THE FOSSILS IN SHANGXI GROUP AND ITS IMPLICATION FOR TECTONICS, SOUTHERN ANHUI, CHINA

The Shangxi Group is the local name in southern Anhui Province and it is believed to be the equivalence of the well-known Banxi Group in Hun an Province, southern China. So the area occupied by the Shangxi Group was regarded as a part of the ''Jiangnan old land' of Presinian till it was challenged by the present authors years ago. After we postulate d that there may be some strata of Palaeozoic Era in Shangxi Group, so me microfossils and then macrofossils of Palaeozoic were found in some part of it. The macrofossils, Lingula sp. , Conulariid and the microf ossils indicate that most units of the Shangxi Group are Palaeozoic st rata. Based on the discovery of these fossils and the recognition of t he tectonic-setting of the different tectono-petrologic units in the S hangxi Group, three different stratigraphic sequences (island-arc volc anics, back-arc sediments and the cover of passive margin of Yangtze C ontinental Plate) are established and the tectonic evolution of them i s postulated in the present paper. All the evidences obtained recently from the Shangxi Group indicate that there is no 'Old Land' over the discussed area, but a subduction followed by a collision zone between the island-arc and Yangtze Continental Plate; all these metamorphosed strata were originally island-arc, back-arc basin sediments during the Sinian-late Paleozoic, except the Presinian sandstone distributed in a narrow belt on the northmost margin of the metamorphic terrane.