Following votes by the Pliensbachian Working Group, the Jurassic Subcommission and the International Commission on Stratigraphy, lUGS ratified the proposed Global Boundary Stratotype Section and Point （GSSP） for the...Following votes by the Pliensbachian Working Group, the Jurassic Subcommission and the International Commission on Stratigraphy, lUGS ratified the proposed Global Boundary Stratotype Section and Point （GSSP） for the base of the Pliensbachian Stage （Lower Jurassic） at the base of bed 73b in the Wine Haven section, Robin Hood＇s Bay, Yorkshire Coast, UK. This level contains the characteristic ammonite association Bifericeras donovani Dommergues and Meister and Apoderoceras sp. Complementary data include： a） Strontium-isotope stratigraphy, based on analysis of belemnites which yield a calcite 87Sr/^86Sr ratio for the boundary level of 0. 707425 and data supporting interpretation of continuous sedimentation; b） Belemnite oxygen-isotope data indicate a significant temperature drop （-5 ℃） across the boundary at this locality; c） A Transgressive Systems Tract （TST） initiated in the Aplanaturn Subzone （uppermost Sinemurian） continues into the Lowermost Pliensbachian （Taylori Subzone）; it forms part of a transgressive facies cycle sensu Graciansky et al. （1998）; d） The Upper Sinemurian to lowermost Plensbachian at Wine Haven section has a predominantly norreal magnetic polarity, but two discrete reversed polarity magnetozones are present. The first spans much of the latest Sinemurian Aplanatum Subzone. It terminates 〈0.5m below the Sinemurian-Pliensbachian boundary and may prove a valuable chronostratigraphic marker The second extends from the latest Oxynotum Subzone probably through to the lower part of the Raricostatum Subzone.展开更多
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
Although Madagascar has long been recognized as a biodiversity hotspot for conservation, very little is yet known about its diverse endemic fossils and the original beauty of its geotopes. The richness and endemicity ...Although Madagascar has long been recognized as a biodiversity hotspot for conservation, very little is yet known about its diverse endemic fossils and the original beauty of its geotopes. The richness and endemicity of geodiversity constitute nonrenewable natural resources, which deserve to be valorized and protected. Protection of natural heritage resources, aligned with geotourism, can provide a sustainable way for the population to rise out of poverty. The main purpose of this work is the instauration of Geopark, a long-term project in Madagascar National Parks to support geotourism and sustainable development. Given its outstanding landscape and its unique bio- and geo-diversity, we adopt Isalo Park as a pilot site, and suggest that this specific area is suitable for a Geopark. Following our field investigation, inventory and geodiversity assessments within the park are now underway, which will contribute to the implementation of Isalo Geopark.展开更多
Geological heritage inventory procedures and templates have been principally emerged from European countries. Each of these countries has developed its proper method of inventory based on its natural heritage, recogni...Geological heritage inventory procedures and templates have been principally emerged from European countries. Each of these countries has developed its proper method of inventory based on its natural heritage, recognized on local and/or regional scales. Natural sites were mainly identified and characterized in a particular geological context, which is usually very unique, valuable and impressive;resulting in the protection of the sites. Madagascar is known internationally as a beautifully landscaped island, but the impressive sites were not cataloged. We carried out a series of field inventory of potential geological sites within the Isalo National Park in southern Madagascar. We invented several inventory sheets in order to record the most detailed information about the sites identified within the park. This is to aid in organizing the park and to establish a sustainable base for the creation of a geopark, and also they help us to build a database for geosites and their classifications. This article suggests a prototype model for inventorying intangible geosites, paleosites and geomorphosites. Our inventory sheets help to identify and to promote geological importance of any sites, not only for academia but also for other sectors such as tourism and conservation.展开更多
Amber from Kachin,Myanmar offers a unique window into mid-Cretaceous ecosystems because it provides large sample sets that span a wide range of taxa preserved in exquisite detail at approximately 99 Ma[1].A fringe ben...Amber from Kachin,Myanmar offers a unique window into mid-Cretaceous ecosystems because it provides large sample sets that span a wide range of taxa preserved in exquisite detail at approximately 99 Ma[1].A fringe benefit of such extensive sampling is that inclusions rarely captured in other amber deposits are represented in Kachin amber—even subaquatic taxa.Recent studies have documented inclusions of fully marine groups,such as ammonites[2]and bivalves[3].展开更多
文摘Following votes by the Pliensbachian Working Group, the Jurassic Subcommission and the International Commission on Stratigraphy, lUGS ratified the proposed Global Boundary Stratotype Section and Point （GSSP） for the base of the Pliensbachian Stage （Lower Jurassic） at the base of bed 73b in the Wine Haven section, Robin Hood＇s Bay, Yorkshire Coast, UK. This level contains the characteristic ammonite association Bifericeras donovani Dommergues and Meister and Apoderoceras sp. Complementary data include： a） Strontium-isotope stratigraphy, based on analysis of belemnites which yield a calcite 87Sr/^86Sr ratio for the boundary level of 0. 707425 and data supporting interpretation of continuous sedimentation; b） Belemnite oxygen-isotope data indicate a significant temperature drop （-5 ℃） across the boundary at this locality; c） A Transgressive Systems Tract （TST） initiated in the Aplanaturn Subzone （uppermost Sinemurian） continues into the Lowermost Pliensbachian （Taylori Subzone）; it forms part of a transgressive facies cycle sensu Graciansky et al. （1998）; d） The Upper Sinemurian to lowermost Plensbachian at Wine Haven section has a predominantly norreal magnetic polarity, but two discrete reversed polarity magnetozones are present. The first spans much of the latest Sinemurian Aplanatum Subzone. It terminates 〈0.5m below the Sinemurian-Pliensbachian boundary and may prove a valuable chronostratigraphic marker The second extends from the latest Oxynotum Subzone probably through to the lower part of the Raricostatum Subzone.
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Although Madagascar has long been recognized as a biodiversity hotspot for conservation, very little is yet known about its diverse endemic fossils and the original beauty of its geotopes. The richness and endemicity of geodiversity constitute nonrenewable natural resources, which deserve to be valorized and protected. Protection of natural heritage resources, aligned with geotourism, can provide a sustainable way for the population to rise out of poverty. The main purpose of this work is the instauration of Geopark, a long-term project in Madagascar National Parks to support geotourism and sustainable development. Given its outstanding landscape and its unique bio- and geo-diversity, we adopt Isalo Park as a pilot site, and suggest that this specific area is suitable for a Geopark. Following our field investigation, inventory and geodiversity assessments within the park are now underway, which will contribute to the implementation of Isalo Geopark.
文摘Geological heritage inventory procedures and templates have been principally emerged from European countries. Each of these countries has developed its proper method of inventory based on its natural heritage, recognized on local and/or regional scales. Natural sites were mainly identified and characterized in a particular geological context, which is usually very unique, valuable and impressive;resulting in the protection of the sites. Madagascar is known internationally as a beautifully landscaped island, but the impressive sites were not cataloged. We carried out a series of field inventory of potential geological sites within the Isalo National Park in southern Madagascar. We invented several inventory sheets in order to record the most detailed information about the sites identified within the park. This is to aid in organizing the park and to establish a sustainable base for the creation of a geopark, and also they help us to build a database for geosites and their classifications. This article suggests a prototype model for inventorying intangible geosites, paleosites and geomorphosites. Our inventory sheets help to identify and to promote geological importance of any sites, not only for academia but also for other sectors such as tourism and conservation.
基金This work was supported by the National Natural Science Foundation of China(31672345,41790455,41772008,and 41861134032)the Scientific Research Equipment Development Project of Chinese Academy of Sciences(YZ201509)+2 种基金the Natural Science Foundation of Yunnan,China(2015HA021,2018FA025,2018IA073,and 2019DG050)the Natural Sciences and Engineering Research Council of Canada(2015-00681)the National Geographic Society,USA(EC0768-15).
文摘Amber from Kachin,Myanmar offers a unique window into mid-Cretaceous ecosystems because it provides large sample sets that span a wide range of taxa preserved in exquisite detail at approximately 99 Ma[1].A fringe benefit of such extensive sampling is that inclusions rarely captured in other amber deposits are represented in Kachin amber—even subaquatic taxa.Recent studies have documented inclusions of fully marine groups,such as ammonites[2]and bivalves[3].
