Friday fold: a dome in plane view
The Friday fold is a structural dome in Wyoming, as seen out an airplane window.
structure
Friday folds: Selkirk Fan
The Friday fold is a selection of five fold photos from the Selkirk Fan in the Omineca Belt of British Columbia, submitted by structural geologist Marek Chichanski of De Anza College (California).
Ribs & hackles
Concentric ribs with hackles on a joint face, quartzite (metamorphosed fine-grained quartz sandstone stained with hematite) from Waterton Lakes National Park, southern Alberta.
Paw Paw Tunnel GigaPans
A weekend expedition to GigaPan the C&O Canal’s singular Paw Paw Tunnel results in an exposition on Devonian sedimentation, Alleghanian mountain-building, structural geology, and the incision of the Potomac River to produce entrenched meanders.
Friday fold: soft sed def in Kodiak
The Friday fold is a seaside outcrop of soft sediment deformation (not post-lithification tectonic deformation) on Kodiak Island, Alaska.
What those geologists were looking at
Yesterday, I showed you a scene of geologists (including me) clustered around some (presumably interesting) outcrop. I asked what you thought we might be looking at. Howard Allen, a denizen of this part of the globe, immediately identified the scene as that of the downstream end of the Athabasca Glacier. Several people guessed that we … Read more
Structures seen at Floe Lake
A showcase of geologic structures observed between downpours of rain at Floe Lake, Kootenay National Park, British Columbia. Cleavage, bedding, folds, faults, and strain are all presented for the discerning structural reader’s edification and titillation.
Friday fold: boxiness in Oman
Max Arndt contributed this week’s Friday fold: (click on the image to get to a larger sized version on Max’s Flickr page) That’s the Warah Formation exposed on the Batain Coast of northeastern Oman. This is the thrust front of a thin-skinned fold and thrust belt. I think it’s just lovely! Max has a ton … Read more
Veins perpendicular to foliation
To recap the week so far here on Mountain Beltway: On Monday we looked at some sweet vertical boudinage along the plane of tectonic cleavage (not to mention those folds in a (formerly) horizontal granite dike, now bearing vertical axial planes), and then on Tuesday we looked at a horizontal cut through that same outcrop, … Read more
Deformed pillow basalts from southern Ontario
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!
Exquisite boudinage in Ontario
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.
Friday fold: Nashoba migmatite
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
Blue Ridge Thrust Fault field trip
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…
Overturned bedding in Poleta (?) Formation, White Mountains, California
After a roadside explanation just an hour and a half earlier on how the relationship between bedding and cleavage can reveal whether bedding is likely right-side-up or up-side-down, my students and I were walking up the road to the Ancient Bristlecone Pine Forest in the White Mountains of California, and I saw this outcrop that … Read more
Poleta plume paradise
On Monday, my field course students and I tried to find the Poleta folds, but I had failed to figure out in advance the best access point. Oops. That’s the way the cookie crumbles, when you’ve got big plans but not enough time to enact them with appropriate pre-planning. We had some happy exploration of … Read more
Friday fold: one from the Billy Goat Trail
Meter-scale fold in metagraywacke layers at the head of Mather Gorge, Maryland shore of the Potomac River, highlighted by differential weathering along the layering. Annotated interpretation: Happy Friday!
One from the UTEP Reading Room
Incipient mylonitization of a granite/granitoid, as displayed in a sample on a shelf of one of the meeting rooms adjacent to the Reading Room of the Geological Sciences building at the University of Texas at El Paso. Same side, slightly different lighting conditions: I’d call this a protomylonite. Some of you might prefer the term … Read more
Friday fold: Veach Gap anticline, in GigaPan
GigaPan by Alan Pitts, as part of the M.A.G.I.C. project that we are working on. Here’s another one from a few meters away. Here’s a shot from 2.5 minutes after Alan saw this anticline for the first time. Here’s some shots of my own early visit to the site, after I first found it.
Contorted fractures in the Contorted Bed
Today, let’s zoom in on a little something I saw at the outcrop of the Contorted Bed in downtown Johannesburg, South Africa: What are these things? I only saw them at this one spot. These look to me like en echelon fractures at a high angle to bedding, that were then deformed due to dextral … Read more
Recumbent fold in Sierra de Juarez, Mexico
Callan looks south across the border from Texas. Above the drug-war-ravaged town of Juarez, the Sierra de Juarez Mountains feature an enormous recumbent synform.