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4 December 2015
Friday fold: interference patterns on Elba
Samuele Jæger Papeschi shares one more fold with us: some deformation here… type III (Ramsay…) interference pattern in Cretaceous calcschists… Cavo, Elba Island Awesome! I hope everyone has a great Friday.
7 August 2015
Friday fold: Yin-Yang at Swift Dam
What is Matt looking at here? Matt was one of my Rockies students this summer, a geology major at the University of Virginia. Together with another UVA student and students from Mary Washington University and George Mason University, Matt embarked on a mountain-climbing hike during our evening camping at Swift Dam, near Depuyer, Montana. The hikers were treated to an extraordinary sight when they attained the summit: Click to embiggen; …
31 July 2015
Friday fold: a return to the duplex structure in the Gastropod Limestone
Some time ago, I featured as Friday fold the extraordinarily complex duplex structure to be seen in the Cretaceous “gastropod limestone” member of the Kootenai Formation at Sandy Hollow, Montana. Today, let’s take a deeper look through a couple of hand-shot GigaPan images: Here’s the bigger of the two: link Here’s one with students for scale: link
27 July 2015
Conglomeratic ne plus ultra
There’s something about conglomerates that just draws me in. Here’s a lovely example — you might even say it’s an exemplar — from Sandy Hollow in Montana: That’s the basal conglomerate of the Cretaceous Kootenai Formation, one of the mappable units in this mappable region. Feast your eyes on those well-rounded pebbles!
29 May 2015
Friday fold: Hayward neighbor
The Friday fold is some crumpled sedimentary rock near the Hayward Fault in California.
19 December 2014
Friday Fold: Mist Mountain Formation in Canmore, Alberta
Let’s journey to the Cretaceous today, to see sandstones, shales, and even some coal strata that have been folded during the eastward thrusting that built the Canadian Rockies. Here’s the same fold, in context, shot in GigaPan on a different day, from a different angle. Can you match it up? link Ben Gadd showed me (and my field class) this site last summer. It’s a little west of Canmore. There’s …
4 November 2014
Joints highlighted with hematite, Anapra Sandstone, Cristo Rey
Good morning. Here are two images from last March’s “Border to Beltway” field trip to West Texas, on the north flanks of the Cristo Rey laccolith. Specifically, these are Cretaceous strata of the Anapra Sandstone, looking at the bedding plane of the rocks. Cutting across bedding are a series of fractures (joints) that have been highlighted by the oxidation of iron (rusting) along their edges. In the first photo, the …
27 October 2014
Yamnuska
Driving west from Calgary, your first evidence of entering the Canadian Rockies’ Front Ranges is the startling sheer cliff of Yamnuska, north of the Trans-Canada Highway: Yamnuska’s shape is a function of differential weathering of the two rock units that make up the mountain: Cambrian Eldon Formation limestone, and Cretaceous shales of the Brazeau Formation. The Cambrian is the uppermost of the two, which is a violation of superposition, considering …
29 August 2014
Friday fold: Pleistocene glacial folding of Cretaceous sedimentary rock?
The Friday fold is found in Cretaceous rocks of eastern Alberta – but far beyond the tectonic influence of the Canadian Rockies. So what’s responsible for the folding?
23 August 2014
An examination of the Horseshoe Canyon Formation in eastern Alberta
An expert on the deltaic depositional setting of eastern Alberta’s Horseshoe Canyon Formation shares field evidence and expertise with Callan’s students.
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.