Advertisement

You are browsing the archive for foliation Archives - Mountain Beltway.

9 August 2017

A suite of new 3D models

A showcase of five new 3D digital models of awesome rock samples and outcrops, produced using Agisoft Photoscan.

Read More >>

No Comments/Trackbacks >>


21 July 2017

Friday fold: Sardinia

My friend Ander Sundell at the College of Western Idaho is the source of today’s Friday fold. It’s from somewhere in Sardinia, and I think you’ll find it visually striking: Ander says: The rocks here are Silurian phyllites generated from mudstones that were deposited on the floor of the rheic ocean basin. The color and grain size variation do an excellent job highlighting compositional layering. They were deformed during the …

Read More >>

2 Comments/Trackbacks >>


3 February 2017

Friday fold: Squaw Creek Schist, Idaho

The edge of ancestral North America can be found in the canyon of the Salmon River in western Idaho. Folds exposed the Squaw Creek Schist near Riggins record the stresses of adding terranes on during North America’s westward movement since the breakup of Pangaea. The Friday fold crinkled up during the accretion of a terrane to the growing North American continent.

Read More >>

No Comments/Trackbacks >>


25 November 2016

Friday fold: intrafolial folds in Eriboll mylonite

At the birthplace of the term “mylonite,” we can find Friday folds hidden in the foliation.

Read More >>

2 Comments/Trackbacks >>


22 September 2016

Eyes on some augens in a nice gneiss

Take a look at these gorgeous exposures of augen gneiss in eastern “mainland” Shetland, U.K. Includes 3 GigaPans of the site.

Read More >>

No Comments/Trackbacks >>


12 September 2014

Friday fold: Quartz vein in Catoctin Formation, Point of Rocks, Maryland

I took this image in 2005, when I was working up a geologic history of the C&O Canal National Historical Park. It’s a vein of quartz, gracefully folded within the Catoctin Formation. The exposure is along the railroad tracks at Point of Rocks, Maryland, easternmost extent of the Blue Ridge province on the north shore of the Potomac River. The Culpeper Basin begins about 100 meters to the east of …

Read More >>

2 Comments/Trackbacks >>


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.

Read More >>

1 Comment/Trackback >>


10 May 2013

Friday fold: New Market / Lincolnshire formation contact, Staunton, Virginia

Happy Friday! Here’s a view of the folded contact between the (older, lower) New Market Formation, and the (younger, upper) Lincolnshire Formation, as exposed in Staunton, Virginia: The contact has been folded, pretty intensely: The New Market Formation is massive, light-colored, and exhibits fenestral texture here. The Lincolnshire is darker, more thinly-bedded, and is chock full of fossil invertebrates. Explore it for yourself in this M.A.G.I.C. GigaPan: link A closer …

Read More >>

No Comments/Trackbacks >>


29 April 2013

Kink bands in highly strained Laurel Formation, Rock Creek Shear Zone, DC

Last week before GSW, I spent several pollen-choked hours in Rock Creek Park, GigaPanning some of the rocks of the Rock Creek Shear Zone. Here are some exposures in the bed of Broad Branch that show lovely kink banding. In at least one spot, you can see a conjugate pair, so these rocks were (1) sheared out in a ductile shear zone, producing the foliation, and then (2) compressed under …

Read More >>

No Comments/Trackbacks >>


1 April 2013

“Outcrops” on the barn at Peirce Mill, DC

The Friday before last, I was in DC for a fun geology/botany field trip, and I got the opportunity to stroll around the barn at historic Peirce Mill, a historical grain mill along Rock Creek in Rock Creek Park, Washington, DC. The barn is immediately south of Tilden Street NW. It appears to have been constructed from local stone: metamorphic rocks of the Rock Creek Shear Zone, a ductile fault …

Read More >>

No Comments/Trackbacks >>