Search results for "Cave"
showing 10 items of 606 documents
Coarse-grained cryogenic aragonite as end-member of mineral formation in dolomite caves
2018
Abstract Cryogenic carbonate particles (single crystals and aggregates) have recently been recognized as important witnesses of permafrost dynamics, as they can be used to estimate the thickness and timing of development of permafrost. In this study, the petrography and geochemistry of coarse-grained cryogenic aragonite (CGCAr) identified in Zoolithen Cave in NE Bavaria, Germany, are described in detail for the first time. We provide a sequence of carbonate precipitation during freezing, where CGCAr mark the final crystallization phase in freezing water on ice. Our results support the notion that host rock composition, solution chemistry, and cave ventilation play an important role for arag…
Constraining speleothem oxygen isotope disequilibrium driven by rapid CO2 degassing and calcite precipitation: Insights from monitoring and modeling
2020
Abstract Oxygen isotopes are the most commonly applied speleothem proxy for reconstructing Quaternary changes in precipitation and/or temperature. These interpretations are either limited to qualitative wetting and drying trends or rely on theoretical, experimental and/or empirical equilibrium isotope fractionation factors for more quantitative constraints. These various fractionation factors have similar temperature sensitivities, but their absolute values differ, and cave calcite does not appear to generally precipitate in isotopic equilibrium with its drip water. Rapid CO2 degassing paired with calcite precipitation, both occurring under disequilibrium conditions, are a set of mechanisms…
Hydrogeochemistry and fractionation pathways of Mg isotopes in a continental weathering system: Lessons from field experiments
2012
Abstract The potential of magnesium isotope records from cave carbonate archives (speleothems) has been documented but remains underexplored. This is due to the limited knowledge regarding the complex suite of physico-chemical and biological disequilibrium fractionation processes affecting meteoric fluids in the soil zone, the carbonate hostrock and calcite precipitation in the cave. This study presents δ 26 Mg data from a monitored cave in Germany (Bunker Cave) including rain water (δ 26 Mg: − 0.70 ± 0.14‰), soil water (δ 26 Mg: − 0.51 ± 0.10‰) and drip waters (δ 26 Mg: − 1.65 ± 0.08‰) sampled between November 2009 and May 2011. Field precipitation experiments, i.e., calcite precipitat…
Textural features and isotope geochemistry of the Scillato travertine (north-central Sicily): genetic implications.
2015
The travertine deposit, outcropping near the Scillato town (north-central Sicily), was originated by precipitation of calcium carbonate from the Scillato springs, documented as bicarbonate-enriched waters due to dissolution of the Madonie mountains carbonate rocks. This deposit is today well represented by the Travertine Cave, essentially constituted by stalactites and stalagmites in which travertine typically appears laminated with alternation of light and dark laminae. Mineralogical analysis have revealed the almost exclusive presence of calcite and observation under the polarized-light microscope showed different textural features, like presence of debris and porous portions, micritic po…
Disequilibrium carbon and oxygen isotope fractionation in recent cave calcite: Comparison of cave precipitates and model data
2013
Abstract Speleothem proxy data provide important information in continental palaeo-climate research due to their precise chronology and wide geographic distribution. Despite a continuously growing number of field and numerical studies designed to study stable isotope fractionation effects, many aspects remain a matter of debate. Here, carbon and oxygen isotope ratios from cave drip water and calcite precipitates sampled on watch glasses in the Bunker Cave (Western Germany) are compared with the values expected for isotopic equilibrium. Furthermore, the field data are compared with the results of a numerical model simulating stalagmite growth and stable isotope ratios. Two drip sites with di…
Are oxygen isotope fractionation factors between calcite and water derived from speleothems systematically biased due to prior calcite precipitation …
2021
Abstract The equilibrium oxygen isotope fractionation factor between calcite and water (18αcalcite/H2O) is an important quantity in stable isotope geochemistry and allows in principle to infer temperature variations from carbonate δ18O if carbonate formation occurred in thermodynamic equilibrium. For this reason, many studies intended to determine the value of the oxygen isotope fractionation factor between calcite and water (18αcalcite/H2O) for a wide range of temperatures using modern cave calcite and the corresponding cave drip water or ancient speleothem carbonate and fluid inclusion samples. However, the picture that emerges from all of these studies indicates that speleothem calcite i…
Modelling carbon isotopes of carbonates in cave drip water
2011
Abstract C isotopes in cave drip water are affected by both the C isotope composition of soil air and host rock carbonate. Furthermore, the C isotope composition of cave drip water strongly depends on the calcite dissolution system, i.e., open, closed and intermediate conditions. Here, we present a calcite dissolution model, which calculates the 14C activity and δ13C value of the dissolved inorganic carbon of the drip water. The model is based on the chemical equations describing calcite dissolution ( H 2 O + CaCO 3 + CO 2 ⇔ Ca 2 + + 2HCO 3 - ). The most important improvement, relative to previous models, is the combination of the open and closed system conditions in order to simulate the C…
Peñón de la Zorra y Puntal de los Carniceros (Villena, Alicante): Revisión de dos conjuntos de yacimientos campaniformes en el corredor del Vinalopó
2002
En el presente artículo se revisa la información existente sobre dos yacimientos campaniformes del Alto Vinalopó –Peñón de la Zorra y Puntal de los Carniceros–. Su importancia dentro de la investigación en tierras levantinas los ha convertido en una referencia casi obligatoria desde su publicación por parte de J. M. Soler García. In this article is cheked information about two bell beaker sites from Vinalopo Valley –Peñón de la Zorra and Puntal de los Carniceros–. The importance of this archaeological sites of investigation concerning Levante areas have got that these places would be an obligatory reference since the publication by J.M. Soler Garcia.
A new Diplura species from Georgia caves, Plusiocampa (Plusiocampa) imereti (Diplura, Campodeidae), with morphological and molecular data
2021
A new dipluran species, Plusiocampa (Plusiocampa) imereti Sendra & Barjadze sp. nov., from the deep zone in three caves in the Imereti region, Georgia, is described. This new troglobitic Plusiocampa is an addition to four others known Diplura from around the Black Sea region, two Dydimocampa and two Plusiocampa s. str. The present study also provides the first CO1 sequences for the Plusiocampinae taxa and the first molecular data for cave-dwelling Plusiocampa species. Although bootstrap values were low, the maximum-likelihood phylogenetic tree grouped Plusiocampa (P.) imereti Sendra & Barjadze sp. nov. with two Plusiocampa s. str. species from Eastern Europe. Morphologically, P. (P.…
Campodeidae (Hexapoda: Diplura) from Kyrgyzstan, Central Asia, with the description of a remarkable new genus and species
2021
Samples collected in Central Asia, Kyrgyzstan, have revealed a hitherto unknown diversity of Campodeidae (Diplura) in soil and cave habitats, including a new genus and species, Kyrgyzstancampa sanare Sendra & Ferreira gen. et sp. nov., Turkmenocampa edaphica Sendra & Sánchez-García sp. nov. and a previously recognized soil-dwelling species, Campodea (Dicampa) catalana Denis, 1930. Kyrgyzstancampa sanare Sendra & Ferreira gen. et sp. nov. was collected in the deep zone of an interesting geological and cultural cave, Ak-Turpak Cave, located near the western margin of Kadamjay District, Batken Province. This genus belongs to the subfamily Campodeinae, sharing the morphology of the …