2009 Portland GSA Annual Meeting (18-21 October 2009)

Paper No. 10
Presentation Time: 9:00 AM-6:00 PM


MILLER, Lauren1, SIMMS, Alexander Ray1, CRUSE, Anna1, ATEKWANA, Eliot A.1, YOKOYAMA, Yusuke2 and RODRIGUEZ, Antonio3, (1)Boone Pickens School of Geology, Oklahoma State University, 105 Noble Research Center, Stillwater, OK 74078-3031, (2)Ocean Research Institute/Department of Earth and Planetary Sciences, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo, 164-8639, Japan, (3)Institute of Marine Sciences, University of North Carolina, 3431 Arendell St, Morehead City, NC 28557, lemille@okstate.edu

Climatic instability at 8.2 ka is identified by multiple climate proxies from Greenland ice cores and other climate proxies found throughout the globe. The 8.2 ka event is characterized in the Gulf of Mexico by a warming and drying trend, which influences weathering patterns. Magnetic susceptibility of sediment and rock has been suggested as a tool to indicate changes in weathering patterns, source areas, trace metals, and grain sizes, each of which may also provide a record of paleoclimate. We test the utility of magnetic susceptibility in recording the 8.2 ka event within Holocene estuarine deposits from five cores taken in three bays along the Texas coast of the Gulf of Mexico: Baffin, Corpus Christi, and Galveston Bays. Measurements were taken at 5 cm intervals in the five different cores. Radiocarbon dates were used to calculate sedimentation rates in order to date anomalies in magnetic susceptibility. Multiple anomalies were found in the upper 4 to 10.4 m that we associate with other climatic events of the late Holocene or due to groundwater induced diagenesis noted by the presence of several carbonate nodules. The analysis indicates three anomalies in magnetic susceptibility near the 8.2 ka event at 8.7 ka, 8.3 ka, and 8.1 ka. The values of the anomalies are significantly larger than the magnetic susceptibility of the samples above and below these dates. Trace metals indicate several anomalies at the magnetic susceptibility spikes; however, Fe concentrations are not elevated compared to background levels because magnetic hosts were impervious to the digestion process. X-ray fluorescence studies are underway to determine the nature of the anomalies in magnetic susceptibility. This finding is in partial agreement with other studies suggesting the 8.2 ka event may have been marked by more than one climate change or shift. The correlation of the climatic events within multiple bays along the Texas coast also suggests that magnetic susceptibility may provide a correlation tool within estuarine fills from across the Gulf of Mexico Basin and perhaps across the globe.