Callan presents a collection of well-exposed amygdules, seen along the Dark Hollow Falls trail in Shenandoah National Park, Virginia. These white dots on a green background are the signatures of (1) Iapetan rifting, and (2) Alleghanian metamorphism.
Seen in rip-rap on the side of Naked Creek, a week ago yesterday: This boulder is exotic to its current location. It is typical of medium- and coarser-grained diabase from the Culpeper Basin, a Triassic rift valley east of the Blue Ridge. The main minerals are plagioclase (light-colored) and pyroxene (dark colored).
One of Callan’s former students leads a field trip to examine the western edge of the Blue Ridge geologic province, attempting to answer the question of whether the Blue Ridge / Valley & Ridge contact is indeed the trace of a thrust fault. Breccias and S-C fabrics tell part of the story…
Returning to his February field trip in west Texas, Callan examines the contact zone where the Red Bluff Granite intruded into a group of surficial rocks, including columnar-jointed basalt.
The Castner Marble is an extraordinary Mesoproterozoic limestone (later re-crystallized and metamorphosed) that exhibits some primary structures (both explicit and ambiguous) and some secondary (tectonic) overprints. It’s exposed in the Franklin Mountains of west Texas.
Callan’s field studies class journeys to Searles Lake, California, a playa rich in evaporite minerals both prosaic and exotic.
This is insane. Check it out – a malachitized and azuritized log, on display in front of the Geological Sciences building at the University of Texas at El Paso: Have you ever seen anything like that? It’s cool meets cool. Awesome.
With my new “macrogigapan” rig from Four Chambers Studio, I produced a single image last week as part of my Mid-Atlantic Geo-Image Collection project (M.A.G.I.C.). I’m still learning the ropes of the machine – I shot about 3 times as many photos as I needed to to make this gigapan. Lessons learned, yet again. Anyhow … Read more
With my new “macrogigapan” rig from Four Chambers Studio, I produced this image last week before I left on vacation: [gigapan id=”94714″] That sample measures 18.5 cm long, and is about 4.9 cm wide. Pretty good resolution, eh?