| Cenomanian-Coniacian Sea-level Change and Dissolved Oxygen Fluctuations in Tethys-Himalaya: Evidences from Benthic Foraminifera of Gamba, Tibet |
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| 作者姓名： | JIA Jianzhong WAN Xiaoqiao CHEN Puli LI Guobiao JIANG Tian and QU Haiying |
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| 作者单位： | 1 State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China;2 Petroleum Exploration and Exploitation Institute, Sinopec Northwest Oil Field Company, ürümqi 830011, Xinjiang, China |
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| 基金项目： | This research was financially supported by the project of National key basic research and development of China (“973” project) “Late Mesozoic Greenhouse Climatic – environmental evolution of East Tethys (No. 2012CB822000-G).” |
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| 摘 要： | Benthic foraminifera, preserved in the Late Cretaceous organic carbon-rich sediments of Gamba, southern Tibet, provide high-resolution proxies for sea-level changes and dissolved oxygen fluctuations of southeastern Tethys. The fossils were statistically analyzed and divided into three faunas of "Cenomanian fauna", "Turonian fauna", and "Coniacian fauna". A middle neritic-upper bathal environment (50-250m) was estimated considering the ratios of planktonic and epifaunal benthic foraminifera (P/(P+E)), the morphological analysis according to the studies of recent foraminifera and the abundant distributions of depth-related species such as Alabamina creta, Laevidentalina sp., Praebulimina spp., Pleurostomella cf. naranjoensis, Pyrulina sp., Quinqueloculina spp., Haplophragmoides spp., etc. The result shows an almost parallel trend with the global transgressive and regressive cycles, but the former fluctuates more frequently at upper Cenomanian, which probably indicates tectonic instability of the continental margin. According to the benthic foraminiferal richness (BFN), Shannon-Weiner diversity (H(s)), as well as benthic foraminiferal oxygen index (BFOI), five periods of oxygen depleted conditions (dysoxic-anoxic) have been recognized. They correspond to the OAE2, the lower Turonian, the upper Turonian, the Turonian-Caniacian boundary event and the probably OAE3. In addition, the oxygen fluctuations in Gamba might be controlled directly by sea-level changes, while the paleoproductivity and oxygen conditions interacted with each other under oxygen deficiency environments.
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| 关 键 词： | benthic foraminifera bottom water oxygen sea-level Cretaceous Tethys-Himalaya |
| 收稿时间： | 2012/7/14 0:00:00 |
| 修稿时间： | 2012/10/10 0:00:00 |
Cenomanian-Coniacian Sea-level Change and Dissolved Oxygen Fluctuations in Tethys-Himalaya: Evidences from Benthic Foraminifera of Gamba, Tibet |
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| Authors: | JIA Jianzhong WAN Xiaoqiao CHEN Puli LI Guobiao JIANG Tian QU Haiying |
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| Institution: | 1. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences,Beijing 100083, China
2. Petroleum Exploration and Exploitation Institute, Sinopec Northwest Oil Field Company,(U)rümqi 830011,Xinjiang, China |
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| Abstract: | Benthic foraminifera, preserved in the Late Cretaceous organic carbon‐rich sediments of Gamba, southern Tibet, provide high‐resolution proxies for sea‐level changes and dissolved oxygen fluctuations of southeastern Tethys. The fossils were statistically analyzed and divided into three faunas of “Cenomanian fauna”, “Turonian fauna”, and “Coniacian fauna”. A middle neritic‐upper bathal environment (50–250m) was estimated considering the ratios of planktonic and epifaunal benthic foraminifera (P/(P+E)), the morphological analysis according to the studies of recent foraminifera and the abundant distributions of depth‐related species such as Alabamina creta, Laevidentalina sp., Praebulimina spp., Pleurostomella cf. naranjoensis, Pyrulina sp., Quinqueloculina spp., Haplophragmoides spp., etc. The result shows an almost parallel trend with the global transgressive and regressive cycles, but the former fluctuates more frequently at upper Cenomanian, which probably indicates tectonic instability of the continental margin. According to the benthic foraminiferal richness (BFN), Shannon‐Weiner diversity (H(s)), as well as benthic foraminiferal oxygen index (BFOI), five periods of oxygen depleted conditions (dysoxic‐anoxic) have been recognized. They correspond to the OAE2, the lower Turonian, the upper Turonian, the Turonian‐Caniacian boundary event and the probably OAE3. In addition, the oxygen fluctuations in Gamba might be controlled directly by sea‐level changes, while the paleoproductivity and oxygen conditions interacted with each other under oxygen deficiency environments. |
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| Keywords: | benthic foraminifera bottom water oxygen sea-level Cretaceous Tethys-Himalaya |
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