A loess-paleosol record of climate and vegetation change during the past 27,000 years from South-East of the Caspian Sea, Iran

Loess and paleosols are valuable terrestrial archives of past climate change in arid and semiarid Asia, yet most of the available records are located in central Asia and China, with only few records from western Asia. Here we report on a loess-paleosol sequence retrieved from the Gorgan Plain Southeast of the Caspian Sea that extends back to ca. 27,000 years ago. By combining palynological and micromorphological data with granulometry and magnetic properties in different horizons, we infer past changes in soil formation and vegetation composition, and the related climatic conditions. In order to set up a more reliable chronological framework, we applied luminescence and radiocarbon dating. Our results suggest a dry and cold glacial period characterized by steppe vegetation and loess deposition until about 24,000 years ago. Climate conditions during the Last Glacial Maximum (19-23,000 years ago) were relatively wet followed by a drying trend towards the end of the deglaciation. Our record suggests a relatively wet early Holocene but remains inconclusive for the late Holocene due to concurrent anthropogenic impact. We argue that changes in wintertime temperature and precipitation have been decisive in shaping the vegetation and soil formation in our study area during the Holocene, whereas changes in the position of the westerlies together with sea-level fluctuations of the Caspian Sea controlled the regional climate during the last glacial period.