Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (4): 371-384.DOI: 10.13745/j.esf.sf.2021.12.6

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Rehabilitation status of denuded land in the eastern Qaidam Basin: Geophysical and thermochronological evidences

WANG Jiaqi1,2(), LI Zongxing1,2,*(), LIU Kui3   

  1. 1. Key Laboratory of Petroleum Geomechanics, China Geological Survey, Beijing 100081, China
    2. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
    3. Chinese Academy of Geological Sciences, Beijing 100037, China
  • Received:2021-01-15 Revised:2021-12-23 Online:2022-07-25 Published:2022-07-28
  • Contact: LI Zongxing

Abstract:

On the basis of geological field survey of the eastern Qaidam Basin, the contact relationships and development characteristics of unconformities in the basin were analyzed. Combined with geophysical and apatite fission track data and through seismic stratigraphic analysis, the rehabilitation status of denuded land in the eastern Qaidam Basin were evaluated. The results showed that during the period of Late Yanshanian movement, erosion thickness in the eastern Qaidam Basin ranged between 500-2300 m. In the basin’s southern and northern margins erosion thickness ranged between 1100-2000 and 1200-2300 m, respectively, and reduced gradually to 500-1000 m at the basin center. The overall denudation decreased gradually from the edge to the center of the basin, with its western section significantly more denuded than the eastern counterpart. The Yanshanian movement in the eastern Qaidam basin occurred between 87-62 Ma. During this period, the basin as a whole experienced weakly SE-NW compression. which caused the differential uplifting in the eastern part of the Qaidam basin to form the Olongbulukon belt prototype, further controlling oil and gas accumulation in the region. On the one hand, differential uplifting caused severe formation denudation in some areas, leading to loss of oil and gas; on the other hand, structural compression caused further burial of main source rocks in the affected area, where Jurassic source rocks further matured to generate hydrocarbons. The underlying Carboniferous source rock underwent secondary hydrocarbon generation; at the same time, a series of near-EW-trending traps were formed under compression, which favored oil and gas accumulation.

Key words: Yanshanian movement, unconformity, denudation restoration, apatite fission track, eastern Qaidam Basin

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