Comparing the modern, Quaternary, and Neogene records of climate controlled hillslope sedimentation in southeast Nevada

The vast majority of all sediment is derived from hillslopes, Attempts to u nderstand what controls variability in the sedimentary record should theref ore consider the primary variability of hillslope sediment yield to deposit ional basins, But our understanding of controls on sedimentation, particula rly climatic controls, is limited by poor understanding of the links betwee n hillslopes and depositional systems, This is partly because the applicati ons of geomorphic research to sedimentology are not fully realized. The lon g-term hillslope stratigraphic records of this study provide a crucial phys ical link between hillslope sediment sources and depositional basins, and b etween geomorphology and sedimentology. We compare rare Neogene colluvium and buried hillslopes preserved in superp roximal basin-fill exposures to their Quaternary and modern equivalents in two tectonically quiescent basins in southeastern Nevada. Field and laborat ory geomorphic and sedimentologic methods are employed to document the prov enance of proximal basin sediment, the character and relative amount of sed iment produced on local hillslopes at different times, the hillslope weathe ring and transport processes occurring through time, and the role that rock -type differences have played. Physical weathering processes have dominated the production of angular, peb bly colluvium on both ancient and modern slopes, and overland flow has been the main process transporting detritus off slopes. Although hillslope proc esses and products in the study area remained the same in upper Miocene, Pl iocene, Pleistocene, and modern records, process rates have varied greatly, indicating that orbital-scale climatic cyclicity can be, but is not always , well expressed in the stratigraphy of continental basins. The vast majori ty of basin sediment in the study area is derived from hillslopes underlain by volcanic rather than carbonate bedrock, and rock type is the dominant c ontrol on sediment yield and landscape development in this tectonically ina ctive, dry setting.