川东地区下-中三叠统的锶同位素曲线及年代地层划分

Sr isotopic curve of the Lower-Middle Triassic of East Sichuan and the chronostratigraphic division

从川东邻水和渠县采集的73个下-中三叠统锶同位素样品获得了对应于地层累计厚度的锶同位素演化曲线。与C.Korte等利用特提斯和中欧地区219个锶同位素数据及古生物学研究所得出的对应于地质年龄值的上二叠统-三叠系锶同位素曲线对比,将川东下-中三叠统剖面进行了年代地层的划分对比。根据剖面中获得的牙形石化石,讨论了对四川地区三叠系底界的确定,认为应尽可能采用综合的地层学方法对沉积地层进行年代地层划分对比。

Strontium isotope stratigraphy is a new method to divide and contrast strata. This paper sets up an evolution curve of the strontium isotopic composition corresponding to the accumulative thickness based on 73 unaltered marine carbonate samples collected from Linshui and Quxian of East Sichuan. It is correlated with a curve corresponding to geologic time set up by C. Korte et al in the Upper Permian-Middle Triassic. The curve is based on 219 unaltered marine carbonate samples collected from the Asian Tethys and middle Europe and on the study of paleontology. And the section of Middle-Upper Triassic in East Sichuan is dated. The base of Triassic in Siehuan is discussed and defined according to the conodonts collected from some sections, and synthetical methods should be used in the chronostratigraphic division.