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| Titel |
Alpine permafrost thawing during the Medieval Warm Period identified from cryogenic cave carbonates |
| VerfasserIn |
M. Luetscher, M. Borreguero, G. E. Moseley, Christoph Spötl, R. L. Edwards |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 7, no. 4 ; Nr. 7, no. 4 (2013-07-09), S.1073-1081 |
| Datensatznummer |
250017986
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| Publikation (Nr.) |
 copernicus.org/tc-7-1073-2013.pdf |
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| Zusammenfassung |
| Coarse crystalline cryogenic cave carbonates (CCCcoarse) dated to
the last glacial period are common in central European caves and provide
convincing evidence of palaeo-permafrost during this time. Little is known,
however, about the exact nature of the environment in which
CCCcoarse formed as no modern analogue setting is known. Here, we
report the first findings of sub-recent, albeit inactive, CCCcoarse
from a cave of the Western Alps which is located in the present-day
permafrost zone. The globular shape and the presence of ubiquitous euhedral
crystal terminations are comparable to previously reported aggregates from
the last glacial period and strongly suggest that these aggregates formed
subaqueously in pools lacking agitation. Furthermore, stable isotope values
of mm-sized spheroids point to calcite precipitation in a closed system with
respect to CO2, strongly supporting the hypothesis of a cryogenic origin
associated with the freezing of water ponds. U-series analyses revealed three
clusters of late Holocene calcite precipitation intervals between 2129 and
751 a b2k. These ages correlate with known periods of elevated summer
temperatures, suggesting that warming and thawing of the frozen catchment
above the cave allowed water infiltration into the karst system. The growth
of CCCcoarse resulted from the re-freezing of this water in the
still cold karst cavities. |
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