--> Eustasy as the Dominant Control on Deltaic Deposition--A Quaternary Example from the Texas Gulf Coast, by K. C. Abdulah and J. B. Anderson; #90986 (1994).

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Abstract: Eustasy as the Dominant Control on Deltaic Deposition--A Quaternary Example from the Texas Gulf Coast

Kenneth C. Abdulah, John B. Anderson

Eustasy, tectonics, and sediment supply are accepted widely as the primary controls on clastic deposition. However, there is considerable debate concerning which factor, if any, is dominant. Controversial topics include "forced regressions" and the nature of deposition during falling sea level, the timing of turbidite sedimentation, and the timing and predictability of incised-valley fill sequences.

We present here the results of a study of the evolution of the Brazos and Colorado fluvial/deltaic systems during the last 200,000 years. Using the SPECMAP oxygen isotope curve as an independent proxy of global sea level, the study traces deposition through two lowstands and two highstands of sea level. Delta lobes and incised valleys were mapped using platform borings, core data, and a 5,000 kilometer grid of high-resolution seismic data covering the central Texas continental shelf and upper slope.

Chronostratigraphic controls, provided by radio-carbon dates, biostratigraphic markers, and an oxygen isotope record generated within the study area, allow us to position the events on the SPECMAP curve.

Eustasy is the dominant factor controlling deposition within the study area. Deltas cover significant portions of the continental shelf during highstands. Turbidites are associated with lowstands, and lowstand deltas can be related to fifth-order eustatic cycles. Backstepping deltas, and the infilling of incised valleys, characterize transgressions.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994