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Eustatic control on alluvial sequence stratigraphy; a possible example from the Cretaceous-Tertiary transition of the Tornillo Basin, Big Bend National Park, West Texas, U.S.A.

Stacy C. Atchley, Lee C. Nordt and Stephen I. Dworkin
Eustatic control on alluvial sequence stratigraphy; a possible example from the Cretaceous-Tertiary transition of the Tornillo Basin, Big Bend National Park, West Texas, U.S.A.
Journal of Sedimentary Research (May 2004) 74 (3): 391-404

Abstract

Paleosol-bearing alluvial strata of latest Cretaceous and earliest Tertiary age are continuously exposed along Dawson Creek, in Big Bend National Park, west Texas, U.S.A., and exhibit a three-tier hierarchy of depositional cyclicity. Meter-scale, fluvial aggradational cycles (FACs) occur as fining-upward successions that are gradationally overlain by paleosols or are sharply overlain by the coarser-grained base of the succeeding FAC without an intervening paleosol. FACs stack into decameter-scale, fluvial aggradational cycle sets (FAC sets) that also fine upward, and from base to top contain either a gradual upsection increase in soil maturity and soil drainage or a somewhat symmetrical pattern of increasing and decreasing paleosol maturity. Longer-period trends of FAC thickness, lithologic proportions, paleosol maturity, and paleosol drainage indicate that two complete, and two partial, hectometer-scale fluvial sequences occur within the study interval. From base to top, each sequence is characterized by an asymmetric increase and decrease in FAC thickness, a decrease in the pro-portion of sand-prone fluvial facies, an increase in paleosol maturity, and better paleosol drainage. Whereas FACs and FAC sets are interpreted to record cyclic episodes of channel avulsion and stability, and longer-term avulsive channel drift within the alluvial valley, respectively, fluvial sequences may coincide with third-order sea-level changes within the North American Western Interior Seaway. As such, the Cretaceous-Tertiary (K-T) transition within the Tornillo Basin may provide an example of megascale stratigraphic cyclicity that is controlled by eustatic sea level within a fully fluvial succession. Thickening and thinning successions of FACs record a third-order period of accelerating (transgressive-equivalent) and decelerating (highstand-equivalent) base-level rise, and subsequent base-level fall (falling stage- to lowstand-equivalent). Sequence boundaries are placed at the sharp inflection between thinning and thickening FACs. Sand-prone facies and immature, more poorly-drained paleosols are associated with the transgressive-equivalent portion of each sequence, and mudrock-dominated overbank facies and their associated mature, well-drained paleosols are associated with the highstand- and falling stage-equivalent.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 74
Serial Issue: 3
Title: Eustatic control on alluvial sequence stratigraphy; a possible example from the Cretaceous-Tertiary transition of the Tornillo Basin, Big Bend National Park, West Texas, U.S.A.
Affiliation: Baylor University, Department of Geology, Waco, TX, United States
Pages: 391-404
Published: 200405
Text Language: English
Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States
References: 75
Accession Number: 2004-057655
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 3 tables, geol. sketch maps
N29°00'00" - N29°41'60", W103°45'00" - W102°49'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200417
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