HR: 0800h
AN: U31A-0013    [Abstracts]
TI: Relatively high sea levels of the last million years
AU: * Bowen, D Q
EM: DQBowen@aol.com
AF: David Q Bowen, School of Earth, Ocean and Planetary Sciences, Cardiff University, Cardiff, CF103YE United Kingdom
AB: Estimates of the elevations of relatively high sea levels (above present) of the last million years continue to be problematical because of critical unknown factors. Such sea levels have been estimated: by inferences drawn from oxygen isotope measurements on benthic foraminifera - using Mg/Ca ratios to eliminate the temperature term; and from marine and littoral stratigraphic units and shoreline geomorphology, the actualities of which are essential for confirming estimates by other means. Both approaches encounter major difficulties: the former because local or regional hydrologic effects are difficult to estimate; the latter, because of the ambiguity of water levels inferred from corals, marine or littoral lithofacies, repeated marine occupation of shorelines on relatively low uplift coastlines (do `stable` coastlines exist?) and, not least, considerable uncertainty for shoreline age estimates, especially for those older than event 5.5. On rapidly uplifting coastlines, at or near plate margins, some success has been obtained in separating the uplift and sea level terms. But a long-standing problem at intraplate locations is the need to quantify medium-term uplift rates, between shorter-term (Holocene) and longer-term (earlier Pleistocene) ones. Approaches to these problems are reviewed and, using boundary parameters defined by late Pleistocene and late Pliocene shorelines, sea-level estimates are presented from Australasian and Atlantic intraplate locations and Pacific plate margin locations. These are correlated with benthic oxygen isotope stratigraphy from Site 849 and with Antarctic (EPICA) palaeotemperatures. Such correlations allow inferences to be drawn about trends in the evolution of relatively high sea levels, ice-sheet evolution and melt-water sources. A major reorganization of the `ocean-ice-sheet-sea-level system` occurred after oxygen isotope stages 12/11; thereafter, the role of the Laurentide Ice Sheet became progressively more important, and relatively higher sea levels obtained.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1827 Glaciology (1863)
DE: 1833 Hydroclimatology
DE: 1620 Climate dynamics (3309)
SC: Union [U]
MN: 2004 AGU Fall Meeting