The 20th annual Symposium will be held on Thursday, April 23, 2009.

Analysis of a Basanitic Hydrovolcano at Minna Saddle, Antarctica
Norris 100, 2:45 PM

Meagan  Bosket,   '09 15
   Major: Geology
   Hometown: Eureka, MT

Sponsor(s): Thomas Wilch
Support: FURSCA- Julia Robinson Burd, '31 Memorial Fellowship, Taylor Fund for Undergraduate Research, National Science Foundation

Abstract: 
The Minna Saddle volcanic mapping project has three sections: an analysis of field data, a lithofacies and petrographic analysis, and a geochemical analysis.

The 0.5 X 1 kilometer outcrop is comprised of a well-preserved sequence of layered volcaniclastic rocks. Using observations made in the 2007-8 field season along with detailed descriptions of 25 hand samples and 33 thin sections, the rock outcrop has been divided into several lithofacies. Each of these lithofacies is indicative of a change in the eruptive and/or depositional mechanism. The alternating coarse and fine layers and sedimentary structures indicate variable water and magma interaction during the eruptive phase. Abundant deformation structures indicate that the outcrop was saturated following the eruption.

Geochemical analysis of two volcanic bombs and one volcaniclastic sample was completed using x-ray fluorescence, ICP-MS, 40Ar/39Ar geochronology, and electron microprobe analysis. The outcrop has been dated to an age of 0.92 ± 0.30 million years and it is basanitic in composition.

The field observations and lithofacies analysis are used to reconstruct the eruptive style(s) of the nunatak and determine what the deposits indicate about syneruptive ice levels. The main depositional mechanism was turbulent base surges brought on by discrete pulses of the eruption through the addition of discrete amounts of water or magma to the vent. The geochemical analysis helps to determine the outcrop’s relationship to the surrounding volcanism.

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