Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA

Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2 ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26 m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2 ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism.     

Further evidence of abrupt Holocene drowning of the Black Sea shelf

A 1999 survey of the Black Sea continental shelf off the north central Turkish seaport of Sinop using a side-scan sonar, small remotely operated vehicles, and a series of dredge lowerings located, inspected and sampled an exposed high-energy paleoshoreline at a depth of 155 m. Radiocarbon dating of mollusk shells collected from this ancient beach revealed that the marine flooding of the Black Sea took place between 7460 and 6820 yr B.P. (all ages are reported in radiocarbon years, not calendar years, without correction for reservoir age or dendro-calibration) changing it from a lacustrine to marine environment. This relic surface remained in contact with the bottom waters of the Black Sea for a long period of time before being draped by a thin layer of sapropel mud. Wood samples recovered from this same location were very well preserved and yielded dates as old as 3580 yr B.P.     

Luminescence dating of Middle Pleistocene (MIS 7) marine shoreline deposits along the eastern coast of Tunisia: A comparison of K-feldspar and Na-feldspar IRSL ages

In the present study, we applied the IRSL_50°C dating method to both K- and Na-feldspar coarse grains from interglacial coastal deposits in north-eastern Tunisia. We used the yellow IRSL_50°C signal of Na-feldspars and the blue IRSL_50°C signal of K-feldspars. The key-sites for this study are at El Hajeb (Sahel area) and Dar Oufa (Cap Bon Peninsula). These deposits belong to the “Douira Unit” which has previously been assigned to marine isotope stage (MIS) 7 on the basis of amino acid ratios and chronostratigraphic evidence.In order to assess the reliability of the IRSL_50°C ages of the “Douira Unit”, we extended the IRSL dating technique to K- and Na-feldspars from two MIS 5 samples, with independent age control, collected within shallow-marine sands in the Sahel area and on the Jerba island (southern Tunisia).Two protocols of age correction for the observed fading in K- and Na-feldspars have been applied: (1) the Huntley and Lamothe (2001) fading correction and (2) the dose rate correction developed by Lamothe et al. (2003). The fading corrected IRSL ages of the “Douira Unit” and both MIS 5 control samples, measured on K- and Na-feldspars, are in good agreement with their expected ages.