APPLICATION OF MICROELEMENTS ANALYSIS IN IDENTIFYING SEDIMENTARY ENVIRONMENT——TAKING QIANJIANG FORMATION IN THE JIANGHAN BASIN AS AN EXAMPLE

The compositions of microelements in clay minerals,mud rock and gypsum in lake sediments are very sensitive to the change of sedimentary environment.It may reveal lake-level change.The lithology change of sediment in saline lake in vertical is distinct,this change is controled by the balance in supply,evaporation and sediment of the river,which lead to the change of lake level.The paper mainly introduces using microelements,B,S,Ba,Ti,Fe,P,Mn etc.,in the Qianjiang Sag of the Jianghan Basin as an indication for sedimentary environment change to analyse the characteristics of change in different sequence and different systems tract,and discusses paleoclimate and sedimentary environment in different sequence.The content of B in sedimentary rock is more then in igneous rock commonly.The content of B is 135×10^-6 in shale and(1～40)×10^-6 in sand rock.The content of Sr is 0.8‰～1‰ in saline lake and 0.1‰～0.3‰ in freshwater.