The discovery of Early Paleozoic nautiloid fossils in Zhongba area of Tibet and its geological significances

Fossils of Endociratidae of nautilaoid (cephalopods) were recently discovered in Zhongba area, southwestern Tibet. The fossils occur in calcareous schist and schistositized crystalline limestone dated as the Middle and Upper Permian Quga Formation and tectonically classified as the Zhongba microterrane of the Yarlung Zangbo suture. The discovery of nautiloid fossils provides evidence for diversified stratigraphic classification and disorganization of the Quga Formation within the microterrane. It is therefore inferred that there probably exist the Devonian and Carboniferous strata in the microterrane, the Lower Paleozoic strata might be correlatible among the Lhasa terrane, Tethys Himalaya and Zhongba microterrane, and the Zhongba microterrane might have had an affinity to the North China plate or/and Yangtze plate.