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Abstract: Lower Cretaceous Depositional Systems, West Texas
R. W. Scott, E. J. Kidson (1)
Two surface stratigraphic cross sections of Lower Cretaceous rocks in West Texas contain four depositional systems: coastal plain, carbonate shelf, platform-shelf margin, and shelf basin. These systems consist of lithofacies, megafossil paleocommunities, and palynomorph assemblages that represent specific environments. The vertical succession of deeper and shallower, or low - and high-energy facies indicates depocenter cycles of subsidence and progradation. The diversity and abundance of palynomorph morphotypes seem to be reliable environmental tools because they vary with other environmental indicators.
These depositional systems comprise depositional sequences, which are transgressive-regressive stratigraphic units bounded at least in part by unconformities: the Trinity, Fredericksburg, lower Washita, and the Upper Cretaceous upper Washita sequences. Some of the sequence boundaries are synchronous within the limits of a paleontologic zone, but others are clearly time-transgressive. These sequences can be correlated in cross sections from a detailed measured section at Fort Stockton to Big Bend National Park and to the Southern Quitman Mountains.
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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES
(1) Amoco Production Company, P.O. Box 591, Tulsa, Oklahoma
Copyright © 1999 by The Gulf Coast Association of Geological Societies