MAGNETOSTRATIGRAPHY OF THE MIO-PLIOCENE GRAY FOSSIL SITE, WASHINGTON COUNTY, EAST TENNESSEE
In order to better constrain the GFS age and depositional history, a composite section comprising of a 38.0 m core to Knox basement and a 12.0 m exposed section have been sampled for paleomagnetic analysis. All studies were carried out at the University of Florida Rock and Paleomagnetism Laboratory. NRM and bulk magnetic susceptibility data exhibit strong correlations to each other and to changes in core lithology. IRM studies and demagnetization behavior indicate that magnetite is the dominant carrier of the NRM. All samples were demagnetized using stepwise thermal (N=11) or alternating field (N=42) demagnetization. Nine thermal demagnetization samples were rejected from the study because of inconsistent results attributable to the high organic content of these sediments. AF demagnetization was very successful. The combined results from the composite section yield a magnetostratigraphy characterized by seven polarity reversals. Although no unique tie to the magnetic polarity timescale is possible with the current age constraints provided by vertebrate taxa, magnetostratigraphic data suggest that the GFS had a depositional history that exceeds 1.0 myr.