末次冰期东北地区食草动物群的演替及其环境意义

SUCCESSION OF LARGE HERBIVOROUS FAUNAS AND ENVIRONMENTAL EVOLUTION IN NORTHEAST CHINA DURING THE LAST GLACIAL MAXIMUM

距今40ka年来东北地区大型食草动物记录显示,该区末次冰期极盛期前后,在冻土苔原大背景下可能经历了40ka B.P.森林草原、34.3ka B.P.疏林草原、30ka B.P.森林草原、22ka B.P.疏林草原、18ka B.P.森林草原、17ka B.P.疏林草原、14ka B.P.无树干草原及11ka B.P.疏林草原的演变过程,环境最恶劣最干冷的时段似乎在14ka B.P.前后.同时,该哺乳动物组合曲线与气候变化、冰川波动及海面升降等研究结果具有很好的可比性.整个环境演变过程还可与陕西关中渭河流域的3个哺乳动物群（咸阳动物群、蒲城动物群和大荔动物群）所反映的环境演变过程相对比,只是关中地区进入最干冷的无树干草原环境较早.研究认为,之所以产生这种差异是由于地区地理位置的差别,导致受东亚季风影响的强度不同,因而进入盛冰期的时间也有或早或晚的差别.

Sites of large herbivores fossils in Northeast China and adjacent areas for the period of 40~10ka B.P.mainly include sites of Guxiangtun （40ka B.P.）, Huadian （34.3ka B.P.）, Yushu（30ka B.P.）, Xiaogushan（30ka B.P.）, Yanjiagang（22ka B.P.）, Shandingdong（18ka B.P.）, Gulongshan（17ka B.P.）, Yunlianghe（14ka B.P.）and Qingshantou（11ka B.P.）.We analyzed percentages of forest or grassland and recovered climate evolution process of the last glacial（40~10ka B.P.）based on large herbivorous animals.Our record of mammal assemblages is in good comparison with the record of climate change in the North China Plain, with records of global sea level change and glacier fluctuation in North America, and as well as with δ18 O record of Core V-28-238 from the Pacific Ocean（see figure 3）.Records of large herbivores from Northeast China for the past 40ka show that this area probably had a frozen tundra background and experienced the subsequent environmental changes： forest grassland at 40ka B.P., open forest grassland at 34.3ka B.P., forests grassland at 30ka B.P., open forest grassland at 22ka B.P., forest grassland at 18ka B.P., open forest grassland at 17ka B.P., tree less prairie at 14ka B.P., open forest grassland at 11ka B.P., and the worst environment in the dry and cold period at about 14ka B.P.This series of changes are comparable to the environmental evolution reflected by three mammalian faunas from the Guanzhong Basin of Shaanxi Province.The only difference between the two regions is that a dry, cold climate and a frozen tundra environment occurred in the Guanzhong Basin（inland）at 17ka B.P., earlier than that in Northeast China（coastal）at about 14ka B.P.It thus indicates that onset of the Last Glacial Maximum environment may have happened with a geographical difference, possibly due to geographically different intensity of the East Asia monsoon.