Age assignment of a diatomaceous ooze unit deposited in the western Amundsen Sea Embayment after the last glacial maximum

Reliable dating of glaciomarine sediments deposited on the Antarctic shelf since the Last Glacial Maximum (LGM) is challenging because of the rarity of calcareous (micro-) fossils and the recycling of fossil organic matter. Consequently, radiocarbon (C-14) ages of the acid-insoluble organic fraction...

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Bibliographic Details
Published in:Journal of Quaternary Science
Main Authors: Hillenbrand, Claus-Deiter, Smith, J.A., Kuhn, G, Esper, O, Gersonde, R, Larter, Robert, Maher, B, Moreton, Steven, Shimmield, Tracy, Korte, M
Format: Article in Journal/Newspaper
Language:English
Published: 2010
Subjects:
Geosciences
Multidisciplinary
ANTARCTIC ICE-SHEET
RESERVOIR CORRECTION
HOLOCENE RETREAT
CONTINENTAL-SHELF
SOUTHERN-OCEAN
ROSS-SEA
MARINE-SEDIMENTS
Paleontology
GEOMAGNETIC DIPOLE-MOMENT
CLIMATE EVOLUTION
PALEOENVIRONMENTAL RECONSTRUCTIONS
Amundsen Sea
Antarc*
Antarctic
Antarctica
Ice Sheet
Ross Sea
Southern Ocean
West Antarctica
Online Access:https://pure.uhi.ac.uk/en/publications/fc3f6060-2b23-4d1d-9a66-34a261928d7d
https://doi.org/10.1002/jqs.1308
Description
Summary:Reliable dating of glaciomarine sediments deposited on the Antarctic shelf since the Last Glacial Maximum (LGM) is challenging because of the rarity of calcareous (micro-) fossils and the recycling of fossil organic matter. Consequently, radiocarbon (C-14) ages of the acid-insoluble organic fraction (AIO) of the sediments bear uncertainties that are difficult to quantify. Here we present the results of three different methods to date a sedimentary unit consisting of diatomaceous ooze and diatomaceous mud that was deposited following the last deglaciation at five core sites on the inner shelf in the western Amundsen Sea (West Antarctica). In three cores conventional C-14 dating of the AIO in bulk samples yielded age reversals down-core, but at all sites the AIO C-14 ages obtained from diatomaceous ooze within the diatom-rich unit yielded similar uncorrected C-14 ages between 13 517 +/- 56 and 11 543 +/- 47 years before present (a BP). Correction of these ages by subtracting the core-top ages, which probably reflect present-day deposition (as indicated by 210Pb dating of the sediment surface at one core site), yielded ages between ca. 10500 and 8400 cal. a BP. Correction of the AIO ages of the diatomaceous ooze by only subtracting the marine reservoir effect (MRE) of 1300 a indicated deposition of the diatom-rich sediments between 14 100 and 11 900 cal. a BP. Most of these ages are consistent with age constraints between 13.0 and 8.0 ka for the diatom-rich unit, which we obtained by correlating the relative palaeomagnetic intensity (RPI) records of three of the sediment cores with global and regional reference curves. As a third dating technique we applied conventional radiocarbon dating of the AIO included in acid-cleaned diatom hard parts extracted from the diatomaceous ooze. This method yielded uncorrected C-14 ages of only 5111 +/- 38 and 5106 +/-?38 a BP, respectively. We reject these young ages, because they are likely to be overprinted by the adsorption of modern atmospheric carbon dioxide onto the surfaces ...

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