Environmental change and human activity in the northeastern part of the North China Plain during early MIS-2

摘要

Marine isotope stage 2 (MIS-2), the coldest and the longest glacial during the last glacial period, was an important interval for the development and evolution of microlithic cultures. The Zhaocun site, located in the northeastern part of the North China Plain, is not only the first Late Paleolithic site discovered in the southern piedmont of the Yan Mountains, but also an important representative of Late Pleistocene strata and fossil fauna in North China. However, there have been few studies of the upper cultural layer at the site which have focused on the development of Paleolithic culture, especially the microlithic technology, in the context of environmental changes; moreover, no absolute age determinations are available. Here we present a study of the paleoenvironmental record of the Zhibuchang profile at the Zhaocun site during the interval of 27.6-23.6 cal. kyr BP. We conducted a stratigraphic study based on pollen and grain-size analyses of 78 samples from the profile, and obtained 7 AMS C-14 dates. During 27.6-26.6 cal. kyr BP, the regional vegetation was relatively diverse meadow steppe dominated by Artemisia and Asteraceae. The climate, although colder and drier than today, was the warmest record within the studied profile, and was relatively favorable for human beings. From 26.6 cal. kyr BP, with the onset of the Last Glacial Maximum, the climate became colder and more variable, with two extreme climatic events occurred at 26.2-25.5 cal. kyr BP and 24.3-23.6 cal. kyr BP, respectively. A cold wet event from 26.2 to 25.5 cal. kyr BP led to a drastic decline in local biodiversity, which would have resulted in food shortages for human beings. In addition, previous areas available for human activities were gradually flooded due to the rising river level, forcing the relocation of human beings and resulting in the termination of the cultural layer. A cold dry event from 24.3 to 23.6 cal. kyr BP, which may correspond to North Atlantic Heinrich event 2, caused a further deterioration of the environment for human beings, and may be a major cause of the absence of microlithic cultural remains on the northeastern part of the North China Plain during late MIS-2.