Preliminary Study Of Paleoclimate Changes In Hetao Area Since Late Glacial: A Case Study In Dengkou County Of Inner Mongolia

With human closely focusing on the environmental problem, we urgently need to foresee the future status of environmental changes. The study of environmental changes during geological time, especially the climate cycle from the Quaternary period, can largely provide a method and reference to forecast global environmental change. This study, based on the analysis of calcium carbonate content and organic carbon isotope, try to reconstruct the paleoclimatic processes in the study area.The results indicate that the sediments are of primary fluvial-lacustrine origin, with partical aeolian deposit being mixed. The paleoclimate evolution sequence since the late glacial was established, showing 5 distinct paleoclimatic periods. The first stage (12.2ka BP to 11.5ka BP)was characterized by relatively cold and dry climate, with a rapid cooling process occurring around the 11.5ka BP. The climate afterward became extremely cold and dry, probably corresponding to Younger Dryas event. The climate during the second stage, ranges from 11.5ka BP to 10ka BP, was slightly warmer. The third stage from 10ka BP to 8.8ka BP was dominated by the warm and humid climate, favoring the plant growth in this area. The fourth stage (8.8ka BP to 6.3ka BP)was a cooler period, possibly relating to the climatic deterioration. The climate since 6.3ka BP became a bit warmer, locally fluctuated by the human activities.On regional scale, the climatic variations in Hetao area shows similar traits in term of cooling Younger Dryas event and Holocene warm period with those in neighboring areas. The climate change of Hetao plain is characterized by variations of drought-cold or wet-warm periods. The climate in the cold period was dry and the vegetation was scarce, whilst in the warm period the climate was warm and the vegetation was rich.Paleoclimatic variation processes were closely associated with the Yellow River evolution. In early and middle Holocene the climate was humid, resulting in the occurring of integrated Great Lake in Hetao plain. The Yellow River during this time is an inland river. In the late Holocene the climate was dry-cold, the Yellow River migrated its channels from north to south.