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

18 August 2022

Quarrying soapstone

Earlier this summer, I was lucky enough to visit a soapstone quarrying operation in Schuyler, Virginia, right on the Albemarle/Nelson County line. These soapstone bodies are metamorphosed ultramafic intrusions into the Neoproterozoic sedimentary deposits of the Lynchburg Group. The protolith peridotite sill crystallized at ~580 Ma, meaning the host sediments are older than that (but younger than the Grenvillian basement complex that underlies both). Then both plutonic rock and sedimentary …

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16 August 2022

Kinked metavolcanics of the Castine Formation, eastern Maine

Callan shares a few outcrops from coastal Maine, part of the Avalonia terrane that accreted to ancestral North America during the Acadian Orogeny. They are volcaniclastic rocks, coarse and fine, and showing both overprinting kink bands and cross-cutting basaltic dikes.

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16 April 2021

Friday fold: Colorado cluster

Friday means folds –
This week, we head to the Colorado Rockies for a butterfly-like presentation of a ptygmaticly folded granite dike within biotite schist.

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29 January 2021

Friday fold: revisiting the Geoscience Communication Pardee Symposium

I have two Friday folds for you today, both by geovisualizers who contributed to the 2019 Geological Society of America Pardee Symposium on Geoscience Communication in Phoenix, Arizona: The first is a painting by talented geoartist Emma Theresa Jude, showing a fold at Caithness, Scotland. The fold in question can be seen at the site of Figure 5 of this paper. I love Emma’s art. What other lovely folds have you …

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24 July 2020

Friday fold: Totier Creek phyllite

Exploring his new digs in Charlottesville, Callan is introduced to a large exposure of phyllite at a dam’s spillway. The foliation there is folded in many ways. Share in a dozen field photos of the site…

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7 February 2020

Friday fold: Kings Canyon

The Friday fold shows disharmonic crumpling in marbles of the Boyden Cave Root Pendant in California’s Sierra Nevada. The GigaPan image displayed is part of the digital legacy of Ron Schott, who passed away a year and a half ago.

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24 January 2020

Friday fold: Pelham Parkway

A roadside boulder in the Bronx shows folded gneissic banding. It’s another guest-submitted Friday fold!

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13 December 2019

Friday fold: blueschist & eclogite at Jenner, California

A pre-Fall Meeting field trip to the coast of northern California yields rare sights of garnet-bearing blueschist, plus eclogite, some pillow basalts, birds, waves, wind, and a lot of rain.

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8 November 2019

Friday fold: Rist Canyon cobble

From a creek bed in northern Colorado, the Friday fold distorts foliation in early Proterozoic quartzofeldspathic gneiss, peppered with small almandine garnets.  

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9 August 2019

Friday fold: crumpled green metavolcanics from St. Anthony

The Friday fold erupted out of a volcano, completing the second part of its two stage cooling history, then later got folded and metamorphosed. It was found atop a high cliff near the northern Newfoundland town of St. Anthony.

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