Research On High-resolution Sequence Stratigraphy Of Upper Triassic Of Shiwandashan Basin In Guangxi

Taking upper Triassic of Shiwandashan Basin in Guangxi as an example andbased on geological survey and exploration, the sedimentary environment andevolution, high-resolution sequence stratigraphic division, and coal accumulation areanalyzed by detailed description and analysis of field section observation.According to features of the field observation of stratigraphic profile and drillingcores such as lithology and sedimentary structure, the upper Triassic can be dividedinto6class and24types of lithofacies. Paleontological features and geochemicalfeatures instructs the continental oxidizing environment.Two types of sedimentarysequence are summarized. Three types of sedimentary facies including fluvial facies,lake facies and alluvial fan facies are recognized by lithofacies in vertical and planecombination and distribution. Pingdong Formation is mainly shore and shallow lakefacies, and Fulongao Formation is mainly braided river facies.Upper Triassic can be divided into three system tract including lowstand systemtract, transgressive system tract and highstand system tract. Taking drilling coreprofile as example, according to identification marks of sequence interface, combinedwith structure and sedimentary background, drilling position and core developmentcharacteristics, the sequence interface of drilling core are recognized. The types ofshort term datum level include type A and type C, which can be furtherly divided intofive class. Type A is mainly distributed in channel and point bar deposits, and type Cin low-lying sedimentary area such as flood plain.