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14 September 2018
A trip back to Archean sedimentary rocks in Barberton, South Africa, reveals a few folds on the roadside…
7 September 2018
The first Friday of September calls out for a fold. The Burle Business Park in Lancaster, Pennsylvania has an answer – several of them, in fact!
27 July 2018
Hiking Siyeh Pass in Glacier in Glacier National Park on Tuesday with my Montana State University field course, we spotted a few new folds in the Empire Formation (a transitional unit between Helena Formation and Grinnell Formation). Here is one of the students serving as a sense of scale, with interesting features on either side of him: On the left, there are small scale folds in a regular little train: …
6 July 2018
Last week, I spent two perfect days camping with family at Usal Beach, in Mendocino County, California. Along the beachside cliffs there, I spotted plenty of lovely turbidites: graywacke and shale and a little bit of conglomerate that had been scraped off the subducted Farrallon Plate to help contribute to the bulk of the Franciscan complex. That accretionary process imparted some stresses on these deep-sea deposits, and in many places …
23 June 2018
Fifteen years after mapping deformed rocks of the Sierra Crest shear zone system in the high Sierra, a family vacation brings Callan back to the pre-batholith metasedimentary rocks which show a pronounced strain.
1 June 2018
Marli Miller is a senior instructor at the University of Oregon. She is the author of Roadside Geology of Oregon and (with Darrel Cowan) Roadside Geology of Washington. She’s also a very talented geological photographer. She launched a website recently to showcase her work and make it available for instructors: Geology Pics. After chatting with Marli a bit in Flagstaff at the Rocky Mountain / Cordilleran section meetings of GSA …
7 May 2018
A visual challenge via Twitter to determine stratigraphic younging direction ends with equivocal results. So let’s use GIGAmacro imagery to school your sedimentological students on how three primary sedimentary structures look different right-side-up versus up-side-down.
20 April 2018
A guest Friday fold from Graham Andrews of West Virginia University: Graham describes this as an almost along axis view of a huge isocline in the Damaraland belt, Namibia Thanks for sharing! And a happy Friday to all.
10 April 2018
Roadcuts in Kentucky show Ordovician limestones of two distinct types, replete with fossils and primary sedimentary structures, and juxtaposed by a fault, one strand in the Kentucky River Fault System.
6 April 2018
Darrel Cowan of the University of Washington has pitched in a Friday fold. Check this lovely scene out: Darrel says this is a recumbent fold in the Upper Triassic Nizina and Chitistone limestones. I took the photo when I worked for Shell in 1973 or 1974. I’m pretty sure it is on the west wall of the canyon occupied by the Root Glacier, several kilometers NW of McCarthy, Alaska. The …