Home | Business News | Browse by Publication | G | Georgia Journal of Science

Section III: Earth & Atmospheric Sciences.

Article Excerpt
8:30 EXPLORING ALGAL MORPHOLOGY DURING EARLY DECOMPOSITION: CONNECTIONS TO ANCIENT ORGANIC REMAINS**, Ashley Manning* and Julie Bartley, University of West Georgia, Carrollton, GA 30118. The early fossil record consists entirely of microbial fossils, the first of which were unicellular and filamentous bacteria. During the Proterozoic, the record additionally contains single-celled planktonic eukaryotes (acritarchs), dominantly preserved in shales and a few macroscopic remains. The relatively simple morphology of these fossils makes them difficult to identify reliably and, particularly, to connect these remains to extant taxonomic groups. Furthermore, it is difficult to know whether preserved features reflect taxonomy or are instead due to taphonomic processes. Taphonomic alternation may be responsible for creating the morphotypes seen, leaving the original taxonomy unrecognizable. In this project, we are observing morphological features that are preserved or created during early post-mortem decomposition of modern megascopic algae. In this experiment, we aim to connect specific features observed in these modern algae to structures seen in ancient meso-and macroscopic algal remains, such as Grypania, Chuaria, and ancient organic films. In making these observations, we will identify specific processes that might have produced ancient features such as folding, rolling, or ultrastructural alteration and connect these to specific taxonomic groups.

8:45 INVESTIGATION OF METAMORPHIC CONDITIONS ASSOCIATED WITH THE GROWTH OF CENTIMETER-SCALE GARNET PORPHYROBLASTS AT THE GARNET HILL LOCALITY, WEST-CENTRAL GEORGIA**, Nelson Spratt IV* and C.A. Berg, University of West Georgia, Carrollton, GA 30118. Samples collected from the Garnet Hill locality contain idiomorphic garnet porphyroblasts up to two centimeters in diameter that have grown in a fine-grained phyllitic matrix. This study is a preliminary assessment of the metamorphic conditions associated with the development of this texture, and an investigation of how changes in pressure, temperature, fluid composition, and/or deformation during garnet growth may be manifested in the internal textures and chemical zoning of these porphyroblasts. Thin-sections cut approximately through the centers of the large garnet porphyroblasts were oriented orthogonal to the dominant matrix foliation, and either parallel or orthogonal to the weakly-developed mineral stretching lineation in these samples in order to identify metamorphic mineral assemblages and deformational fabrics preserved in the matrix and within the garnet porphyroblasts themselves. Analysis on the SEM-EDS instrument at UWG will identify important accessory phases and microscopic inclusions and to determine the spatial distribution of inclusion assemblages. Chemical mapping using the SEM-EDS provides preliminary data on garnet chemistry and internal chemical zonation. Crystallographic orientation of subcrystals within the garnet porphyroblasts, the degree of development of low-energy grain boundaries, and deformationa! fabrics preserved within the matrix will be examined using electron backscatter diffraction (EBSD) mapping.

9:00 PRELIMINARY RESULTS FROM HIGH-RESOLUTION MAGNETIC SURVEY OVER LARAMIDE AND BASIN AND RANGE STRUCTURE, BIG BEND NATIONAL PARK, TEXAS, John Allison*, C. Parham* and C. Poppeliers, Augusta State University, Augusta, GA 30904. We present results of a ground-based magnetic survey of two Tertiary-aged intrusions in the northern portions of Big Bend National Park, TX. Ongoing field mapping of Cretaceous sedimentary rocks has identified numerous intrusions that appear to be cross cut by Laramide and post-Laramide deformation in the South Persimmon Gap Laccolith (SPGL) and Dagger Mountain areas. We use the results of several magnetic profiles...