Marland, F.C.; Kjerfve, B., and Smith, J.S., 2023. Emergent sandy barriers formed Sapelo Island (Georgia, U.S.A.) during Heinrich events and in the Holocene. Journal of Coastal Research, 39(6), 1068–1081. Charlotte (North Carolina), ISSN 0749-0208.
Sapelo Island’s core consists of five separate barrier islands corresponding to five Heinrich events, H5–H1. During the present interglacial rise of the sea, Holocene barriers (H0) were attached to the most recent paleo-barrier, H1. All barriers have a recurved spit with an intervening backbay tidal marsh. Each barrier is composed of several dune ridges. Beach ridge editions were not formed at their present locations. Sand and other materials emerged from below sea level on the shelf in transgressive, elevated H seas and in the last post-glacial rise of the Holocene interglacial. Fourteen spurious increases of higher sea levels of warmer water in Dansgaard-Oeschger (D-O) events were followed by cooling H intervals with extreme waves during gales, hurricanes, and possibly tsunamis. Deltaic surplus materials on the shelf rolled shoreward. Storms drove deposits onshore in predominant wave episodes of overwash. Pliocene and Pleistocene sand surpluses on the continental shelf in relict river channels and deltas were and are source deposits. The preserved varved chronology is based on analyses of pollen and microfossils from Lake Tulane, Florida. Lake Tulane provides a continuous timeline of comparable radiocarbon ages to Sapelo. Both sites are considered coeval. Overwash deposits on the dry sand beach above average tides were forerunners of dune formation. After storms, backshore sand was trapped within strandlines of Spartina marshwrack. Materials caught in the straw mulch on the dry sand produced aeolian dune ridges during windswept Nor’easters. High dunes grew from low and coalesced into a series of barriers to form Sapelo Island.