Stratigraphy of Upper Pennsylvanian Cyclic Carbonate and Siliciclastic Rocks, Western Paradox Basin, Utah

Abstract Upper Pennsylvanian strata of the Paradox, Honaker Trail and Elephant Canyon Formations are exposed along the Colorado River and its tributaries in Cataract Canyon (in and near Canyonlands National Park). The 1200 foot aggregate thickness of this section is subdivided into 33 cycles which have a calculated mean period of 455 k.y. Cycles are the dominant stratigraphic element and the fundamental unit of correlation in this study. They are defined by regionally correlative subaerial exposure surfaces and typically contain systematic deepening and shallowing facies successions of both marine and continental origin. They are spatially and temporally analogous to mid-continent cyclothems and fourth-order depositional sequences. Cycles stack as a series of progradational clinoforms to compose cycle-sets consisting of five or more cycles. Cycles can be subdivided into as many as 10 high-frequency cycles which exhibit repeatable oscillations between a limited range of facies. Lower cycles of Desmoinesian through Early Missourian age are primarily composed of carbonate strata and have a northeastward stepping, progradational geometry which records the final stages of filling of the Paradox Basin. Subsequent cycles (middle Missourian-Virgilian) have increasing siliciclastic content and record a gradual westward shift in the basin depocenter. Upper cycles (Virgilian through Wolfcampian) are composed of siliciclastic flood plain, fluvial and eolian sediments which stack as a series of southwestward stepping depositional clinoforms. The arkosic composition and aggradational to southwestward progradational geometry of these deposits suggest a provinance in the Uncompahgre Uplift. Large-scale eolian cross beds are present within asymmetric, upward-deepening facies successions which are typically contained within the thicker, more steeply dipping foreset position within cycles. The thickest sets of this facies are present in the most seaward cycles immediately below and above the cycle-set boundary at the low-stand turnaround of base level. Stratigraphic evidence indicates that deposition of this facies is closely linked to a rising water table. Maximum aggradation appears to occur when eolian sediment supply is in balance with sea-level rise. Preservation occurs with continued sea-level rise and flooding of dune field.