Detailed Facies Anatomy of Transgressive and Highstand Systems Tracts from the Upper Cretaceous of Southern Utah, U.S.A.
Robert D. Hettinger, Peter J. McCabe, Keith W. Shanley, 1993. "Detailed Facies Anatomy of Transgressive and Highstand Systems Tracts from the Upper Cretaceous of Southern Utah, U.S.A.", Siliciclastic Sequence Stratigraphy: Recent Developments and Applications, Paul Weimer, Henry Posamentier
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In the northern part of the Kaiparowits Plateau of southern Utah, excellent outcrops allow the detailed examination of Upper Cretaceous offshore, shoreface, estuarine, and coastal plain strata within an established sequence-stratigraphic framework. A lower sequence boundary, referred to as the Calico sequence boundary, is overlain by a 25- to 60-m-thick succession of strata interpreted as a transgressive systems tract. These strata consist of amalgamated braided river sandstones that pass upward into heterolithic estuarine strata and, in turn, into distal shoreface sandstones capped by a widespread fossiliferous horizon. Separating the heterolithic estuarine deposits from the overlying shoreface sandstone is a widespread erosion surface covered by a conglomerate of sub- to well-rounded pebbles. This surface is a ravinement surface or transgressive surface of erosion within the transgressive systems tract. The transgressive systems tract is overlain by up to 80 m of progradationally stacked parasequences, consisting of offshore and shoreface strata interpreted as the deposits of a highstand systems tract. In a landward direction the shoreface strata pinch out and highstand deposits are represented by coal-bearing coastal plain strata. A second sequence boundary, referred to as the Α-sequence boundary, erosionally overlies these shoreface strata and, in turn, is overlain by an estuarine unit up to 38 m thick. These estuarine strata comprise a second transgressive systems tract that is capped by an erosion surface overlain by offshore strata. This study provides a useful analog for the interpretation and correlation of strata in less well exposed areas and particularly in the subsurface. This paper also provides facies dimensions of shoreface parasequences that may allow for better modeling of variations in reservoir compartmentalization within a sequence-stratigraphic framework.
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Applying depositional sequence stratigraphic concepts to the interpretation of siliciclastic depositional systems is becoming an increasingly important tool in petroleum geology. After a succession of breakthroughs during the 1970s and 1980s, sequence stratigraphic concepts now have entered a phase of intense application and documentation, especially with regard to successful implementation in the field of petroleum geology. Workers have applied these concepts to a variety of databases, ranging from outcrop to cores to electric logs and to multifold seismic data. Clearly, sequence stratigraphic concepts embody–not a rigid model or template–but rather a way of looking at geology. This volume has two purposes: to compile some recent applications of siliciclastic sequence stratigraphic concepts, and to present new studies focused on refining conceptual models. This memoir grew out of a 1991 symposium, "Variations in Depositional Systems Within a Sequence Stratigraphic Framework: Applications to Exploration," organized by the authors at the AAPG annual meeting at Dallas. Robert Loucks and Rick Sarg have edited a companion volume, also published by AAPG,“Entitled Carbonate Sequence Stratigraphy: New Developments and Applications.”