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You are browsing the archive for February 2010 - Page 2 of 3 - Mountain Beltway.

20 February 2010

GSW spring field trip

A few photos from last May’s spring field trip with the Geological Society of Washington… Here’s the group at Chain Bridge Flats (far westernmost-Washington, D.C.), looked at the metamorphic rocks there — a metagraywacke melange¬† known as the Sykesville Formation. Another group shot, with field trip leaders Tony (khaki shirt) and Gary (red jacket) Fleming in the foreground: Euhedral metamorphic pyrite crystals (porphyroblasts): An elusive bedding plane in the Sykesville …

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19 February 2010

Visitation

Guess which day I launched the blog? Thanks to everyone who has stopped by so far. I’ve gotten the same question several times from several readers, so let me address it here for everyone’s edification: Yes, NOVA Geoblog will be left “as is,” where it is. You can link to it, or bookmark it, or rely on its presence as you see fit. It’s “fossilized!” The comments are now closed, …

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Fossil crinoid stem

Today, you get a photo of a fossilized crinoid stem, from the Mississippian-aged Lodgepole Limestone of the Bridger Range, north of Bozeman, Montana. A pencil is provided for scale: Zoomed-in a bit, and cropped. The segments (“columnals”) show up nicely: Crinoids are echinoderms, the invertebrate phylum which includes sea urchins and sea stars. However, at first glance you might think they were plants, as they are sessile (mainly sessile, anyhow) …

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18 February 2010

U.K. sediment survey

A friend forwarded this via e-mail to me today… U.K. readers may be interested in participating. Millstone Grit? Kimmeridge Clay? Old Red Sandstone? Durness Limestone? Yorkshire Lias? ………. What are YOUR top three British sediments? BSRG (British Sedimentological Research Group) are conducting a small survey to find out what formations geologists consider the “best” sedimentary deposits across the United Kingdom. This sounds like a loony piece of work (and it …

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"Prehistoric": D.C.

Mark your calendars! Prehistoric: D.C. will profile (part of) the ancient past of Washington, D.C., in an episode to air February 28, 9pm, on the Discovery Channel.

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Salamander shear

Whilst discussing how to quantify strain with my GMU structural geology students recently, I hit upon a cool analogy. In order for you to understand the analogy (assuming you’re not a structural geologist), I’ll have to review some background information first. Stick with it, and I promise you a salamander at the end. Structural geologists are interested in how rocks deform. If we have some idea of the original shape …

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17 February 2010

Focused photo of turbidite

Since yesterday’s live-blogging the rock sample prep routine turned out blurry, I figured I owed it to this sample, and to you, to give everyone a better look. So I scanned it this morning. Penny for scale. Assuming that your computer screen is vertical, this is in the same orientation as when it was deposited: coarse at the bottom, fine at the top.

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Dalmatian pluton

Continuing with some photos from eastern California… After checking out the faulted moraine, but before heading up the hill to check out the indurated shear zone (which you can just see in the background of this photo), we stopped to check out this visually-striking outcrop: Look at the glee on the faces of Kurt (green shirt) and Marcos (running; he’s so excited!). We were all pretty jazzed by this polka-dotted …

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16 February 2010

Graded bed sample

Today during Physical Geology lab, I used our grinding wheel to plane down a turbidite sample than I collected this past December down in Chilean Patagonia. Thanks to the technological miracle of blogging via iPhone, I can send it to you in a mere 45 seconds. Enjoy the graded bed: let it transport you back to the Cretaceous, in a deep marine basin with periodic influxes of mud and sand. …

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Mini debris flow

Small-scale debris flows as a muddy slurry flowed over weathered-out chunks of the Bishop Tuff. Probably about two days old. Southern edge of the Volcanic Tableland, last September.

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