NO.lMass Extinetion一A Fundamental Indieator for Major Natural Divisions of Geoiogieal History···一··-··一x“D“ovi(徐道一), Zhang Qln、en(张勤文)and su。Ylyln(孙亦因)The Marine Cretaeeous in the Western Part of the Tarim Basin of Xinjiang and Its Depositional Environments···············1···························.·一·...·...............…… ·····、···········,·……Hao Yichun(郝治纯), zeng xuelu(曾学鲁)and Gu。xlan…