Another landform seen out the window of that very productive photo-flight last March: That’s a breached plunging anticline – doubtless a Laramide structure. This was over Wyoming; I think here. Looking north-ish, along the axis of the fold: Note that the lengths of section line A and B are not equal: this anticline is asymmetric. … Read more
Callan describes the geology along his new commute from the Fort Valley east to the Annandale campus of NOVA. The driving route traverses the Valley & Ridge, Blue Ridge, and Piedmont provinces, including the Culpeper Basin, and stops just shy of the Coastal Plain.
A sketch of the Massanutten Synclinorium is presented, made with a Wacom Cintiq stylus/monitor combination.
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.
The Friday fold “guest fold” series continues with a folded ultramylonite from South Africa.
Another guest submission for the Friday fold: Callan – Please find enclosed a collection of photos you could possibly use for a future Friday Fold blog post. The following photos were all taken by me on Sunday, April 29th, in the vicinity of Bedford Peak and the Maple Springs Trailhead (Silverado Canyon Road), Cleveland National … Read more
Callan and his wife hike Cory Pass in Banff National Park, Canada, and encounter some geology, some solitude, and a spectacular landscape.
Have you ever seen Archean pillow basalts? How about Archean pillow basalts that have grown much taller through vertical extrusion along a ductile shear zone? Come to the southern Superior Craton to see more!
Callan shares images of extraordinary boudinage outcrops in strained Archean meta-basalts on the Quetico-Wabigoon subprovince boundary within the southern Superior Craton. Ogle these gorgeous structures in awe and wonder.
The Friday fold is a contribution from the Massachusetts Geological Survey. It shows a migmatite with lovely structure. An upcoming (free) field trip to this location will be part of the 2012 Structural Geology and Tectonics Forum: an event readers may be interested in attending
I got this note via email last week. Hi Callan, First of all, congratulations to your blog. It is just great. I would like to contribute to your “Friday fold” section. A few words about myself. I am born in Austria and did my BSc and MSc at the Montanuniversitaet Leoben. In September 2011 I started … Read more
Callan reviews two books about climate change: the nonfiction account by Michael Mann, and a fictional thriller set in the warmed Arctic of the future.
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.
When are sedimentary layers also faults? …When the slab-like layers slip over and under one another during the act of folding. Structures traditionally confined to faults show up on the bedding plane in these circumstances. Callan shares a shiny example from West Virginia in the form of an animated GIF.
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.
In December, Callan found an outcrop of Neoproterozoic-aged turbidites in South Africa, on the eastern shore of False Bay.
One of Callan’s former advisers, Dave Lageson of Montana State University, heads to the summit of the world’s tallest mountain with his graduate student, the accomplished mountaineer Conrad Anker.
Callan and his field studies students encounter a lesson in the White Mountains of eastern California that combines bedding, cleavage, folding, and even fossil archaeocyathids!