The Oxfordian （Late Jurassic） carbonate-dominated ptatform outcropping in the Swiss Jura Mountains offers a good biostratigraphic, sequence-stratigraphic, and cyclostratigraphic framework to reconstruct changes in f...The Oxfordian （Late Jurassic） carbonate-dominated ptatform outcropping in the Swiss Jura Mountains offers a good biostratigraphic, sequence-stratigraphic, and cyclostratigraphic framework to reconstruct changes in facies distribution at a time-resolution of 100 ka. It thus allows interpreting the dynamic evolution of this platform in much more detail than conventional palaeogeographic maps permit. As an example, a Middle to Late Oxfordian time slice is presented, spanning an interval of about 1.6 Ma. The study is based on 12 sections logged at cm-scale. The interpreted depositional environments include marginal-marine emerged ;ands, fresh-water lakes, tidal fiats, shallow lagoons, ooid shoals, and coral reefs. Although limestones dominate, marly intervals and dolomites occur sporadically. Major facies shifts are related to m-scale sea-level changes linked to the orbital short eccentricity cycle （100 ka）. The 20-ka precession cycle caused minor facies changes but cannot always be resolved. Synsedimentary tectonics induced additional accommodation changes by creating shallow basins where days accumulated or highs on which shoals or islands formed. Autocyclic processes such as lateral migration of ooid and bioclastic shoals added to the sedimentary record. CEimate changes intervened to control terrestrial run-off and, consequently, siliciclastic and nutrient input. Coral reefs reacted to such input by becoming dominated by microbialites and eventually by being smothered. Concomitant occurrence of siliciclastics anddolomite in certain intervals further suggests that, at times, it was relatively arid in the study area but there was rainfall in more northern latitudes, eroding the Hercynian substrate. These examples from the Swiss Jura demonstrate the highly dynamic and （geologically speaking） rapid evolution of sedimentary systems, in which tectonically controlled basin morphology, orbitally induced climate and sea-level changes, currents, and the ecology of the carbonate-producing organisms interacted t展开更多
20091785 Chen Muhong(Key Laboratory of Marginal Sea Geology,South China Sea Institute of Oceanology,Guangzhou 510301,China);Zhang Lanlan Distributions of Radiolarian Diversity and Abundance in Surface Sediments of the...20091785 Chen Muhong(Key Laboratory of Marginal Sea Geology,South China Sea Institute of Oceanology,Guangzhou 510301,China);Zhang Lanlan Distributions of Radiolarian Diversity and Abundance in Surface Sediments of the South China Sea and Their Environmental Implications(Earth Science,ISSN1000-2383,CN42-1233/P,33(4),2008,p.431-442,5 illus.,1 table,27 refs.)Key words:Radiolaria,South China SeaThe South China Sea(SCS)has relatively complete physiographical units and ecologic environments,where there are a lot of preservative radiolarian species and specimens in the sediments.The methods of quantitative statistics and clustering were used展开更多
基金the financial support of the Swiss National Science Foundation,which is gratefully acknowledged(Projects No.20 41888,20-43150,20-46625,20-67736,and 20-109214)
文摘The Oxfordian （Late Jurassic） carbonate-dominated ptatform outcropping in the Swiss Jura Mountains offers a good biostratigraphic, sequence-stratigraphic, and cyclostratigraphic framework to reconstruct changes in facies distribution at a time-resolution of 100 ka. It thus allows interpreting the dynamic evolution of this platform in much more detail than conventional palaeogeographic maps permit. As an example, a Middle to Late Oxfordian time slice is presented, spanning an interval of about 1.6 Ma. The study is based on 12 sections logged at cm-scale. The interpreted depositional environments include marginal-marine emerged ;ands, fresh-water lakes, tidal fiats, shallow lagoons, ooid shoals, and coral reefs. Although limestones dominate, marly intervals and dolomites occur sporadically. Major facies shifts are related to m-scale sea-level changes linked to the orbital short eccentricity cycle （100 ka）. The 20-ka precession cycle caused minor facies changes but cannot always be resolved. Synsedimentary tectonics induced additional accommodation changes by creating shallow basins where days accumulated or highs on which shoals or islands formed. Autocyclic processes such as lateral migration of ooid and bioclastic shoals added to the sedimentary record. CEimate changes intervened to control terrestrial run-off and, consequently, siliciclastic and nutrient input. Coral reefs reacted to such input by becoming dominated by microbialites and eventually by being smothered. Concomitant occurrence of siliciclastics anddolomite in certain intervals further suggests that, at times, it was relatively arid in the study area but there was rainfall in more northern latitudes, eroding the Hercynian substrate. These examples from the Swiss Jura demonstrate the highly dynamic and （geologically speaking） rapid evolution of sedimentary systems, in which tectonically controlled basin morphology, orbitally induced climate and sea-level changes, currents, and the ecology of the carbonate-producing organisms interacted t
文摘20091785 Chen Muhong(Key Laboratory of Marginal Sea Geology,South China Sea Institute of Oceanology,Guangzhou 510301,China);Zhang Lanlan Distributions of Radiolarian Diversity and Abundance in Surface Sediments of the South China Sea and Their Environmental Implications(Earth Science,ISSN1000-2383,CN42-1233/P,33(4),2008,p.431-442,5 illus.,1 table,27 refs.)Key words:Radiolaria,South China SeaThe South China Sea(SCS)has relatively complete physiographical units and ecologic environments,where there are a lot of preservative radiolarian species and specimens in the sediments.The methods of quantitative statistics and clustering were used
