The Climatic And Environmental Evolution During The Past25.5Ka Years From Baiyangdian In Hebei,China

The climatic and environmental evolution is a very important research field in the past researches of the global change. This research can contribute to better predict the trend of climatic and environmental evolution in the future. The Baiyangdian is located in the North China Plain, and in the East China Monsoon Region. So it is very sensitive to climate changes and becomes the ideal area to study the Quaternary paleoenvironment. In the article, we selected Laohetou section as research object, and established the believable time scale by the method of AMS-14 C. What’s more, the history of climate variations since 25.5 ka BP was reconstructed with grain size, magnetic susceptibility, geochemistry and some other regular proxies. The results can keep pace with the former records in regional area and the world.Laohetou profile is located in the west of Baiyangdian depression. A 610 cm deep sediment profile was studied in this paper. The AMS14 C measured data revealed that the sediment profile deposited since 25.5 cal ka BP. Combined with chronological data, grain size characteristics, susceptibility and sedimentary characteristics, geochemistry characteristics the evolutionary process and environment features during the past 25.5cal ka BP were reconstructed. Results showed that there were seven stages as following:Ⅰ 25.5—20.9 cal ka BP(610~515 cm). The environmental conditions was a fluvial facies and wind accumulation period,the climate was cold and dry.Ⅱ 20.9—10.7 cal ka BP(500~388 cm). The fluvial action is weakened, and wind accumulation may be strengthened, the climate was cold and dry.Ⅲ 10.7—8.6 cal ka BP(388~335 cm). As precipitation increased and water accumulates, lakes expanding during this stage.Ⅳ 8.6—7.2 cal ka BP(335~299 cm). The environmental conditions was a wind accumulation period, the climate was cold and dry.Ⅴ 7.2—3.2 cal ka BP(299~200 cm) The environmental was a lacustrine facies period, the climate was warm and wet.Ⅵ 3.2—1.3 cal ka BP(200~110 cm)The environmental was a a fluvial facies;,Ⅶ 1.3 cal ka BP—now(110~0 cm),The precipitation decreases, but fluvial function is still obvious.