Types and Main Characteristics of Devonian Sedimentary Basin in South China

The passive continental margina are formed in southern, western and northern margins of Huaxia Plate during Devonian because of the opening of Old Tethys. According to the crust character, tectonic activity, sedimentation and vocanism etc., the sedimentary basins in South China can be divided into eight types: intracontinental strike-slipping basins, intracontinental depression basin, intracontinental marginal fault basin, continental marginal strike-slipping basin and intercontinental depression basin, intracontinental marginal fault basin, contintinental marginal strike-slipping basin and intercontinental basin. The formation and evolution of the basin are controlled by the basement fault activity, change of transgression- regression and sedimentation, including four stages: beginning, enlarging and differentiation of the basin, strong rifting-depression and shallowing-filling. In the beginning stage, tectonic active is not obvious, developed terrigenous clastic sediments. However, during the enlarging and differentiating periods, tectonic activity is strong and followed by submarine vocanism and sensitive transgression, deep-water basin initiated and occurred shelf-elastics and carbonate ramp sedimentation. During strong rifting-depressing stage, tectonic activity is strongest, vocanism is obvious, transgression is great and developed deep-water basin sedimentation, lithofacies differentiation was very obvious. Youjiang area and Nanling area are all passive margin of yangtze paleocontinent, but lithofacies-tectonic framework is obviously differentiated: the former is mainly NW direction intensive rifit-ing-depression, while the latter is typical of NE direction basement faulting-slipping. The author think these are the result of spreading of Jinshajiang River-Ailaoshan Mountain of Old Tethys, resulting in contamporneously intensive rifting in Youjiang area. During pre-Devonian, developed serveral NE direction basement faulting zones in Nanling area. Under the influence of transform fault resulted from ocean basin spreading, these basement fault zones developed right-lateral strike slipping, and finally formed Nanling strike-slipping basin.