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The Upper Devonian orbital cyclostratigraphy and numerical dating conodont zones from Guangxi,South china

science china earth sciences 2005年第1期48卷 32-41页

作者： gong yiming, xu ran, tang zhongdao & li baohua faculty of earth science, china university of geosciences, wuhan 43.074, china Laboratory of Marine Geology, Tongji university, Shanghai 200092, china 1. faculty of earth science China University of Geosciences 430074 Wuhan China 2. Laboratory of Marine Geology Tongji University 200092 Shanghai China

The hierarchically organized laminae, bundles, bundlesets and superbundlesets which correspond to a sub-Milankovitch, obliquity or precession, eccentricity and long eccentricity cyclothems, respectively, have been distinguished from the Upper Devonian Fras-nian-Famennian (F-F) transitional carbonate successions deposited in the carbonate-basin and slope facies of Guangxi, South china. The durations of cyclothems are 8000-10000a, 16667a or 33333a, 100000a and 400000a, respectively. The ratio of eccentricity to precession, eccentricity to obliquity, and long eccentricity to eccentricity is 1 : 6, 1 : 3 and 1 : 4 in the Devonian, respectively. Orbital cyclostratigraphical studies show that the durations of the conodont falsio-valis Zone, transitans Zone, punctate Zone, Lower hassi Zone, Upper hassi Zone, jamieae Zone, Lower rhenana Zone, Upper rhenana Zone, linguiformis Zone, Lower triangularis Zone, Middle triangularis Zone and Upper triangularis Zone are 0.4, 0.4, 0.4, 0.3, 0.4, 0.2, 0.8, 0.6, 0.8, 0.3, 0.3 and 0.3 Ma from bottom to top, respectively, and the duration of the Frasnian is 4.3 Ma. The conodont is the normal marine organism of the latest mass extinction (the latest linguiformis Zone) and the first recovery (including the whole Lower triangularis and Middle triangularis Zone) in the F-F transition. The conodont mass extinction and recovery lasted 200000-100000a and 0.6 Ma, respectively. We consider that average durations of the fossil zones calculated by reported numerical ages divided by fossil zone numbers within a stage or series or system cannot discovery complications and non-uniformity of evolutionary organisms and environments.

关键词： orbital cyclostratigraphy, conodont zone, numerical dating, mass extinction, Devonian, Guangxi, South china.

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Devonian Frasnian-Famennian Transitional Milankovitch Cycles and High-Resolution Stratigraphic Correlation

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Acta Geologica Sinica(English Edition) 2001年第4期75卷 354-363页

作者： gong yiming faculty of earth science, china university of geosciences, wuhan, 43.074li baohua Laboratory of Marine Geology, Tongji university, Shanghai 200092and WU Yi Guangxi Institute of Geology, Nanning 530023 faculty of earth science China University of Geosciences Wuhan 430074 Laboratory of Marine Geology Tongji University Shanghai 200092 Guangxi Institute of Geology Nanning 530023 [?]4gong yiming Born in October 1958 graduated from the Department of Geology Wuhan College of Geology in 1981 received his Ph.D. degree in china university of geosciences in 1991. He is now a professor in the same university mainly engaged in high-resolution stratigraphy ichnology (trace fossils) and sedimentary geology. E- Mail: ymGONG@***

Four hierarchical cyclothems, superbundlesets, bundlesets, bundles and laminae, have been identified from the Devonian Frasnian-Famennian carbonate strata in Guangxi, South china. Their hierarchical structures, ratio relationships and sequence in conodont zones are continuous and stable and can be traced across different facies zones and sedimentary basins. Our data show that hierarchically organized superbundlesets, bundlesets, bundles and laminae correspond to the long eccentricity, eccentricity, obliquity or precession and sub-Milankovitch cycles respectively. Their periods were 400,000, 100,000, 33,333, 16,667 and 8,000–17,000 a, respectively. The ratios of long eccentricity to eccentricity, eccentricity to obliquity, and eccentricity to precession in the Devonian are 1:4, 1:3 and 1:6 respectively. Using these hierarchical Milankovitch cyclothems, chronostratigraphical division and correlation can be realized at a resolution of 100 ka or 10 ka at the Frasnian-Famennian transition. The time intervals of the Upper rhenana Zone, linguiformis Zone, and the Lower, Middle and Upper triangularis Zone are 0.6, 0.8, 0.3, 0.3 and 0.3 Ma, respectively. Sea-level changes of the Frasnian-Famennian transition were not coherent and synchronous at the resolution of 100 ka or 10 ka in the basin-slope carbonate sequences of Guangxi, South china.

关键词： Milankovitch cycle high-resolution stratigraphic correlation sea-level change numerical dating Devonian Guangxi South china

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Relationships between bacterial-algal proliferating and mass extinction in the Late Devonian Frasnian-Famennian transition:Enlightening from carbon isotopes and molecular fossils

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science china earth sciences 2005年第10期48卷 1656-1665页

作者： gong yiming1,2, xu ran1, tang zhongdao1, SI Yuanlan3 & li baohua4 1. faculty of earth science and State Key Laboratory of Geological Processes and Mineral Resources, china university of geosciences, wuhan 43.074, china 2. Institute of Resources & Environments, Henan Polytechnic university, Jiaozuo 454003, china 3. Department of Computer science, South-Central university for Nationalities, wuhan 43.074, china 4. Laboratory of Marine Geology, Tongji university, Shanghai 200092, china faculty of earth science and State Key Laboratory of Geological Processes and Mineral Resources china university of geosciences wuhan china Institute of Resources & Environments Henan Polytechnic university Jiaozuo china Department of Computer science South-Central university for Nationalities wuhan china Laboratory of Marine Geology Tongji university Shanghai china

Studies show positive shifts of inorganic and organic carbon isotope values (δ 13Ccarb and δ 13Ckerogen) from +0.43 (‰ V-PDB) to +3.54 (‰ V-PDB) and from ?29.38 (‰ V-PDB) to ?24.14 (‰ V-PDB), respectively, B* (Ba* = Ba/ (Al2O3 X 15%)) values from 0.015 to 0.144, TOC values from 0.02% to 0.21%, V/Cr values from 0.3 to 2.0, Sr/Ba values from 3.20 to 49.50 in the Late Devonian Frasnian Upper rhenana zone to the top linguiformis zone of the Yangdi sec-tion deposited in carbonate slope facies of Guilin, Guangxi, South china, which indicates that biomass, productivity, organic carbon burial and salinity increase and that oxygenation near the boundary between sediments and waters decreases from the Late Devonian Frasnian Upper rhenana zone to the top linguiformis zone. Abundance of molecular fossils increases and normal alkanes, isoprenoid hydrocarbon, terpanes and steranes are dominated from the Late Devonian Frasnian to the bottom of Famennian, which shows that the predecessors of molecular fossils of the Frasnian-Famennian (F-F) transition are dominated by marine phytoplankton, zooplankton and benthic bacteria with no photosynthesis. Therefore, it is considered that the F-F transitional mass extinction with a multistage, selection and global synchronizing was caused by bacte-rial-algal proliferating, continuing deterioration of the shallow marine ecoenvironment of the mid-dle-lower latitudes. A simple cause and effect chain can be expressed as: appearance of seed plants and multi-storied forests → enhanced chemical and biochemical weathering and pe-dogenesis → wide development of soils → increasing riverine nutrient fluxes in epicontinental sea → from superoligotrophic to eutrophic in epicontinental sea → proliferating of marine phyto-plankton and zooplankton → frequent red tide and anoxia → mass extinction of shallow marine organisms in the middle-lower latitudes. It is worth notice that the factor drawdown of atmos-pheric Pco2, climatic cooling and sea level falling c

关键词： mass extinction, bacteria-algae, carbon isotopes, molecular fossils, biodiversity, Late Devonian, Guangxi, South china.

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Late Devonian red tide and mass extinction

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Chinese science Bulletin 2002年第13期47卷 1138-1144页

作者： gong yiming li baohua SI Yuanlan WU Yi faculty of earth science China University of GeosciencesWuhan 430074China Laboratory of Marine Geology Tongji UniversityShanghai 200092China Department of Computer science South-Central University for NationalitiesWuhan 430074China Guangxi Institute of Geology Nanning 530023China

Molecular stratigraphical, carbonate carbon isotopic, stratigraphical and paleontological data show that algal booming, eutrophication, anoxia, hypersalinity, positive δ13C excursion and biomass decreasing occurred in the offshore carbonate environments of the Frasnian-Famennian (F-F) transition, which hints that red tide might frequently take place in the F-F transition of Guangxi, South china. We suggest that the mass extinction of the reef ecosystems and the shallow-water marine organisms in the F-F transition of the lower-middle latitudes may be related to the frequent occurrence of red tide in that time.

关键词： red tide eutrophication mass extinction Devonian South china.

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