LUMINESCENCE CHRONOLOGY OF PLEISTOCENE SEA LEVEL INDICATORS ALONG THE US ATLANTIC COAST

The dating of Pleistocene sea level indicators beyond the upper age limit of the radiocarbon method is of prime importance in the study of past sea levels thought to be analogous to the “anthropogenic” future high-stand along the US eastern board. In spite of robust U-series ages reported over the last three decades, there are several marine coastal units that remain undatable by this method as they do not contain corals or other datable material. The application of optically-stimulated luminescence dating methods to regional beach and estuarine facies have contributed to increase significantly the number of absolute ages available. These chronologies are the subject of considerable interest even though some young ages have raised concerns, as they would imply high relative sea level during the last glaciation or complex regional glacial isostatic adjustments.

Both quartz and feldspar, the common dosimeters in luminescence, have been used in dating programs. Quartz OSL have yielded a considerable number of ages ranging from MIS3 to late MIS5, mostly from Carolina. The application of feldspar IRSL has been hampered by the occurrence of luminescence instability known as anomalous fading. This misbehaviour has limited the potential of developing a robust chronology for the interglacials of the Middle Pleistocene as the age range of feldspar luminescence is known to be able to reach well beyond 300 ka, particularly in the regional low dose-rates context.

Over the last decade, new approaches have been proposed to solve or circumvent anomalous fading in feldspar. Among others, the post-isothermal IRSL (pIt-IRSL)method is now being applied to several critical sections in both Virginia and Carolina. Comparisons between quartz OSL, feldspar pIt-IRSL and corals U-Th ages is being investigated in order to better correlate and synchronize sea level changes along the US coast over Middle and Late Pleistocene.