AEOLIAN LOESS AND PALEOENVIRONMENTAL CHANGES

A typical aeolian loess stratum is found on the Shengshan islandsin East China Sea at first. This island is located at about 122‹40' E,30‹55'N in East China Sea. The loess strata of 3-8 M in thickness distribute on the top and slop of the rock mountain of this island with the elevation about from 80 to 100 meters. The similar loess strata have also been found in the other small islands of the Zhoushan archipelago. Being continuous deposition of the loess strata, it contains a lot of information of the paleoenvironmental change and studying on the loess in the islands have important geological significance in recognizing the Quaternary loess distribution in China and East Asia, depositing process and the evolution of paleoenvironment of the East China Sea . Through a series of analysis on the loess strata in the Island and comparing to the Xiashu loess strata in the western hilly of the Yangtze River Delta, the following conclusions can be made: 1.The analysis results on the loess (e.g. grain size, heavy mineral, phytolith analysis, pollens and spores, magnetic susceptibility, geochemical composition , surfical features of quartz grains, IRSL dating and so on) show that the loess in the Shengshan Island is aeolian in origin deposited under the cold-dry climatic condition. The sediment features are similar to the Xiashu loess in the western hilly of the Yangtze River Delta. 2.In according to the IRSL dating and strata comparison with the loess strata in the western hilly of the Yangtze River Delta, the loess in the Shengshan Island is mainly deposited during the last glacial period. 3. The material resources of the loess in the islands came from the Northwest China and Central China transported by west-wind during the late Glacial Period. 4.During the last glacial period, the aeolian dust may have been widely deposited in the East China plain, the Yellow Sea and East China Sea, and even on the Korea Peninsula, Japanses Islands and the neighboring sea areas. Therefore, the eastern limit of the loess deposits in late Pleistocene in China is farther eastward than that had been recognized. 5. The diagram of curve of grain size, and magnetic susceptibility show that there areseveral climatic fluctuations with several different dust materials during the aeolian deposition period.