Tuesday, 28 August 2007 - 2:10 PM
2.P1.C-3
One hundred negative magnetic anomalies over the West Antarctic Ice Sheet (WAIS), in particular Mt. Resnik, a subaerially erupted volcanic peak, indicate eruption through at least one field reversal
John Behrendt, INSTAAR, University of Colorado, Boulder, CO 80309-0450, Carol Finn, USGS, Federal Center, Denver, CO 80225, David Morse, UTIG, University of Texas, Austin, TX 78759, and Don Blankenship, The University of Texas at Austin.
Mt. Resnik is one of 18 subglacial, subaerially-erupted volcanoes which have high elevation and high bed relief beneath the West Antarctic Ice Sheet (WAIS) in the Central West Antarctica (CWA) aerogeophysical survey. Mt. Resnik, 300 m below the surface of the WAIS, has 1.6 km topographic relief. It has an associated complex negative magnetic anomaly. We calculated and interpreted magnetic models fit to the Mt. Resnik anomaly as a volcanic source comprising both reversely and normally magnetized 0.5-2.5-km thick flows subaerially during a time of magnetic field reversal. The Mt. Resnik model may represent the reversal at 780 Ka (or earlier). There are ~100 short-wavelength, steep-gradient, negative magnetic anomalies observed over the WAIS, or about 10% of the approximately 1000 short-wavelength, shallow-source, high-amplitude (50->1000 nT) "volcanic" magnetic anomalies in the CWA survey. These negative anomalies also indicate volcanic activity during a period of magnetic reversal >780 Ka.