1 Introduction Stratigraphy,placing the sequence of events in Earth history into order,is a fundamental part of the geosciences.Traditionally the starting point is a regional stratigraphy,based on lithological,mappabl...1 Introduction Stratigraphy,placing the sequence of events in Earth history into order,is a fundamental part of the geosciences.Traditionally the starting point is a regional stratigraphy,based on lithological,mappable units,correlated by fossils with local,regional and global chronostratigraphical schemes.Chronostratigraphic units were traditionally defined on their fossil content,as essentially unit stratotypes.But,commonly there were no clear boundaries.展开更多
Late Ordovician shelly faunas occur at several localities in the(O|¨)stersund area of J(a|¨)mtland,central Sweden,an area that today is included in the Lower Allochton of the Swedish Caledonides.The Late Ord...Late Ordovician shelly faunas occur at several localities in the(O|¨)stersund area of J(a|¨)mtland,central Sweden,an area that today is included in the Lower Allochton of the Swedish Caledonides.The Late Ordovician faunas of J(a|¨)mtland have developed against a background of intense and rapid global climate change.The faunas are present approximately in the middle of the Kyrk(?)s Quartzite in the east and occur in the uppermost Kogsta Siltstone in the west. Changes in faunas and depositional environments provide regional evidence of these global cooling and regressive events.The faunas occur in shale and siltstone facies and are used to effect展开更多
The Global boundary Stratotype Section and Point(GSSP)for the base of the Hirnantian Stage(the uppermost of the Ordovician System)is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan No...The Global boundary Stratotype Section and Point(GSSP)for the base of the Hirnantian Stage(the uppermost of the Ordovician System)is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan North section.The section is located near Wangjiawan village,42 km north of Yichang city(western Hubei,China),at 30°58′56″N and 111°25′10″E.The GSSP level coincides with the first appearance of the graptolite species Normalograptus extraordinarius(Sobolevskaya).Secondary markers include the onset of a positive carbon-isotope excursion,and a slightly earlier first appearance of Normalograptus ojsuensis(Koren and Mikhailova).The Wangjiawan North section possesses continuity of sedimentation and biozonation with completeness of exposures,abundant and well-preserved graptolites and shelly fossils,i.e.the Hirnantia-Dalmanitina shelly fauna which is a key element for recognition of the Hirnantian Stage.The Wangjiawan North,South and Riverside sections possess favorable facies and widespread correlation potential,are free from structure complication,metamorphism and other alteration,and have good accessibility.The Riverside section in particular possesses amenability to isotopic age determination.The beginning of the Hirnantian was followed by a global episode of a major extinction event,which happened in the Diceratograptus mirus Subzone.The proposal was voted by the International Subcommission on Ordovician Stratigraphy in October,2004,approved by the International Commission on Stratigraphy in February,2006,and ratified by the International Union of Geological Sciences in May,2006.展开更多
IGCP 503‘Ordovician Palaeogeography and Palaeoclimate’was established in 2004 primarily to identify the main drivers,both biological and geological,of the Great Ordovician Biodiversification Event.From the outset of...IGCP 503‘Ordovician Palaeogeography and Palaeoclimate’was established in 2004 primarily to identify the main drivers,both biological and geological,of the Great Ordovician Biodiversification Event.From the outset of the project it was clear that this event was part of a larger-scale,long-term,multifaceted process that included the end Ordovician extinction and Silurian recovery,if not more.IGCP 503 thus developed a major network that included scientists whose interests spanned the entire Lower Palaeozoic and encompassed a range of disciplines from classical palaeontology and palaeoecology through isotope geochemistry to climate modelling.展开更多
基金the Leverhulme Trust for financial support.This is a contribution to IGCP 653 project’The onset of the Great Ordovician Biodiversification Event’.
文摘1 Introduction Stratigraphy,placing the sequence of events in Earth history into order,is a fundamental part of the geosciences.Traditionally the starting point is a regional stratigraphy,based on lithological,mappable units,correlated by fossils with local,regional and global chronostratigraphical schemes.Chronostratigraphic units were traditionally defined on their fossil content,as essentially unit stratotypes.But,commonly there were no clear boundaries.
文摘Late Ordovician shelly faunas occur at several localities in the(O|¨)stersund area of J(a|¨)mtland,central Sweden,an area that today is included in the Lower Allochton of the Swedish Caledonides.The Late Ordovician faunas of J(a|¨)mtland have developed against a background of intense and rapid global climate change.The faunas are present approximately in the middle of the Kyrk(?)s Quartzite in the east and occur in the uppermost Kogsta Siltstone in the west. Changes in faunas and depositional environments provide regional evidence of these global cooling and regressive events.The faunas occur in shale and siltstone facies and are used to effect
文摘The Global boundary Stratotype Section and Point(GSSP)for the base of the Hirnantian Stage(the uppermost of the Ordovician System)is defined at a point 0.39m below the base of the Kuanyinchiao Bed in the Wangjiawan North section.The section is located near Wangjiawan village,42 km north of Yichang city(western Hubei,China),at 30°58′56″N and 111°25′10″E.The GSSP level coincides with the first appearance of the graptolite species Normalograptus extraordinarius(Sobolevskaya).Secondary markers include the onset of a positive carbon-isotope excursion,and a slightly earlier first appearance of Normalograptus ojsuensis(Koren and Mikhailova).The Wangjiawan North section possesses continuity of sedimentation and biozonation with completeness of exposures,abundant and well-preserved graptolites and shelly fossils,i.e.the Hirnantia-Dalmanitina shelly fauna which is a key element for recognition of the Hirnantian Stage.The Wangjiawan North,South and Riverside sections possess favorable facies and widespread correlation potential,are free from structure complication,metamorphism and other alteration,and have good accessibility.The Riverside section in particular possesses amenability to isotopic age determination.The beginning of the Hirnantian was followed by a global episode of a major extinction event,which happened in the Diceratograptus mirus Subzone.The proposal was voted by the International Subcommission on Ordovician Stratigraphy in October,2004,approved by the International Commission on Stratigraphy in February,2006,and ratified by the International Union of Geological Sciences in May,2006.
文摘IGCP 503‘Ordovician Palaeogeography and Palaeoclimate’was established in 2004 primarily to identify the main drivers,both biological and geological,of the Great Ordovician Biodiversification Event.From the outset of the project it was clear that this event was part of a larger-scale,long-term,multifaceted process that included the end Ordovician extinction and Silurian recovery,if not more.IGCP 503 thus developed a major network that included scientists whose interests spanned the entire Lower Palaeozoic and encompassed a range of disciplines from classical palaeontology and palaeoecology through isotope geochemistry to climate modelling.
