A robust stratigraphic framework and a coherent depositional ramp model for the Zitai,Dawan,Meitan and Ningkuo formations of Floian–Darriwilian age(Early–Middle Ordovician)in the Yangtze(Daoba,Xiangshuidong,Daling,G...A robust stratigraphic framework and a coherent depositional ramp model for the Zitai,Dawan,Meitan and Ningkuo formations of Floian–Darriwilian age(Early–Middle Ordovician)in the Yangtze(Daoba,Xiangshuidong,Daling,Gudongkou and Honghuayuan sections)and Jiangnan regions(Nanba section)was created based on lithofacies and major element analysis.Three siliciclastic(LF1–3)and six carbonate(LF4–9)lithofacies are recognized representing sediments that were deposited in mixed siliciclastic and carbonate ramp environment.The intensity of mixed sedimentation and terrigenous input were evaluated using the elemental proxies Intensity of Mixed sedimentation(IM)and Aluminum Accumulation Rate(Al AR),as well as their mean values during certain time intervals.Mixed sediments are most well-developed along the marginal Yangtze region,strongly impacted by recurrent influx of westerly derived terrigenous materials in response to global eustatic changes and regional tectonic movements,shaping the gently southeast-dipping morphology.Regular terrigenous influx resulted in periods of enhanced primary productivity on the Yangtze Ramp as evidenced by matching biodiversity peaks in planktonic organisms,i.e.,chitinozoans and acritarchs.Brachiopods and other shelly fauna were also able to proliferate as new niches developed along the gently dipping ramp floor with substrate changes.The biodiversification patterns suggest that terrigenous influx controlled in part by regional tectonics played a more important role than previously thought in the development of Great Ordovician Biodiversification Event in South China.展开更多
Review of the literature on Ordovician conodont diversification in palaeoplates of North and Western China reveals that four diversity peaks are present in North China,occurring in the middle Tremadocian,early Floian,...Review of the literature on Ordovician conodont diversification in palaeoplates of North and Western China reveals that four diversity peaks are present in North China,occurring in the middle Tremadocian,early Floian,late Floian,and late Darriwilian,with three of these peaks(excepting that in the late Floian)also being recorded in Tarim.Three diversification intervals are present in North China,during the Tremadocian,late Floian,early and middle Darriwilian;comparable intervals are observed in the early and late Tremadocian,early Floian,and the Middle Ordovician in Tarim.The main conodont diversification episode in both palaeoplates took place in the Darriwilian,at the time of the Great Ordovician Biodiversification Event.A comparison of conodont diversity patterns in different palaeoplates(North China,Tarim,and South China)demonstrates that conodont radiation events mainly occurred within the Tremadocian,Floian,and Darriwilian.Conodont diversifications in these paleoplates also display some differences.In contrasting with Tarim and South China,North China witnessed a rapid conodont diversification during late Floian time.Conodont diversity in North China and Tarim increased continually and reached a peak in the late Darriwilian,concurrent with a prominent decreasing trend in South China.Differences of conodont diversification in these three palaeoplates may be related to their palaeogeography and tectonic history.When conodont diversifications in North China and Tarim are analysed on the background of palaeoenvironments,the main episodes are seen to be partly coincident with second order sea-level changes,particularly in North China.In general,conodont radiation correlates with large scale transgressions.展开更多
基金funded by National Natural Science Foundation of China(Grant Nos.42102130,41972011)Natural Science Foundation of Jiangsu Province(Grant No.BK20191101)+2 种基金Chinese Academy of Sciences(Grant No.XDB26000000)China Scholarship Council(Grant No.202004910207)State Key Laboratory of Palaeobiology and Stratigraphy。
文摘A robust stratigraphic framework and a coherent depositional ramp model for the Zitai,Dawan,Meitan and Ningkuo formations of Floian–Darriwilian age(Early–Middle Ordovician)in the Yangtze(Daoba,Xiangshuidong,Daling,Gudongkou and Honghuayuan sections)and Jiangnan regions(Nanba section)was created based on lithofacies and major element analysis.Three siliciclastic(LF1–3)and six carbonate(LF4–9)lithofacies are recognized representing sediments that were deposited in mixed siliciclastic and carbonate ramp environment.The intensity of mixed sedimentation and terrigenous input were evaluated using the elemental proxies Intensity of Mixed sedimentation(IM)and Aluminum Accumulation Rate(Al AR),as well as their mean values during certain time intervals.Mixed sediments are most well-developed along the marginal Yangtze region,strongly impacted by recurrent influx of westerly derived terrigenous materials in response to global eustatic changes and regional tectonic movements,shaping the gently southeast-dipping morphology.Regular terrigenous influx resulted in periods of enhanced primary productivity on the Yangtze Ramp as evidenced by matching biodiversity peaks in planktonic organisms,i.e.,chitinozoans and acritarchs.Brachiopods and other shelly fauna were also able to proliferate as new niches developed along the gently dipping ramp floor with substrate changes.The biodiversification patterns suggest that terrigenous influx controlled in part by regional tectonics played a more important role than previously thought in the development of Great Ordovician Biodiversification Event in South China.
基金supported by National Natural Science Foundation of China(Grant Nos.41202005,41221001,40825006)State Key Laboratory of Palaeobiology and Stratigraphy(Grant No.Y126110409)+1 种基金Chinese Academy of Sciences(Grant No.KZCX2-YW-Q05-01)a contribution to Project IGCP 591:The Early to Middle Paleozoic Revolution
文摘Review of the literature on Ordovician conodont diversification in palaeoplates of North and Western China reveals that four diversity peaks are present in North China,occurring in the middle Tremadocian,early Floian,late Floian,and late Darriwilian,with three of these peaks(excepting that in the late Floian)also being recorded in Tarim.Three diversification intervals are present in North China,during the Tremadocian,late Floian,early and middle Darriwilian;comparable intervals are observed in the early and late Tremadocian,early Floian,and the Middle Ordovician in Tarim.The main conodont diversification episode in both palaeoplates took place in the Darriwilian,at the time of the Great Ordovician Biodiversification Event.A comparison of conodont diversity patterns in different palaeoplates(North China,Tarim,and South China)demonstrates that conodont radiation events mainly occurred within the Tremadocian,Floian,and Darriwilian.Conodont diversifications in these paleoplates also display some differences.In contrasting with Tarim and South China,North China witnessed a rapid conodont diversification during late Floian time.Conodont diversity in North China and Tarim increased continually and reached a peak in the late Darriwilian,concurrent with a prominent decreasing trend in South China.Differences of conodont diversification in these three palaeoplates may be related to their palaeogeography and tectonic history.When conodont diversifications in North China and Tarim are analysed on the background of palaeoenvironments,the main episodes are seen to be partly coincident with second order sea-level changes,particularly in North China.In general,conodont radiation correlates with large scale transgressions.
