上海地区上更新统“暗绿色硬土层”沉积环境及其地质成因探讨

Sedimentary Environment and Geological Genesis of Upper Pleistocene“Dark-green Stiff Clay Layer”in Shanghai Area

“暗绿色硬土层”是上海地区的标志性沉积层。根据“暗绿色硬土层”的平面、断面分布特征及测年数据,结合最新的第四纪气候研究成果,探究其沉积环境及地质成因。研究表明,“暗绿色硬土层”的分布受古河道控制,原始黏性土层沉积于晚更新世的末次冰期冰消期和YD冰进期,并于YD冰进期出露地表固结硬化。“暗绿色硬土层”的缺失并非后期受古河流冲刷造成,而是YD冰进之前未沉积形成黏性土层,或YD冰进期间沉积的黏性土层未出露地表经历硬化固结过程。

“Dark-green stiff clay layer”is a marker sedimentary layer in Shanghai area.According to its plane and section distribution characteristics and dating data,combined with the latest research results on Quaternary climate,the sedimentary environment and geological genesis are explored.Studies show that the distribution of“dark-green stiff clay layer”is controlled by paleochannels.The original clay layer was deposited in last deglacial period and Younger Dryas period at late Pleistocene,and the surface consolidation hardening was exposed in Younger Dryas period.The lack of“dark-green stiff clay layer”was not caused by the erosion of ancient rivers in the later period,but failed to deposit into the clay layer before Younger Dryas period,or the clay layer deposited during Younger Dryas period did not expose the surface to undergo hardening and consolidation.