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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 43 (1993), Pages 453-464

Sequence Stratigraphic and Depositional Framework of the Paleocene Lower Wilcox Strata, Northwest Gulf of Mexico Basin

Liangqing Xue, William E. Galloway

ABSTRACT

The lower Wilcox strata and upper part of the Midway marine shale comprise a single genetic sequence and are subdivided into 4 map units (I - IV, from oldest to youngest) by regional flooding surfaces. The lower Wilcox sequence is bounded by maximum flooding surfaces associated with the Big Shale at the top and Midway marine shale at the bottom. The lower Wilcox sequence shows extensive shelf-margin progradation, high sedimentation rate, and thick progradational parasequences.

The lower Wilcox depositional systems are outlined on the basis of the net-sandstone isopach maps, which are contoured using a log data base of about 500 wells. Map unit I includes several fluvial-dominated delta systems, reflecting the initial progradation of the lower Wilcox depositional episode. Unit II contains the classic Rockdale delta system, Cotulla barrier-bar system, and strandplain system described by Fisher and McGowen in 1967. Unit III is the turning point of the depositional styles within the L. W. genetic sequence. The progradational patterns of units I and II were replaced by the retrogradational style dominated by deposits of wave-dominated delta, strandplain, barrier-bar, lagoon, and shelf-slope systems. Several wave-dominated delta systems progressively backstepped landward during deposition of units III and IV. The delta-type evolution in the Houston Embayment (major depocenter) reflects the initial high rates of sediment supply followed by decreasing supply and consequent increasing marine influence and accommodation domination.


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