Full
PENG Zhongqin,born in 1981,Ph.D.,professorate senior engineer,is engaged in research on shale gas geological investigation,evaluation and research. E-mail: 17360988@qq.com.
Outline
During the Early Cambrian,organic-rich shales of the Liuchapo Formation and Niutitang Formation developed in northwestern Hunan,exhibiting good shale gas exploration potential. To address the issues of insufficient precision in Early Cambrian stratigraphic correlation and unclear mechanisms of carbon isotope evolution,this study systematically collected 133 carbonate rock samples from the drilling core of the Well Xiangzhangdi-1 (with a well depth of 2018.25 m and a core recovery rate of 98%). Analyses were conducted on the evolution trends of carbon and oxygen isotopes( C, O),as well as studies on shift events and stratigraphic correlation. Five negative C anomalies(with amplitudes up to 12.1‰)and three positive anomaly events(with amplitudes approaching 9‰)were identified in the Early Cambrian slope facies area of northwestern Hunan,revealing their synchrony with global carbon cycle events such as BACE and ZHUCE. The results show that the Ediacaran-Cambrian boundary(BACE event)corresponds to the peak of negative C shift(-9.8‰),consistent with records from Siberia,Morocco,and the South China platform facies. Positive shift events(ZHUCE,CARE)are coupled with intervals of high organic matter abundance(with TOC peak values reaching 10.5%),indicating that enhanced carbon burial driven by biological prosperity is the main controlling factor for positive C shifts. This study establishes a carbon isotope stratigraphic framework for Early Cambrian boreholes in the South China slope facies,providing a chemostratigraphic basis for regional shale gas sweet spot prediction.
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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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