A Record Of Environmental Change Between80,000and38,000Calendar Years B.P. Indicated By Diatom Assemblages From Maar Lake Huguangyan

The last glacial period, the Greenland ice core record24times rapidly climatic fluctuation events, named as Dansgaard-Oeschegar oscilations. Six large-scale glacier drift events occurred in the North Atlantic, indicating a rapid cooling event, called as H events, which corresponding to the cold event of the DO. During the last glacial, these aburpt cliamte changes have been recorganized in a lot of paleoclimatic records in high latitudes of Northern Hemisphere. In the mid-latitude, high-resolution stalagmite also provided the brupt events record, which confirm closely linkage with high latitudes climatic system in Northern Hemisphere. In low-latitude, especially in tropical regions, we need more records to confirm the linkage between high and lower latitudes climatic system changes.Maar lake is located in Zhanjiang, Guangdong Province, in southern China. It is in a climate-sensitive zone, affected by the winter and summer monsoons. Maar lake is closed and the sediments provide a high-resolution records of paleoenvironmental change. Maar lake preserve diatoms very well, which provides a sensitive indicator of millennial time scale climate change.The following conclusions are from the record of Maar Lake Huguangyan C core between80and38ka B.P.:1.33genes and178species of diatom have been recorgnaized. The main planktonic species include:Aulacoseira granulata, A. ambigua, Cyclotella krammeri, C.ocellata, C.stelligera, C.pesudostelligera. The main benthic species include:Achnanthes acares, A.holsatica, A.sacula, Cymbella minuta, Nitzchia fonticola, N.frustulum, Punctastriata pinnata, Pseudostaurosira elliptica, Staurosira construns and S.fasciculata.2. We divided the records into3zones, in accordance with the ratio between planktonic and benthic species, zone Ⅱ was divided into2subzones, so as zone Ⅲ., for a total of five subzones.Zone Ⅰ:age was80-67ka B.P.; depth was2930.5-2578.5cm.Zone Ⅱ:age was67-48ka B.P.;depth was2578.5-2081.5cm. Subzone Ⅱ-1:age was67-59ka B.P.; depth was2578.5-2367.5cm. Subzone Ⅱ-2:age was59-48ka B.P.; depth was2367.5-2081.5cm.Zone Ⅲ:age was48-38ka B.P.; depth was2081.5-1829cm. Subzone Ⅲ-1:age was48-40ka B.P.; depth was2081.5-1859cm. Subzone Ⅲ-2:age was40-38ka B.P.; depth was1859-1829cm.3. The ratio between planktonic and benthic species indicate that orbital time scale climatic changes in the study interval. Between80and67ka B.P., planktonic species dominated, indicating high water level of lakes; between67and48ka B.P.,benthic species dominated, indicating low water level of lakes; between48and38ka B.P., planktonic diatoms dominant again, indicating high water level of lakes.4. The ratio of planktonic and benthic species records millennial-scale abrupt climate changes, such as H6, H5and H4events and DO oscilations21-9event.5. The millennial time sale climatic changes record from Maar Lake diatoms indicate that the Northern Hemisphere climatic system has a significant impact on low-latitude climatic system..6. The changes in diatom biodiversity of Maar Lake dependent on the changes in micro-environment; Biodiversity increased when micro-environment change to simple; In contrast, biodiversity decreased when micro-environment change to complex.