The summer of 2011 will not be a quiet one in the Geology Department. In addition to a full complement of Geology majors working on research, the department is abuzz with construction as we convert the geology library into a new and commodious classroom. More than a dozen Geology majors are currently on campus collecting data and readying themselves for field campaigns.
I am collaborating on a project with Professor Brent Owens and four undergraduates to better understand the geology of the eastern Blue Ridge region in central Virginia. Our study area is located about two hours northwest of Williamsburg and the research is supported by a grant from the U.S. Geological Survey. We are producing a geologic map of the Alberene 7.5’ quadrangle, a patch of ground about 155 km square located just south of Charlottesville, in order to learn the geologic secrets of the Blue Ridge.
The Alberene Dream Team. From left to right- Andrea Jensen, Kevin Quinlan, an astonished Professor Brent Owens, Alex Johnson, and Molly Hahn discuss geologic research in the eastern Blue Ridge.
So why study this region? The rocks in the Alberene quadrangle are old and record a long history that includes two episodes of mountain building and two episodes of crustal rifting. Some Appalachian geologists place a tectonic suture (the boundary between ancient tectonic plates) in the eastern Blue Ridge whereas others are more circumspect. We are going to resolve that issue.
Shaded relief map of the Alberene 7.5’ quadrangle and surrounding area. Note the southwest-to-northeast ‘grain’ of the topography, a reflection of the underlying bedrock layers and their structure.
Molly Hahn’s research is focused on understanding the geometry and timing of brittle deformation (faulting and fracturing) in the rocks of this region. We’d like to know when the rocks broke, but deciphering the fracture geometry also aids in predicting the distribution and abundance of groundwater. The Alberene quadrangle is endowed with numerous mafic rocks (dark and dense rocks loaded with iron and magnesium) whose age and tectonic origin have long been debated; Andrea Jensen’s research will determine when and how these rocks formed. Alex Johnson is mapping the contact between 1 billion year old granitic rocks (exposed in the northwest part of the area) and a sequence of younger metamorphosed sedimentary rocks- is this boundary a fault or an unconformity (if you are uncomfortable with unconformities check out-Who’s unconformable? ). Rocks in the southern part of the area are sedimentary rocks of Mesozoic age (~200 million years old) and formed in a rift basin that presaged the opening of the Atlantic Ocean- Kevin Quinlan is working to understand the structural architecture of this basin and its later reactivation.
We leave for the green hills of the eastern Blue Ridge early on Monday morning. As the summer rolls on I’ll provide updates on the adventures, misadventures, and research discoveries of the Alberene Dream Team.