论文部分内容阅读
Carbon isotope(δ~(13)C_(org)) 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 positiveδ~(13)C_(org) 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 inδ~(13)C_(org) from the uppermost Silurian to the lowermost Devonian.Theδ~(13)C_(org) 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 deposits.
Carbon isotope (δ ~ (13) C_ (org)) analyzes 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 δ ~ (13) C_ (org) shifts 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 lodont 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 shiftinδ ~ (13) C_ (org) from the uppermost Silurian to the lowermost Devonian.Theδ ~ (13) C_ (org) variations across the Silurian / Devonian Boundary (SDB) at the two sections in South China exhibit a shift in carbon isotopic composition s imilar 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 XX-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 wi th non-marine deposits.