西秦岭西成地区泥盆系研究的新进展

西秦岭“西汉水群” 的地层时代和划分对比是一个长期争议的问题。本文通过对地层的岩性特征、生物群、矿物及地球化学特征的分析,重建了地层系统,并首次研究了本区的牙形石,确定了地层层序及地质时代,指出前人建为上、下关系的“洞山组(D_3)”、“西汉水组(D_2~2)”和“安家岔组(D_2~1)”实属同期异相地层。新的地层系统包括黄家沟组、红岭山组和双狼沟组。中、上泥盆统界线在红岭山组中部。

THE NEW ADVANCE ON STUDYING DEVONIAN IN XICHENG COUNTY, QINLfNG MOUNTAINS

The subdivision, correlation and dating of "xihanshui System" in western Qinling Mountain, which was named by Ye Lianjun and Guan Shicong ( 1944) , have been argued for many years. In this paper, a new stratigraphic system is suggested by studying its lithological character, fauna, mineral and geochemical characteristic. Conodonts firstly found in this area are used for difining stratigraphic sequence. The new stratigraphic system consist of three formations. "Huangjiagou formation" is made up of sandstone, slate and muddy limestone, which is Eifelian; "Honglingshan formation" is composed of packstone, wackestone, bindstone, framestone etc. , which is Givetian to upper gigas subzone of Frasian; "Shuanglanggou formation" is made up muddy slate and silty slate, which is uppermost gigas subzone to Famenian.The boundary of middle/upper Devonian lies the middle part of "Honglingshan formation" .