Search results for "Stalagmite"
showing 10 items of 46 documents
230Th/U-dating of a late Holocene low uranium speleothem from Cuba
2010
We present 22 U-series ages for a stalagmite from north-western Cuba based on multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) and thermal ionisation mass spectrometry (TIMS). Our results reveal that the stalagmite continuously grew within the last ~1400a. Low uranium content of the sample and thus, extremely low 230Th concentrations limit the precision and accuracy of 230Th/U-dating by TIMS. Samples measured by MC-ICPMS show a high variability of 232Th content along the growth axis with some sections significantly affected by initial 230Th from a detrital phase. An a-priori bulk earth ratio for (238U/232Th) cannot be used to accurately account for this initial 230Th.…
Holocene climate variability in Central Germany and a potential link to the polar North Atlantic: A replicated record from three coeval speleothems
2016
Here, we present high-resolution trace element and stable isotope records from three coeval Holocene stalagmites from the Herbstlabyrinth cave system, Central Germany. All stalagmites were precisely dated using MC-ICPMS 230Th/U-dating. One stalagmite started to grow at 13.62 ± 0.13 ka BP, covering the late Glacial; the other two speleothems started to grow at 11.13 ± 0.08 and 10.26 ± 0.08 ka BP, respectively. The combined record covers the entire Holocene. The interpretation of the different climate proxies is supported by data from a detailed cave monitoring programme. Cold conditions during the Younger Dryas are reflected by intermittent stalagmite growth at the Herbstlabyrinth. The δ18O…
Cuban stalagmite suggests relationship between Caribbean precipitation and the Atlantic Multidecadal Oscillation during the past 1.3 ka
2012
Here we present the first high-resolution δ18O record of a stalagmite from western Cuba. The record reflects precipitation variability in the northwestern Caribbean during the last 1.3 ka and exhibits a correlation to the Atlantic Multidecadal Oscillation (AMO). This suggests a relationship between Caribbean rainfall intensity and North Atlantic sea-surface temperature (SST) anomalies. A potential mechanism for this relationship may be the strength of the Thermohaline Circulation (THC). For a weaker THC, lower SSTs in the North Atlantic possibly lead to a southward shift of the Intertropical Convergence Zone and drier conditions in Cuba. Thus, this Cuban stalagmite records drier conditions…
Paleoclimate variability during the Blake geomagnetic excursion (MIS 5d) deduced from a speleothem record
2014
To evaluate possible connections between climate and the Earth's magnetic field, we examine paleoclimate proxies in a stalagmite (PA-8) recording the Blake excursion (∼112–∼116.4 ka) from Cobre cave (N Spain). Trace element, δ13C, δ18O, δ234U, fluorescent lamination, growth rate, and paleomagnetic records were synchronized using a floating lamina-counted chronology constrained by U–Th dates, providing a high-resolution multi-proxy paleoclimate record for MIS 5d. The alpine cave setting and the combination of proxies contributed to improve the confidence of the paleoclimatic interpretation. Periods of relatively warm and humid climate likely favored forest development and resulted in high sp…
Holocene climate variability in Sicily from a discontinuous stalagmite record and the Mesolithic to Neolithic transition
2006
AbstractFabric and stable isotopic composition of a Holocene stalagmite (CR1) from a cave in northern Sicily record changes in paleorainfall in the early Holocene. High δ13C stable isotope values in the calcite deposited from ca. 8500 to ca. 7500 yr ago are interpreted as reflecting periods of high rainfall. The wet phase was interrupted by two periods of multi-century duration characterized by relatively cool and dry winters centered at ca. 8200 and ca. 7500 yr ago, highlighted by low δ13C and δ18O values. A high variability of δ13C values is recorded from ca. 7500 to ca. 6500 yr ago and indicates that the transition from a pluvial early Holocene to the present-day climate conditions was p…
Reconstruction of drip-water δ<sup>18</sup>O based on calcite oxygen and clumped isotopes of speleothems from Bunker Cave…
2013
Abstract. The geochemical signature of many speleothems used for reconstruction of past continental climates is affected by kinetic isotope fractionation. This limits quantitative paleoclimate reconstruction and, in cases where the kinetic fractionation varies with time, also affects relative paleoclimate interpretations. In carbonate archive research, clumped isotope thermometry is typically used as proxy for absolute temperatures. In the case of speleothems, however, clumped isotopes provide a sensitive indicator for disequilibrium effects. The extent of kinetic fractionation co-varies in Δ47 and δ18O so that it can be used to account for disequilibrium in δ18O and to extract the past dri…
Modelling the δ18O value of cave drip water and speleothem calcite
2010
Abstract Stable isotope signals recorded in speleothems have provided important insights about past climate variability in recent years. Quantitative reconstruction of mean annual temperature and the amount of precipitation, however, remains difficult because the stable isotope signals are influenced by various processes. Here we present a drip water model, which shows how these climate parameters affect the oxygen isotope signal of cave drip water. In the model the dependence of the δ 18 O value of drip water on mean annual temperature is established by correlation to the amount of winter precipitation and winter temperature. Application of the model to two caves in western Germany reveals…
Detection and origin of different types of annual laminae in recent stalagmites from Zoolithencave, southern Germany: Evaluation of the potential for…
2016
Abstract. An arrangement of three stalagmites from Zoolithencave (southern Germany) was analysed for different types of annual laminae using both microscopic and geochemical methods. The speleothems show visible laminae (consisting of a clear and a brownish, pigmented layer pair) as well as fluorescent and elemental laminae. The age of the speleothems was constrained to 1800 to 1970 AD by 14C-dating of a charcoal piece below the speleothems, detection of the 14C bomb peak, as well as counting of annual laminae. Dating by the 230Th/U-method was impossible due to detrital contamination. On the annual time-scale, the variability of Mg, Ba, and Sr is controlled by Prior Calcite Precipitation (P…
Determination of aragonite trace element distribution coefficients from speleothem calcite–aragonite transitions.
2016
The processes that govern the incorporation of (trace) elements into speleothems can often be linked to environmental changes. Although element incorporation into speleothem calcite is now reasonably well understood, current knowledge regarding trace element variability in speleothem aragonite is very limited. Of particular interest is whether trace element distribution coefficients are above or below one in order to assess the extent to which prior aragonite precipitation has affected speleothem aragonite trace element records. This study uses nine calcite-to-aragonite transitions in seven speleothems from diverse environmental settings to derive the first quantitative estimates of the dis…
Processes affecting the stable isotope composition of calcite during precipitation on the surface of stalagmites: Laboratory experiments investigatin…
2016
Abstract We present a theoretical derivation of the exchange time, τex, needed to establish isotopic equilibrium between atmospheric CO2 in a cave and HCO3− dissolved in a thin water film covering the surface of a speleothem. The result is τ ex = τ red ex · [ HCO 3 - ] K H · p CO 2 cave , where τ red ex depends on the depth, a, of the water film and on temperature. [ HCO 3 - ] is the concentration of bicarbonate, p CO 2 cave the partial pressure of CO2, and KH is Henry’s constant. To test the theory we prepared stagnant or flowing thin films of a NaHCO3 solution and exposed them at 20 °C to an CO2 containing atmosphere of p CO 2 500, 12,500, or 25,000 ppmV and defined isotope composition. T…