We now return to Mount Washington, New Hampshire, where our intrepid heroes summit the mountain in a mere three hours (from Pinkham Notch via the Lion Head): To refresh your memory of the story so far, we had seen metamorphosed turbidites, like this one (new image): …and checked out some gorgeous metamorphic porphyroblasts of “pseudoandalusite,” … Read more
At last weekend’s northeastern / north-central GSA meeting in Pittsburgh, David Saja of the Cleveland Museum of Natural History presented a talk entitled, “Geometric Analysis of Folded Greywacke Layers from Pacheco Pass, California.” [Abstract link] In addition to the standard PowerPoint presentation that 99% of GSA speakers use, David also brought in some hand-samples (what … Read more
Walking back to my hotel after departing the Northeastern / North-central GSA section meeting on Sunday, I noticed this fine shear band cutting across a polished slab of granite on the exterior of an office building in downtown Pittsburgh: You’ll notice some grain-size reduction along that shear zone, and what looks to be a decent … Read more
Background geology of the Sugarloaf Mountain area. (March 2010) Primary structures in the meta-sandstone of the Sugarloaf Mountain Quartzite. (yesterday) Background on tension gashes. (August 2010)
More from Mount Washington, New Hampshire: some folds in the Madison Member of the Littleton Formation (schist) along the auto road near Cragway Springs (just past 5 miles up; see map below): IMAGE SOURCE The folds are asymmetrical, with long west-dipping limbs, and shorter east-dipping limbs. Happy Friday!
That title sounds kinky, right? Well, calm down. I’m behind the curve on the latest Accretionary Wedge (as I was for the one before that), but here’s a quick image to join the parade of geologic photos that Ann is hosting. While it’s not my favorite, it’s definitely a favorite, more by virtue of the … Read more
Another fold seen in the Catoctin Formation, where last week we encountered a very different style of folding — chevrons overprinting Catoctin foliation. Here, we instead have a light colored vein that appears to have been buckled into a semi-ptygmatic form. The trace of the foliation in the Catoctin is discernible, too. Enjoy your Friday!
Last Sunday morning, two of my former GMU students, Aaron and Alan, led a hike for the GMU Geo-Club to Thoroughfare Gap, a water gap in the Bull Run Mountains of Virginia’s eastern Blue Ridge province. I’ve mentioned the Weverton Formation structures we saw there, and a nice example of a hackle fringe in previous … Read more
Another serendipitous sighting on last weekend’s field trip to Thoroughfare Gap was this boulder of Weverton Formation, lying in the no-man’s-land between the railroad tracks and Broad Run: As you look at this boulder, I hope you will notice what caught my eye and prompted me to take the photo. There’s a big flat surface … Read more
Callan joins some students from George Mason University on a field trip to the rock exposures at Thoroughfare Gap, Virginia, where meta-sedimentary rocks are exposed in the eastern Blue Ridge province.