Wooster Geoscientists to Share Results of Research at Annual GSA Meeting

WOOSTER, Ohio - Research by geoscientists at The College of Wooster will be presented at the Geological Society of America's (GSA) 118th annual meeting, Oct. 22-25, at the Pennsylvania Convention Center in Philadelphia. The three-day event will feature presentations on a variety of topics, including six by Wooster faculty members and students.

Robert Varga, the Ross K. Shoolroy Associate Professor of Geology and Natural Resources, and senior Andrew Horst will present "Paleomagnetism of the Peach Springs Tuff Revisited." Together, they will summarize many years of work directed at understanding the history of large volcanic eruptions in an extensive region of the desert southwest during the period 20-17 million years ago. This area, which is centered on both sides of the Colorado River in northwestern Arizona and southeastern California, is significant because it was highly stretched through faulting during the same general time period, according to Varga. "Volcanic rocks laid down during this stretching event provide the geologic record used to reconstruct the complex history of the area," he said. "We try to match volcanic rocks from mountain range to mountain range in an attempt to figure out how these rocks might fit back together. Our presentation will discuss how we are using the magnetic properties of these rocks as a tool to match or correlate volcanic rocks between mountain ranges."

Jade Star Lackey, visiting assistant professor of geology, along with junior Kamilla Fellah and sophomore Robert Nowak, will discuss "Oxygen Isotope Evidence for the Origin of Garnet in the Peraluminous South Mountain Batholith, Nova Scotia." Lackey's talk relates to understanding the origin and evolution of the South Mountain batholith in Nova Scotia, a domain of granitic rocks that formed in the Devonian (370 million years ago) as the continents of North America and Africa collided with each other. "By measuring the oxygen isotope composition of the minerals garnet and zircon in the granites (the first analyses of this type reported for the batholith), we 'fingerprint' the relative contribution of pre-existing crust, sedimentary rocks, and the mantle to the magmas from which they crystallized," said Lackey. "Understanding the relative contribution of the three different 'reservoirs' helps us evaluate how magmas were formed and modified during the tectonic collision. Ultimately, this and related work addresses the big questions of how the processes of continental growth and crustal recycling have operated throughout Earth history."

Mark Wilson, the Lewis M. and Marian Senter Nixon Professor of Natural Resources and Geology, along with senior Cordelia Dennison-Budak and recent graduate Jeffrey Bowen will talk about "Half-Borings and Missing Encrusters on Brachiopods in the Upper Ordovician: Implications for the Paleoecological Analysis of Sclerobionts." Their work is the analysis of a common set of borings found in the shells of brachiopods (marine organisms with bivalved shells) in Ordovician rocks (about 450 million years old). "The borings are odd because they look like shallow ditches cut across the shells," said Wilson "It is clear that they were originally tubular borings cut half-way into the brachiopod and halfway into something which was attached to the brachiopod. We suggest that the missing attaching organisms were bryozoans (another marine organism) that had since fallen off the brachiopod shells, leaving as evidence these 'half-borings.' An assumption in this kind of paleontology is that attaching organisms, such as bryozoans, stay permanently attached to their hosts. We have evidence that this is not true, and it makes a difference when we reconstruct the ecology of these ancient communities."

Greg Wiles, associate professor of geology, along with senior Eva Lyon and Dan Lawson of the Cold Regions Research Engineering Laboratory in Hanover N.H., will address "Extension of a Multi-Millennial Tree Ring Series from Southern Coastal Alaska using Subfossil Wood from Glacier Bay National Park and Preserve: A Record of Subarctic Climate Forcing." The trio will share the results of a new project aimed at assembling long tree-ring records of past temperature change from Glacier Bay National Park and Preserve, Alaska. In addition, Wiles and senior Nathan Malcomb will present "Tree-Ring Based Mass Balance Estimates for Wolverine Glacier, Southern Alaska, A.D. 1554-1987." The two will talk about the results of using a network of tree-ring chronologies from the Pacific Northwest in a study that reconstructs glacier mass balance data from Alaska. Both of these studies are concerned with putting the recent changes in glacier and warming in a longer term, century to millennial-scale context.