贵州南部志留纪沉积盆地分析

Analysis of Silurian Sedimentary Basin in the South of Guizhou

贵州南部志留纪沉积盆地是一个地台型克拉通盆地。它由石牛栏期的海侵序列及韩家店期的海退序列所组成,第一阶段的海侵序列乃与太康运动使地壳抬升后的地壳下沉所致,第二阶段的海退序列与加里东运动形成的地壳上升有关。

The Silurian sedimentary basin in the south of Guizhou is one that is encircled by paleoconti-nents. with Jiangnan paleocontinent in the east of the basin,Niushoushan paleocontinent in the west, Northern Guangxi paleocontinent in the south and Central Guizhou paleocontinent in the north, and with only one strait (a tidal inlet) formed between Jiangnan paleocontinent in the north - east of the basin and Huangpin - Shibin adjacent to Central Guizhou Paleocontinent and connected with the sea areas of Northern Guizhou I . The Tectonic Setting of Basin Formation The Silurian sedimentary basin is a cratonic one with a stable Platform. As the Late Mid -Or-dovician tectonic movement caused the crust to rise, the Yangtze plate was subduced by the South China plate, making the whole region of Southern Guizhou rise and become a paleocontinent. Up to the Shiliurian Age of Silurian Period, the crust sank and accepted transgression, causing Southern Guizhou to be developed into a cratonic basin surrounded by paleocontinents. Because of the Caledonian movement, the Yangtze Plate was again subduced by the South China plate. In the Late Mid - Silurian period the history of this cratonic sedimentary basin came to an end. So the depositional time of the basin was approximately from the Shiliunanian Age to the Hanjiadianian Age of Silurian period. II . The Sedimentary Association and Lithofacies Association in Each Depositional Period I. The sedimentary Association in the Shiliunanian Age In the Shiliunanian Age of Silurian,sea water entered the south of Guizhou through a tidal inlet in Shibin and Huangpin. As the early transgression happened in this period, sea water was very shallow and the lithofacies association. In every area of this basin, the sedimentary sequence was characterized by such a transgression sequence as an inversed grain sequence from basal conglomerate, uptidal flat mudstone, silt - mudstone to mud - siltstone between tidal flat and silt - stone. 2. The Sedimentary Association and Lithofacies Association in the Hanjiadianian Age(下转323页) The early Hanjiadianian Age was the high period of transgression in the south of Guizhou. In this period, the dividing of depositional facies zones was distinct,from quartz sandstone of the rising tidal delta between Huangpin,Shib-in and Kaili to pellet micrite, quartz micrite of the tidal flat lagoon facies in Duyun - Guiding and then to mudlime-stone and micrite of the bay facies in Guiyang. The Late Hanjiadian Age was a regression period, so the sea water became shallow again, and from the tidal inlet (Shibin - Huangpin) to the bay tidal flat (Guiyang) the rock association was characterized by mud - siltstone, silt - mudstone and little siltstone, with every place typical of a regression sedimentary sequence from mid - tidal flat to up - tidal flat facies. III. The Conclusion The sedimentary of Silurian cratonic sedimentary basin in the south of Guizhou consists of the transgression sequence of the Shiliunanian Age and regression sequence of the Hanjiadianian Age, the former caused by the crust subsiding as the tectonic movement caused the crust to rise and the latter related to the rising of the crust because of the Caledonian movement form.