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
Through a combined analysis of sedimentary characteristics, C and O isotopes, Mg and Sr trace elements of a stalagmite from Heshang Cave, Hubei, with uranium-series dating, alaeo-palaeoclimatic and palaeoenvironmental...Through a combined analysis of sedimentary characteristics, C and O isotopes, Mg and Sr trace elements of a stalagmite from Heshang Cave, Hubei, with uranium-series dating, alaeo-palaeoclimatic and palaeoenvironmental information from 19.0ka to 6.9ka in the Hubei area is obtained. The Average resolution is 17a, and the local resolution is 7a. The following results are obtained: (1) from 19.0-16.6 kaBP: C and O isotope is lighter, the climate is cold and wet;(2) 16.6-11.1 kaBP: C, O isotope is a little heavy, temperature rises, rainfall is inclined to be little;(3) 11.1-10.3 kaBP: an excursion during dry and hot period responds to Younger Dryas Event;(4) 10.3-6.9 kaBP: C, O Isotope is lighter, but Mg/Sr value is bigger, which shows temperature is continuing rising and rainfall is greater. These reflect the variation tends from wet-cold climate, to dry-hot climate, and to wet-warm climate in history, and some climatic variation trends of thousand years and hundred years cycle are got.展开更多
Stalagmite growth rates are usually considered to reflect changes in paleoclimate and paleoenvironment.However,how exactly growth rates are affected by climate and environment is still unclear.We launched a monitoring...Stalagmite growth rates are usually considered to reflect changes in paleoclimate and paleoenvironment.However,how exactly growth rates are affected by climate and environment is still unclear.We launched a monitoring and modeling program that lasted approximately 4 years on two active drip sites in Heshang Cave,central China.We collected comprehensive quantitative data on growth rates,cave temperature,CO2 concentration,drip rate and drip-water chemistry to better understand the relationship between stalagmite growth and cave environment.By laying out glass substrates,we successfully grew stalagmite calcite crystals with rhombic characteristics,and quantified growth rates by measuring the long and short axes of calcite crystals under a microscope.Combined with coeval environmental data,we explicitly examined the roles of cave temperature,drip rate and drip-water chemistry in controlling the micro-scale growth of stalagmite calcite.Results show that growth of stalagmite calcite crystals at two drip sites exhibited similar seasonal variations - generally faster in the summer months,at ～3 μm d-1,and slower during the late winter to early spring,at ～1.5 μm d-1.Variations in calcite growth rates were mainly determined by changes in cave temperature,with the growth rate increasing by 8.1%/°C and 6.6%/°C at the two locations.This indicates the potential use of stalagmite growth rates as a seasonal-resolution paleo-temperature proxy in some ventilated caves.On the other hand,the effect of drip rate and drip-water Ca2+ and SIC values on growth rates were not significant.展开更多
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In this study, field sample collection is supported and helped by associate professor Wan Junwei.professor Han Qingzhi and other people in Engineering Institute.of China University of geosciences (Wuhan). The authors would like to thank them all. This wo
文摘Through a combined analysis of sedimentary characteristics, C and O isotopes, Mg and Sr trace elements of a stalagmite from Heshang Cave, Hubei, with uranium-series dating, alaeo-palaeoclimatic and palaeoenvironmental information from 19.0ka to 6.9ka in the Hubei area is obtained. The Average resolution is 17a, and the local resolution is 7a. The following results are obtained: (1) from 19.0-16.6 kaBP: C and O isotope is lighter, the climate is cold and wet;(2) 16.6-11.1 kaBP: C, O isotope is a little heavy, temperature rises, rainfall is inclined to be little;(3) 11.1-10.3 kaBP: an excursion during dry and hot period responds to Younger Dryas Event;(4) 10.3-6.9 kaBP: C, O Isotope is lighter, but Mg/Sr value is bigger, which shows temperature is continuing rising and rainfall is greater. These reflect the variation tends from wet-cold climate, to dry-hot climate, and to wet-warm climate in history, and some climatic variation trends of thousand years and hundred years cycle are got.
基金supported by the National Natural Science Foundation of China(40531004 and 41072262)
文摘Stalagmite growth rates are usually considered to reflect changes in paleoclimate and paleoenvironment.However,how exactly growth rates are affected by climate and environment is still unclear.We launched a monitoring and modeling program that lasted approximately 4 years on two active drip sites in Heshang Cave,central China.We collected comprehensive quantitative data on growth rates,cave temperature,CO2 concentration,drip rate and drip-water chemistry to better understand the relationship between stalagmite growth and cave environment.By laying out glass substrates,we successfully grew stalagmite calcite crystals with rhombic characteristics,and quantified growth rates by measuring the long and short axes of calcite crystals under a microscope.Combined with coeval environmental data,we explicitly examined the roles of cave temperature,drip rate and drip-water chemistry in controlling the micro-scale growth of stalagmite calcite.Results show that growth of stalagmite calcite crystals at two drip sites exhibited similar seasonal variations - generally faster in the summer months,at ～3 μm d-1,and slower during the late winter to early spring,at ～1.5 μm d-1.Variations in calcite growth rates were mainly determined by changes in cave temperature,with the growth rate increasing by 8.1%/°C and 6.6%/°C at the two locations.This indicates the potential use of stalagmite growth rates as a seasonal-resolution paleo-temperature proxy in some ventilated caves.On the other hand,the effect of drip rate and drip-water Ca2+ and SIC values on growth rates were not significant.
