甘肃省北山野马街组的建立

THE ESTABLISHMENT OF THE YEMAJIE FORMATION IN THE BEISHAN MOUNTAINS,GANSU

甘肃省肃北县马宗山乡平头山北坡，出露一套变质碎屑岩。１９６８年，甘肃省区调二队将它划归蓟县系平头山群上岩组；１９８１年，缪长泉、高振家等在该群中采获叠层石，将其划归青白口系大豁落山群；１９８９年，甘肃省“地质志”将期厘定为大豁落山群下岩组，并确定与下伏平头山群的关系为平行不整合。因研究程度不够，均未正式命名。笔者依据岩石地层单位的划分原则与北山地层系统，对该套地层重新进行了研究划分，确定了单位层型与界线层型，并命名为野马街组。本文描述了该组层型剖面及延伸变化，并对时限进行了讨论。

There outcrops a sequence of metaclastic rocks on the north slope of Mount Pingtou at Mazongshan Town-ship,Subei county,Gansu province.In 1968 the Second Regional Geological Survey Party assigned it to the UpperRock Formation of the Pingtoushan Group of the Jixian system.In 1981 Miu Changquan,Gao Zhenjia et al. foundstromatolite fossils in this group and then assigned it to the Daholuoxhan Group of the Qingbaikou System.In themonograph“Regional Geology of Gansu Province”published in 1989,it is defined as the Lower Rock Formation ofthe Dahuoluoshan Group and determined to be underlain disconformably by the Pingtoushan Group. It has not beenformally named owing to limited studies, In light of the principles of lithostratigraphic classification and the strati-graphic system of the Beishan Mountains,the author has restudied the stratigraphic classification of this sequence,determined the unit stratotype and boundary-stratotype and named it the Yemajie Formation.This paper describesthe stratotype section of this formation and its extension and change and discusses its time span.