黔桂地区二叠系层序地层格架及相对海平面变化研究

黔桂地区的二叠系以其明显的相分异而引入注目,在连陆台地上发育煤系地层,而在连陆台地边缘及孤立台地上发育海绵生物礁,形成一个典型的“台－盆－丘－槽”的古地理格局,并且相分异最明显的时期正好是生物礁发育的时期。二叠系包括三个统即船山统、阳新统和乐平统,船山统与阳新统之交的黔桂运动主幕不整合面以及阳新统和乐平统之交的东吴运动主幕不整合面特征明显,同时还代表了沉积盆地性质发生较大变化的界面。在二叠系中,船山统与下伏石炭系顶部的地层构成1个三级沉积层序（SQ19）,阳新统包含4个三级层序（SQ20－SQ23）,乐平统包括2个三级层序（SQ24,SQ25）。该地区的另一个特别是在二叠纪与三叠纪之交发生了较为典型的台地淹没事件,形成一个较为典型的淹没不整合面。因此,层序界面类型可以根据其所代表的地质涵义而划分为四大类型：构造不整合面、沉积不整合面,淹没不整合面以及它们的相关面。

Study on Sequence Stratigraphic Framework and Relative Sea-level Changes of the Permian in Guizhou and Guangxi Areas, South China

The Permian system in Guizhou and Guangxi provinces of south China is characterized by obviously different depositional facies, such as the coal measures in connective platform and the sponge reefs in its margin as well as in isolated platforms, which formed a specially sedimentary setting of "platform-basin-hill-trough". The period with the most apparent differences in depositional facies is correspond to the developing period of sponge reefs. The Permian system in researching areas could be divided into three series, which are named as Chuanshanian series. Yangsingian series and Lepingian series respectively. Two obvious unconformities can be recognized in the Permian of these areas, one is related to the main episode of Qiangui epeirogeny in the transitional period between the Chuanshanian epoch and the Yangsingian epoch, another was formed during the main episode of the Dongwu revolution in the transitional period between Yangsingian epoch and Lepingian epoch. These unconformities delegate not only the typical sequence boundaries but also the changing surfaces of sedimentary-basin natures. Several third-order sequences, which are described as SQ19 to SQ25 in this paper could be discerned in Permian system. The Chuanshanian series and the top part of the Carboniferous constitute one third-order sequence(SQ19). In settings of isolated platform and inter-platform ditch is composed by a set of limestones belonging to the middle to upper part of the Maping Fm. . However, in the background of the connective platform, Maping limestones makes up its transgressive system tract and the coal-measures of the Liangshan Fm. forms its high-stand system tract. The strata of Yangsinian epoch could be divided into four third-order sequences(SQ20-SQ23), whose general charaters could be summarized as follow: transgressive system tract and the early high-stand system tract consist chiefly of limestones of open-platform facies; more dololimestones and limedolostones of restricted-platform facies are developed in late high-stand system tract; in the margin of the connective and the windward parts of isolated platform, SQ23 is marked by a set of sponge-reef limestones. Two third-order sequences (SQ24 and SQ25) could be discerned in the Lepingian series. The SQ24 is composed by a set of coal-measures called the Longtan Fm. in the setting of the connective platform and is also constituted by a special set of coal-measures thatshan Fm. in the isolated platform but is represented by grainstones of beach fades in the margin of the connective platform. The SQ25 consist of a set of sponge-reef limestones in the margin of the connective platform and the windward part of isolate platform, which is a set of limestones of open-platform facies called the Changxing Fm. in the connective platform. In the background of inter-platform ditch, both SQ24 and SQ25 are constituted by a set of deep-water sediments called the Linghao Fm. . The particular drowning event of carbonate platform occurred in transitional period between the Permian and Triassic, lead to the generation of a drowning nonconformities. In term of their geological meanings, sequence boundaries could be grouped into four types, which are tectonic nonconformity, sedimentary nonconformity, drowning nonconformity and their relative surfaces.