Carbon isotope （δ13Corg） analyses of non-marine clastic rocks and neritic carbonates and black shales spanning the Silurian/Devonian transition are compared from two richly fossiliferous sequences in Qujing of East...Carbon isotope （δ13Corg） analyses of non-marine clastic rocks and neritic carbonates and black shales spanning the Silurian/Devonian transition are compared from two richly fossiliferous sequences in Qujing of East Yunnan and Zoige of Sichuan, South China. The two sections, Xishancun and Putonggou sections in South China, reveal positive δ13Corg shifts happening in the Upper Pridoli and Lower Devonian and reaching peak values as heavy as -25.2‰ （Xishancun） and -19.9‰（Putonggou） in the lowermost Lochkovian following the first occurrence of the thelodont Parathelodus and the conodont Icriodus woschmidti woschmidti （only in Putonggou Section and together with Protathyris-Lanceomyonia brachiopod fauna）. These results replicate a globally known positive shift in δ13Corg from the uppermost Silurian to the lowermost Devonian. The δ13Corg variations across the Silurian/Devonian Boundary （SDB） at the two sections in South China exhibit a shift in carbon isotopic composition similar to the detailed SDB curves from the borehole Klonk-1 drilled at top of the Klonk Global Standard Stratotype-Section and Point （GSSP） in the Prague Basin, Czech Republic. In addition, four microvertebrate assemblages, including the Liaojiaoshan, Xishancun, Yanglugou and Xiaputonggou assemblages, are recognized from the Silurian/Devonian transition exposed in the Xishancun and Putonggou sections, respectively. The results from both carbon isotope stratigraphy and microvertebrate assemblage sequences suggest that the SDB in South China is located at the base of the Xishancun Formation （between sample QX-20 and sample QX-21） in the Xishancun Section and the lower part of the Xiaputonggou Formation （between sample ZP-09 and sample ZP-10） in the Putonggou Section. The isotopic trend for organic carbon together with the changes of microvertebrate remains across the SDB can offer an approach to a potential correlation of the SDB from different sedimentary facies, which help to correlate the marine with non-marine展开更多
The Silurian-Devonian interval is an essential period in Earth history for witnessing the rise of sarcopterygian fishes and terrestrial vascular plants.In addition to its implication in global stratigraphic correlatio...The Silurian-Devonian interval is an essential period in Earth history for witnessing the rise of sarcopterygian fishes and terrestrial vascular plants.In addition to its implication in global stratigraphic correlation,the precise location of the Silurian-Devonian boundary(SDB)in East Yunnan closely relates to the minimal and maximal estimated dates for the lungfish-tetrapod split.Several geochemical indicators including the values and curves ofδ^(13)C_(org),δ^(13)Ccarb and TOC are obtained from the continuous SDB sequence in Dahe,Yiliang County,East Yunnan.The results reveal the significant positiveδ^(13)C_(org) shifts in the upper part of the Yulungssu Formation and the lower part of the Xishancun Formation,and the peak value(−20.0‰)in the sample YD-25 from the lowermost of the Xishancun Formation,replicating theδ^(13)C_(org) variation trend from the uppermost Silurian to the lowermost Devonian worldwide.Theδ^(13)C_(org) variation across the SDB at the Dahe Section resembles the SDB curve from the borehole Klonk-1 drilled at the top of the Klonk GSSP in the Prague Basin,Czech Republic.As such,we place the SDB in the Dahe Area between the samples of YD-17 and YD-18 from the lowermost part of the Xishancun Formation.This SDB assignment is corroborated by new findings of Early Devonian thelodont Parathelodus from the lower part of the Xishancun Formation in Qujing Area.The resolution of the SDB in Dahe,coupled with available paleontological data and the biostratigraphic zonation in East Yunnan,has provided vital data for the geological ages of the fish-bearing strata in East Yunnan.The earliest rhipidistian Youngolepis from the Xishancun Formation(Lochkovian,Devonian)and earliest stem-sarcopterygian Psarolepis from the Kuanti Formation(Ludfordian,Silurian)in East Yunnan indicate that the split between lungfish and tetrapods occurred between 426.5 and 416.0 Ma.展开更多
基金supported by the Basic Research Projects of Science and Technology: Research on standard sections and some GSSPs in China (2006FY120300-6)the Major State Basic Research Projects (2006CB806400) of MST of China+2 种基金the Creative Research Project of CAS (KZCX2-YW-156)the National Natural Science Foundation of China (40930208)the Important National Science and Technology Specific Projects (2008ZX05008-001)
文摘Carbon isotope （δ13Corg） analyses of non-marine clastic rocks and neritic carbonates and black shales spanning the Silurian/Devonian transition are compared from two richly fossiliferous sequences in Qujing of East Yunnan and Zoige of Sichuan, South China. The two sections, Xishancun and Putonggou sections in South China, reveal positive δ13Corg shifts happening in the Upper Pridoli and Lower Devonian and reaching peak values as heavy as -25.2‰ （Xishancun） and -19.9‰（Putonggou） in the lowermost Lochkovian following the first occurrence of the thelodont Parathelodus and the conodont Icriodus woschmidti woschmidti （only in Putonggou Section and together with Protathyris-Lanceomyonia brachiopod fauna）. These results replicate a globally known positive shift in δ13Corg from the uppermost Silurian to the lowermost Devonian. The δ13Corg variations across the Silurian/Devonian Boundary （SDB） at the two sections in South China exhibit a shift in carbon isotopic composition similar to the detailed SDB curves from the borehole Klonk-1 drilled at top of the Klonk Global Standard Stratotype-Section and Point （GSSP） in the Prague Basin, Czech Republic. In addition, four microvertebrate assemblages, including the Liaojiaoshan, Xishancun, Yanglugou and Xiaputonggou assemblages, are recognized from the Silurian/Devonian transition exposed in the Xishancun and Putonggou sections, respectively. The results from both carbon isotope stratigraphy and microvertebrate assemblage sequences suggest that the SDB in South China is located at the base of the Xishancun Formation （between sample QX-20 and sample QX-21） in the Xishancun Section and the lower part of the Xiaputonggou Formation （between sample ZP-09 and sample ZP-10） in the Putonggou Section. The isotopic trend for organic carbon together with the changes of microvertebrate remains across the SDB can offer an approach to a potential correlation of the SDB from different sedimentary facies, which help to correlate the marine with non-marine
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(Grant Nos.XDB26000000,XDA19050102)the National Natural Science Foundation of China(Grant Nos.42072026,41972006&41530102)the Key Research Program of Frontier Sciences of CAS(Grant No.QYZDJ-SSWDQC002).
文摘The Silurian-Devonian interval is an essential period in Earth history for witnessing the rise of sarcopterygian fishes and terrestrial vascular plants.In addition to its implication in global stratigraphic correlation,the precise location of the Silurian-Devonian boundary(SDB)in East Yunnan closely relates to the minimal and maximal estimated dates for the lungfish-tetrapod split.Several geochemical indicators including the values and curves ofδ^(13)C_(org),δ^(13)Ccarb and TOC are obtained from the continuous SDB sequence in Dahe,Yiliang County,East Yunnan.The results reveal the significant positiveδ^(13)C_(org) shifts in the upper part of the Yulungssu Formation and the lower part of the Xishancun Formation,and the peak value(−20.0‰)in the sample YD-25 from the lowermost of the Xishancun Formation,replicating theδ^(13)C_(org) variation trend from the uppermost Silurian to the lowermost Devonian worldwide.Theδ^(13)C_(org) variation across the SDB at the Dahe Section resembles the SDB curve from the borehole Klonk-1 drilled at the top of the Klonk GSSP in the Prague Basin,Czech Republic.As such,we place the SDB in the Dahe Area between the samples of YD-17 and YD-18 from the lowermost part of the Xishancun Formation.This SDB assignment is corroborated by new findings of Early Devonian thelodont Parathelodus from the lower part of the Xishancun Formation in Qujing Area.The resolution of the SDB in Dahe,coupled with available paleontological data and the biostratigraphic zonation in East Yunnan,has provided vital data for the geological ages of the fish-bearing strata in East Yunnan.The earliest rhipidistian Youngolepis from the Xishancun Formation(Lochkovian,Devonian)and earliest stem-sarcopterygian Psarolepis from the Kuanti Formation(Ludfordian,Silurian)in East Yunnan indicate that the split between lungfish and tetrapods occurred between 426.5 and 416.0 Ma.
