SEDIMENTARY CHARACTERISTICS AND EVOLUTION OF THE UPPER PALEOZOIC COAL-BEARING STRATA IN THE XISHAN COALFIELD, EASTERN ORDOS BASIN, CHINA

The Upper Paleozoic strata in the eastern North China is an important stratigraphic system of deep oil and gas exploration. For a long time, this field has not received much attention, and there are few studies on the sedimentary characteristics of the Upper Paleozoic coal-bearing strata in this area. In this paper, through the observation and measurement of the Upper Paleozoic profiles in the southwestern part of the Xishan coalfield, eastern Ordos Basin, combined with the previous research results, the sedimentary facies types and sedimentary evolution of the Upper Paleozoic in this area were systematically analyzed. The results show that the Upper Paleozoic strata in this area mainly developed sedimentary systems such as the barrier coastal facies, carbonate platform facies, delta facies, meandering facies and paroxysmal fluvial facies. The Benxi Formation and the Taiyuan Formation mainly developed the barrier coastal facies and carbonate platform facies deposits. The Shanxi Formation developed delta facies deposits, the Lower Shihezi Formation and Upper Shihezi Formation developed meandering river facies deposits, and the Shiqianfeng Formation developed paroxysmal fluvial facies deposits. The sedimentary evolution of the Upper Paleozoic strata mainly undergoes the process of transformation from marine sediments to marine-continental transitional sediments, which eventually transforms into continental sediments.