HOLIVAR2006 Abstracts
Construction of the calendar time scale for Lake Wigry sediments on the basis of radiocarbon dating.
N. Piotrowska1, I. Hajdas2, G. Bonani2, M. Gąsiorowski3 and H. Hercman3
1Silesian University of Technology, Institute of Physics, Department of Radioisotopes, Krzywoustego 2, 44-100 Gliwice, Poland
2AMS 14C lab, ETH Hoenggerberg, HPK H27, CH-8093 Zurich, Switzerland
3Polish Academy of Sciences, Institute of Geological Sciences, Twarda 51/55, 00-818 Warsaw, Poland
Contact: Natalia Piotrowska (natalia.piotrowska@polsl.pl)
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The main objective of the study is the construction of a calendar time scale for the sediments deposited in southern part of Lake Wigry (Słupiańska Bay), Poland, on the basis of 14C and 210Pb measurements. The 5.20 m long core and several short cores were recovered and subjected to lithological and palaeobiological analyses (palynology, cladocera, diatoms).
The sediments are composed mostly of carbonates with relatively high 14C apparent ages. Research work carried out for Lake Wigry included sampling of a sediment core from Słupiańska Bay, selection and preparation of various fractions of the sediment (macrofossils, plant remains, wood fragments, alkali-soluble fraction, pollen), radiocarbon measurements, and calendar age model building. Most of the organic samples have been dated using the AMS technique, and these measurements have been performed in ETH Zurich.
The investigations included also the measurements of radiocarbon activity in carbonate fraction of the sediment, and in this case the measurements were carried out by means of gas proportional counting (GPC) technique in the Gliwice Radiocarbon Laboratory.
The results were subjected to critical analysis, which enabled the exclusion of the dates affected by reservoir effect as well as outlying data, and finally the non-linear age model, enhanced by 210Pb dating in the uppermost part of the sediment column, has been developed. The statistical tools used for construction of the models include the Bayesian analysis applied during calibration of radiocarbon dates with regard to stratigraphical position of the samples and generalised additive models (GAM).
The radiocarbon reservoir effect was also estimated on the basis of the above measurements and modelled using GAM. Some attempts to interpret the change of carbon isotope composition as a proxy of environmental change were undertaken.
Natalia Piotrowska defended her PhD in radiocarbon dating of Lake Baikal and Lake Wigry sediments several months ago. She works as assistant at the Silesian University of Technology, trying to teach physics to some reluctant students, but her favourite work and main scientific interest is AMS radiocarbon dating applied in geosciences and archaeology.