Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (4): 82-97.DOI: 10.13745/j.esf.sf.2020.4.21

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Paleo-wind direction and paleogeographic significance of Late Jurassic to Early Cretaceous anemoarenyte in the southeastern Wanggaxiu coal mine, Qaidam Basin

CHEN Zhengyu1(), LIU Yongqing2, JIANG Xiaojun1,*(), KONG Zhigang1, GAO Wanli3, QIAN Tao3, KUANG Hongwei2, XU Huan4   

  1. 1. Department of Earth Sciences, Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650093, China
    2. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
    3. Institute of Geological Mechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
    4. School of Earth Sciences, East China University of Technology, Nanchang 330013, China
  • Received:2019-10-13 Revised:2020-03-20 Online:2020-07-25 Published:2020-07-25
  • Contact: JIANG Xiaojun

Abstract:

The Qaidam Basin is one of the main petroleum basins in western China. Much progress has been made over the past 70 years in the oil and gas exploration and basic geological research in the basin. However, the restoration and structural evolution of the Mesozoic prototype basin in Qaidam are still in dispute, which has affected the petroleum exploration process. In the current project, we conducted a comprehensive geological survey on the sedimentology, petrology and sedimentary facies analysis of Mesozoic strata around the present Qaidam Basin. We first discovered a set of anemoarenyte depositions of coastal and shallow lacustrine facies in the original Cretaceous Quanyagou Formation, located 10 km southeast of the Wanggaxiu coal mine near the Delingha-Dulan Road. Our study on a 1∶100 sedimentary-structural and rock characteristics determination section showed that large tabular cross-beddings, grain and fall flow anemoarenyte structures, and a large number of traces, burrows, mud cracks and liquefied bending bedding structures of coastal and shallow lacustrine facies below the water table developed on the profile. In addition, we collected many paleowind sedimentary structural data, such as tabular cross-bedding and oblique bedding. We also conducted a systematic laboratory study using paleowind direction data correction and rose diagram. The results show that the Quanyagou Formation paleowind is NW directed, consistent with the regional research data from the Late Jurassic to Early Cretaceous in northern China. The vertical successions of the Quanyagou Formation, changing from alternation of aeolian and water laid to aeolian dominated to water laid dominated deposits, indicate climatic oscillation from relatively arid to humid conditions. Previous studies have suggested that aeolian deposition is an important hydrocarbon reservoir. Therefore, the newly discovered set of coastal and shallow lacustrine facies anemoarenyte depositions is of great significance for oil and gas exploration in the Mesozoic Qaidam Basin, and can also help advancing research on the restoration and tectonic evolution of the basin.

Key words: the Qaidam Basin, Late Jurassic to Early Cretaceous, anemoarenyte, paleowind direction

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