XUAN Xiaona, ZHAO Qin, ZHOU Limin, YANG Huawei, XU Hongyang , LIU Feng , CHEN Pujiao, REN Shaofang

(Key Laboratory of Geo-information Science of Ministry of Education, East China Normal University, Shanghai 200241,China)

Abstract: Based on systematical analysis of grain size and element geochemistry of the hard clay samples from Suzhou Area, China, it is found that the hard clay consists essentially of silty grains of 4 to 63 um in size, with an average grain diameter of 5.2 to 7.1Φ and also a small amount of fraction with diagram higher than 63 um. It tends to display the bimodal patterns of distribution. The grain size characteristics of the hard clay samples are very close to those of the Xiashu Loess; they show characteristics of typical eolian sediments; The discriminant parameter for the sedimentological environment calculated by the statistical parameters of grain size and the C-M plots of the hard clay show the same result. Results also show that the hard clay underwent moderate chemical wreathing. The major elements such as Na and P were migrated and leached, while the elements Mn and Al were slightly enriched during the chemical weathering process. Results reveal that the hard clay from Suzhou area have the same origin as the Xiashu Loess; it’s a kind of aeolian deposition. In addition, the grain size and chemical characteristics of the upper hard clay are obviously different from the lower. The lower hard clay is coarse in size, and its chemical weathering intensity is much weaker than the upper. The reason is that they might have been deposited during last glacial maximum; the stronger winter monsoon severely influenced the loess of the upper hard clay.

Key Words: grain size; element geochemistry; paleoclimate; hard clay; Suzhou

EARTH AND ENVIRONMENT Vol.45, No.5, Tot No.319, 2017, Page 555-566