Speleothems as indicators of wet and dry periods, 2007, Fairchild Ian John And Mcmillan Emily Anne

Calcareous speleothems provide a record of dripwater composition which in turn is a function of climatic conditions. The historical focus of speleothem palaeoclimate studies has been on the derivation of palaeotemperatures through oxygen isotope studies. However, it is now realized that water availability is a more generally important control on their characteristics. Growth rate and growth morphology in principle should give rise to recognizable changes at low flow. However, accidental plumbing effects during aquifer evolution, can also lead to variations in water supply and it is not easy to distinguish these effects. In areas where there is a strong amount effect on the ?18O composition of atmospheric precipitation, the speleothem ?18O composition can be a direct (and inverse) function of rainfall. High-resolution methods are now available to distinguish the composition and relative abundance of winter and summer precipitation in speleothems which formed from drips of seasonally-varying composition. Two seasonally varying processes can be responsible for significant geochemical effects during the year. Seasonal (normally summer) dryness enhances CO2-degassing which leads to elevated ?13C, Mg/Ca and Sr/Ca in dripwaters, characteristics which are transferred to speleothems. The same effects can arise by enhanced degassing at low PCO2. High-resolution analysis can distinguish the seasonal processes and, where conducted at several time intervals, allows a more confident interpretation of longer-term records.

Speleothems as indicators of wet and dry periods., 2007, Fairchild Ian John, Mcmillan Emily Anne

Calcareous speleothems provide a record of dripwater composition which in turn is a function of climatic conditions. The historical focus of speleothem palaeoclimate studies has been on the derivation of palaeotemperatures through oxygen isotope studies. However, it is now realized that water availability is a more generally important control on their characteristics. Growth rate and growth morphology in principle should give rise to recognizable changes at low flow. However, accidental plumbing effects during aquifer evolution, can also lead to variations in water supply and it is not easy to distinguish these effects. In areas where there is a strong amount effect on the ?18O composition of atmospheric precipitation, the speleothem ?18O composition can be a direct (and inverse) function of rainfall. High-resolution methods are now available to distinguish the composition and relative abundance of winter and summer precipitation in speleothems which formed from drips of seasonally-varying composition. Two seasonallyvarying processes can be responsible for significant geochemical effects during the year. Seasonal (normally summer) dryness enhances CO2-degassing which leads to elevated ?13C, Mg/Ca and Sr/Ca in dripwaters, characteristics which are transferred to speleothems. The same effects can arise by enhanced degassing at low PCO2. High-resolution analysis can distinguish the seasonal processes and, where conducted at several time intervals, allows a more confident interpretation of longer-term records.

Speleothems as indicators of wet and dry periods, 2007, Fairchild I. J. , Mcmillan E. A.

Calcareous speleothems provide a record of dripwater composition which in turn is a function of climatic conditions. The historical focus of speleothem palaeoclimate studies has been on the derivation of palaeotemperatures through oxygen isotope studies. However, it is now realized that water availability is a more generally important control on their characteristics. Growth rate and growth morphology in principle should give rise to recognizable changes at low flow. However, accidental plumbing effects during aquifer evolution, can also lead to variations in water supply and it is not easy to distinguish these effects. In areas where there is a strong amount effect on the δ18O composition of atmospheric precipitation, the speleothem δ18O composition can be a direct (and inverse) function of rainfall. High-resolution methods are now available to distinguish the composition and relative abundance of winter and summer precipitation in speleothems which formed from drips of seasonally-varying composition. Two seasonallyvarying processes can be responsible for significant geochemical effects during the year. Seasonal (normally summer) dryness enhances CO2-degassing which leads to elevated δ13C, Mg/Ca and Sr/Ca in dripwaters, characteristics which are transferred to speleothems. The same effects can arise by enhanced degassing at low PCO2. High-resolution analysis can distinguish the seasonal processes and, where conducted at several time intervals, allows a more confident interpretation of longer-term records.

Isotopic composition of atmospheric precipitation and karstic springs of the north-west slope of the Crimean Mountains, 2011, Dublyansky Y. V. , Klimchouk À. B. , Amelichev G. N. , Tokarev S. V. , Spötl C.

Atmospheric precipitation was sampled for isotopic analyses according to GNIP protocol at two stations in Crimea,  Ukraine: Simferopol (24 months) and Chatyrdag (15 months). In addition, several karstic springs and one well tapping deep karstic  aquifer were sampled. The δD vs. δ 18 O relationship is only slightly differs from global Meteoric Water Line. Variable degrees of  correlation with the air temperature and the precipitation amount suggest that the isotopic composition of precipitation is affected  by several processes (e.g., air temperature and supply of moisture from different sources). Interestingly, drastically different make-ups of precipitation were observed simultaneously at two stations located only 23 km apart.  Waters in seven karstic springs discharging at Dolgorukovsky massif (2), Chatirdag (1), Baidarsky basin (3), and Mangup-kale  (1) have isotopic compositions that follow local meteoric water line but are lighter than weighted annual mean values for their  respective catchment areas. Isotopic composition of the underground stream in Krasnaya (Red) cave is nearly constant and thus,  decoupled from changes in both the isotopic composition of atmospheric precipitation in the recharge area and the flow regime  (flood or base flow). This suggests a strong buffering and homogenizing role of the soil cover and the epikarst zone, as well as  the predominant role of winter recharge on these karst massifs. Still lighter isotopic composition of deep karstic water tapped by  a borehole is tentatively explained by old, pre-Holocene age of this water.

Isotopic composition of atmospheric precipitation and karstic springs of the north-west slope of the Crimean Mountains, 2012, Dublyansky Y. V. , Klimchouk À. B. , Amelichev G. N. , Tokarev S. V. , Spötl C

 

Isotopic composition of atmospheric precipitation and karstic springs of the north-west slope of the Crimean Mountains, 2012, Dublyansky Y. V. , Klimchouk À. B. , Amelichev G. N. , Tokarev S. V. , Spotl, C.

Atmospheric precipitation was sampled for isotopic analyses according to GNIP protocol at two stations in Crimea, Ukraine: Simferopol (24 months) and Chatyrdag (15 months). In addition, several karstic springs and one well tapping deep karstic aquifer were sampled. The δD vs. δ18O relationship is only slightly differs from global Meteoric Water Line. Variable degrees of correlation with the air temperature and the precipitation amount suggest that the isotopic composition of precipitation is affected by several processes (e.g., air temperature and supply of moisture from different sources). Interestingly, drastically different makeups of precipitation were observed simultaneously at two stations located only 23 km apart. Waters in seven karstic springs discharging at Dolgorukovsky massif (2), Chatirdag (1), Baidarsky basin (3), and Mangup-kale (1) have isotopic compositions that follow local meteoric water line but are lighter than weighted annual mean values for their respective catchment areas. Isotopic composition of the underground stream in Krasnaya (Red) cave is nearly constant and thus, decoupled from changes in both the isotopic composition of atmospheric precipitation in the recharge area and the flow regime (flood or base flow). This suggests a strong buffering and homogenizing role of the soil cover and the epikarst zone, as well as the predominant role of winter recharge on these karst massifs. Still lighter isotopic composition of deep karstic water tapped by a borehole is tentatively explained by old, pre-Holocene age of this water