Michael H. Gardner, 1995. "The Stratigraphic Hierarchy and Tectonic History of the Mid-Cretaceous Foreland Basin of Central Utah", Stratigraphic Evolution of Foreland Basins, Steven L. Dorobek, Gerald M. Ross
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A high-resolution stratigraphic framework links nonmarine through marine-shelf deposits across the Turonian–Coniacian foredeep basin exposed in central Utah. This record of cyclic lithologic change and biostratigraphic and isotopic age data document basin-scale patterns of foreland basin deposition. Three temporal and spatial scales of stratigraphic cyclicity are recognized in the middle Cretaceous foreland basin of central Utah, each recording base-level changes of different periodicity. A long-term stratigraphic cycle spans early Turonian through middle Coniacian Stages (93.25 to 88.8 Ma; 4.5 my in duration) and is a 500-m-thick upward-coarsening succession of marine and nonmarine deposits bounded by deposits formed during eustatic transgressions. Four intermediate-scale stratigraphic cycles (300 m thick, 1 to 2 my in duration) punctuate this succession, each recording an episode of eastward shoreline pro-gradation followed by transgression. Intermediate-scale successions are defined by the stacking pattern of small-scale stratigraphic cycles (40 m thick, 0.25 my in duration) defined by progressive upward change in stratal geometry and facies.
In proximal portions of the marine foreland basin, the lowest two intermediate-term stratigraphic cycles (Mytiloides and Woollgari sequences) are westward-thickening mudstone-dominated clastic wedges. Seventy kilometers into the basin, these stratigraphic sequences show depositional thinning in successive short-term stratigraphic cycles over a westward migrating peripheral bulge. Deposition of the third intermediate-term cycle (Hyatti sequence) records the development of two spatially discrete depositional systems in central Utah. This sequence is broadly tabular and probably records a 1–2-my period of tectonic quiescence and foreland basin expansion. The final intermediate-term cycle (Ferronensis sequence) records an increase in sediment supply from the southwest related to structurally controlled longitudinal drainage of a moderate to large fluvial system.
Changes in stratal geometry and facies architecture across these stratigraphic sequences record accelerated subsidence, basin contraction, and westward migration of a peripheral bulge, followed by basin expansion and widespread deposition of coarse clastics. In other foreland basins, such patterns of basin filling have been related to episodic tectonism, but a coeval tectonic event is not recognized in the adjacent orogenic belt. Because Turonian marine mudstones overlap the hanging wall of the initial thrust and constrain its cessation, these foreland basin depositional patterns appear to record viscoelastic responses to thrust deformation. There is, however, strong evidence for important eustatic sea-level changes in the middle Cretaceous. Accordingly, criteria used to distinguish tectonic versus eustatic controls on foreland basin deposition may be overly simplistic.
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Stratigraphic Evolution of Foreland Basins - A strong case can be made that foreland basins are where the casual links between sedimentation and tectonic events were first recognized, as evidenced by the interpretations of geologists working in classic foreland areas. This Special Publication was derived from a Research Symposium entitled ?Stratigraphic Sequences in Foreland Basins ?held at the AAPG-SEPM joint annual meeting on June, 1992, in Calgary, Alberta, Canada. This volume provides a well-balanced perspective of current research on foreland basin stratigraphy and also serves as another element in the evolving framework that comprises our understanding of foreland basins. Given that so many of earth?s resources are found in foreland basins and that foreland basin strata often provide the only preserved record of the tectonic events that led to basin development, the impetus for continued studies of foreland basin strata should remain for many generations of geologists to come.