ESR-dating of the Arctic sediment core PS1535 dose-response and thermal behaviour of the CO2¯-signal in foraminifera

ESR-spectra of foraminifera in arctic sediment cores display the CO2--signal (g = 2.0006). Research on the thermal behaviour of the CO2--signal shows that both natural and artificial irradiation generates a precursor and a thermal unstable component of the CO2--signal. The precursor can be transfered to the stable radical, and unstable radicals can be removed by heating. The signal-change by heating depends on the irradiation dose. Because of the varying response on thermal treatment, the dose-response curves show systematic differences depending on the applied procedure (single- or multi-aliquot method with or without heating). A model for the description of the CO2--signal-change is presented. The combination of two exponential saturation functions seems to be an adequate analytical description of the dose-response curve of the CO2--signal in foraminifera. Due to the limited thermal stability this signal can be used for dating foraminifera with ages up to about 190 ka. (C) 2000 Elsevier Science Ltd. All rights reserved.