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Geoscience ›› 2023, Vol. 37 ›› Issue (05): 1264-1281.DOI: 10.19657/j.geoscience.1000-8527.2023.037

• Sedimentology • Previous Articles     Next Articles

Reconstruction of Provenance and Paleo-sedimentary Environment of the Chang 8 Oil Layer in the Southwestern Margin of the Ordos Basin: Evidence from Petrogeochemistry

CHEN Xi1,2(), XIAO Ling1,2(), WANG Mingyu3, HAO Chenxi4, WANG Feng5, TANG Hongnan6   

  1. 1. School of Earth Science and Engineering, Xi’an Shiyou University, Xi’an, Shaanxi 710065, China
    2. Shaanxi Provincial Key Laboratory of Oil and Gas Accumulation Geology,Xi’an, Shaanxi 710065, China
    3. No.10 Oil Production Plant, PetroChina Changqing Oilfield Company, Qingcheng, Gansu 745100, China
    4. No.2 Oil Production Plant, PetroChina Changqing Oilfield Company, Qingyang, Gansu 745100, China
    5. Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu, Sichuan 610059, China
    6. No.1 Oil Production Plant, PetroChina Changqing Oilfield Company, Yan’an, Shaanxi 716000, China
  • Received:2022-07-25 Revised:2023-04-10 Online:2023-10-10 Published:2023-11-14

Abstract:

Geochemical characteristics of sedimentary rocks recorded important sedimentary and source region tectonic information, which can be an effective means to understand the provenance and paleo-sedimentary environment.Based on geochemical analysis of 14 mudstone and silty mudstone samples in combination with core logging data, the provenance and paleoenvironment of the Chang 8 oil layer of the Yanchang Formation in the southwestern margin of Ordos Basin have been systematically studied.The main conclusions are as follows: The source region was an active continental margin, and the local source of the Chang 8 oil layer is mainly from the metamorphic and igneous rocks of the Qin-Qi orogenic belt in the southwestern margin of the Basin.Combined with different element abundance and ratios and sedimentary marker, our results show that the paleoclimate was dominated by semi-humid-semi-arid, hot arid climatic conditions, and the paleotemperature was generally higher than 15 ℃ and the average temperature of the Yanchang period.Water depth during the Chang 8 deposition was shallow, the paleosalinity was dominated by freshwater environment.The paleo-redox environment was oxidizing under shallow water.The paleoenvironment conditions and sufficient material source provided favorable conditions for the development of the shallow water deltaic sedimentary system.

Key words: Ordos Basin, elemental geochemistry, paleo-sedimentary environment, provenance, Chang 8 oil layer

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