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| Titel |
Stable isotopic, petrographic and trace element analyses of two stalagmites from Sirtlanini Cave, SW Turkey: insights into Mid-Late Holocene environmental and climatic change |
| VerfasserIn |
Emily Peckover, Jennifer Mason, Onur Ozbek, Alina Marca, Peter Rowe, Julian Andrews, Steve Noble, John Brindle, Alper Baba, Alan Kendall, Sa'ad Al-Omari |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103938
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| Publikation (Nr.) |
 EGU/EGU2015-5357.pdf |
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| Zusammenfassung |
| Palaeoclimatic and palaeoenvironmental reconstructions from two Holocene stalagmites
(HY-8 and HY-9) from Sirtlanini Cave, southwest Turkey have been created using
petrographic, stable isotope and trace element analyses where the stratigraphy of the
stalagmites overlaps from ~6 ka. The cave elevation is 830 metres a.s.l., located
100 km northwest of Lake Golhisar, which has yielded a low resolution Holocene
isotopic record (Eastwood et al. 2007), and 120 km northwest of Caltilar Höyük,
the site of one of the earliest urban settlements in the region (Momigliano et al.,
2011).
Both stalagmites contain prominent dark grey-blue layers up to a few mm thick. Trace
element analysis reveals that these layers contain elevated Fe, Mn and Zn concentrations
suggesting enhanced mobilization of these elements, possibly adsorbed to organic matter on
100 nm to 1 μm soil particles (Hartland et al. 2012). Raman spectroscopy identifies the
presence of soot within the layers and evidence for plant material has been identified by
SEM along with detritus (clay, quartz). This suggests increased infiltration though
the karst, probably due to decreased vegetation cover, a conclusion supported by
positive δ13C excursions associated with some grey layers. It is likely that episodes of
burning occurred above the cave either due to natural wild fires or anthropogenic
activity.
The δ18O record of HY-8 shows no long term trend but fluctuates about a mean of -6.3
oḢowever it is punctuated by several shorted lived excursions of 1 ‰ - 2.5 ‰ amplitude.
δ13C decreases steadily (-6‰ to -10 ) through the Mid/Late Holocene with numerous short
lived excursions, many >2‰ and some (not exclusively) associated with grey layers .
Carbon and oxygen are poorly correlated, although sympathetic trends are seen during some
excursions. δ18O values have probably responded to changes in winter rainfall amounts with
δ13C likely reflecting fluctuating vegetation density above the cave, particularly when δ18O
corresponds.
Petrographic examination of HY-8 reveals a complex fabric. The majority of the
stalagmite shows an open fabric of dendritic calcite. Calcite is believed to be primary based
on continuous presence of spikey inclusions though dendritic fabric may indicate isotopic
disequilibrium. Laminations are defined by compact dendrites but grey layers are defined and
bound by dissolution layers. The fabric of the grey layers is mostly microcrystalline believed
to be caused by the presence of organic material (Frisia and Borsato 2010). However one
prominent layer is defined by equant calcite, implying a thicker film of water. Analysis of the
transition between grey layer microcrystalline and dendritic calcite will further
resolve the effects on calcite precipitation caused by the inclusion of organics and
detritus. Generally petrography will allow investigation into the effects of using
fabrics which may potentially alter the environmental signal for stable isotopic
interpretation.
Further study seeks to establish age models, examine petrography in more detail and to
compare stable isotopic records from both stalagmites. We aim to clarify the links between
climatic and environmental changes in the region and the temporal isotopic, trace element
and petrographic changes observed in the speleothems.
References
Eastwood, W.J., et al. (2007) J. Quat. Sci., 22, 327-341.
Hartland, A., et al. (2012) Chem. Geol. 304-305, 68-82.
Momigliano, N., et al. (2011) Anatolian Studies, 6, 61-121.
Frisia, S., & Borsato, A. (2010) Developments in Sedimentology, 61, 269-318. |
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