By | Hali Englert ’15
Castle Rock, Colorado

 I am pursuing the origin of these rocks for clues to Antarctica’s history and our future.

My investigation of the geologic history of Antarctica began when I received in the mail a dozen dropstones, the largest just the size of a split deviled egg. Dropstones are isolated fragments of rock found within sedimentary rocks. It was a strange feeling, pulling the rocks out of their sealed baggies, exposing them to air for the first time in almost 30 years. I was so in awe of these little rocks that I would cradle them in my hands as I moved around the lab, terrified to lose or break a little piece of history older than me by over a billion years. 

These dropstones came from core samples taken off the coast of Antarctica from the Weddell Sea—the southernmost part of the Atlantic Ocean— by the International Ocean Discovery Program (IODP) in 1987. The cores have been stored in the IODP at Texas A&M University, where we conducted our primary research using X-ray Fluorescence (XRF) spectroscopy. 

Our aim in examining the Weddell cores was to interpret more of the Pliocene climate of 5 million to 1.6 million years ago. My role was to examine the dropstones that had been carried out to sea on icebergs and deposited on the ocean floor to determine their possible origins on the continent of Antarctica. 

This involved an arduous process of cutting, crushing, and polishing these rocks into forms in which they can be examined via light microscopy, Scanning Electron Microscope (SEM), or XRF spectroscopy. Along with other data collected by my research team, part of a project funded by the Keck Geology Consortium, we will be able to better understand what happens when ice sheets, like that which once covered the Weddell Sea, melt. This information could prove very important as we deal with the coming effects of climate change. 

It’s a tremendous task—interpreting the history of the little rocks ice-rafted out to sea and deposited in a warm climate perhaps similar to our future climate. It has been an eye-opening experience and I haven’t even processed all my data yet. Over the course of my senior year at Macalester, I am pursuing the origin of these rocks for clues to Antarctica’s history and our future.



November 18 2014

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