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| Titel |
A High-Resolution, Multi-Proxy Palaeoclimate Study of the Central Northern Mediterranean |
| VerfasserIn |
T. E. Horsfield, Michael Rogerson, G. M. Henderson, E. J. Rohling, A. Mihevc, M. Budja, M. Prelovsek, T. J. Coulthard, G. M. Greenway |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067657
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| Zusammenfassung |
| Two stalagmites, SLO-1 and SLO-2, collected from Postojna cave, Slovenia show very high
growth rates (~0.28mmyr-1), and grew to impressive lengths – SLO-1 measures
2.2m (2200mm) and SLO-2 measures 1.38m (1380mm). This record is constrained
by U-Th and α-mass spectrometry dates collected on both stalagmites, indicating
growth between 16 and 0.6ka BP. Together, these samples provide a potentially
exceptionally complete and high-resolution record of climate in the central northern
Mediterranean for the Holocene. Moreover, within these stalagmites, there is an
overlapping period between ~4.5 and ~9.1ka which allows cross-validation of two
records.
Stable isotope data collected to date form a continuous, 1-mm resolved record for the
upper 554mm of SLO-2, resulting in a record covering ~1.5ka, from ~0.6ka BP to ~2.1ka
BP and a series of “Hendy tests”, which indicate that kinetic fractionation has been small.
The stable isotope data spans the Medieval Warm Period and Dark Ages Cool Period and
shows a marked cyclic variability probably reflecting the balance of winter and
summer precipitation. Regionally cooler periods show typically isotopically negative
(winter-like) δ18Ocalcite values, whereas regionally warm periods show relatively positive
(summer-like) values. High temperature fluctuations between summer and winter
in Slovenia result in large (~6) variations in δ18Oprecipitation. Such a dramatic
shift between winter and summer precipitation makes changes in winter/summer
balance more noticeable in these samples than in other areas. Shorter scale variability
is also prevalent, especially when longer term variations have been removed by
detrending. This is in spite of the aquifer feeding the stalagmites being well-mixed, which
would ordinarily hinder finer resolution records. This may be due to an influence of
cave ventilation affecting the fractionation of isotopes once the drip has entered the
cave.
The climate record is in good agreement with known climate fluctuations, including the
periods mentioned above, as well as the very beginning of the Little Ice Age, with the
potential for the record to be extended much further back in time.
In addition to the stable isotope record, trace element analysis has also been performed
using two methods, inductively coupled plasma optical emission spectrometry (ICP-OES)
and X-ray fluorescence (Itrax). Included in this study is the first direct calibration of the two
techniques for a stalagmite in an attempt to discern the efficacy of the two techniques. Itrax
poses many advantages over the more conventional ICP methods, perhaps the most important
being the ability to perform non-destructive analysis on the stalagmite surface. A successful
calibration would validate the use of the faster, cheaper Itrax method as an alternative to ICP. |
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