UPPER SILURIAN SUCCESSION AT THE SANHECHANG SECTION,YINJIANG,GUIZHOU PROVINCE AND ITS IMPLICATIONS TO THE SPATIAL DISTRIBUTION OF THE XIAOXI FORMATION AND THE LITHOLOGY OF THE THIRD RED BEDS IN THE QIAN-YU-XIANG BORDER REGION
The Silurian marine clastic red beds in the Yangtze region are an important component and characteristic of the Silurian system in South China,whose three sets of red beds are conspicuous and serve as important correlation markers in the field.Among them,the third set(upper Ludlow to lower Pridoli)has been reported only from the sedimentary regions around but inside the Yangtze Platform.Although the third red bed is reported occasionally from the interior of the Yangtze Platform,its lithologic features and spatiotemporal distributions remains poorly understood.The Sanhechang section in the Yinjiang County,Guizhou Province,SW China provides a window to explore the spatiotemporal distribution of the Xiaoxi Formation and the lithologic characteristics of the third red bed in the northeastern Guizhou-eastern Chongqing-western Hunan border region.The Xiaoxi Formation in the Sanhechang section is comprised of sandstones,argillaceous siltstones,and a few mudstones,with eight thin red layers.The occurrence of large trace fossils,cuticle-like phytodebris,and the remains of nematophyte fossils in the formation suggests the late Ludlow to early Pridoli in age.The Xiaoxi Formation is correlative to the Chejiaba Formation in the Guangyuan area of Sichuan Province,the Guandi Formation in the Qujing area of Yunnan Province,and the Xiaoxi Formation in the Yinjiang area of Guizhou Province.Compared with the first and second red beds in the Yangtze region,and the third red bed in the surrounding areas of the Yangtze Platform,the third red bed in the border region we studied here is limited in spatiotemporal distribution and is thin in thickness.The remarkable differences of this third red bed from others are likely due to the insufficient supply of terrigenous debris,and unique redox condition related to water depth where the red beds formed.
Late SilurianXiaoxi Formationspatiotemporal distributionthe third red bedGuizhou
万方数据
维普
