Following votes by the Valanginian Working Group,the International Subcommission on Cretaceous Stratigraphy and the International Commission on Stratigraphy,the Executive Committee of the International Union of Geolog...Following votes by the Valanginian Working Group,the International Subcommission on Cretaceous Stratigraphy and the International Commission on Stratigraphy,the Executive Committee of the International Union of Geological Sciences unanimously approved in December 2024 the Global Stratotype Section and Point(GSSP)for the Valanginian Stage(Cretaceous System).展开更多
The role of mantle plume in the final stages of rifting of the East Gondwana crustal fragments remains equivocal with only limited evidence so far reported from the southern part of Peninsular India.Here,we report for...The role of mantle plume in the final stages of rifting of the East Gondwana crustal fragments remains equivocal with only limited evidence so far reported from the southern part of Peninsular India.Here,we report for the first time a suite of columnar basalts from the Mesoarchean Coorg Block in the Southern Granulite Terrain(SGT)of India and characterize these rocks through field,petrological,geo-chemical,and isotope geochronological studies.The basalts show porphyritic texture with phenocrysts of pyroxene and plagioclase embedded in fine groundmass.Geochemical data reveal tholeiitic flood basalt affinity with affinities of plume-related magmatism.The zircon U-Pb data of the rocks yield a weighted mean age of 137 Ma,thus corresponding to the Valanginian Age of the Early Cretaceous Period.We suggest the possible geochemical affinity of the studied rocks Kerguelen plume basalts which provide new insights into magmatism associated with the final stages of East Gondwana rifting.展开更多
Globally elevated temperatures during the Cretaceous extreme greenhouse climate interval were punctuated by the Valanginian cooling event,which was characterized by a positive carbon isotope excursion,global cooling,a...Globally elevated temperatures during the Cretaceous extreme greenhouse climate interval were punctuated by the Valanginian cooling event,which was characterized by a positive carbon isotope excursion,global cooling,and a glacial event approximately at 135 Ma.Disentangling ocean temperature and continental ice volume trends enables us to better understand climate fluctuations over deep time.We investigated the ocean temperature-ice sheet dynamics of glaciation events that occurred in the Cretaceous greenhouse world.New clumped isotope andδ^(18) O data from sites in the Tethyan Ocean show that seawater temperatures decreased by 5-6°C,consistent with the development of glacial periods,and maximum ice volumes about half the size of present-day Antarctica.This cooling event provides a counter-example to other Mesozoic climate transitions driven by changes in atmospheric greenhouse gas contents.Our results emphasize the importance of quantitatively reconstructing continental ice volume,providing further support for exploring deep-time Earth climate dynamics.展开更多
基金support of a project(2021-2023)funded by the Polish and French Ministries of foreign affairs(Partenariat Hubert Curien,cf.the current palaeomagnetic study that also includes the contribution of Chmielewski Andrezj,Iwanczuk Jolanta and Ploch Izabela from the Polish Geological Institute of Warsaw,colleagues who are hereby thanked)the CNRS SYSTER program(WOAW SYSTER French project,with the contribution of two students Lea Baubant and Durel Franchevel who are acknowledged),Project APVV-20-0079(Slovakian National Grant Agency,thanks to Diana Olveczka)and various grants from the Laboratoire de Geologie de Lyon.
文摘Following votes by the Valanginian Working Group,the International Subcommission on Cretaceous Stratigraphy and the International Commission on Stratigraphy,the Executive Committee of the International Union of Geological Sciences unanimously approved in December 2024 the Global Stratotype Section and Point(GSSP)for the Valanginian Stage(Cretaceous System).
基金supported by the“Startup Grant for the University Teachers”of the University of Kerala.
文摘The role of mantle plume in the final stages of rifting of the East Gondwana crustal fragments remains equivocal with only limited evidence so far reported from the southern part of Peninsular India.Here,we report for the first time a suite of columnar basalts from the Mesoarchean Coorg Block in the Southern Granulite Terrain(SGT)of India and characterize these rocks through field,petrological,geo-chemical,and isotope geochronological studies.The basalts show porphyritic texture with phenocrysts of pyroxene and plagioclase embedded in fine groundmass.Geochemical data reveal tholeiitic flood basalt affinity with affinities of plume-related magmatism.The zircon U-Pb data of the rocks yield a weighted mean age of 137 Ma,thus corresponding to the Valanginian Age of the Early Cretaceous Period.We suggest the possible geochemical affinity of the studied rocks Kerguelen plume basalts which provide new insights into magmatism associated with the final stages of East Gondwana rifting.
基金supported by the National Natural Science Foundation of China BSCTPES project(41988101)Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0708)+1 种基金the National Natural Science Foundation of China(42102021),the Chinese Academy of Sciences,Strategic Priority Research Program(XDA20070301)the Special Research Assistant Funding Project of Chinese Academy of Sciences(2021000015).
文摘Globally elevated temperatures during the Cretaceous extreme greenhouse climate interval were punctuated by the Valanginian cooling event,which was characterized by a positive carbon isotope excursion,global cooling,and a glacial event approximately at 135 Ma.Disentangling ocean temperature and continental ice volume trends enables us to better understand climate fluctuations over deep time.We investigated the ocean temperature-ice sheet dynamics of glaciation events that occurred in the Cretaceous greenhouse world.New clumped isotope andδ^(18) O data from sites in the Tethyan Ocean show that seawater temperatures decreased by 5-6°C,consistent with the development of glacial periods,and maximum ice volumes about half the size of present-day Antarctica.This cooling event provides a counter-example to other Mesozoic climate transitions driven by changes in atmospheric greenhouse gas contents.Our results emphasize the importance of quantitatively reconstructing continental ice volume,providing further support for exploring deep-time Earth climate dynamics.
