Dating of late Pleistocene and Holocene relative sea levels in coastal Delaware
Date
1975
Authors
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Publisher
University of Delaware
Abstract
Delaware is a region of moderate climate and tidal range with a coast dominated by lagoon-barrier and estuarine systems. The area is affected by subsidence of the Baltimore Canyon geosyncline. A eustatic sea-level rise due to ice melting after the peak Wisconsin glaciation is coupled with this subsidence to produce a rapid local relative sea-level rise. ☐ Salt marsh peats have been dated with the Carbon-14 technique to obtain former positions of sea level. A curve is plotted, showing the present local relative sea level rise is 12.5 cm (0.41 ft) per century, much less than in the recent past. ☐ Comparison of the curve from the Delaware region with published eustatic curves indicates present subsidence rates of 6.2 cm (.2 ft) per century, less than in the recent past. ☐ Compaction of Holocene marsh.es is occurring at rates of up to 30% in 10,000 years. These materials are organic muds, not true peats, and thus do not compact as much. ☐ Sedimentation rates in the tidal marshes range from 3 to 21.6 cm (.1 to .7 ft) per century, with a mean of 14.5 cm (.5 ft) per century. This agrees with the rates of sea-level rise, indicating that ô€€’his is a control on the rate of marsh sediment accretion. Corrections to the radiocarbon dates, involving more accurate determination of half-life and tree ring corrections, allow greater accuracy in determinations of relative sea level, compaction rates, sedimentation rates, and paleogeography. Regression analysis leads to better reliability in curve construction than visual data fitting techniques.