西秦岭地区二叠—三叠系界线地层研究

在西秦岭地区南秦岭带广泛发育碳酸盐岩型二叠、三叠系。本文以选部益哇沟剖面为例，对该区界线地层进行研究，从岩石地层划分、生物地层划分以及地球化学元素最优分割研究出发，确定了二叠、三叠系界线点，证明牙形石Ｈｉｎｄｅｏｄｕｓｐａｒｖｕｓ可作为三叠系开始的标志，并且二叠、三叠系是连续的。沉积环境分析表明，三叠纪初期相对于二叠纪末发生了一次海侵。

RESEARCH OF PERMIAN-TRIASSIC BOUNDARY STRATA,IN WEST QINLING AREA

arbonate-type Permian and Triassic strata are widespread in south Qinling Belt,W6st Qinling. This paper mainly studies the Yiwagou section of Tewo county, Gansu province. In view of the division of lithology, biostratigraphy and optimal partition of geochemical elements of the Permian-Triassic boundary strata, it is testified that the conodont Hindeodus parvus can be regarded as a biostratigraphic criterion of the lowest part of the Triassic and the Permian-Triassic boundary strata of this area is successive. According to the analysis of sedimentary environment, another transgression started at the beginning of Early Triassic in contrast to what happened at the terminal Permian.