南秦岭文县地区三河口群微古植物化石的发现及其地质意义

Discovery of microflora fossils in the Sanhekou Group in the Wenxian area South Qinling and their significance

在南秦岭西段文县北部三河口地区,古生代浅变质沉积岩系三河口群分布广泛,前人将其划分为桥头组、屯寨组和洋汤寨组。在其中部的屯寨组中首次发现了微古植物化石,计30多个种属,时代确定为晚震旦世,为三河口群的划分与解体提供了新的依据,证实桥头—康县裂陷盆地是南秦岭新元古代裂陷海槽的组成部分。

The Sanhekou Group,a Paleozoic low grade metasedimentary series is widespread in the Sanhekou area in the northern part of Wenxian County in western sector of the South Qinling. Predecessors assigned it to the Qiaotou Formation Tunzhai Formation and Yangtangzhai Formation. During 1∶50000 mapping many microflora including more than 30 genera and species were first found in the Tunzhai Formation in the middle part of the group. The authors believe that their age is late Sinian. This furnishes new evidence for the stratigraphic division and disintegration of the Sanhekou Group. This data also validate that the Qiaotou-Kangxian rift basin is a part of the late Proterozoic South Qinling aulacogen.