36Cl exposure ages of alluvial limestone boulders, near Yenice, Karabük, northern Turkey

Published: 18-05-2020| Version 1 | DOI: 10.17632/563y2fyd5k.1
Contributor:
Kevin P. McClain

Description

An alluvial fan formed in the Filyos River Valley, resulting from landslide and fluvial activity in the Şimşir River. Debris flows were transported through Şeker Canyon and into the Filyos River Valley, creating an alluvial fan. The alluvial layers overly older fluvial fill terrace layers. Chemical preparations were performed at the İTÜ Kozmo-Lab in Istanbul, Turkey. The final AgCl targets were sent to the CNRS-ASTER, Aix en Provence, France for measurements using Accelerated Mass Spectrometry. Major and trace element concentrations of aliquots were measured at AcmeLabs, Canada.

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- On the landform surface, the least disturbed areas of the uppermost 2-4.5 cm of three well-rooted, rounded, limestone boulders were extracted by hammer and chisel for cosmogenic 36Cl exposure dating. - One sample of a similar sized limestone boulder was collected from the modern river channel for calculation of minimum 36Cl inheritance. - Chemical preparations were performed according to procedures described in Sarıkaya et al., (2015). - Samples were crushed and sieved to gather a 0.25-1 mm fraction. This fraction was leached in deionized water and 10% HNO3 then dissolved in HDPE bottles with 2 M HNO3 as in Schlagenhauf et al., (2010). - 0.1 M AgNO3 was added to the solution - Samples were dissolved and AgCl was precipitated. - Sulfur was removed from the final solution by precipitation of BaSO4 via the addition of saturated Ba(NO3) and reacidifying with concentrated HNO3. - Final AgCl targets were sent to the CNRS-ASTER, Aix en Provence, France for measurements using Accelerated Mass Spectrometry (AMS). - After AMS, the total Cl was calculated using the isotope dilution method of Desilets et al., (2006). - Aliquots of leached samples were used to determine the major and trace element concentrations at the AcmeLabs, Canada. - To estimate local 36Cl production rates, a combination of rates provided by the CRONUS-Earth (Cosmic-Ray Produced Nuclide Systematics on Earth) project and Marrero et al. (2016) were used. - Calculations of exposure ages were made using the CRONUS Web Calculator (http://www.cronuscalculators.nmt.edu) (Marrero et al., 2016). - To perform an inheritance correction, a similar size channel boulder was sampled to estimate the inheritance using its concentration of nuclides. This concentration was subtracted from the concentrations in the three limestone boulder samples. Desilets, D., Zreda, M., Almasi, P.F., Elmore, D., 2006. Determination of cosmogenic 36Cl in rocks by isotope dilution: innovations, validation and error propagation. Chem. Geol. 233, 185–195. Marrero S.M., Phillips, F.M., Caffee, M.W., Gosse, J.C., 2016. CRONUSEarth cosmogenic 36Cl calibration. Quaternary Geochronology 31, 199-219. https ://doi.org/10.1016/j.quage o.2015.10.002 Sarıkaya, M.A., Yildirim, C., Çiner, A., 2015. Late Quaternary alluvial fans of Emli Valley in the Ecemiş Fault Zone, south central Turkey: Insights from cosmogenic nuclides. Geomorphology 228, 512–525. Schlagenhauf, A., Gaudemer, Y., Benedetti, L., Manighetti, I., Palumbo, L., Schimmelpfennig, I., Finkel, R., Pou, K., 2010. Using in situ Chlorine-36 cosmonuclide to recover past earthquake histories on limestone normal fault scarps: A reappraisal of methodology and interpretations. Geophys. J. Int. 182, 36–72.