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Paleoenvironment Reconstruction and its Relationship with Halite-Potash Deposition in Ordovician Majiagou Formation, Shanbei Depression, Ordos Basin
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 81st EAGE Conference and Exhibition 2019, Jun 2019, Volume 2019, p.1 - 5
Abstract
Zhenjia1 Well is selected as the research target in this study, which locates in Shanbei depression, Ordos basin. The continuous cores from Ordovician Majiagou Formation were systematic sampled and through the analyses on stable isotopes, normal and trace elements, we attempt to reconstruct the paleoenvironment and discuss its relationship with halite-potash deposition. The following achievements can be obtained: (1) Paleotemperature during the depositional period of Majiagou Formation yields a value from 17.3°C to 30.7°C while Ma5-6(the sixth submember in the fifth member of Majiagou Formation) possesses the highest value, which indicates a warm-torrid climate. (2) The paleosalinity rises from the bottom of Majiagou Formation and peaks until the early period of Ma5-6, which indicates that this interval maintains a high degree of evaporation. (3) Five geochemical proxies of normal and trace elements are mutually corroborated and indicate the characteristics of shallow sea level, fierce oxidation and drought during Ma5-6. (4) Through the comparison of δ13C curves, we modify the depositional model in Ordos basin and the supplement of brine mainly derives from the east. Lithological characteristics, paleotemperature, paleosalinity and the orientation of brine supplement in Majiagou Formation indicate that the paleoenvironment in Ma5-6 is the most favorable for halite-potash deposition.