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

Interpretations of Eruptive and Depositional Environments of the Minna Bluff Volcanic Complex, Antarctica
Poster Session-Science Complex Atrium, 4:00 PM

Laura  Painter,   '09 83
   Major: Geology
   Hometown: Hillsdale, MI

Sponsor(s): Thomas Wilch
Support: National Science Foundation

Abstract: 
Detailed analysis of volcanic and sedimentary rock samples from Minna Bluff, Antarctica, provides important clues about the original eruptive and depositional conditions. Minna Bluff is a 45 km long volcanic peninsula that extends east from Mt. Discovery into the Ross Ice Shelf in Antarctica. Minna Bluff is composed of hundreds of overlapping volcanic deposits erupted between 12 and 6 million years.

More than 150 rocks from Minna Bluff were processed and prepared as microscopic thin section slides. The rock thin sections, along with hand samples, were then analyzed for mineralogy, alteration textures, grain shape, size, and sorting. One important distinction that can be assessed in the samples is whether there was any interaction between the erupting magma and water, which may indicate eruption during a glacial period. Another important distinction is the type of sedimentary structures and textures, which may indicate either a volcanic or sedimentary mode of deposition.

Three key lithofacies (rock-depositional environment) associations were observed: 1) pillow lavas and glassy breccias, indicative of rapid water cooling; 2) oxidized lavas indicative of no water interactions and ice-free conditions; and 3) glacial and other sedimentary deposits indicative of inter-eruptive erosional events and deposition. The thin section results combined with field data indicate that the Minna Bluff volcanic complex formed during changing environmental conditions. The rocks record eruptions during small glaciations, eruptions during non-glacial intervals, and periods of overriding by a large-scale ice sheet.

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