The Global boundary Stratotype Section and Point(GSSP)for the base of the Drumian Stage(Cambrian Series 3)is defined at the base of a limestone(calcisiltite)layer 62 m above the base of the Wheeler Formation in the St...The Global boundary Stratotype Section and Point(GSSP)for the base of the Drumian Stage(Cambrian Series 3)is defined at the base of a limestone(calcisiltite)layer 62 m above the base of the Wheeler Formation in the Stratotype Ridge section,Drum Mountains,Utah,USA.The GSSP level contains the lowest occurrence of the cosmopolitan agnostoid trilobite Ptychagnostus atavus(base of the P.atavus Zone).Secondary global markers near the base of the stage include the DICE negativeδ^13C excursion,the onset of a long monotonic^87Sr/^86Sr isotopic shift,and the transgressive phase of a eustatic event.Faunal turnovers close to the base of the Drumian Stage are recognized as the base of the Bolaspidella Zone(polymerid trilobites)in Laurentia,the historic base of the Floran Stage in Australia,the base of the Dorypyge richthofeni Zone(polymerid trilobites)in South China,and the base of the Gapparodus bisulcatus-Westergaardodina brevidens Assemblage-zone(conodonts)in Baltica and South China.The last occurrence of the cosmopolitan trilobite Ptychagnostus gibbus occurs in the lower part of the Drumian Stage,and the base of the Hydrocephalus hicksii Zone(polymerid trilobites)as used in Siberia and Baltica occurs near the base of the stage.展开更多
The Global boundary Stratotype Section and Point(GSSP)for the base of the Guzhangian Stage(Cambrian Series 3)is defined at the base of a limestone(calcisiltite)layer 121.3 m above the base of the Huaqiao Formation in ...The Global boundary Stratotype Section and Point(GSSP)for the base of the Guzhangian Stage(Cambrian Series 3)is defined at the base of a limestone(calcisiltite)layer 121.3 m above the base of the Huaqiao Formation in the Louyixi section along the Youshui River(Fengtan Reservoir),about 4 km northwest of Luoyixi(4 km southeast of Wangcun),in northwestern Hunan,China.The GSSP is exposed in a road cut at a position of 28°43.20'N and 109°57.88'E.The GSSP level contains the lowest occurrence of the cosmopolitan agnostoid trilobite Lejopyge laevigata(base of the L.laevigata Zone).Secondary global markers near the base of the stage include the appearance of either L.calva or L.armata just below the base of the stage,the appearance of conodonts associated with the base of the Laiwugnathus laiwuensis Zone,and the transgressive phase of a small eustatic event.Faunal turnovers close to the base of the Guzhangian Stage are recognized as near the base of the Boomerangian Stage in Australia,the base of the Aldanaspis Zone(polymerid trilobites)in Siberia,and the base of the Paradoxides forchhammeri Zone in western Avalonia.The horizon corresponding to the first appearance of L.laevigata is near the peak of a rather long negativeδ13C excursion of up to 0.58‰.展开更多
基金supported in part by a grant from the U.S.National Science Foundation(EAR-0106883)to Babcock.
文摘The Global boundary Stratotype Section and Point(GSSP)for the base of the Drumian Stage(Cambrian Series 3)is defined at the base of a limestone(calcisiltite)layer 62 m above the base of the Wheeler Formation in the Stratotype Ridge section,Drum Mountains,Utah,USA.The GSSP level contains the lowest occurrence of the cosmopolitan agnostoid trilobite Ptychagnostus atavus(base of the P.atavus Zone).Secondary global markers near the base of the stage include the DICE negativeδ^13C excursion,the onset of a long monotonic^87Sr/^86Sr isotopic shift,and the transgressive phase of a eustatic event.Faunal turnovers close to the base of the Drumian Stage are recognized as the base of the Bolaspidella Zone(polymerid trilobites)in Laurentia,the historic base of the Floran Stage in Australia,the base of the Dorypyge richthofeni Zone(polymerid trilobites)in South China,and the base of the Gapparodus bisulcatus-Westergaardodina brevidens Assemblage-zone(conodonts)in Baltica and South China.The last occurrence of the cosmopolitan trilobite Ptychagnostus gibbus occurs in the lower part of the Drumian Stage,and the base of the Hydrocephalus hicksii Zone(polymerid trilobites)as used in Siberia and Baltica occurs near the base of the stage.
基金supported in part by grants from the Chinese Academy of Sciences(KZCX2-YW-122)the Ministry of Science and Technology of China(2006FY120300)+2 种基金National Natural Science Foundation of China(40332018)to Pengby a grant from the U.S.National Science Foundation(EAR-0106883)to Babcockby a grant from National Natural Science Foundation of China(40672023)to Zuo.
文摘The Global boundary Stratotype Section and Point(GSSP)for the base of the Guzhangian Stage(Cambrian Series 3)is defined at the base of a limestone(calcisiltite)layer 121.3 m above the base of the Huaqiao Formation in the Louyixi section along the Youshui River(Fengtan Reservoir),about 4 km northwest of Luoyixi(4 km southeast of Wangcun),in northwestern Hunan,China.The GSSP is exposed in a road cut at a position of 28°43.20'N and 109°57.88'E.The GSSP level contains the lowest occurrence of the cosmopolitan agnostoid trilobite Lejopyge laevigata(base of the L.laevigata Zone).Secondary global markers near the base of the stage include the appearance of either L.calva or L.armata just below the base of the stage,the appearance of conodonts associated with the base of the Laiwugnathus laiwuensis Zone,and the transgressive phase of a small eustatic event.Faunal turnovers close to the base of the Guzhangian Stage are recognized as near the base of the Boomerangian Stage in Australia,the base of the Aldanaspis Zone(polymerid trilobites)in Siberia,and the base of the Paradoxides forchhammeri Zone in western Avalonia.The horizon corresponding to the first appearance of L.laevigata is near the peak of a rather long negativeδ13C excursion of up to 0.58‰.
