Full
LIANG Xinping,born in 1987,is an assistant professor researcher at Peking University. She is engaged in research on shale oil and gas geology. E-mail: Xinping.liang@pku.edu.cn.
Outline
The formation of organic matter reflects the integrated physical,chemical,and biological responses to key global and regional geological events occurring across the lithosphere,hydrosphere,atmosphere,and biosphere. Organic-rich shales of Paleogene-Eocene age in terrestrial lake basins of eastern China are characterized by extensive lateral distribution,high total organic carbon(TOC)content,and considerable stratigraphic thickness—making them ideal archives for investigating the controls on organic-rich shale deposition under multi-sphere interactions. This study focuses on the Middle Eocene Shahejie Formation in the Jiyang Depression(Bohai Bay Basin)and integrates geochemical proxies—including TOC and total sulfur(TS)concentrations,organic carbon isotopic composition( ),iron speciation,and pyrite sulfur isotopes( )—with regional stratigraphic data from eastern China basins. Our findings indicate that TOC values in the Shahejie Formation range from 1 wt% to 10 wt%,with most samples exhibiting a TOC/TS ratio>2,a highly reactive iron to total iron ratio>0.38,and a pyrite iron(FePy)to FeHR ratio<0.6. These geochemical signatures suggest that organic shale accumulation was primarily driven by elevated primary productivity under warm-humid paleoclimatic conditions,further modulated by co-occurring tectono-volcanic processes—including volcanic input,hydrothermal fluid influx,and episodic marine incursions. Comparative analysis across eastern China basins reveals that widespread Middle Eocene organic carbon burial was ultimately governed by deep-Earth-driven geological events that facilitated cross-sphere exchange of mass and energy. Although volcanic,hydrothermal,and marine inputs may have introduced additional sulfate,bacterial sulfate reduction efficiently depleted the sulfate reservoir,establishing ferruginous(anoxic,non-sulfidic)bottom-water conditions conducive to the preservation of organic matter.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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