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| Titel |
Holocene climate change, permafrost and cryogenic carbonate formation: insights from a recently deglaciated, high-elevation cave in the Austrian Alps |
| VerfasserIn |
Christoph Spötl, H. Cheng |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 10, no. 4 ; Nr. 10, no. 4 (2014-07-22), S.1349-1362 |
| Datensatznummer |
250117016
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| Publikation (Nr.) |
 copernicus.org/cp-10-1349-2014.pdf |
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| Schlagwörter |
Höhle, Eishöhle, Speläothem, Paläoklima, Klimawandel, Permafrost, Stabile Isotope, Altersdatierung, Holozän, Quartär, Karbonat, Kryogen, Hochstegenmarmor, Jura, Mesozoikum |
| Geograf. Schlagwort |
Österreich, Tirol, Schwaz (Bezirk), Tuxer Alpen |
| Blattnummer |
149 [Lanersbach] |
| Blattnummer (UTM) |
2230 [Mayrhofen] |
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| Zusammenfassung |
Cryogenically formed carbonate particles represent a rather new class of
speleothems whose origin is directly linked to the presence of perennial ice
in the subsurface. Recent studies concluded that dating these deposits
provides important time constraints on the presence and the thickness of
permafrost, e.g., during the last glacial period. More precisely, these
carbonates record episodes of progressive karst water freezing. Such
conditions have been associated with periods of permafrost thawing allowing
the infiltration of meltwater into formerly dry, frozen caves.
To shed more light on the origin of the coarsely crystalline variety of these
cryogenic cave carbonates – CCCcoarse for short – we examined a
high-elevation cave site in the western part of the Austrian Alps which is
located in an area dominated by permafrost features and transformed from an
ice cave into an essentially ice-free cave during the past decade. Two side
chambers of the main gallery revealed cryogenic calcite deposits whose
isotopic composition indicates that they formed in individual pools of water
carved in ice which underwent very slow freezing under closed-system
conditions, i.e., enclosed in ice. 230Th dating shows that most of these
carbonates formed ca. 2600 yr BP. Based on comparisons with other
palaeoclimate archives in the Alps this thawing episode did not occur during
a climate optimum, nor did CCCcoarse form in this cave during,
e.g., the Roman or the Medieval Warm Periods. Our results suggest that the
occurrence of CCCcoarse, at least in mountain regions
characterized by discontinuous permafrost, may be more stochastic than
previously thought. Given the inherent heterogeneity of karst aquifers and
the important role of localized water infiltration in modifying the thermal
structure of the subsurface, we caution against attributing
CCCcoarse occurrences solely to peak warming conditions, while
confirming the unique significance of these deposits in providing robust age
constraints on permafrost thawing episodes. |
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