A Study On Sedimentary Characteristics Of Yecheng Depression,Southwest Tarim Basin

In order to reveal the Palaeogene stratigraphic distribution and sedimentary facies of Yecheng depression, Southwestern of Tarim Basin. According to the outcrops, achieved mass of data about rock-assemblage characteristics and distribution, Combined with log information and the analysis of sample testing, the results show that the Palaeogene of Yecheng depression can be divided into five formations from bottom to top:Altashi, Qimugen, Kalataer and Wulagen formation. Altashi formation deposited a thick gypsum rock sandwiched dolomites, and the development stable dolomitic limestone on the top for its features. Green, The lithology of Qimugen formation is gray green, red, purple red mudstone clamp gypsum layer. General characteristic is weathering appearance of "red on green under". Marine carbonate is the main rocks of Kalataer formation, which had gray skeletal hidden limestone and oyster reef limestone, and contains rich oyster fossils. gray green mudstone and calcareous sandstone with thin layer limestone are the main rocks of Wulagen formation, It contains mass of main fossils. Strata of Palaeogene got thinner from west to east. Two large scale transgression-regression cycles can be distinguished in Palaeogene, and each formation or section developed typical and relatively single sedimen-tary facies. From bottom to top developed bay-gypsum delta, tidal-flat facies, evaporative mudstone-limestone, carbonate platform and tidal mudtone fla. Favorable reservoir of Kalataer formation is carbonate rocks that distribute Keliyang-Yuliqun and Heshilafu area.