b'Opaline Cements of the Altamaha Formation in Central Georgia: a petrographic analysisTravis M. WestSponsor: Dr. Mark S. Groszos, Department of GeosciencesThe Altamaha Formation of central Georgia consists of well-indurated Miocene sandstones. Previous workers, as well as this study, have documented opaline and silica cements in these rocks. The origin of these cements and their associated depositional environment is unclear. This study is an attempt to better characterize these cements through petrographic analysis and hand sample examination. Various samples have been collected from the Central Georgia Coastal Plain region including locations from Ashburn, Georgia to Soperton, Georgia. These rocks are poorly sorted, angular, well-indurated, feldspathic to sub-feldspathic sandstones. They generally show significant volumes of matrix and silica cements. Minor amounts of clay and carbonate cements have also been observed. The previously mentioned matrix is problematic because these rocks are not graywackes. The formation is interpreted to be terrestrial due to the presence of terrestrial fossils along with terrestrial depositional features. Initial analysis of thin sections revealed that some of the cement is true opaline though other portions of cement appear to be chalcedonic quartz or in transition from opaline to chalcedonic quartz. In hand sample, these cements are opaque white with conchoidal fracture and do not show opaline luster.Properties of an Iron Octahedrite Meteorite collected at Odessa Meteorite Crater, Odessa, TXCameron G. HesterSponsor: Dr. Martha Leake, Department of Astronomy and PhysicsAn iron octahedrite was analyzed through observations of its physical and chemical properties in order to understand and classify those characteristics common to iron meteorites. The total weight of the meteorite was 406.37 grams. It exhibits a high degree of magnetism, high specific gravity, and nickel content of at least 1.0 x 10^-3%. The meteorites surface is stained with iron oxide and covered in regmaglypts resulting from ablation during its fall through the Earths atmosphere. A portion of the sample weighing 20.79 grams was removed in order to produce an etched, polished thin section for petrographic analysis. The area from which the thin section was cut has been highly polished and prepared to be etched with an acid solution in order to reveal a Widmansttten pattern on the meteorite. A Widmansttten pattern visually represents the octahedral structure in the metal formed by laminae of kamacite and taenite. Utilizing reflected light microscopy, the average kamacite band width is measured and used to further classify the octahedrite in the range of coarsest to finest, as well as estimate its cooling rate. The purpose of this study is to become familiar with the process of investigating and documenting an iron meteorites qualities.76'