华南泥盆纪沉积盆地类型和主要特征

Types and Main Characteristics of Devonian Sedimentary Basin in South China

泥盆纪时期,随着古特提斯洋的开启,于华南板块南、西、北缘形成被动陆缘构造背景.根据地壳性质,同沉积断裂活动,沉积作用和火山作用等特点,将区内沉积盆地分为八种类型,即陆内走滑盆地、陆内凹陷盆地、陆内断陷盆地、陆缘断拗盆地、陆缘断陷盆地、陆缘裂谷盆地、陆缘走滑盆地和陆河洋盆、盆地的演化受到构造活动、海水进退规程和沉积作用控制。开始阶段的构造活动不强烈,以滨岸陆源碎屑沉积为主。海盆扩大分异阶段的构造活动明显,有海底火山活动,海侵范围扩大,深水盆地开始发育,但以陆棚碎屑岩和碳酸盐缓坡沉积为主。强烈裂陷—走滑阶段是构造活动高潮期,火山活动强烈,海侵范围最大,深水盆地最发育,沉积相分异十分显著。右江地区和南岭地区同样位于扬子古陆的被动陆缘,但岩相构造格局显著不同,右江地区以北西向断裂拉张裂陷作用为主,而南岭地区则多表现为北东向基底断裂的走滑活动。笔者认为这种特点是古特提斯洋扩张作用和基底构造性质影响所致。

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.