| There are many difficulties in Early Palaeozoic of South China, which have become a focus of geologists. Proceeding from the flysch in southern Hunan and Jiangxi provinces and northern Guangdong province, the author observed the Early Palaeozoic strata and sedimentary facies, and explored the sedimentary environment and structural evolution.Under the guidance of stratigraphy, paleontology, sedimentology, lithofacies palaeogeography, geochemistry, plate tectonics, and geotectonics, based on analysis of sedimentologic, tectonics, and geochemical features of field outcrops, in combination with large amounts of regional geologic data and the latest findings home and abroad, the study first focused on the sedimentary features, environment and configuration of early Palaeozoic in southern Hunan and Jiangxi provinces and northern Guangdong province, then extended to the restoration of the lithofacies palaeogeography pattern of South China basin, then the reconstruction of geotectonic framework and evolution of Cathaysia craton, South China basin and Yangtze craton.The paper has the following three new findings:First, radiolaria was found for the first time in Cambrian and Middle Ordovician system in South China, which provides a key new evidence for the solution of some historic problems. Second, the analysis of rock texture for greywacke in the south side of South China basin indicates it is typical deepwater gravity flow deposit, belonging to submarine fan. In addition, careful petrologic and lithologic analysis of flysch in South China basin suggests there is a lithologic transition belt left by the advancement of detrital material toward northwest between northern Guangdong province and southern Hunan and Jiangxi provinces.The paper comes to the following conclusions: ① the arenaceous-pelitic flysch in South China is a set of subsea fan formed by gravity flow, where the sandstone with a foreign matter content of 33% is greywacke, of relatively low compositional and textural maturity. Horizontal bedding, massive bedding and parallel bedding are commonly seen.② Eleven lithofacies and four lithofacies combinations have been found in South China basin. The eleven facies are massive sandstone, mudstone-normal graded sandstone, mudstone-parallel bedding sandstone, massive mudstone, parallel bedding mudstone, carbonaceous mudstone, silicate, radiolaria chert, radiolaria carbonaceous mudstone, dark argillaceous limestone-lamellar limestone, and nodular limestone. The four lithofacies combinations are submarine fan mid-fan subfacies, outer fan subfacies, continental uplife-deep sea plain subfacies, deep sea- carbonate platform transitional facies.③Structural pattern of the South China was two land mass with a sea basin between them in early Paleozoic. The Cathysia is the provenance of the South China flysch sediments. Deeply and broad low-latitude sea basin, which contains radiolarias, occurred in Pingxiang-Yongzhou area. Lithofacies between the Cathysia and Yangtze continents gradually transited, without a clear boundary.④The South China experienced structural evolution of two episodes of expansion and shrink. The basin was tensioned to a deep sea basin at early Cambrian, and condensed sections with black carbonaceous shales containing radiolarias can be seen. The basin slight shrinked at middle Cambrian, and flysch sediments were developed. The basin re-opened at early Ordovician to the largest at middle Ordovician, and condensed sections with siliceous rocks containing radiolarias were developed. The basin closed from southeast to northwest beginning at late Ordovician, and deep-water flysch sediments were still dominated. Till Silurian, thick sediments in the basin formed the South China Orogenic belt by thrusting and folding. ⑤ Geochemical study shows the north margin of Cathaysia craton has both the features of passive continental margin and active continental margin, which are distinct from those of continental island arc and oceanic island arc. |
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