A study of eolian loess and its lower boundary in China
Teng Zhihong; Shen Xiping(Department of Geology, Northwest (Design Room, Tap Water Company University, Xi'an, 710069) of Xi'an, Xi'an, 710069)
As clearly indicated by the Atlas of the relationships of Chinese rocky deserts, gravel deserts, deserts and loess with the main wind directions compiled by the author and others, the widely distributed thick loess deposits in Northwest China is mainly controlled by wind and many other multiple factors. A comprehensively comparative study of the texture of loess strata in Loessial Plateau, Tianshan Mt. and northern piedmont of Kunlun Mt. of Xinjiang shows that they are of the same horizon in the earliest deposits of the typical eolian loess in different regions and different geomorphic units, that is, all of them started at the lower siltstone (L15) in the loess sections. However the deposits below them are quite different. The time of the lower siltstone deposit is of late Early Pleistocene,i. e. 1. 2Ma B. P. , by means of the magnetostratigraphical study of all the typical sections in Loessial Plateau and repeatedly isotopical dating of the andesitic basalt below the loess stratum in Yutian county of Xinjiang. The start of eolian loess deposit has a genetic relationship with the intensively neotectonic uplifting of the orogenic belts (such as Kunlun Mt., Tianshan Mt., Qilian Mt. and Qinling Mt., ect. ) and their regional environment variation. In the meantime, this Pleistocene event stratum is notably coincident with events of paleontology, neotectonics, geomorphology and tektite formed by impact of outspace flying objects.
【CateGory Index】： P588.2