Based on 33 U/Th dates and 1020 oxygen isotopic data from stalagmite Y1 from Yamen Cave, Guizhou Province, China, a record of the Asian Summer Monsoon (ASM) was established. The record covers the last deglaciation and...Based on 33 U/Th dates and 1020 oxygen isotopic data from stalagmite Y1 from Yamen Cave, Guizhou Province, China, a record of the Asian Summer Monsoon (ASM) was established. The record covers the last deglaciation and the early Holocene (from 16.2 to 7.3 ka BP) with an average oxygen isotope resolution of 9 years. The main millennial-scale deglacial events first identified in Greenland (Greenland Interstadial Events: GIS 1e through GIS 1a) and later in China are clearly present in the Y1 record. By analogy to earlier work, we refer to these as Chinese Interstadials (CIS): CIS A.1e to CIS A.1a. The onset of these events in Y1 δ18O records are nominally dated at: 14750±50, 14100±60, 13870±80, 13370±80, and 12990±80 a BP. The end of CIS A.1a or the beginning of the Younger Dryas (YD) event is nominally at 12850±50 a BP and the end of the YD dates to 11500±40 a BP. The δ18O values shift by close to 3‰ during the transition into the Bφlling-Allerφd (BA, the onset of CIS A.1e) and at the end of the YD. Comparisons of Y1 to previously published early Holocene records show no significant phase differences. Thus, the East Asia Monsoon and the Indian Monsoon do not appear to have been out of phase during this interval. The Y1 record confirms earlier work that suggested that solar insolation and North Atlantic climate both affect the Asian Monsoon.展开更多
Systematic mass spectrometric 230Th ages are reported for a Ponies coral reef terrace from Dengloujiao, Leizhou Peninsula, South China Sea. Seven episodes of coral growth were recognized in this terrace: 7125±96,...Systematic mass spectrometric 230Th ages are reported for a Ponies coral reef terrace from Dengloujiao, Leizhou Peninsula, South China Sea. Seven episodes of coral growth were recognized in this terrace: 7125±96, 6764±29, 5826±37, 5006±54, 2543±24, 1915±15, and 1513±22 calendar years before present (cal. aBP). 50% of the coral age popula-tion fall between 7200 and 6600 cal. aBP, marking post-glacial stabilization of global sea level. Considering the facts that (i) Dengloujiao reef flat was measured at 1.6-2.5 m above modern tidal datum plane; (ii) modern Parties corals in the South China Sea are living at least ~1 m below the modern tidal datum plane; (iii) the top 20-30 cm of the reef was eroded; and (iv) crustal subsidence in the region since mid-Holocene was negligible, we conclude that the above age groups record at least two major periods (7200-5000 and 2500-1500 cal. aBP) of high sea-level at least 2.9-3.8 m above the present-day level.展开更多
A 26-cm-long stalagmite (XY2) from Xinya Cave in northeastern Chongqing of China has been ICP-MS 230Th/U dated, showing a depositional hiatus at 2.3 cm depth from the top. The growth of the 2.3―26 cm interval determi...A 26-cm-long stalagmite (XY2) from Xinya Cave in northeastern Chongqing of China has been ICP-MS 230Th/U dated, showing a depositional hiatus at 2.3 cm depth from the top. The growth of the 2.3―26 cm interval determined by four dates was between 57 ka and 70 ka, with a linear growth rate of 0.023 mm/a. We have analyzed 190 samples for δ 18O and δ 13C, mostly in the 2.3―26 cm part. The δ 18O and δ 13C values between 57 ka and 70 ka reveal decadal-to-centennial climatic variability during the glacial in-terval of Marine Isotope Stage 4 (MIS4), exhibiting much higher resolution than that of the published Hulu and Dongge records during this interval. Speleothem δ 18O in eastern China, including our study area can be used as a proxy of summer monsoon strength, with lighter values pointing to stronger summer monsoon and higher precipitation, and vice versa. Two decreases in the δ 18O signature of XY2 record around 59.5 and 64.5 Ka are argued to correspond to the Dansgaard-Oeschger (D-O) events 17 and 18 respectively. The Heinrich event 6 (H6) can be identified in the record as a heavy δ 18O peak around 60 ka, indicating significant weakening of the monsoon in Chongqing during the cold period. The XY2 δ 18O record shows very rapid change toward to the interstadial condition of the D-O event, but more gradual change toward to the cold stadial condition. This phenomenon found in the Greenland ice core records is rarely observed so clearly in previously published speleothem records. According to SPECMAP δ 18O record, the glacial maximum of MIS 4 was around 64.5 ka with the boundary of MIS 3/4 around 60 ka. Unlike the marine record, the speleothem record of XY2, China, exhibits much high fre-quency variations without an apparent glacial maximum during MIS 4. However, the timing of MIS 3/4 boundary seems to be around 60 ka when the H6 terminated, in agreement with the marine chronology. The growth period of sample XY2 during glacial times probably reflects a local karstic routing of water, rather than having cli展开更多
Lianhua Cave in the southern suburb of Zhengjiang City is one of the few hominid fossil-containing localities in Jiangsu Province.A human lower molar and numerous mammalian fossils of 16 species were recovered during ...Lianhua Cave in the southern suburb of Zhengjiang City is one of the few hominid fossil-containing localities in Jiangsu Province.A human lower molar and numerous mammalian fossils of 16 species were recovered during an excavation season in 1981. Based on biostratigraphic studies,this site has been assigned to Late Pleistocene in time. 230Th/ 234U and 227Th/ 230Th age determinations were carried out on two in situ collected mammalian teeth,obtaining broadly consistent dates ranging from 104 to 136 ka,which should be indicative to the age of the hominid tooth.Morphologically the human tooth has been classified to late \%Homo sapiens\%. If correct,the present dates imply an early presence of late \% Homo sapiens\% in the lower reaches of Yangtse River.Parallel studies on Ganqian (Tubo),Liujiang and Bailiandong hominid sites in Guangxi,southern China,yielded similar results.Taken together,much earlier than previously estimated appearance of modern humans might be a general phenomenon in extended areas of China.展开更多
The khondalite series, which are characterized by aluminum-rich gneisses (schists) consisting of sillimanite-garnet-biotite-monzonite gneiss, garnet-biotite-monzonite gneiss, graphite-sillimanite-biotite schist, and g...The khondalite series, which are characterized by aluminum-rich gneisses (schists) consisting of sillimanite-garnet-biotite-monzonite gneiss, garnet-biotite-monzonite gneiss, graphite-sillimanite-biotite schist, and garnet-amphibole two-pyroxene granulites occurring as lenses and layers within gneisses (schists), were discovered in Tula area of western segment of Altyn Tagh. The petrology and geochemistry indicate that the protoliths of aluminum-rich gneisses (schists) are aluminum-rich pelitic and pelitic arenaceous sedimentary rocks, the protoliths of basic granulites are continental tholeiitic basalts. Therefore, the khondalite series may be produced at continental margin. They had suffered granulitic facies metamorphism with peak temperatures of 700–850°C and pressures of 0.8–1.2 GPa. The U-Pb and Pb-Pb isotopic dating of zircons provided the ages of 447–462 Ma representing the ages of peak granulitic metamorphism. The U-Pb dating of detrital zircons from aluminum-rich gneisses yielded older upper intercept ages which reflect the times of older materials derived from source rocks of the gneiss protoliths.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 40231008, 40902053, 90511004, 40672165, 40772216)US National Science Foundation (Grant No. 052535)+4 种基金Science Foundation of Southwest University (Grant No. SWUB-2008047)Foundation of Karst Dynamics Laboratory, MLR (Grant No. 2006-05)National Key Program of Science and Technology (Grant No. 2006BAC01A16)Natural Science Foundation Project of Chongqing (Grant No. CSTC, 2009BA0002)Geological Survey Project of MLR (Grant No. 1212010634805)
文摘Based on 33 U/Th dates and 1020 oxygen isotopic data from stalagmite Y1 from Yamen Cave, Guizhou Province, China, a record of the Asian Summer Monsoon (ASM) was established. The record covers the last deglaciation and the early Holocene (from 16.2 to 7.3 ka BP) with an average oxygen isotope resolution of 9 years. The main millennial-scale deglacial events first identified in Greenland (Greenland Interstadial Events: GIS 1e through GIS 1a) and later in China are clearly present in the Y1 record. By analogy to earlier work, we refer to these as Chinese Interstadials (CIS): CIS A.1e to CIS A.1a. The onset of these events in Y1 δ18O records are nominally dated at: 14750±50, 14100±60, 13870±80, 13370±80, and 12990±80 a BP. The end of CIS A.1a or the beginning of the Younger Dryas (YD) event is nominally at 12850±50 a BP and the end of the YD dates to 11500±40 a BP. The δ18O values shift by close to 3‰ during the transition into the Bφlling-Allerφd (BA, the onset of CIS A.1e) and at the end of the YD. Comparisons of Y1 to previously published early Holocene records show no significant phase differences. Thus, the East Asia Monsoon and the Indian Monsoon do not appear to have been out of phase during this interval. The Y1 record confirms earlier work that suggested that solar insolation and North Atlantic climate both affect the Asian Monsoon.
基金This work wassupported by Australian Kesearch Council, University of Queensland and the National Natural Science Foundation of China (Grant No. 49902014).
文摘Systematic mass spectrometric 230Th ages are reported for a Ponies coral reef terrace from Dengloujiao, Leizhou Peninsula, South China Sea. Seven episodes of coral growth were recognized in this terrace: 7125±96, 6764±29, 5826±37, 5006±54, 2543±24, 1915±15, and 1513±22 calendar years before present (cal. aBP). 50% of the coral age popula-tion fall between 7200 and 6600 cal. aBP, marking post-glacial stabilization of global sea level. Considering the facts that (i) Dengloujiao reef flat was measured at 1.6-2.5 m above modern tidal datum plane; (ii) modern Parties corals in the South China Sea are living at least ~1 m below the modern tidal datum plane; (iii) the top 20-30 cm of the reef was eroded; and (iv) crustal subsidence in the region since mid-Holocene was negligible, we conclude that the above age groups record at least two major periods (7200-5000 and 2500-1500 cal. aBP) of high sea-level at least 2.9-3.8 m above the present-day level.
基金the National Natural Science Foundation of China (Grant Nos. 40672165, 90511004, 40672202)the Academician Special Project of Chongqing Science Committee (Grant No. 2003-7835)
文摘A 26-cm-long stalagmite (XY2) from Xinya Cave in northeastern Chongqing of China has been ICP-MS 230Th/U dated, showing a depositional hiatus at 2.3 cm depth from the top. The growth of the 2.3―26 cm interval determined by four dates was between 57 ka and 70 ka, with a linear growth rate of 0.023 mm/a. We have analyzed 190 samples for δ 18O and δ 13C, mostly in the 2.3―26 cm part. The δ 18O and δ 13C values between 57 ka and 70 ka reveal decadal-to-centennial climatic variability during the glacial in-terval of Marine Isotope Stage 4 (MIS4), exhibiting much higher resolution than that of the published Hulu and Dongge records during this interval. Speleothem δ 18O in eastern China, including our study area can be used as a proxy of summer monsoon strength, with lighter values pointing to stronger summer monsoon and higher precipitation, and vice versa. Two decreases in the δ 18O signature of XY2 record around 59.5 and 64.5 Ka are argued to correspond to the Dansgaard-Oeschger (D-O) events 17 and 18 respectively. The Heinrich event 6 (H6) can be identified in the record as a heavy δ 18O peak around 60 ka, indicating significant weakening of the monsoon in Chongqing during the cold period. The XY2 δ 18O record shows very rapid change toward to the interstadial condition of the D-O event, but more gradual change toward to the cold stadial condition. This phenomenon found in the Greenland ice core records is rarely observed so clearly in previously published speleothem records. According to SPECMAP δ 18O record, the glacial maximum of MIS 4 was around 64.5 ka with the boundary of MIS 3/4 around 60 ka. Unlike the marine record, the speleothem record of XY2, China, exhibits much high fre-quency variations without an apparent glacial maximum during MIS 4. However, the timing of MIS 3/4 boundary seems to be around 60 ka when the H6 terminated, in agreement with the marine chronology. The growth period of sample XY2 during glacial times probably reflects a local karstic routing of water, rather than having cli
文摘Lianhua Cave in the southern suburb of Zhengjiang City is one of the few hominid fossil-containing localities in Jiangsu Province.A human lower molar and numerous mammalian fossils of 16 species were recovered during an excavation season in 1981. Based on biostratigraphic studies,this site has been assigned to Late Pleistocene in time. 230Th/ 234U and 227Th/ 230Th age determinations were carried out on two in situ collected mammalian teeth,obtaining broadly consistent dates ranging from 104 to 136 ka,which should be indicative to the age of the hominid tooth.Morphologically the human tooth has been classified to late \%Homo sapiens\%. If correct,the present dates imply an early presence of late \% Homo sapiens\% in the lower reaches of Yangtse River.Parallel studies on Ganqian (Tubo),Liujiang and Bailiandong hominid sites in Guangxi,southern China,yielded similar results.Taken together,much earlier than previously estimated appearance of modern humans might be a general phenomenon in extended areas of China.
文摘The khondalite series, which are characterized by aluminum-rich gneisses (schists) consisting of sillimanite-garnet-biotite-monzonite gneiss, garnet-biotite-monzonite gneiss, graphite-sillimanite-biotite schist, and garnet-amphibole two-pyroxene granulites occurring as lenses and layers within gneisses (schists), were discovered in Tula area of western segment of Altyn Tagh. The petrology and geochemistry indicate that the protoliths of aluminum-rich gneisses (schists) are aluminum-rich pelitic and pelitic arenaceous sedimentary rocks, the protoliths of basic granulites are continental tholeiitic basalts. Therefore, the khondalite series may be produced at continental margin. They had suffered granulitic facies metamorphism with peak temperatures of 700–850°C and pressures of 0.8–1.2 GPa. The U-Pb and Pb-Pb isotopic dating of zircons provided the ages of 447–462 Ma representing the ages of peak granulitic metamorphism. The U-Pb dating of detrital zircons from aluminum-rich gneisses yielded older upper intercept ages which reflect the times of older materials derived from source rocks of the gneiss protoliths.
