Sporopollen records and implications for surface processes: A case study of Shell Ridge in the Qaidam Basin, Qinghai-Tibetan Plateau

Shell Ridge, located in the hyperarid enclosed Qaidam Basin in the northeastern Qinghai-Tibetan Plateau with millions of articulated Corbicula fossils, is a rare and distinctive geomorphic unit on Earth. Early studies reported that the ridge was a lake shoreline, while recent studies demonstrated that the ridge was an ancient river channel. Previous palynological studies that followed the interpretation of lacustrine sediments had difficulty explaining the observations, such as relatively scarce sporopollen fossils in finer sediments and more abundant sporopollen fossils in coarser layers. We recently conducted a palynological analysis of the ridge and found eight assemblages. Our results provide palynological evidence of the fluvial attributes of the ridge, with much lower total sporopollen concentrations in finer deposits due to deposition in an enclosed oxbow lake without sufficient transportation and higher concentrations in coarser layers due to input from the surrounding vegetated mountains into the river water. Our study demonstrates the potential of sporopollen data in the interpretation of surface processes, in addition to the routine interpretations of the paleoclimate.