|Affiliation(s)||PI||Project period||Funded by|
|DEES||Berger, Glenn W||06/15/2006 - 05/31/2011||National Science Foundation|
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 30-800 ka (kyr) time range. The goal of the project is numeric dating of key deposits younger than about 100 ka, which is critical for development of local and ocean-wide chronostratigraphies. Reconnaissance work in the Arctic Ocean by the PI shows that photon-stimulated-luminescence (PSL) and thermoluminescence (TL) dating are promising for pre-Holocene interglaciation deposits at some ridge tops (e.g., western ocean), and that most basin and other ridge sites are not promising. Jakobsson and colleagues showed that PSL dating of last-interglaciation (ca. 120 ka) horizons at a central-ocean ridge-top site can be accurately dated by PSL. However, because the PI analyzed only a few core tops ('clock-zeroing' tests), 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 (last ca. 100 kyr) is uncertain. This projectl seeks to apply PSL methods to additional core tops and down-core horizons collected from several ridges and plateaus during the 2005 Healy-Oden Trans-Arctic Expedition (HOTRAX05) and to analyze for the first time specially collected 'zero-age' sediment from sea ice. Most bottom sediment in this ocean comes from dirty sea ice.
Intellectual merit: Project results will quantify the potential of modern luminescence methods for dating Arctic Ocean sediments. In addition, by firmly establishing PSL dating for this region, the project will play an important role in permitting expansion of Quaternary paleoceanographic and paleoclimatic knowledge of the Arctic Ocean and its links to, and influence on, subpolar global systems. The proposed laboratory effort will enable testing the PI'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 PI results at the Lomonosov Ridge that only horizons >80-90 kyr there are suitable for PSL dating. Also, this project may resolve a PI-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.