Geoarcheology in the Georgia Bight:
A Study of Gray's Reef National Marine Sanctuary (NOAA) and J Reef, Georgia
ABSTRACT: Fluctuations in sea level and variable rates of shoreline change can greatly alter the availability of land for human habitation. Gray's Reef National Marine Sanctuary (GRNMS) may have been a site of ancient human settlement during the last geologic time period and thus may hold the key to ancient culture and history along the coast. Studies are currently examining this possibility.
PURPOSE: Scientists studying the geoarchaeology of Gray's Reef and nearby J-Reef are attempting to document the reefs' existance above sea level during geologic time. Such documentation would provide the foundation for studies concerning the possible existance of prehistoric humans and their prey in this area.
DESCRIPTION: Researchers currently believe that both Gray's Reef and nearby J-reef existed above sea level, exposed to air from approximately 15,000 to 3 million years ago, implying these areas to have been coastal and available for human settlement. High resolution sea floor imaging was used to examine the ocean bottom to substantiate this hypothesis. Researchers previously searching for plant and animal fossils from these geologic time frames (Pleistocene Age: 18,000 to 3 million years ago and Holocene Age: present to 18,000 years ago) and analyzation is currently underway to determine if fossilized bone samples found in the area are of marine or terrestrial origin. Results will be evaluated to determine when these reef areas of the continental shelf were exposed to air, documenting their existence above sea level.
PROJECT PARTICIPANTS: GRNMS; University of Georgia; Rice University; Coastal Carolina University
PROJECT TIME LINE: (Status: Year 3)
BENEFIT: Geographically, the late Pleistocene age marked a great expansion of human settlement in the New World. Radiocarbon dating studies indicate humans entered the New World, including what is now Georgia, by 12,000 BP-when sea level was 60 feet below its current level. From archaeological findings in the southeastern US, it is clear that these prehistoric inhabitants, or Paleoindians, occupied and hunted the coastal plain. Fossilized remains of these have been found on Gray's Reef. Dating samples will help to identify which animals were present, since particular species existed in certain eras.
YEAR 1· Archeological findings, Sea Floor Imaging Survey, Preliminary data analysisRepeat sampling; further survey Gray's Reef bone bed; perform fossilized bone carbon dating
YEAR 2 · Bone-bed underwater survey, Sea floor sampling and imaging, Core analysis
YEAR 3 · Bone-bed underwater survey
PRELIMINARY RESULTS: Fossil bones were found in the central part of the study area during spring 1996 scuba dives.
A fragment of fossilized bone and a mineralized burrow cast were dated at 18,970+/-400 years before present.
In addition, coring studies revealed sediment from J-Reef to have laminated (layered) sequences of quartz sand and silt with high organic concentrations (wood). These wood chips are coniferous (probably eastern cedar or juniper) indicating a cold climate existed during the tree's growth period.
Alternatively, the core from Gray's Reef clearly depicts geologic time boundary around 18,000 years ago, but has little preserved organic material.
