The studies of the oxgen and carbon isotopes of the rainwater in Guilin area, the drip water and the present carbonate deposit in Panlong cave of Guilin show that: (i) as to the general characteristics of the oxygen i...The studies of the oxgen and carbon isotopes of the rainwater in Guilin area, the drip water and the present carbonate deposit in Panlong cave of Guilin show that: (i) as to the general characteristics of the oxygen isotopes of the rainwater within a year and between years, the δ18O values decrease with an increase of air temperature and the rainfall, and the correlation between δ18O values and the mean monthly air temperature is much better than that between δ18O values and the rainfall, and the δ18O values of the rainwater during the summer monsoon are much smaller than those during winter monsoon; (ii) δ18O values of the drip water have a quite good correlation with the δ18O values of the rainwater in the same period; (iii) when the conditions are appropriate, δ13C can be used as an environmental proxy, that is, the smaller δ13C of speleothems is, the larger the proportion of C3 plants is and the more plentiful the rainfall is. On the contrary, C4plants may be prevailing or the environment may be a stony desert caused by climate changes or human activity.展开更多
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
Understanding of hydrological processes in caves is important to help us interpret paleoclimate records from speleothems. In this study, we integrated hydrogeological and hydrogeochemical properties to characterize th...Understanding of hydrological processes in caves is important to help us interpret paleoclimate records from speleothems. In this study, we integrated hydrogeological and hydrogeochemical properties to characterize the hydraulic behavior of karst waters in the Heshang Cave, Central China. Using geological and topographical analyses, we identified regional watershed boundaries and hydrogeological connections that were controlled by anticlinal geometry and faults. Water samples were collected from the Heshang Cave and potential recharge sites. Geochemical data of c（Sr^2＋）/c（Ca^2＋） and c（Mg^2＋）/c（Ca^2＋） ratios suggest that the drainage system in Heshang Cave consists of two flow paths. For vadose waters, including drip water and rimstone pool water, c（Sr^2＋）/c（Ca^2＋） ratio ranges from 0.000 6 to 0.001 1, and c（Mg^2＋）/c（Ca^2＋） ratio ranges from 0.97 to 1.1, indicating that recharge was mainly from rainfall infiltration through the overlying Cambrian dolomite stratum. In contrast, slope current and underground river waters have higher c（Sr^2＋）/c（Ca^2＋） ratios （values from 0.002 2 to 0.002 8）, and lower c（Mg2＋）/c（Ca^2＋） ratios （values from 0.50 to 0.64）. These waters show homogeneous isotopic composition （δ^18O： -7.15‰- -6.95‰; δD： -52.73‰- -51.31‰）, implying recharge of allogeneic water from the Xiaocr River via karst conduits that pass through Ordovician limestone and Cambrian dolomite stratum.展开更多
Stalagmite is one kind of secondary carbonates formed in limestone caves(speleothem). After cave water droplets containing Ca2+and HCO3 drip onto floor, carbonate in the water might become supersaturated due to CO2 de...Stalagmite is one kind of secondary carbonates formed in limestone caves(speleothem). After cave water droplets containing Ca2+and HCO3 drip onto floor, carbonate in the water might become supersaturated due to CO2 degassing under certain conditions, resulting in the formation of stalagmite in a process year after year. Stalagmite is one of important geological archives for paleoclimate research. The advantages include wide spatial distribution, suitable for U-Th and U-Pb dating, enriched in climate proxies, continuity, long time span, comparability and lower sampling cost etc. These factors have propelled stalagmite paleoclimate research to the forefront of global paleoclimatology with an irreplaceable role. The stalagmite paleoclimate study started in the western countries, mainly in Europe and America in 1960 s–1970 s, while the relevant research in China was progressively developed in the 1980 s–1990 s after the Reform and Opening up. Although there was a huge gap between the overall research level in China and western countries, a solid research foundation, as well as a number of talent teams were established during the period. In the 21 st century, starting from the publication of stalagmite records from Hulu Cave in Nanjing in 2001, the stalagmite paleoclimate research in China has ushered in a flourishing development and a real leap on the basis of international cooperation, resulting in significant international impacts. The landmark achievements, including establishment of the world’s longest(640000 years) East Asian monsoon stalagmite record, as well as the longest Indian monsoon(280000 years),South American monsoon(250000 years), North American westerly climate(330000 years), Central Asian westerly climate(135000 years), and northwestern China westerly climate(500000 years), have laid a milestone in the paleoclimate study in these climate domains. Importantly, these stalagmite records have revealed the relationship of Asian monsoon variations with solar insolation climate change in polar regions展开更多
文摘The studies of the oxgen and carbon isotopes of the rainwater in Guilin area, the drip water and the present carbonate deposit in Panlong cave of Guilin show that: (i) as to the general characteristics of the oxygen isotopes of the rainwater within a year and between years, the δ18O values decrease with an increase of air temperature and the rainfall, and the correlation between δ18O values and the mean monthly air temperature is much better than that between δ18O values and the rainfall, and the δ18O values of the rainwater during the summer monsoon are much smaller than those during winter monsoon; (ii) δ18O values of the drip water have a quite good correlation with the δ18O values of the rainwater in the same period; (iii) when the conditions are appropriate, δ13C can be used as an environmental proxy, that is, the smaller δ13C of speleothems is, the larger the proportion of C3 plants is and the more plentiful the rainfall is. On the contrary, C4plants may be prevailing or the environment may be a stony desert caused by climate changes or human activity.
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supported by the National Natural Science Foundation of China (Nos.91125009,91325101,and 06013024)
文摘Understanding of hydrological processes in caves is important to help us interpret paleoclimate records from speleothems. In this study, we integrated hydrogeological and hydrogeochemical properties to characterize the hydraulic behavior of karst waters in the Heshang Cave, Central China. Using geological and topographical analyses, we identified regional watershed boundaries and hydrogeological connections that were controlled by anticlinal geometry and faults. Water samples were collected from the Heshang Cave and potential recharge sites. Geochemical data of c（Sr^2＋）/c（Ca^2＋） and c（Mg^2＋）/c（Ca^2＋） ratios suggest that the drainage system in Heshang Cave consists of two flow paths. For vadose waters, including drip water and rimstone pool water, c（Sr^2＋）/c（Ca^2＋） ratio ranges from 0.000 6 to 0.001 1, and c（Mg^2＋）/c（Ca^2＋） ratio ranges from 0.97 to 1.1, indicating that recharge was mainly from rainfall infiltration through the overlying Cambrian dolomite stratum. In contrast, slope current and underground river waters have higher c（Sr^2＋）/c（Ca^2＋） ratios （values from 0.002 2 to 0.002 8）, and lower c（Mg2＋）/c（Ca^2＋） ratios （values from 0.50 to 0.64）. These waters show homogeneous isotopic composition （δ^18O： -7.15‰- -6.95‰; δD： -52.73‰- -51.31‰）, implying recharge of allogeneic water from the Xiaocr River via karst conduits that pass through Ordovician limestone and Cambrian dolomite stratum.
基金supported by the National Natural Science Foundation of China(Grant Nos.41888101&41731174)
文摘Stalagmite is one kind of secondary carbonates formed in limestone caves(speleothem). After cave water droplets containing Ca2+and HCO3 drip onto floor, carbonate in the water might become supersaturated due to CO2 degassing under certain conditions, resulting in the formation of stalagmite in a process year after year. Stalagmite is one of important geological archives for paleoclimate research. The advantages include wide spatial distribution, suitable for U-Th and U-Pb dating, enriched in climate proxies, continuity, long time span, comparability and lower sampling cost etc. These factors have propelled stalagmite paleoclimate research to the forefront of global paleoclimatology with an irreplaceable role. The stalagmite paleoclimate study started in the western countries, mainly in Europe and America in 1960 s–1970 s, while the relevant research in China was progressively developed in the 1980 s–1990 s after the Reform and Opening up. Although there was a huge gap between the overall research level in China and western countries, a solid research foundation, as well as a number of talent teams were established during the period. In the 21 st century, starting from the publication of stalagmite records from Hulu Cave in Nanjing in 2001, the stalagmite paleoclimate research in China has ushered in a flourishing development and a real leap on the basis of international cooperation, resulting in significant international impacts. The landmark achievements, including establishment of the world’s longest(640000 years) East Asian monsoon stalagmite record, as well as the longest Indian monsoon(280000 years),South American monsoon(250000 years), North American westerly climate(330000 years), Central Asian westerly climate(135000 years), and northwestern China westerly climate(500000 years), have laid a milestone in the paleoclimate study in these climate domains. Importantly, these stalagmite records have revealed the relationship of Asian monsoon variations with solar insolation climate change in polar regions
