Disintegration of the Wanbaogou Group and discovery of Early Cambrian strata in the East Kunlun area

Abstract：Through 1∶50 000 regional geological survey, the authors have preliminarily ascertained that all the four rock associations in the original Wanbaogou Group are bounded by faults or ductile shear zones and distributed as banded tectonic slices. Mapping has found that the group actually consists merely of volcanic rock associations and carbonate rock associations, in which a Sm-Nd isochron age of 1441±230 Ma and some stromatolites have been obtainsed. So the two rock associations are determined to be of Meso- to Neoproterozoic age. During reconnaissance mapping, the authors found that the original upper and lower clastic rock associations of this group are synonymous, from which predecessors and the authors had found Early Cambrian microfossil plants and small -shelly fossils. On that basis, the original Wanbaogou Group is disintegrated. The disintegrated Wanbaogou Group is only composed of the volcanic rock association and carbonate rock association and renamed the Wanbaogou Group-complex, in which two formal formation-rank tectono-stratigraphic units are established, i.e. the Wenquangou Formation-complex and the Qingbanshisuzhan Formation-complex. On the basis of the fossils and rock associations, the age of the original upper and lower clastic rock associations are revised and identified to be Early Cambrian and a new formation, the Salawula Formation, is established.