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    东昆仑地区万保沟群的解体及早寒武世地层的新发现

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

    • 摘要: 提要:通过1∶5万区调工作,初步查明原万保沟群4个组间均以断层(韧性剪切带)为界面,在空间上呈条带状构造岩片态势展布。经填图发现该群实际上仅由火山岩组和碳酸盐岩组构成。并在火山岩组和碳酸盐岩组中分别获得了(1441±230)Ma Sm-Nd全岩等时线年龄和叠层石化石,确定其时代为中—新元古代;在地质填图中发现该群原上、下碎屑岩组属同物异名现象,笔者及前人获得了早寒武世微古植物化石及小壳动物群化石。据此,对原万保沟群进行了解体,解体后的万保沟群仅由火山岩组和碳酸盐岩组构成,重新厘定为万保沟群,并在群内新建两个正式组级构造地(岩)层单位,即温泉沟组和青办食宿站组。而将原上、下碎屑岩组依据古生物化石、岩石组合特征,重新厘定其时代为早寒武世,并新建立沙松乌拉组。

       

      Abstract: 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.

       

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