HR: 11:50h
AN: PP42A-07    [Abstracts]
TI: Two new methods for high-resolution Micro-XRF analyses of trace elements in speleothems
AU: * Tamburini, F
EM: federica.tamburini@erdw.ethz.ch
AF: ETH-Zentrum, Sonneggstrasse 5, Zurich, 8092 Switzerland
AU: Ariztegui, D
EM: daniel.ariztegui@terre.unige.ch
AF: Dept. of Geology, Rue de Maraichers 13, Geneva, 1205 Switzerland
AU: Frisia, S
EM: frisia@mtsn.tn.it
AF: Museo Tridentino di Scienze Naturali, Via Calepina, Trento, 38100 Italy
AU: Borsato, A
EM: borsato@mtsn.tn.it
AF: Museo Tridentino di Scienze Naturali, Via Calepina, Trento, 38100 Italy
AU: Coccioni, R
EM: cron@info-net.it
AF: Dept. of Geology, Loc. Crocicchia, Urbino, 61022 Italy
AB: Trace elements (TE) variability in speleothems encodes climatic signals mediated by the geomorphic and hydrologic environment at annual scale. Current research involves modelling by appropriate transfer functions to recover aspects of the original signal. This requires knowledge of the dependency of element partitioning on growth rate and of the effects of sector zoning. Until recently, there was a lack of analytical methods that would allow high temporal resolution and the simultaneous scanning and mapping of multiple TE concentrations through time (along the growth axis of stalagmites) and space (along single growth layers). The XRF microscope/scan yields rapid, non-destructive, multi-elemental analysis (80 TEs) on the 50$\mu$m scale along the growth axis of whole specimens. Because of the relatively rapid analytical time, several parallel scans can be performed to assess the reproducibility of the data and recognize patterns of lateral distribution of the tracers. The beam penetrates into the sample material to a few ?m, giving a local average and a decadal resolution for slow-growing specimens (<50$\mu$m/year). Synchrotron radiation micro-XRF yields spot sizes at sample surface in the 1$\mu$m-range, allowing resolution at monthly to annual changes in speleothems. Scans and maps of the elemental distribution (on 1 cm-long sections) provide immediate insight on simultaneous concentration changes for several TEs across and along single growth layers, and recognition of processes that are unrelated to environmental changes. Oxidation states are obtained by tuning the energy of the incident beam across the absorption K-edge. The method is not applicable to whole stalagmites, requires long analytical times, and provides semi-quantitative concentration distributions. We applied these methods to two Holocene stalagmites. Both examples show simultaneous spatial and temporal concentration changes for some TEs that can be unequivocally ascribed to climate-related processes. Coupling these two methods has the potential to become an extremely powerful tool in palaeoclimate research.
DE: 1694 Instruments and techniques
DE: 1065 Trace elements (3670)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting