Dr. Paul A. Schroeder

Research Interests - Paul A. Schroeder

My research interests center around the detailed crystal-chemical characterization of minerals associated with weathering and diagenetic environments. Particularly as these minerals serve as proxies to record geochemical conditions throughout earth history and as these minerals serve as indicators of environmental change. Clay minerals are the most common and reactive solid components in the Earth's surface therefore, most of my research activities involve the study of these fine grain particles using, non-traditional spectroscopic methods such as nuclear magnetic resonance, vibrational spectroscopy, stable isotopes, as well as traditional chemical and diffraction methods. Research activities include: Biomineralization in hot spring environments Recent interdisciplinary collaboration with microbiologists have led to my studies in Geomicrobiological Interactions and Carbon Flow in Extreme Thermal Springs. I have just completed a study on biosignatures in sinters from Yellowstone National Park and have started biomineralizaton studies in Kamchatka, Russia along with an international team of scientists. This work is being supported by two of the National Science Foundations programs including: (1) Biocomplexity and the Environment: Coupled Biogeochemical Cycles and (2) Microbial Observatories. In this unique collaborative and interdisciplinary effort along with 7 other scientists, we will address questions related to understanding the role of micro-organisms in hot springs. What this may boil down to for non-scientists may be as mundane as discovering novel enzymes for manufacturing processes or as esoteric as a better understanding of how life began. Geologic record of climate change A National Science Foundation supported study of A modern test of the assumptions used for determining paleo-atmospheric carbon dioxide from goethite-bound carbon. The concept of using goethite-bound carbon isotopes as a proxy for estimating paleo-atmospheric PCO₂ throughout the Phanerozoic has been a kingpin for paleoclimatic modeling efforts such as Bob Berner's GEOCARB model. In this study we propose a modern test of the underlying assumptions used by Crayton Yapp, developer of the goethite inferred paleo-atmospheric PCO₂ barometer. The work is being performed on soil/saprolites found overlying granite terrains in the Piedmont of Georgia, including Panola Mt. Georgia. NSF Project description In our most recent work we have found that carbon is bound in gibbsite. Sanples collected from a residual weathering profile developed on a Paleozoic granite in the Georgia Piedmont, were examined for ¹⁴C content and found to be geologically young. The study site, located at the Panola Mountain Research Watershed, has developed a granite/saprolite/soil regolith in which ¹⁴C-gibbsite model ages deep within the profile (C-horizon) average about 8000 years. Near the surface (A- and B-horizon) ¹⁴C gibbsite model ages range from 2100 to 4200 years. Quartz has acquired 26Al and 10Be inventories suggesting a near-surface residence time of at least 90,000 years. This age disparity supports the notion that secondary minerals undergo significant recrystallization as weathering fronts propagate into the landscape. Combining the results of ¹⁴C, ²⁶Al, and ¹⁰Be analyses offers the potential to assess differential rates of chemical weathering and continental denudation in order to understand better the links between rates of silicate rock weathering, climate, and soil residence times. X-ray Diffraction and Vibrational Spectroscopy A National Science Foundation supported Intruement and Facilities grant to upgrade the X-ray diffraction and FTIR facilities for mineralogical research. NSF EAR-9911501 . This grant from the National Science Foundation Earth Sciences Instrument and Facilities Program provides partial support for the costs of upgrading the X-ray diffraction (XRD) and Fourier transform infrared spectrometer (FTIR) facilities for mineralogical research in the Geology Department at the University of Georgia (UGA). These upgrades at UGA will allow continued analytical support to a robust geological research and teaching program. Approximately 50 geology students per year receive practical training and/or theoretical familiarization with these analytical methods. XRD and FTIR labs are generally considered cost-effective analytical facilities and are commonly used by geological industries. For this reason, students who receive training are placed at a competitive advantage in the job market. Kaolin Research Investigations of impurities associated with kaolin deposits. The quality and nature of kaolin ore are important factors in the manufacturing of high-end paper coating products. One of the problems with processing the mined kaolin is the difficulty in stripping the kaolin of all the impurities without drastically reducing or losing the usable product. I have developed a novel spectroscopic method for quantifying trace contaminants in clay ores. My published works on kaolin crystal-chemistry in the clay deposits have given new insights to their geologic origins and industrial utilization. In association with his work in the Georgia kaolin district, I have also co-discovered the first in-place evidence for a 35 million year old major meteorite impact deposit in the southeastern United States. Other research projects include studies of Discriminating short- and long-range iron ordering in kaolinite using vibrational spectroscopy. It is a two year project funded by English China Clay International Inc (now IMYERYS). Research projects have also included (a) Studies of impurity phases associated with East Georgia Kaolin Deposits, a two year project supported by the J.M. Huber Corporation and (b) Investigation of ordering schemes for Fe substitution in kaolinite using ²⁷Al and ²⁹Si MAS NMR spectroscopy supported by English China Clay International Inc.