CHEMICAL WEATHERING OF THE LOESS IN THE SOUTH OF LIAONING PROVINCE AND ITS IMPLICATIONS FOR ENVIRONMENTAL CHANGE

Abstract

Chemical elements of the Zhoujiagou loess in the south of Liaoning province are analyzed.According to the chemical indexes of alteration(CIA),Na/K,and the element migration orders,together with the grain size and mineralogy of the deposits,we studied the weathering features of the Zhoujiagou loess profile.Results show that the contents of SiO2,Al2O3,TFe2O3 in the south of Liaoning province are obviously higher than those in Luochuan of Shanxi province,while the contents of MgO、CaO、Na2 O,which are close to the loess in Zhenjiang and the paleo-soil in Shanxi province,are lower in the south of Liaoning province.The change in K2O、MnO、TiO2 is not obvious in all the regions studied,while the content of P2O5 is lower in the south of Liaoning than that in Zhenjiang.It is deduced that the chemical weathering in the south of Liaoning province is characterized by the leaching of not only Na and Ca,but also K and Si to some extent.The early stage of chemical weathering,which is featured by leaching of Na and Ca,is completed,and at present it is in the stage of leaching K and Si out comparing to the elements migration pattern in the Luochuan loess.The migration and accumulation of elements are different in the Lishi and Malan loess in the Zhoujiagou profile.The evolution of the chemical weathering in the profiles indicates that the paleo-climate changed abruptly from warm and humid in Middle Pleistocene to cold and dry in Late Pleistocene.The intensity of chemical weathering in these study regions are in an order of the Xiashu loess PAASLuochuan loess(not including the acid dissolution components)Luochuan loess(total samples)UCC.These differences were caused by the climate conditions during Late Quaternary.