Vibracore and Tree Stump Data from the Marsh Near Mary Hammock, McIntosh County, GA

The purpose of this study was to determine the geologic/ sedimentologic history of the marsh near Mary Hammock, a marsh island in McIntosh County, GA. During the Summer of 2009, a vibracore machine was used to extract six sediment cores (MT01 through MT06) from the marsh north of Mary Hammock. In addition, tree stumps buried under the marsh were recorded, and one was extracted and analyzed, to facilitate in understanding the sedimentological history of the marsh. A GPS unit was used to record the precise locations and elevations of the core extraction sites and stumps. The cores were then transported to the Georgia Southern Coastal Research Lab at the Skidaway Institute of Oceanography (SkIO), in Savannah, GA, for analysis. The tree stump was brought back to the University of Georgia for analysis. Although there was a large degree of bioturbation in the marsh near Mary Hammock, sediment core analysis (visual inspection, X-Ray analysis, particle size analysis, and analysis of organic matter content), and stump analysis (species determination and radiocarbon dating), revealed three main facies in the marsh. The topmost layer is recent marsh. The middle layer is a sandy layer, representing the former upland surface prior to sea level rise, inundation, and marsh formation (around 5,000 to 4,000 years ago). The bottom layer is a highly compact greenish-gray clay layer. The conclusion is that the former upland surface, consisting mostly of sandy soils, was inundated due to sea level rise around 4,200 B.P. Marsh sedimentation occurred after this, depositing fine-grained sediments on top of the sandy surface (Turck and Alexander, 2013).