KMS Nanjing Institute of Geology and Palaeonotology,CAS
Depositional environment of Middle Triassic organic-rich shales in the Ordos Basin, Northwest China | |
Zhao, Xiangdong (赵向东)1,2,3; Wang, Wei (王伟)1,2![]() | |
2021-07-21 | |
Source Publication | GEOLOGICAL JOURNAL
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ISSN | 0072-1050 |
Pages | 12 |
Abstract | The Middle Triassic Tongchuan Formation in the Ordos Basin of northwestern China is a typical lacustrine deposit. A major component of this formation is thick layers of organic-rich shales that are probably a potential hydrocarbon source and preserve the earliest known Mesozoic-type lacustrine ecosystem. The exact depositional environment of the shales in the Tongchuan Formation, however, remains unknown. To address this question, we carried out high-resolution carbon (delta C-13(org)) and sulphur (delta S-34(py)) isotope analysis as well as undertook total organic carbon (TOC)/pyrite contents and pyrite morphology investigation, and framboidal pyrite size measurements in shales of the Bawangzhuang section of the southern Ordos Basin. Remarkably high TOC (23 +/- 9%) and pyrite (7 +/- 3%) contents were obtained from the shales, which indicate a large amount of organic carbon and pyrite burial during shale deposition. Framboids are the dominant pyrite morphology in the pyrite crystals and show large and variable mean diameters (7.0 +/- 1.7 mu m to 14.3 +/- 6.8 mu m) across the section, indicating oxic-dysoxic bottom water during shale deposition. delta C-13(org) and delta S-34(py) revealed narrow and less variable values, ranging from -31.8 parts per thousand to -28.1 parts per thousand, and -4.1 parts per thousand to 4.9 parts per thousand, respectively. The delta C-13(org) values suggest balanced and consistent carbon cycles. Integrated with pyrite content and morphological patterns, consistent delta S-34(py) values probably demonstrate a relatively open environment for the formation of sedimentary pyrite, and thus a shallow chemocline that was quite close to the water-to-sediment interface during shale deposition. Overall, the organic-rich shales of the Tongchuan Formation were probably deposited under oxic-dysoxic bottom-water conditions. Shallow chemocline depth combined with moderately high sedimentation rate and high primary productivity may have played crucial roles in the deposition and formation of the organic-rich shales in the Tongchuan Formation. The shallow chemocline also facilitates the fossil preservation in a lacustrine environment. |
Keyword | Middle Triassic Ordos Basin organic-rich shales primary productivity redox condition |
DOI | 10.1002/gj.4215 |
Indexed By | SCI |
Language | 英语 |
WOS Keyword | SILURIAN HOT SHALES ; YANCHANG FORMATION ; VOLCANIC ASH ; GEOCHEMICAL CHARACTERISTICS ; ISOTOPE CHEMOSTRATIGRAPHY ; SEDIMENTATION-RATE ; SULFUR ISOTOPES ; BLACK-SEA ; CARBON ; PYRITE |
Funding Project | Strategic Priority Research Program of the Chinese Academy of Sciences[XDB26000000] ; Strategic Priority Research Program of the Chinese Academy of Sciences[XDA19050101] ; National Natural Science Foundation of China[42072036] ; National Natural Science Foundation of China[41688103] ; CAS President's International Fellowship Initiative (PIFI) ; Fundamental Research Fund from the China National Petroleum Company[2018D-500805] ; Leverhulme Emeritus Fellowship |
WOS Research Area | Geology |
WOS Subject | Geosciences, Multidisciplinary |
WOS ID | WOS:000675115100001 |
Funding Organization | Strategic Priority Research Program of the Chinese Academy of Sciences ; National Natural Science Foundation of China ; CAS President's International Fellowship Initiative (PIFI) ; Fundamental Research Fund from the China National Petroleum Company ; Leverhulme Emeritus Fellowship |
Publisher | WILEY |
Document Type | 期刊论文 |
Identifier | http://ir.nigpas.ac.cn/handle/332004/38433 |
Collection | 中国科学院南京地质古生物研究所 |
Corresponding Author | Wang, Wei (王伟) |
Affiliation | 1.Chinese Acad Sci, Nanjing Inst Geol & Palaeontol, State Key Lab Palaeobiol & Stratig, Nanjing 210008, Peoples R China 2.Chinese Acad Sci, Ctr Excellence Life & Paleoenvironm, Nanjing 210008, Peoples R China 3.Univ Chinese Acad Sci, Beijing, Peoples R China 4.Northwest Univ, Dept Geol, Xian, Peoples R China 5.PetroChina Co Ltd, Changqing Oilfield Branch, Inst Explorat Dev & Res, Xian, Peoples R China 6.PetroChina, Res Inst Petr Explorat & Dev, Beijing, Peoples R China 7.Nat Hist Museum, Dept Earth Sci, London, England 8.Univ Hong Kong, Dept Earth Sci, Hong Kong, Peoples R China |
First Author Affilication | Nanjing Institute of Geology and Palaeonotology,CAS |
Corresponding Author Affilication | Nanjing Institute of Geology and Palaeonotology,CAS |
Recommended Citation GB/T 7714 | Zhao, Xiangdong ,Wang, Wei ,Xie, Guwei,et al. Depositional environment of Middle Triassic organic-rich shales in the Ordos Basin, Northwest China[J]. GEOLOGICAL JOURNAL,2021:12. |
APA | Zhao, Xiangdong ,Wang, Wei ,Xie, Guwei,Pan, Songqi,Jarzembowski, Edmund A.,&Zheng, Daran .(2021).Depositional environment of Middle Triassic organic-rich shales in the Ordos Basin, Northwest China.GEOLOGICAL JOURNAL,12. |
MLA | Zhao, Xiangdong ,et al."Depositional environment of Middle Triassic organic-rich shales in the Ordos Basin, Northwest China".GEOLOGICAL JOURNAL (2021):12. |
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