratigraphies. Sediment-starved thin flat-lying deposition characterizes the Paleogene. Neogene depositional sequences are distinguished by an increase in sedimentation rate and broad prograding clinoforms. A number of erosional unconformities and associated channels are evident.

We have identified five 3rd-order sequences in the Miocene section by integration of high resolution biostratigraphy, paleobathymetry, and well log signatures with reflection seismic data. Most sequence boundaries are characterized by onlap and unconformities. Each sequence contains a lowstand systems tract, a transgressive systems tract, and a highstand systems tract. Progradational clinoform patterns are the most significant reflection configurations and characterize both lowstand and highstand systems tracts. Clinoform patterns are mostly evident near the paleoshelf-slope transition zone. We interpret the clinoform patterns in the lowstand systems tract as shelf-edge deltaic complex that formed during slowly rising sea-level. Continued sediment supply during highstands resulted in rapid progradation of the delta.

AAPG Search and Discovery Article #90955©1995 GCAGS 45th Annual Meeting and Gulf Section SEPM, Baton Rouge, Louisiana