中文摘要：

发生于中生代—新生代之间的事件是地质历史上一次重大灾变和异常事件,因此白垩系—古近系之间的界线（K/T界线）就成为全球最重要的地质界线之一。通过对塔里木盆地西北缘乌恰地区库孜贡苏河剖面海相上白垩统—古新统地层的岩性和沉积环境变化以及地球化学特征研究,重点利用沉积物色度、有机碳含量、碳酸钙和碳、氧稳定同位素的明显异常变化,结合前人研究资料,论证并证实了该区分布于依格孜牙组和吐依洛克组之间5 cm厚的黏土层为白垩系—古近系界线（K/T界线）,它是白垩纪末期全球重大突变事件的沉积产物,记录了白垩纪末—古近纪初气候和环境变化的信息。它对丰富我国白垩纪—古近纪之间的事件研究、确定塔里木盆地地层年代序列以及恢复该地区古环境都具重要意义。

英文摘要：

The catastrophe and extinctions occurred in late Cretaceous is one of the most severe events during the geo-logical history,a thin clay boundary worldwide deposited on the earth during this period was called＂K-T boundary＂. The nerth western Tarim Basin is an ideal experimental field preserving continuous Late Cretaceous-Paleogene marine stratum and excellent outcrops in China.Previous researchers have done a lot of work and made a series of important achievements,however,the research and discussion on the paleoenvrionment and paleoclimate from Late Cretaceous to Early Paleogene is seldom involved.In this study,Kuzigongsu section of Late Cretaceous-Paleogene strata were selected to investigate the lithology and sedimentary environment changes and geochemical characters of the Late Cretaceous-Paleogene marine stratum.The results showed that the sediment color,calcium carbonate,organic carbon content and carbon/oxygen stable isotope changed abnormally in the 5 cm thick clay layer distributed between the Yigeziya and the Tuyiluoke Formations.The three curves of L＊（lightness）,a＊（reddness）,b＊（yellowness）representing the sediment color index changed slowly within Tuyiluoke Fm,but fluctuated greatly in the part of the Tuyiluoke Fm. The CaCO3 content was also divided into two parts：Lower Cretaceous Yigeziya Fm is higher（average content of 51. 53%）,paleocene Tuyiluoke Fm is lower（average 19.24%）,while the content between the two Formations sharply decreased（4.92%）.The organic carban content maintained stably in Yigeziya Fm.（average content 0.12%）,the lowest value was detected in the gray-green clay between two Formations,the content recovered to0.1%after entering the Yigeziya Fm.The curves of carbon and oxygen isotopes changed with the gray-green calcareous mudstone between the Yigeziya Fm and Tuyiluoke Fm as the turing point,δ13 C suddenly from positive value to negative,and remained negative until 3.78 m deep at the bottom of Tuyiluoke Fm,then turn positive（varying from 0.8‰to