Controls on Coal Distribution in Transgressive-Regressive Cycles, Upper Cretaceous, Western Interior, U.S.A.
Published:January 01, 1988
Timothy A. Cross, 1988. "Controls on Coal Distribution in Transgressive-Regressive Cycles, Upper Cretaceous, Western Interior, U.S.A.", Sea-Level Changes: An Integrated Approach, Cheryl K. Wilgus, Bruce S. Hastings, Henry Posamentier, John Van Wagoner, Charles A. Ross, Christopher G. St. C. Kendall
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The thickest and most extensive Upper Cretaceous coals of the western interior of the United States occur at the top of, and landward of, shoreface and delta front platforms that are stacked vertically. An explanation for this observation was sought through numerical models derived from the interactions of the three fundamental processes that control stratal geometries and lithofacies distributions. These are eustatic fluctuations, tectonic movement, and quantity of sediment delivered to or produced in a sedimentary basin.
The models show that the fundamental building block of marine-shelf, to coastal-plain stratigraphic sequences is the progradational event, expressed in vertical profile as a shallowing-upward succession of facies. The shallowest facies at the top of one event is capped abruptly by the deepest facies at the base of the subsequent event. This facies asymmetry is modeled by sinusoidal sea-level oscillations superimposed on a constant rate of tectonic subsidence; disharmonic variations in either sea level or tectonic movement are unnecessary to produce this asymmetry.
The models simulate a hierarchical stacking of progradational events that display three geometric patterns: seaward-stepping, landward-stepping, and vertical stacking. The models show that the thickest and most extensive coals accumulate when accommodation space in the lower, potentially coal-bearing portion of the coastal plain is near maximum, and when the rate of sea-level change is balanced by the rate of sediment supplied by progradational events. These factors result in vertical aggradation of coastal-plain facies tracts and vertical stacking of the progradational events.
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Sea-Level Changes: An Integrated Approach
Sea-Level Changes: An Integrated Approach - In October 1985, SEPM sponsored a four-day conference entitled ?Sea-Level Changes ? An Integrated Approach.? The purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea-level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues. The conference was successful in bringing together scientists from industry, academia, and government, representing all of the major geosciences disciplines. Presentations of many new papers, plus significant releases of data that were previously held proprietary, provided fertile ground for discussion. This much-cited volume represents the best of the material presented at the conference. Includes the early ?Vail? chart.