Abstract

Recognition of depositional sequences in Upper Cretaceous strata in the Kaiparowits Plateau allows examination of facies-tract geometries within coeval shoreface, alluvial, and coal-bearing strata. Changes in depositional architecture, sandstone-connectedness, sand-shale ratios, coal-bed geometry, and degree of shoreface and foreshore preservation are related to position within a depositional sequence. Base-level falls produced regionally extensive sequence boundary unconformities and a basinward shift in facies tracts. Slow rates of base-level rise resulted in amalgamated fluvial channel complexes, thin discontinuous coal beds, and progradational shoreface parasequence sets. More rapid rates of base-level rise produced vertically isolated meander-belt sandstones, thick extensive coal beds, and aggradational shoreface parasequence sets. The highest rates of base-level rise resulted in retrogradational shoreface parasequences and tidally influenced fluvial systems at least 60 km inland of coeval shoreface deposits.

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