HR: 0830h
AN: OS11A-15    [Abstracts]
TI: Clay Mineralogy of a Pleistocene Barrier Island, Skidaway Island, GA
AU: * Shaffer, M
EM: mshaffer840@hotmail.com
AF: Georgia Perimeter College, Department of Geology, Decatur, GA
AU: Shackford, J K
EM: jshackford1@student.gsu.edu
AF: Georgia State University, Department of Geology, Atlanta, GA 30303
AU: Elliott, W C
EM: geowce@langate.gsu.edu
AF: Georgia State University, Department of Geology, Atlanta, GA 30303
AU: Christensen, B A
EM: bchristensen@gsu.edu
AF: Georgia State University, Department of Geology, Atlanta, GA 30303
AU: Freile, D
EM: dfreile@berry.edu
AF: Berry College, Department of Geology, GA
AU: Hillier, C
EM: xxx@yyy
AF: University of Durham, Department of Geography,
AU: Horton, B P
EM: xxx@yyy
AF: University of Pennsylvania, Sea Level Research Laboratory, Department of Earth and Environmental Science, PA
AB: A dense blue clay underlies various marsh localities near the Skidaway Institute of Oceanography (SKIO). SKIO is located on a Pleistocene barrier island in Georgia. The clay is found in two cores drilled at the high marsh/maritime forest transition zone. It was recovered at a depth of one meter, below unconsolidated marsh sediment. A total of 12 clay samples were collected at 10cm intervals downcore beginning at 100cm, through the clay layer. The thickness of the clay layer is unknown due to core refusal at a heavily iron oxide mottled zone. Samples were examined for the presence of diatoms and foraminifera, neither of which were found to be present, thereby suggesting a non-marine environment, although dissolution may be a factor. Geochemical data also lacks a definite marine signature, thereby confirming the micropaleontological conclusions. Smectite, illite, and kaolinite were found throughout both cores with halloysite present only below a depth of roughly 120cm. These particular clay minerals have been identified in blue clays analyzed in the Carolina Bays of southern North Carolina. Halloysite is typically a metastable phase forming from the weathering of illite to kaolinite, thus the location of the halloysite found in these cores indicates more recent weathering of the parent illite at depth. This is unusual as weathering is normally thought to be more intense closer to the surface. Vermiculite, which is also part of the general weathering scheme of mica, was not identified in the cores based on the behavior of the samples after solvation in ethylene glycol and potassium-saturation. The observed clay assemblage is similar to that of North Carolina Carolina Bays. Carolina Bays are found from Virginia to Georgia, and are found to contain blue clays (Ingram et al., 1959). Morphologically, Carolina Bays are typically elliptical and while the study area is more rounded, this could be due to its modification by an active tidal system.
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 3655 Major element composition
DE: 3665 Mineral occurrences and deposits
DE: 4863 Sedimentation
DE: 4885 Weathering
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly