The Research Of Sequence Stratigraphy And Tempestites Of Llandovery Series Rongxi And Xiushan Formation In Northern Guizhou

This paper chose the research of sequence stratigraphy and tempestites of Silurian in northern Guizhou as the goal. The international and domestic research degree of Silurian chronostratigraphy and biostratigraphy was high and had a good foundation for us.The fourth series and its internal stages divisions of Silurian has already established boundary stratotype sections. The study of Silurian shale gas in the study area is an important topic at present. The research of sedimentology and sequence stratigraphy in the study area is relatively weaker, Thesis topic selection has obvious theoretical and practical significance.This paper selected Silurian Llandovery series in northern Guizhou as the research object, and focuses on the outcrop sequence stratigraphy and tempestite analysis of upper Llandovery series. Through field investigation and measurement, combined with previous research results, the paper has achieved the expected results, including the following aspects:1.This paper revised lithostratigraphic division scheme of northern Guizhou, divided the original Rongxi formation and Majiaochong formation into new Rongxi formation. The Rongxi and Xiushan formation referred to Hanjiadian group which located in Llandovery series telychian stage. Huixingshao formation was located in late telychian stage to early Wenlock series, which was mainly distributed in Xiushan, Yinjjiang, Shiqian area and was missing in other regions.2.Combined with chronostratigraphy, biostratigraphy, lithostratigraphy and characteristics of sedimentary cycles, this paper divided Silurian in the study area into six Orthosequence from Sq1 to Sq6 : Longmaxi formation(Sq1), the lower Shiniulan formation(Sq2), the upper Shiniulan formation(Sq3), Rongxi formation(Sq4), the lower Xiushan formation(Sq5), the upper Xiushan and Huixingshao formation(Sq6). This paper focuses on the research of Sq4 to Sq6 sequence(which was located in Rongxi and Xiushan formation). The detailed structural analysis of high frequency cycles in the upper part of the Zhengan Rongxi formation was carried out, which provides the basis for the establishment of the internal systems. The temporal and spatial variation of sequence development are analyzed, and influenced by the ancient geography, provenance, different uplift from west to east and from south to north, the sedimentary center was along Xiushan and Yinjiang, and the profile thickess gradually reduced to thinner from the east to the west, from the north to the south.3.There is no relevant report about the storm deposits of Llandovery series Rongxi formation in northern guizhou. This paper analyzed the characteristics of the tempestites in Rongxi formation of northern Guizhou, which was inferred that the sedimentary background was the warm coastal to shallow sea. In the relatively shallow water formed calcareous mudstone and thin bedded limestone, and under the action of storm debris and gravels formed. Deposited and preserved below the wave base and the upper shallow muddy background deposition area, which belongs to the allochthonous TEMPESTITES. The rich tempestite sedimentary of Silurian aeroninan stage Shiniulan formation in the north of Guizhou has been reported, combined with Rongxi formation tempestite information, which provide further instructions on the Yangtze platform in Early Silurian was located in low latitude belt of ancient geographical location.