甘肃中西部龙首山一带“韩母山群”的重新厘定

Redefining of the Hanmushan Group in Longshoushan,central-western Gansu Province

关于甘肃龙首山一带"韩母山群"的划分和时代归属,前人曾有不同的认识。依据沉积建造、古生物化石、变质变形等资料,对韩母山群进行解体。将该群下部变质变形较强的烧火筒沟组(钙质砾岩、细碎屑岩夹碳酸盐岩建造)厘定为震旦系,上部变质变形较弱的草大坂组(碎屑岩、碳酸盐岩建造)厘定为寒武系,并将后者与鄂尔多斯西缘下、中寒武统对比。

Based on the information of sedimentary structure,fossils and metamorphic-deformation,the authors hold that the Shaohuotonggou Formation in the lower part of Hanmushan Group,which has high-grade metamorphic conglomerate,fine-grained clastic rock and carbonate assemblages,was formed in Sinian.Whereas the Caodaban Formation in the upper Hanmushan Group,which is characterized by clastic rock and carbonate assemblage of relatively low-grade metamorphism,was formed in Cambrian.The Caodaban Formation is comparable with the Lower and Middle Cambrian strata in the western margin of Ordos basin.