Ordovician System in Keping area of Northern Tarim Basin is dominated by carbonate sediments and can be divided into platform and platform-basin factes zones and subdivided into five different factes types: restricted platform,open platform,platformmarginal shoal,neritic shelf and basin.Geochemical analyses indicates that geochemical characters are closely related tosedi-mentary environment in the study area:1.Different factes types have different geo-chemical characters,the contents of elements K,Na,Fe,Al and trace elements Sr,Ba,Mn,V,Niand B are low in the platform factes zone,but increase largely in the platformbasin factes zone, e. g., the everage content of K is less than 0.01% in the platform factes zone,and it is 0. 95% in the platform-basin factes zone.2.The everage Sr contentand Sr/Ca×1000 ratio tend to increase gradually from restricted platform→open platform→platform marginal shoal→neritic shelf→basin, the ratio increases from 2.9→3.8→5.3→6.0→6.4. The author agrees with J. Veizer at al that this is related to differentprimary carbonate minerals in different sedimentary environments.
