Constraining the age of gravelly beach ridges using rock surface luminescence dating – implications for mapping sea-level variation in the Holocene

• Main Authors: Emerich Souza, Priscila, Sohbati, Reza, Murray, Andrew, Kroon, Aart, Meldgaard, Asger, Clemmensen, Lars B, Nielsen, Lars
• Format: Conference Object
• Language: English
• Published: 2018
• Subjects: Arctic; DeWitt; Fuchs; Greenland
• Online Access: https://curis.ku.dk/portal/da/publications/constraining-the-age-of-gravelly-beach-ridges-using-rock-surface-luminescence-dating--implications-for-mapping-sealevel-variation-in-the-holocene(25419288-077a-485b-b993-a0996139a6fd).html; https://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/374929

Optically stimulated luminescence (OSL) dating of sandy sediment has become an important tool in Quaternary geochronology (e.g. [1] [2] [3]). However, key sites for mapping relative sea level (RSL) variations in the Holocene, such as gravelly beach ridges in Arctic environments, often lack significant fractions of sand suitable for standard OSL dating. More recently, OSL rock surface dating has emerged as a promising technique in determining the depositional age of larger clasts such as cobbles and boulders [4] [5] [6] [7]. The advantage of this new technique over conventional OSL dating is that rocks also record the completeness of resetting of the surface prior to burial – this information is contained in the shape of the luminescence profile with depth into the rock surface [6][8]. Here, we apply OSL rock surface dating to cobble-sized clasts from fossil gravelly beach ridges on the southwest coast of Disko Island (West Greenland). Luminescence-depth profiles show that the natural infrared stimulated luminescence signals have been bleached to depths > 2 mm into the clast surface prior to deposition. Therefore, equivalent doses measured from the surface of these rocks reflect the dose accumulated since the last exposure to daylight. We determine the formation age of these ridges by dating when the cobbles were wave-deposited and discuss the implications of our results for mapping sea-level variation in the Holocene. Preliminary results indicate that we may be able to reconstruct a new RSL curve for the Holocene over a span of ~10 ka using such OSL methods. [1] Murray, A., & Olley, J., 2002. Precision and accuracy in optically stimulated luminescence dating of sedimentary quartz: a status review. Geochronometria (21), 1-16. [2] Rittenour, T., 2008. DOI:10.1111/j.1502-3885.2008.00056.x [3] Fuchs, M., & Owen, L., 2008. DOI:10.1111/j.1502-3885.2008.00052.x [4] Sohbati, R. et al., 2011. DOI:10.2478/s13386-011-0029-2 [5] Simkins, L., Simms, A., & DeWitt, R., 2013. DOI:10.1016/j.quascirev.2013.07.027 [6] Sohbati, R. et al., 2015. DOI:10.1016/j.quageo.2015.09.002 [7] Jenkins, G. et al., 2018. DOI:10.1016/j.quascirev.2018.05.036 [8] Freiesleben, T. et al., 2015. DOI:10.1016/j.radmeas.2015.02.004