滇黔桂地区晚震旦世陡山沱期构造-层序岩相古地理

Sedimentary facies and palaeogeography of the tectonics and sequences in the Yunnan-Guizhou-Guangxi region, southwestern China during the Doushantuoan(Late Sinian)

层序地层是在一个等时地质年代格架内从三维空间上认识一个有成因联系的沉积组合体 ,层序内部沉积地质体的性质、叠置关系和沉积相演变与海平面升降周期变化有对应关系。对滇黔桂地区晚震旦世陡山沱期层序地层研究 ,笔者在上扬子浅海区对晋宁王家湾上震旦统剖面进行实测 ,拟建立浅海区基干层序剖面 ,并把陡山沱组划分为一个 2级层序和四个 3级层序 ;在深海区对广西灵川西岭剖面进行实测 ,拟建立深海地区的基干层序剖面。然后在研究区进行辅助对比剖面的观测 ,以编制该区二级层序海侵体系域和高水位体系域的构造 层序岩相古地理图。通过这些研究 ,使人们从另一个角度去揭示和认识该区在陡山沱期的构造运动、沉积物组合特征与海平面变化的关系 ,从而更进一步弄清该区的时空演化特征。

Sequence stratigraphy is the study of rock relationships within a chronostratigraphic framework of repetitive, genetically related strata bounded by surfaces of erosion or nondeposition, or their correlative conformities. The fundamental unit of sequence stratigraphy provides a chronostratigraphic framework for correlating and mapping sedimentary rocks, and is defined and identified by the physical relationships of strata, including the lateral continuity and geometry of the surfaces bounding the units, vertical and lateral stacking patterns, and the lateral geometry of the strata within these units. The emphasis of the present study on sequence stratigraphy of the Yunnan Guizhou Guangxi region during the Doushantuoan will be on: (1) the measured Upper Sinian Wangjiawan section in Jinning, Yunnan, that made it possible to reconstruct the parent sequence section in the shallow marine areas of the Upper Yangtze area, and (2) the measured Xiling section in Lingchuan, Guangxi, that permitted the parent sequence section in the deep sea areas of the Upper Yangtze area to be reconstructed. The field observations of the auxiliary sections have also been made for the working area in order to compile the sedimentary facies and palaeogeographic maps of the tectonics and sequences in the second order sequences of the transgressive and highstand systems tracts. This approach allows us to reveal the relationship among tectonism, sediment complexes and sea level changes, and to develop the framework of the spatio temporal evolution of this region during the Doushantuoan.