Hu Haoran1,2, Liu Chenglin1,2, Cao Zhe3, Wang Xin3, Zhang Jingyao1,2, Zhou Siyuan1,2, Qiao Tong1,2, Guo Heyi1,2, Zhang Yujia1,2
(1State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum（Beijing）, Beijing 102249,China; 2College of Geosciences, China University of Petroleum（Beijing）, Beijing 102249,China; 3Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 102206, China)
Abstract: The Early Silurian Rhuddanian black shales are globally significant source rocks, yet the differential mechanisms of organic matter (OM) enrichment across varying tectonic settings remain poorly constrained. This study elucidated the coupled controls of tectonics, paleoclimate, and oceanography on OM accumulation by comparing the Longmaxi Formation (Sichuan Basin, South China) and the Tanezzuft Formation (Ghadames Basin, North Africa).Through a systematic analysis integrating lithofacies paleogeography, sequence stratigraphy, and geochemical proxies, the following conclusions are drawn: (1) The global paleogeography was characterized by the juxtaposition of Gondwana in the south and dispersed cratons (such as South China and Laurentia) in the equatorial to northern hemisphere. This specific setting—combined with a rapid sea-level rise and the development of widespread anoxic/euxinic conditions in restricted basins—led to the deposition of organic-rich shales with distinct geochemical signatures (e.g., high TOC) along the margins of Gondwana and in the South China Block; (2) In the Sichuan Basin, located at low paleo-latitudes, OM enrichment was driven by the coupling of high paleo-productivity (fueled by equatorial upwelling) and persistent anoxic/euxinic conditions within a tectonically stable, restricted deep shelf. Here, the synergistic effect of high productivity and high preservation efficiency was the dominant factor; (3) Conversely, in the Ghadames Basin on the Gondwana margin, OM enrichment was driven by high paleo-productivity fueled by nutrient input from intensified continental weathering and upwelling currents during post-glacial transgression; (4) Consequently, a "Tectonic-Sedimentary-Productivity" coupling model is proposed. The spatial distribution of deep shale gas "sweet spots" is determined by the interplay between tectonic subsidence (accommodation space) and paleoceanographic conditions (preservation vs. productivity). This comparative study provides a predictive framework for exploration in similar paleogeographic settings.
Keywords: Early Silurian; Rhuddanian; Organic Matter Enrichment; Deep Shale Gas
Author Profile (first or corresponding author):
Hu Haoran, Male, Ph.D. Student, mainly engaged in petroleum exploration and development geology. E-mail: 1426567747@qq.com
Liu Chenglin, Male, Professor, Ph.D. Supervisor, Ph.D, mainly engaged in petroleum exploration and development geology. E-mail: liucl@cup.edu.cn
Funding: This work was supported by the National Science and Technology Major Project of China (Grant No. 2025ZD1403901), the National Key R&D Program of China (Grant No. 2021YFA071900), the National Natural Science Foundation of China (Grant No. 41872127), the National Natural Science Foundation of China (Grant No. 42272191) and the Chongqing Natural Science Foundation (Grant No. CSTB2024NSCQ-LZX0108).
