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The AAPG/Datapages Combined Publications Database

Utah Geological Association

Abstract


Geology of East-Central Utah, 1991
Pages 77-94

Latest Cretaceous Nonmarine Depositional Systems in the Wasatch Plateau Area: Reflections of Foreland to Intermontane Basin Transition

Karen J. Franczyk, Janet K. Pitman

Abstract

Uppermost Cretaceous nonmarine rocks in the Wasatch Plateau contain several unconformity-bounded sedimentary sequences that document regional changes in depositional environments, drainage directions, and unit thickness. These changes reflect major temporal variations in subsidence patterns, sediment source areas, and depositional and erosional events. The unconformity between the upper Campanian Castlegale Sandstone and the overlying upper Campanian Price River Formation represents a relatively short hiatus. However, during this hiatus, eastward transport of the thrust allochthon segmented the westernmost part of the foreland basin and created a barrier in the Sanpete Valley area that prevented rivers that drained the thrust belt highlands from entering the Wasatch Plateau area. When deposition resumed, rivers flowed northward across the Wasatch Plateau area and deposited the Price River Formation. The upper part of the Price River is white and kaolinitized in many areas of the southern Wasatch Plateau, indicating a prolonged episode of weathering coincident with initial movement on the San Rafael uplift. Uplift of the San Rafael positive element is represented by the thin conglomeratic sandstone that forms the base of the North Horn Formation in the southern Wasatch Plateau. Braided rivers drained the southern part of the rising San Rafael uplift and flowed northwestward into the intermontane basin that was forming between the thrust belt and this uplift. Deposition of the basal North Horn conglomeratic sandstone unit was followed by an influx of detritus from the southwest. The thick sandstone-dominated alluvial facies in the lower part of the North Horn in the southern Wasatch Plateau grades northward over a distance of 30 mi (48 km) into a mud-dominated alluvial facies. These alluvial-dominated conditions were replaced by a shallow-water lacustrine system containing Maastrichtian mollusks that extended from the central part of the basin northward into the southwestern Uinta Basin area.


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