Optically stimulated luminescence dating of Ocean Drilling Program Core 658B : Complications arising from authigenic uranium uptake and lateral sediment movement. / Armitage, Simon.

In: Quaternary Geochronology, Vol. 30, No. Part B, 10.2015, p. 270-274.

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Abstract

Ocean Drilling Program Site 658 lies under the North African summer dust plume, and ought to be an ideal target for optically stimulated luminescence (OSL) dating, since the main clastic input is far-travelled Saharan dust. However, OSL ages for coarse silt-sized quartz (40-63 µm) are systematically lower than independent age estimates when dose rates are calculated using a model which assumes detrital 238U, 232Th and 40K and excess 230Th and 231Pa. Ages which are in good agreement with independent age control are obtained from the coarse silt samples when a correction for authigenic uranium uptake is incorporated into the dose rate model. Authigenic uranium uptake occurs under reducing conditions, which are common at the sediment-water interface, and some degree of authigenic uranium correction may be required for most marine sediments. Using this revised dose rate model, ages produced using fine silt-sized quartz (4-11 µm) are up to 100% older than both independent and coarse silt ages. In addition, the fine silt ages show a consistent pattern of age decrease with depth over 1.5 m of core. 230Th data from Site 658 indicate that this site receives 3 times more sediment laterally than vertically. It is concluded that the fine silt at Site 658 contains a substantial reworked component, making it unsuitable for dating. Conversely the coarse silt fraction, which settles through water at ~40 times the rate of fine silt, appears to be derived from dust input over the site at the time of deposition. Since prominent nepheloid (cloudy) layers occur in various deep ocean basins, and the material suspended in these layers often consists of reworked fine silt-sized sediments, coarser material should be dated where possible.
Original languageEnglish
Pages (from-to)270-274
Number of pages5
JournalQuaternary Geochronology
Volume30
Issue numberPart B
Early online date9 Mar 2015
DOIs
Publication statusPublished - Oct 2015
This open access research output is licenced under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

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