Paper No. 5-16
Presentation Time: 8:00 AM-12:00 PM
DISCONTINUITIES IN THE PROGRADATION OF JEKYLL SPIT TIED TO THE BREACHING OF ST. SIMONS SOUND AND THE SEPARATION OF JEKYLL FROM ST. SIMONS ISLAND, GEORGIA, USA
Jekyll Island consists mainly of Pleistocene upland in the north to which a Holocene spit has accreted in the south. The spit is divided into three parts separated by major discontinuities. Proceeding from west to east (oldest to youngest) these are referenced as Harbor spit (immediately south of Millionaires Village), Beachview spit (extending from Capt. Wylly Rd through the area of the waterpark) and St. Andrews spit (forming the southeastern shoreline from Capt. Wylly Rd to Jekyll Point). Both elevation and preservation of dune topography decrease with age. Vibracores from Harbor spit show that it predates ~2800 BP. and is partly concealed by the vertical accretion of surrounding marsh. Work continues, to obtain radiometric ages for Beachview and St. Andrews spits. However, a comparison of topography suggests that St. Andrews spit is about the same age as beach ridges at the northeast part of the island (Driftwood Dunes) that have been dated as < 1500 BP. Discontinuities in the progradation of the spit suggest interruptions in the supply of sand by longshore transport from the north, most likely implicating changes at St. Simons Sound. Beachview discontinuity, between Beachview and St. Andrews spits probably records the disruption caused by the rerouting of Brunswick River from Jekyll Sound to St. Simons Sound. Harbor discontinuity between Harbor and Beachview spits dates to an earlier disruption around 2800 BP., perhaps an earlier breach at St Simons Sound and possibly the event that severed an original connection between St. Simons and Jekyll islands.