AN IN-DEPTH INVESTIGATION OF SHINARUMP DEPOSITION NEAR HURRICANE, UT AND THE VERMILION CLIFFS, AZ

The Shinarump Conglomerate comprises the basal member of the Upper Triassic Chinle Formation, cropping out widely across the Colorado Plateau. The Shinarump Member is composed of mixed sandy and gravelly fluvial sediments and displays abundant cross-stratification. Previous studies have concluded, based on sedimentological and geochronological data, that the Shinarump represents a series of palaeovalley fill deposits. However, by integrating high-resolution data, it is possible to significantly refine the palaeogeographic interpretation of the southwestern extent of the Shinarump Conglomerate. This study therefore combines data collected from outcrops at the Vermilion Cliffs, AZ and Hurricane, UT, including measurements of over 3000 cross-sets, with 1628 from sites with 15 or more cross-sets exposed, macro-scale fluvial structures mapped using photomosaics, sedimentary provenance data obtained from thin sections and both primary and literature detrital zircon analyses. Preliminary results serve to corroborate previous studies, displaying a strong north-northwest flow signal at Vermilion Cliffs, and northwest signal near Hurricane. Measurement of macroforms also shows a broadly westward vergence, and when combined with thin section and detrital zircon will be used to inform source-to-sink calculations, furthering the understanding of the basin. Future work will focus on expanding the dataset with additional chronological control points to inform models of the evolution of the palaeovalley system, and additional measurements to refine source-to-sink modelling (e.g. point bar dimensions, median grain size etc.).