甘肃龙首山地区韩母山群研究的新进展

甘肃龙首山地区的韩母山群包括下部的烧火筒沟组和上部的草大坂组。对于草大坂组的时代一直存在争议,一种观点根据其岩性主张置于寒武系,另一种观点是因其下部含冰碛砾岩主张置于震旦系。最近在金川黑沟一带的韩母山群的草大坂组中采到许多海百合茎、海绵骨针及瓶筐石化石,基本可以确定草大坂组是一个寒武纪—早奥陶世的地层单位,而非震旦纪地层。震旦纪的烧火筒沟组的冰碛砾岩沉积特征明显,区域上可与贺兰山一带的正目观组相对比。

PROGRESS IN THE STUDYING OF THE HANMUSHAN GROUP IN THE LONGSHOU MOUNTAINS OF GANSU PROVINCE

The Hanmushan Group in the Longshou Mountains in Gansu Province includes the Shaohuotonggou Formation and the overlying Caodaban Formation.The age of the Caodaban Formation has been in dispute.Some geologists regard it as Cambrian in age , whereas others place it in the Cryogenian-Ediacaran because of the presence of glacial diamictite in the lower Caodaban Formation.In our recent geological survey , we have found Calathium (?), crinoids , and poriferan fossils in the Caodaban Formation of the Hanmushan Group at the Heigou section in Jinchuan , Gansu Province.Thus , the Caodaban Formation is likely of Cambrian to early Ordovician in age.The underlying glacial diamictite of the Shaohuotonggou Formation can be correlated with the Zhengmuguan Formation in the Helanshan Mountains.