川黔湘交境寒武纪二级层序的划分及海平面变化

根据时限、造山幕和水深变化，将研究区寒武纪划分为３个二级层序，即早世中层序Ⅱ１，中世和晚世为正层序组Ⅱ２和Ⅱ３，它们都肯ＳＢ１型底界面，二级层序与二级海平面变化对应，从不同块体二级海平面变化比较可看出扬子 块与华北板块、北美板板块极不相同，反映它们之间的距离较大；而与塔里木地块非常一致，说明两者的距离极近，这些异同与三叶虫生物地理分区吻合。

SEQUENCE STRATIGRAPHY OF ORDOVICIAN IN THE NORTHWESTERN HUNAN, CHINA

The study of the outcropped sequence stratigraphy of Ordovician is made for the first time on the paleocontinental margin of the Yangtze plate in the northwestern Hunan, China. Eleven sequences are distinguished according to the practical results from the ten survey sections. All of them are defined as orthosequences or third order sequences except the ninth sequence. The Ordovician orthosequence in the northwestern Hunan can be grouped into two general sets that are considered to be a mesosequence or second order sequence. The lower mesosequence includes the Lianghekou through to the Guniu Stage and upper mesosequence includes Miaopo Stage through to the end of the Ordovician. The sea level curve in Ordovician is also attained, which is correlated to those of North America, Australia and North China.