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Controls on Carbonate Deposition in Rift Basins: Great Salt Lake, Western USA


This study approaches carbonate deposition in extensional settings from a source-to-sink perspective, investigating the influence of basin configuration, structural style, and hinterland catchment morphology and lithology. Great Salt Lake (GSL) is a hypersaline, hydrologically-closed basin within the Basin and Range province, Western USA. The lake is a remnant of the larger, late Pleistocene Lake Bonneville; prominent shorelines document a number of stable levels during the last glacial period. The tectonically-active Wasatch Fault Zone (WFZ) bounds the GSL basin to the east, and the intrabasinal, NW-SE trending East Lake Fault separates the shallower eastern part of GSL from the deeper main part. This study focuses on the central-east portion of GSL: the Weber Segment of the WFZ, the Weber, Ogden and Jordan rivers, and Antelope and Stansbury islands. Basin and catchment characteristics were studied using high-resolution satellite imagery and digital elevation models, complemented by field-based investigations of Lake Bonneville-age and modern carbonate deposits, and geomorphological and sedimentological mapping. Carbonates are found predominantly on the western sides of Antelope and Stansbury islands. Here, the late Pleistocene shorelines have bioherms and carbonate-cemented conglomerates. The bioherms are found on steep hillsides on stable substrates (bedrock or large boulders). The cement within the scree-derived, clast-supported conglomerates does not always fill the pore spaces, suggesting that the clastic sediment flux locally influences carbonate deposition. The equivalent shorelines along the Wasatch Front feature larger volumes of matrix-supported conglomerate; the higher clastic sediment flux appears to have prevented carbonate accumulation. Modern bioherms occur in greater volumes, for example in Bridger Bay, NW Antelope Island, where the stable quartzite substrate is combined with shallow, low-relief bathymetry. Modern oolitic deposits are more widespread along the west and northeast coasts of Antelope Island. Clastic sediment supplied by the Weber and Ogden rivers is deposited in a large, coarse delta, though this does not fill the sub-basin on the eastern side of Antelope Island. Finer sediments from the Jordan River to the south appear sufficient to hinder ooid formation here. Studies of outcrop analogues such as this help us to understand the controls on the location, geometry and heterogeneity of sub-salt carbonate plays.