中扬子地区早三叠世大冶期岩相古地理研究

中扬子地区下三叠统大冶组主要由碳酸盐岩和碎屑岩组成。用单因素分析综合作图法,做出了岩相古地理图１幅。在早三叠世大冶期,整个中扬子海域具“六分”特征、即自北而南依次为北部碳酸盐盆地、北部碳酸盐斜坡、浅水碳酸盐台地、南部碳酸盐斜坡、南部碳酸盐盆地、东南部碎屑滨海。在该时期内,从早到晚,沉积水体不断变浅,至末期,海域普遍抬升而变为碳酸盐台地。

Study on Lithofacies Paleogeography of Daye Formation of Lower Triassic in the Middle Yangtze Region

The study area deals with five provinces,i.e.,ichuan, Guizhou, Hubei,Hunan and Jiangxi.It is mainly in the middle Yangtze region and also include a part of the upper Yangtze region. Daye Formation of lower Triassic is widely distributed in the area and especially well outcropped in the east of Sichuan and west and east of Hubei. The biggest thickness of Daye Formation is 843.8 m and there exist various sedimentary rocks and a well potential of oil and gas. There are two kinds of different rocks in the Daye Formation,i.e.,carbonate rocks and clastic rocks. Carbonate rocks including limestone and dolomites are most widely distributed in the area. This paper has adopts “the single factor analysis and comprehensive mapping method”and the following single factors are selected:thickness, shallow-water grains content, the sedimentary thickness ratio of deep-water to shallow-water, gravity flow sediment content, the basin sedimentary content and terigenous materials content.At the same time, six fundamental single factors are drawn. On the basis of the six fundamental single factor maps,combined with other quantitative and qualitaive information and other regional geological information one piece of lithofacies paleogeographic map of Daye Age of Early Triassic in middle Yangtze region has been drawn. According to the map of the lithofacies paleogeography of Daye Age of Early Triassic,the whole area of the middle Yangtze Sea has six paleogeologic units.From northern area to southern area,there are the north deep-water basin,the northslope,the shallow-water platform,the south slope.the south deep-water basin and south－east clastic beach.From the early period to the late,sedimentary water became shallow,in the last period,the whole sea area uplifted and became carbonate platform.