ABSTRACT

ABSTRACT
Berger
OPP-0612950

Overview: The paleoceanographic and paleoclimatic history of the Arctic Ocean, especially during the last several hundred thousand years, remains largely unknown because of difficulties in numerical dating of sediment cores in the 30 to 800 ka (kyr) time range. The goal is numeric dating of key deposits younger than about 100 ka, which is critical for development of local and oceanwide chronostratigraphies. Reconnaissance work in the Arctic Ocean shows that photonstimulated- luminescence (PSL) and thermoluminescence (TL) dating are promising for pre-Holocene interglaciation deposits at some ridge. Jakobsson et. al., showed that PSL dating of last-interglaciation horizons at a central-ocean ridge-top site can be accurately dated by PSL. However, because the Principal Investigator analyzed only a few core tops, likely effects on PSL dating accuracy of a host of local grain-transport processes remain unquantified, and the potential utility of PSL in this important glacial-interglacial time range is uncertain. He will apply PSL methods to additional core tops and down-core horizons collected during the 2005 Healy-Oden Trans-Arctic Expedition (HOTRAX05).

Intellectual merit: Project results will quantify the potential of modern luminescence dating methods for Arctic Ocean sediments. By firmly establishing PSL dating for this region, the project will permit expansion of Quaternary paleoceanographic and paleoclimatic knowledge of the Arctic Ocean and its links to subpolar global systems. The laboratory effort will enable testing the Principal Investigator's hypothesis that the Chukchi Borderland region is favorable for photonic dating of at least pre-Holocene horizons. The project will determine the suitability of the Alpha Ridge for future luminescence sediment dating and will test an implication of prior Principal Investigator results at the Lomonosov Ridge that only horizons >80 to 90 kyr there are suitable for PSL dating. Also, this project may resolve a Principal Investigator documented ambiguity about the suitability for PSL dating of sediments along the Mendeleev Ridge complex. Uniquely, this project also will quantify the extent to which dirty sea ice contributes (upon melting) to non-zero PSL signals in the bottom sediments. Finally, this project will test the capability of single-grain-quartz PSL dating for isolating true burial ages in core horizons younger than about 100 ka and containing ice-rafted sand, and will use the results of these single-grain analyses to test recent hypotheses of the timing of ice-grounding histories in the Chukchi Borderland.

Broader impacts: This study will support graduate and undergraduate students, with emphasis on recruiting students from underrepresented groups. It will contribute knowledge and experience to Nevada's K12 system through participation in an established teacher training program at DRI. Research results will be disseminated through publications in peer-reviewed journals and at final-project-year conference presentations. Through development of a capability for accurate numeric dating of the Arctic Ocean sediments, the proposed research will lead to fundamental understanding of the evolution of the Northern Hemisphere climate on timescales of Quaternary glacial-interglacial intervals.

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