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21 May 2015
Soft sediment deformation in sandstone and shale, Bolt Mountain
Two nice new examples of soft sediment deformation structures in Pennsylvanian-aged clastic sedimentary rocks from West Virginia.
1 May 2015
Friday fold: Tight syncline/anticline pair in Brallier Formation
The Friday fold shows clastic detritus (turbidites or “flysch” from the Acadian Orogeny) crumpled into tight folds due to the later Alleghanian Orogeny.
6 April 2015
Exploring Mahantango Zoophycos traces in GigaPan
Recently, I posted about an excellent road cut in Fort Valley showing well-developed 10 cm+ Zoophycos trace fossils. Presented here are three new GigaPan images (two outcrop; one macro) of Zoophycos from the Devonian-aged Mahantango Formation: link link link These images are part of a new “virtual field trip” that I organized to supplement my historical geology field trip to examine the geologic history of the Massanutten Synclinorium. The link …
24 March 2015
Martinsburg Formation outcrops in Edinburg Gap
A report from the field: new outcrops of Ordovician-aged turbidites featuring geopetal indicators, fossil content, and a structural overprint imparted during Pangaea’s assembly.
20 March 2015
Friday fold: flexed turbidites
Spring is almost here! As you get ready for the equinox, enjoy this gentle fold on a Friday: These are turbidites (graywacke and shale) of the late Ordovician Martinsburg Formation, seen in Edinburg Gap, western Massanutten Range, greater Shenandoah Valley, Virginia. Bedding is flexed very slightly here, from moderately-dipping to more steep, and then back to moderate again. Slickensides on the top of some exposed layers indicate the beds shifted …
19 March 2015
Zoophycos trace fossils in Mahantango Formation, Fort Valley
A morning’s field trip yields an outcrop of excellent Zoophycos trace fossils in southern Fort Valley, Virginia.
26 December 2014
Friday fold: another gem from the Chancellor Slate
That pretty much speaks for itself, I reckon.
12 December 2014
Friday fold: Miette slate, Alberta
The Friday fold returns to Canada, looking at Neoproterozoic slate and quartzite at the southern terminus of the Icefields Parkway. Bonus features include ripple marks, graded beds, cross-bedding, cleavage, and boudinage.
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 …
8 August 2014
Friday fold: Buckle vs. passive folding in the Chancellor Group slates
The Friday fold is an outcrop in Yoho National Park that showcases differences between buckle folding and passive folding.
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.