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You are browsing the archive for foliation Archives - Page 3 of 4 - Mountain Beltway.

4 January 2013

Friday fold: Up on Opequon Creek

I got a call last month from Rebekah Wiedower, a landowner up in Frederick & Clarke counties (her family’s property includes pieces of both), inviting me to come up and look at some anticlines and synclines that Dan Doctor (USGS) had identified on the bank of Opequon Creek. I was glad to do it, though shooting these photos meant I had to wade across the stream in my sneakers (on …

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7 July 2012

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.

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2 May 2012

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, and it showed moderately distorted lava pillows, And now today, let’s look at one more …

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30 April 2012

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.

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11 April 2012

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…

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18 January 2012

Two new macro GigaPans

With my new “macrogigapan” rig from Four Chambers Studio, I produced these images last week as part of my Mid-Atlantic Geo-Image Collection project (M.A.G.I.C.). … Dive in! Porphyritic andesite from the Beartooth Plateau, Montana: Foliated limestone slate, location unknown: Clicking on the word “GigaPan” in the lower right corner will take you to a fuller-screen view.

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17 November 2011

Shear zone in basement complex

Callan visits a new outcrop of highly-sheared rocks in the basement complex of Virginia’s Blue Ridge province.

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10 November 2011

Shear bands in the Grassy Portage Sill

Continuing now with the discussion of my pre-GSA meeting field trip to examine the structural geology of the Quetico-Wabigoon subprovince boundary within the Superior Craton of southern Ontario, Canada. Our penultimate stop on the second day of the trip was a roadcut exposing the gabbro of the Grassy Portage Sill. This is what it looks like: …Except where it doesn’t. In places, it looks like this, instead: Zooming in a …

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17 June 2011

Friday fold: a granite dike

This Friday, I give you a fold from the shores of the Rockfish River, south of Charlottesville, in Virginia’s Blue Ridge basement complex, and just down the road from the Lawhorne Mill High Strain Zone. The fold distorts (and improves) a felsic dike cutting the darker granite of the basement. You can make this (stitched composite) picture bigger by clicking it: Here’s the texture of the dike granite: Here’s the …

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27 May 2011

Friday fold(s): the Outdoor Lab

Today’s Friday fold takes me back 25 years, to when I visited the Outdoor Lab with my science class in Arlington County Public Schools. I revisited this exemplary outdoor education facility on Tuesday, at the invitation of its director, Neil Heinekamp. Neil wanted a geology “expert” to take a look at their rocks, and I wanted a chance to check out their rocks as part of my expanding examination of …

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