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You are browsing the archive for joints Archives - Page 2 of 9 - Mountain Beltway.

15 April 2014

Bloomsburg Formation exposed near Elizabeth Furnace

As noted previously, I live in a regional scale fold: the differential erosion of the Massanutten Synclinorium has produced the ridge of Massanutten Mountain, which separates the Fort Valley from the Shenandoah and Page valleys on either side. The Fort is “fort” like because the strata which underlie it are relatively friable, soluble, or otherwise erode-able. The ridge-forming layer is the Massanutten Sandstone, a Silurian-aged quartz arenite. Here’s a boulder …

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22 August 2013

Natural Bridge, Virginia

Our three-day karst theme wraps up today with a visit to Natural Bridge, Virginia, an impressive sight: I went to Natural Bridge early last week to give a talk to a group of Road Scholars (an Elderhostel-like program) about the Snowball Earth. Part of my compensation for the talk was a night’s lodging at the Natural Bridge hotel, meals, and tickets to the Natural Bridge’s suite of six tourist attractions, …

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7 May 2013

Brallier Formation 2: tectonic structures

Yesterday we examined primary sedimentary structures (including trace fossils) at an outcrop of Devonian-aged Brallier Formation turbidites between Deerfield and West Augusta, Virginia. Today, we’ll zoom in on the tectonic structures at the site: folds, faults, and joints. Remember, you don’t have to take my word for it. You can explore it for yourself in this M.A.G.I.C. GigaPan: link One thing that’s kind of cool about that GigaPan is the …

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8 April 2013

Nice plume

Another scene from the South Page Valley Martinsburg outcrop featured here last week: a slightly mud-bedecked example of plumose structure. This plume occurs within a single graded bed (turbidite) of the Martinsburg Formation. It gets younger (paleo-up) to the right. The joint propagation that the plumose structure records began somewhere vertically above the area of this photo, and advanced downward, with the plumes spreading out as it grew. Note the …

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22 March 2013

Friday fold: the case of the strangely stout stylolites

Today, we return to my field trip from last week, for a look at an odd outcrop of the Ordovician-aged Edinburg Formation: Note the car key with green lanyard, to provide a sense of scale. It’s folded, as the yellow bedding traces show in this annotated version: But what really caught my eye about this outcrop were the odd stylolites (pressure solution “seams” with a wiggly morphology and a concentration …

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12 March 2013

Five new GigaPans from Thoroughfare Gap

Yesterday, I took five new GigaPans at Thoroughfare Gap, a water gap where Broad Run cuts through Bull Run Mountain, the eastern limb of the Blue Ridge Anticlinorium at my latitude. The rocks here are the Cambrian-aged Chilhowee Group, with bedding tilted moderately to the east during Alleghanian mountain-building in the late Paleozoic. To the west is the crystalline core of this massive regional fold, and to the east is …

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1 March 2013

Friday fold: An odd duck

A USGS colleague shows Callan a bizarre fold outcrop in the Conococheague limestone of the Boyce quadrangle, Virginia.

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20 February 2013

Crazy veins

Callan & his students visit an outcrop on the Icefields Parkway in Alberta, showing a variety of white veins cutting dark rock.

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6 February 2013

Dinosaur footprints in west Texas

Everything’s bigger in Texas, even the footprints…

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9 January 2013

Hoerikwaggo Trail 3: Joints, veins, and Liesegang banding

Callan continues his week-long recounting of his five-day backpacking trip from the Cape of Good Hope to Cape Town, South Africa, along the Hoerikwaggo Trail. Today, we examine the jointing, oxidizing and reducing fluid flow, and the emplacement of ore veins.

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