Oil & Gas Geology ›› 2017, Vol. 38 ›› Issue (4): 711-721.doi: 10.11743/ogg20170408

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Migration of the Cambrian and Middle-Lower Ordovician carbonate platform margin and its relation to relative sea level changes in southeastern Tarim Basin

He Feng1,2,3, Lin Changsong3, Liu Jingyan3, Zhang Zilong1,2, Zhang Junlong4, Yan Bo4, Qu Tailai5   

  1. 1. Beijing Research Institute of Uranium Geology, Beijing 100029, China;
    2. CNNC Key Laboratory of Uranium Resource Exploration and Evaluation Technology, Beijing 100029, China;
    3. China University of Geosciences(Beijing), Beijing 100083, China;
    4. Research Institute of Exploration and Development, PetroChina Daqing Oilfield Company, Daqing, Heilongjiang 163712, China;
    5. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
  • Received:2016-03-07 Revised:2017-06-21 Online:2017-08-28 Published:2017-09-09
  • Contact: 林畅松(1958-),男,教授、博士生导师,沉积盆地分析。E-mail:lincs@cugb.edu.cn。 E-mail:lincs@cugb.edu.cn

Abstract: A comprehensive analysis on cores,thin sections and logging data is combined with seismic facies,seismic attri-butes and palaeo geomorphology to identify platform margin and trace the distribution and migration of platform-margin facies belt in southeastern Tarim Basin during different deposition periods of the Cambrian and the Middle and Lower Ordovician.The rock types of platform-margin facies belt are mainly calcarenite,bioclastic limestone,oolitic limestone and micritic limestone.On seismic reflection profiles,platform margin beach facies present as chaotic or blank reflections,and the reef-beach complexes show mound reflection exteriorly and chaotic reflection or blank reflection interiorly.Both the buildup features with increasing stratum thickness caused by rapid growth of large reef-beach complexes,and the steep slope or distal steepening features caused by decreasing stratigraphic thickness in the basin,are indicators of platform margins.The method that uses natural gamma ray spectrometry logging data to identify carbonate lithology and sedimentary energy is combined with the data of organic carbon,carbon and oxygen isotopes,to map the relative sea level changes and their controlling effect upon platform margin migration in different sedimentary periods in southeastern Tarim Basin.Slope-basin facies with under-developed platform margin had dominated the Early Cambrian.With sea level continuously falling during the Middle to Late Cambrian,restricted platform facies started to take shape with edges migrating basin ward.In the Early Ordovician,the platform margin narrowed due to sea level rising during the Penglai Formation deposition and widened as the sea level falling again during the Lower Yingshan Formation deposition.The upper Yingshan Formation experienced rapid transgression which narrowed the platform edge and the lower Yingshanzu Formation went through falling sea level which turned the platform into open ones and widened the platform margin.However,the platform was again submerged as sea level rapidly rising after the deposition of the Yijianfang Formation.

Key words: reef-beach complex, platform margin, sea level, sedimentary evolution, carbonate rock, Cambrian, Ordovician, Tarim Basin

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