Where Are the Former Glacial Relics in Guilin Area ?
Shi Yafeng, Cui Zhijiu, Li Jijun and Zhou Shangzhe (Lanzhou Institute of Glaoiology and Geocryology, Academia Sinica Department of Geography,Beijing University; Department of Geography Lanzhou University)
Since the 40's of this century, the glacial hypothesis, proposed by Mr. Sun Dian-qing et al. to explain some geomorphological features in the Guilin area has aroused hot debates. In 1985, Mr. Sun went to Guilin again and reiterated his own glacial hypothesis. After a short field investigation in December of 1985, we contend that the glacial hypothesis of Mr. Sun's is certainly untenable. Our main points are as follows. The so called glacial bonlder clay of red-yellowish colour which distributes widely in the Liutang and other areas bears no any resemblance to glacial deposit and no imformation of former glaciation can be found from it.The gravels in the deposit is of high roundness and being well sorted, indicating that they are mainly produced by alluvial processes. Water in alluvial channels, torrents rolling down the mountains and debris flow account for the formation of them. Disturbed structures occurred frequently in the depositional sections have been acclaimed as evidence for glacial hypothesis. However, considering the Karst landscape well developed in the Guilin area, it is not to be wondered that the original structure of the alluvial deposits would be intensively disturbed by Karst corrosion processes among which the uneven subsidence or the bed rock is the main agent. The so called "Longcun Zungenbecken", "Qingpin ice lake basin" and "U-shaped valley" on the eastern side of Jiaqiao mountain are none other than normal water worn land-forms. We are also sceptical about Mr. Sun's "drumlins", for they are generally formed in former ice sheet regions, and it is too crazy to accept an ice sheet to cover the Guilin area in the Quaternary period. A. great deal of data obtained from differential thermal analysis and X ray diffraction analysis of clay mineral. Spore pollen composition analysis and paleo-vertebrate fossil studies have shown that the tropical-subtropical environments prevailed in the Guilin region during Quaternary period. It is unlikely to believe that the snowline had ever depressed so low (300-400m a.s.l.) to meet the development of glaciation in such a low latitude and low land region.