These sediments are often altered by eolian processes. Desert area is shaped by eolian processes and its landforms by erosion and deposition. Also, eolian sedimentation can produce high rates of sediment accumulation. In some places, Carolina Bays are overlain by eolian dunes that are now vegetated. Arthropods, in particular are important to the geologic record of bioturbation of Eolian sediments. Ding's research mainly focuses on the Neogene eolian sediments and ancient climate. The finer grained, sandy deposits consist of eolian and playa lake deposits. Various landforms are found in tropical deserts due to different kinds of eolian process. Others, occurring in rocks of several geologic periods, include lake deposits and eolian (wind) deposits. The formation is an orange eolian sandstone. The Permian continued to be a time of terrestrial deposits, including late-Permian eolian deposits. Its pyramidal shape was formed by eolian drifted grains of sand. In "eolian deflation", the wind continually removes fine-grained material, which becomes wind-blown sand. Eolian processes are major factors in shaping desert landscapes. The bulk of red clay consists of eolian dust.