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Geoscience ›› 2022, Vol. 36 ›› Issue (01): 118-129.DOI: 10.19657/j.geoscience.1000-8527.2021.198

• Marine Geology • Previous Articles     Next Articles

Geochemical Constraints on the Sedimentary Environment of Wenchang Formation in Pearl River Mouth Basin and Its Paleoenvironmental Implications

GAO Yangdong1(), LIN Heming1, WANG Xudong1, QIU Xinwei1, QUE Xiaoming1, LI Min1, ZHAO Zeying2, CHEN Yan2()   

  1. 1. CNOOC China Limited, Shenzhen Branch, Shenzhen,Guangdong 518000, China
    2. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
  • Received:2021-02-15 Revised:2021-06-18 Online:2022-02-10 Published:2022-03-08
  • Contact: CHEN Yan

Abstract:

Terrestrial input is the main external nutrient source for the growth of oil parent matter (e.g.bacteria, algae, phytoplankton) in lacustrine environment. Paleoclimate conditions affect terrigenous input, and lacustrine sedimentary environment controls organic matter preservation. Understanding the paleo-lacustrine environment is critical to predict organic matter abundance in source rocks. Here, we present new geochemical data from source rocks of the Wenchang Formation in the Lufeng Sag of Pearl River Mouth Basin. Element geochemical indices, e.g.CIA, V/Cr, Mn/Al, Sr/Cu and Ti/Al, altogether reveal the climate,lake-level, paleo-oxygen and paleo-salinity conditions and show that the paleo-environment played an important role in controlling the source rocks. High level of chemical weathering corresponds to high organic matter in the lower part of E2w3 and E2w4. Lake-level and paleo-oxygen changes are responsible for the organic matter enrichment of E2w. Meanwhile, the paleo-salinity are less relevant. The organic-rich source rocks of the E2w4 and E2w3 (lower part) of the LF-A well in the Lufeng Sag were likely formed in a deep and reduced lake with strong chemical weathering, under the conditions of warm-humid climate, sufficient nutrient supply, and high productivity.

Key words: Pearl River Mouth Basin, Wenchang Formation, sediment geochemistry, paleo-environment, source rock

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