Haven’t had cell service for a couple of days, so getting caught up on posts. On Monday afternoon, we visited a great exposure of the Wilhite Slate. The Wilhite Slate is part of the Walden Creek Group, which is the uppermost part of the Ocoee Supergroup and overlies the Great Smoky Group. These are the Precambrian sedimentary rocks that were metamorphosed in the Ordovician and thrust over the Valley and Ridge rocks during the final stages of the assembly of Pangea.
At this exposure, numerous synclines and anticlines are present, with well developed axial planar cleavage. The students spent some time walking the roadcut, sketching structures, and measuring strike and dip of both bedding and foliation. Here’s a view of one of the anticlines. The northern limb (on the left) is nearly vertical, while the southern limb dips ~40° to the south. The axial planar cleavage is exceptionally well-developed and dips ~60° to the south. The strike of all of these planes is around N40E.
Of all the geologic structures in the Southern Appalachians, none are more significant than the Great Smoky Thrust. Forming the leading edge of the Blue Ridge, it defines the end of the Valley and Ridge and the start of much higher topography, higher metamorphic grade, more complex structures, and the first appearance of older, Precambrian rocks. It records over 400 km of displacement, bringing the metamorphosed and penetratively deformed Ocoee Supergroup up on top of Ordovician Knox Group dolostones. Its geometry is fairly flat, and several erosional windows have been cut through it. One of those windows is located near Townsend, TN, partially within Great Smoky Mtn. Natl. Park.
After camping Sunday night at Cades Cove, we set out this morning to see this structure. Here at White Oak Sink, the fault is exposed behind a waterfall where a small stream enters a cave system. On the trail to White Oak Sink, the Metcaf phyllite is easily seen, which has a strong cleavage fabric that dips to the South. Here is a shot of these rocks. Pictures of the Great Smoky Thrust behind the waterfall at White Oak Sink will have to come later since I didn’t take any pictures of it with my phone!
This morning we drove north to see folds and faults in the TN Valley and Ridge. Our first stop was to see the Copper Creek thrust, one of the major faults in this area. It is beautifully exposed in a roadcut on TN-31. Here, Lower Cambrian Rome Fm., mostly shale, is thrust over Middle Ordovician Moccasin Fm. micrite.
We also viewed an anticline in the hanging wall thrust sheet with “S” shaped parasitic kink folds, deformed mudcracks, and a thrust duplex structure.
Not bad before lunch!
Yesterday we left the ONU campus, 13 of us in an Olivet minibus. We drove south to Knoxville, TN, where we spent the night at the E TN Nazarene campground. We appreciate their hospitality, which makes trips like this possible for our students.
Today, we are headed to see faults and folds of the Valley and Ridge. A number of primary sedimentary structures and secondary deformation structures wil make for some excellent geology! More to come!
Students in GEOL 366: Structural Geology & Field Methods are spending their Spring Break exploring the geology of the southern Appalachian mountains! We leave Saturday morning and return the following Friday. We’ll see lots of faults & folds & other evidence of the powerful forces that shape the Earth as we see it today. Our time will be spent in the Valley & Ridge of eastern Tennessee, the Blue Ridge foothills, and a transect across the Blue Ridge into North Carolina, Georgia, & South Carolina to see the changes in mineralogy, rock type, & structure with increasing metamorphic grade. Stay tuned to the blog here or our department Facebook page to see the updates as we travel next week! Here’s a snapshot of the Big Map that shows the area where we’re headed:
Geologic Map of the Southern Appalachians & Surrounding Regions
I took dry-erase marker to plexiglass today in order to do our first educational mark-up of the Big Map that I posted about a week ago. Our first topic? Tectonic plates! The boundaries of the North American, Pacific, Juan de Fuca, Nazca, Caribbean, South American, and Eurasian plates were all marked with blue marker, and each plate was labelled with its name. The final touch was to add some vectors (showing magnitude and direction!) to indicate relative plate motions. We’ll leave it up for a couple of weeks so people can come by and have another look at our world. After that, another topic will be in order! In the future, expect to see mark-ups for volcanoes, rivers, glaciers, & more! What would you like to see on it? Here’s a photo of the mark-up – not a great quality picture, but hopefully gets the point across!
Locations of tectonic plates marked in blue, as well as vectors showing relative motion.
A very large geologic map of North America & surrounding areas is being hung in the hallways of Reed Hall! This map is the 2005 Geologic Map of North America, published by the Geological Society of America. At about 6′x6′ wide & tall, it is large enough that a small class group can view and discuss it together. It is a thing of beauty! It will be used by geoscience faculty to aid in teaching about our Earth. A thin piece of plexiglass will be mounted over the top with a frame around the exterior. The plexiglass will allow faculty to use dry-erase markers to temporarily write and draw over the top of the map to highlight various geological themes, such as tectonic plates, volcanoes, earthquakes, glaciers, river drainage basins, and more! We hope that this will be a great resource for our students’ education.