Abstract:

Clay minerals and trace elements are widely distributed in the different types of sediments,which are so sensitive to environment change.The characteristics of clay minerals (sedimentary differentiation,mineral assemblages, and mineral composition and contents) has provided the information of environment change during their formation process.After studying the typical lithogeochemical parameters of high-resolution sequence units in the 3rd and 4th of Shahejie Fm in the fall-wall of Shengbei fault,Dongying depression,it has been found that mineral composition (including clay minerals and cements),chemical constituents (trace elements) would be periodically changed with the pace of change cycle of lake surface controlled by paleoclimate.The contents of illite + mixing-stratified illite/semectite and kaolinite +chlorite as well as paleosalinity show distinct change features above and below high-resolution sequences boundary.In the water transgressive system, the content of kaolinite is increased but the content of semectite and value of paleosalinity are gradually reduced from bottom to top.However these characteristics in water regressive system would be opposite. On the sequence boundary under different transgressive and regressive water systems,the contents of dolomitic cement is relatively high,while the contents of calcitic and mixing cements is relatively low.

Key words: clay minerals, trace element, cement, paleosalinity, high-resolution sequence stratigraphy, Dongying depression