USE OF GEOCHRONOLOGICAL TECHNIQUES TO CONSTRAIN GEOLOGICAL RECORDS FROM POCKOY ISLAND, S.C.: PHYSICAL SAMPLES AND DISCUSSION

InfraRed Stimulated Luminescence (IRSL) data collections were run on a series of quartz-rich sand samples collected from three vibracores at Pockoy Island, S.C., part of Botany Bay Heritage Preserve, a SCDNR-managed property that is also the site of two paleo-Native American shell rings dating to the Late Archaic (~4300 years bp). An additional sample was collected from a fourth vibracore taken on a hammock island between Pockoy and Edisto Islands. Vibracores were collected during a 2019 excavation of the most seaward of the two shell rings. This shell ring, and the surface locations of two of the vibracores collected in 2019, have since been lost to shoreline retreat.

The choice of sampling interval and confidence of depositional facies interpretations is critical to the interpretation of geochronological data. Using the Central Age Model of Galbraith and Roberts (2012), correction for fading (Auclair 2003), and the correction model of Huntley and Lamothe (2001), the IRSL data supplied a range of late Pleistocene MIS 4 to 3 ages (69.99 +/- 7.37 to 54.16 +/- 5.57 ka). Those calculated ages provide a variety of interpretations for isostatic adjustment and relative sea-level position, or for differences in facies interpretation.

Sample PI_01 (66.76 +/- 8.31 ka; 1.93-2.32 m depth, +0.44- +0.05 m elev) is the most seaward with PI_02 (54.16 +/-5.57 ka; 1.73-2.08 m depth, -0.28- -0.63 m elev) being more landward and PI_03 (62.65 +/- 8.05 ka; 1.40-1.70 m depth, +0.11- -0.19 m elev) being most landward on Pockoy Island. PI_04 (69.99 +/-7.37 ka; 1.40-1.70 m depth, +0.14- -0.16 m elev) was collected on the small hammock island between Pockoy and Edisto. While the ages with their +/- 2ơ’s mostly overlap, PI_04’s age is mostly likely somewhat older, which is expected from geographic position.

We present one of the four cores as a representative example to allow lithologic examination. This will facilitate discussion of the choice of sample interval and facies assignment. The facies assignment, selection of the sampled interval, and geochronologic age have implications of stratigraphic correlations in other coastal locations in the southeastern U.S.