| Fischer Plots of Wumishan Cyclothems,Precambrian Records of Third-OrderSea-Level Changes |
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| 作者姓名： | Mei Mingxiang Faculty of Earth Sciences and Mineral Resources China University of Geosciences Beijing Ma Yongsheng China Petrochemical Corporation |
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| 作者单位： | Mei Mingxiang,Zhou Hongrui,Du Benming,Luo Zhiqing,Guo Qingyin(Faculty of Earth Sciences and Mineral Resources, China University of Geosciences,);Ma Yongsheng(China Petrochemical Corporation SINOPEC,)
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| 基金项目： | the National Natural Science
Foundation of China (No. 49802012) and also by the Ministry of
Science and Technology (SSER). |
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| 摘 要： | INTRODUCTIONThe Mesoproterozoic Wumishan Formation in Jixian,Tianjin is a succession of 3 300 m thick carbonate strata (Fig.1) where stromatolite biostromes and thrombolite bioherms arebest developed. The formation period of Wumishan Formation,about 100 Ma ((310120) Ma, (l 2071 10) Ma. Wang et al.,1995), is categorized as the Ectasian period of the Mesoproterozoic. Varieties of stromatolites in Wumishan Formation,such as Pseudogymnosolen mopanyuense, Scyphus parous,Conophoton conse…
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Fischer Plots of Wumishan Cyclothems, Precambrian Records of Third-Order Sea-Level Changes |
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| Mei Mingxiang Faculty of Earth Sciences and Mineral Resources,China University of Geosciences,Beijing Ma Yongsheng China Petrochemical Corporation.Fischer Plots of Wumishan Cyclothems,Precambrian Records of Third-OrderSea-Level Changes[J].Journal of China University of Geosciences,2001,12(1). |
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| Authors: | Mei Mingxiang Ma Yongsheng Zhou Hongrui Du Benming Luo Zhiqing Guo Qingyin |
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| Institution: | 1. Faculty of Earth Sciences and Mineral Resources, China University of Geosciences,
2. China Petrochemical Corporation SINOPEC, |
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| Abstract: | The Mesoproterozoic Wumishan Formation ((1 310±20) Ma-(1 207±10) Ma) in Jixian, Tianjin represents a succession of 3 300 meter thick carbonate strata where are the best developed stromatolite biostromes and thrombolite bioherms. These biostromes and bioherms, together with tidal-flat dolomites and muddy dolostones, form Wumishan cyclothems with approximately symmetrical facies-succession fabrics, which belong to carbonate meter-scale cyclic sequences of peritidal type. These cyclothems are overlain by lagoon dolomitic mudstones and shales and by frequently developed paleosol layers, indicating that the boundary of Wumishan cyclothems is marked by an instantaneously-exposed punctuated surface. Viewed form the regularly vertical stacking patterns of Wumishan cyclothems in long-term sequences, 26 third-order sequences may be discerned in Wumishan Formation. These third-order sequences may also be incorporated into six second-order sequences. In order to study the variation range of third-order sea-level changes and the formation period of third-order sequence, 626 cyclothems are discerned in the middle and upper parts of Wumishan Formation where the outcrops are well developed. In terms of the total thickness and the formation period of Mesoproterozoic Wumishan Formation, the crust subsidence rate in the sedimentary period of Wumishan Formation is supposed to be 3 meters at each interval of 100 thousands years. Based on this assumption, Fischer plot might be designed to simulate the third-order sea-level changing pattern. |
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| Keywords: | Wumisban cyclothems Fischer plots Mesoproterozoic Jixian of Tianjin |
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