Showing papers on "Sea-level curve published in 1991"

Marine transgression, shoreline emergence: Evidence in seabed and terrestrial ground temperatures of changing relative sea levels, Arctic Canada

Abstract: Precise temperatures to depths of several hundred meters have been measured in abandoned petroleum exploration wells in coastal and offshore areas of the Canadian Arctic. In these regions, changes in relative sea level during the Quaternary have left a strong thermal signature on deep ground temperatures. Surface temperature changes of the order of 10–20 K accompanied shoreline emergence due to uplift in some regions and marine transgression due to eustatic changes in sea levels in others. Classical, analytic techniques are used to demonstrate that these anomalous features are a direct consequence of recent changes in sea level. In coastal areas of the Queen Elizabeth Islands, modelling of the large, near-surface temperature-depth gradients and the distinct curvature in the measured profiles yield emergence times in general agreement with dates taken from emergence curves. The analysis suggests that surface temperatures of these coastal areas were 16–19 K higher than at present from the Late Wisconsinan until emergence in the Holocene, suggesting either marine conditions for this period or glacial ice cover with basal temperatures near the pressure melting point. In contrast, at two offshore wells on the Beaufort Shelf, analyses of the negative temperature-depth gradients below the seabed and profile curvature yield times of marine transgression generally consistent with the published sea level curve for the area. The analyses suggest that surface temperatures of some present offshore areas were 10–16 K lower than today's sea bottom temperatures from the Late Wisconsinan until marine transgression in the Holocene. The characteristic ground temperature profiles measured in such arctic areas provide independent evidence for the relative changes in sea level indicated by proxy data. It is especially valuable for these areas, where there is little historical record and from which datable material, such as shells, driftwood, and pumice fragments, may be scarce or ambiguous. These effects may not be observable in temperate areas because of the smaller contrast in sea bottom and terrestrial temperatures.