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You are browsing the archive for March 2015 - Mountain Beltway.

27 March 2015

Friday fold: Isla Escarpada, Chile

I’m very nearly delinquent on posting the Friday fold… Here you go – a Google Earth view of a differentially-weathered fold partly above and partly below sea level in Chilean Patagonia, south of Puerto Natales: They call it Isla Escarpada. Awesome. Here’s a Google Maps link if you want to explore it yourself. Happy Friday!

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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.

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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 …

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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.

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16 March 2015

Mechum River Formation, near Batesville, VA

A quick virtual field trip to the Neoproterozoic glaciogenic sedimentary rocks from the central Virginia Blue Ridge province: Can you feel the chill of Snowball Earth?

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6 March 2015

Friday fold: Mazatzal Orogeny, Arizona

Reader Mike Pendergrass contributes this Friday’s fold: I found your blog a couple years ago and I share your love of structural geology.  I did my Master’s Thesis while at Northern Arizona University in the early 80’s and mapped an area on the Mazatzal Mountains of central Arizona.  The Mazatzals in my field area contain metasedimentary rocks that were deformed in the Mazatzal Orogeny (~1.6-1.7 billion years ago).  The stratigraphy …

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5 March 2015

Book report

Callan reviews 11 books he’s read in the past 11 months, some having to do with geology, many with the intellectual heritage of scientific insight, a few about history, two biographies, and some about random things.

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3 March 2015

Ichnofossils in Gog quartzite

At the Spiral Tunnels overlook on the Trans-Canada Highway, you can look at trains. Or, you can check out some lovely trace fossils in boulders which divide the viewing area from the highway: These are in the Gog Formation, a Cambrian-aged quartz arenite, mostly fused to quartzite nowadays… I know which subject I would choose to spend my time looking at…

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