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
The concentration of 39 trace elements in coal from the late Permian taken from the eastern Yunnan-western Guizhou region was determined using inductively coupled plasma mass spectrometry. It was found that the mean c...The concentration of 39 trace elements in coal from the late Permian taken from the eastern Yunnan-western Guizhou region was determined using inductively coupled plasma mass spectrometry. It was found that the mean content of Ti, V, Cr, Mo, Co, Ni, Y, and Zr is higher than the national average. The occurrence of Mn, Ni, and Co in the different coalfields is distinctly different. Most of the enriched transition metal elements exist mainly as inorganic minerals. In the Zhina coalfield, Co, Ni, and Nb are primarily associated with sulfur. Mn, Cs, and Mo are mostly sulfides. Almost all Co was organic and a significant part of the Ni is also organic in the Liupanshui coalfield. Cs, Co, and Ni are related to sulfur in the coal taken from eastern Yunnan. Carbonate is the main form of Mn in the coal from eastern Yunnan and the Liupanshui coalfield. Ti is the oxide in the coal samples where Ti is enriched. Zr is in the form of zircon in the samples where Zr is enriched. The situation for most of the transition metal elements is consistent with terrestrial genesis. Coal seams are universally influenced by the sea. The strongly seawater effected peat bog with a reductive and alkaline environment favors the relative enrichment of Mn. A reducing environment is conducive to transition metal element enrichment.展开更多
Based on an analysis of the circulation in May associated with the interannual variation of the onset of Yunnan’s rainy season, this study examined the rela-tionship between Arctic Oscillation (AO) and the onset timi...Based on an analysis of the circulation in May associated with the interannual variation of the onset of Yunnan’s rainy season, this study examined the rela-tionship between Arctic Oscillation (AO) and the onset timing of the rainy sea-son by using the NCEP/NCAR reanalysis and observational precipitation data for 1961-2010. The results indicated that, on an interannual time scale, intense Asian summer monsoon and an active EU-pattern wave train circulation in its positive phase, associated with a cold cyclonic cell covering the western part of the East Asian subtropical westerly jet (EASWJ), jointly contributed to the onset of the rainy season in May. Otherwise, the onset might be suppressed. The cold cyclonic cell over East Asia likely led to the southward shift and enhancement of EASWJ as well as its secondary circulation around the jet entrance, which could provide a favorable dynamic and thermal condition for rainfalls in Yunnan as was revealed in previous studies on 10 - 30-day time scale. Further examination showed that the preceding wintertime AO played a significant role in the timing of the onset of the rainy season before the mid-1980s’ by mostly modulating the wave-train-like circulation over East Asia in May. During that time period, when the AO index of the previous winter was positive (negative), Yunnan’s rainy season tended to begin earlier (later) than normal. Correspond-ingly, the precipitation in May was also closely linked to wintertime AO.展开更多
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.
基金financially supported by the National Natural Science Foundation of China (No. 40730422)
文摘The concentration of 39 trace elements in coal from the late Permian taken from the eastern Yunnan-western Guizhou region was determined using inductively coupled plasma mass spectrometry. It was found that the mean content of Ti, V, Cr, Mo, Co, Ni, Y, and Zr is higher than the national average. The occurrence of Mn, Ni, and Co in the different coalfields is distinctly different. Most of the enriched transition metal elements exist mainly as inorganic minerals. In the Zhina coalfield, Co, Ni, and Nb are primarily associated with sulfur. Mn, Cs, and Mo are mostly sulfides. Almost all Co was organic and a significant part of the Ni is also organic in the Liupanshui coalfield. Cs, Co, and Ni are related to sulfur in the coal taken from eastern Yunnan. Carbonate is the main form of Mn in the coal from eastern Yunnan and the Liupanshui coalfield. Ti is the oxide in the coal samples where Ti is enriched. Zr is in the form of zircon in the samples where Zr is enriched. The situation for most of the transition metal elements is consistent with terrestrial genesis. Coal seams are universally influenced by the sea. The strongly seawater effected peat bog with a reductive and alkaline environment favors the relative enrichment of Mn. A reducing environment is conducive to transition metal element enrichment.
文摘Based on an analysis of the circulation in May associated with the interannual variation of the onset of Yunnan’s rainy season, this study examined the rela-tionship between Arctic Oscillation (AO) and the onset timing of the rainy sea-son by using the NCEP/NCAR reanalysis and observational precipitation data for 1961-2010. The results indicated that, on an interannual time scale, intense Asian summer monsoon and an active EU-pattern wave train circulation in its positive phase, associated with a cold cyclonic cell covering the western part of the East Asian subtropical westerly jet (EASWJ), jointly contributed to the onset of the rainy season in May. Otherwise, the onset might be suppressed. The cold cyclonic cell over East Asia likely led to the southward shift and enhancement of EASWJ as well as its secondary circulation around the jet entrance, which could provide a favorable dynamic and thermal condition for rainfalls in Yunnan as was revealed in previous studies on 10 - 30-day time scale. Further examination showed that the preceding wintertime AO played a significant role in the timing of the onset of the rainy season before the mid-1980s’ by mostly modulating the wave-train-like circulation over East Asia in May. During that time period, when the AO index of the previous winter was positive (negative), Yunnan’s rainy season tended to begin earlier (later) than normal. Correspond-ingly, the precipitation in May was also closely linked to wintertime AO.
