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23 August 2011

My best flutes

Fellow geobloggers Brian and Eric have been getting all flutey on us lately, so I figure it’s a good time to show my best photo of flute casts: As the annotated copy suggests, this was taken on the side of the Pennsylvania Turnpike back in March 2008, when four Honors students and I drove up to Buffalo for a northeastern section GSA meeting. The strata are probably Devonian in age, …


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22 August 2011

Negative halite molds from Belt argillite

As a follow up to last week’s post about halite casts in a hand sample I collected in western Montana’s Belt Supergroup, here’s another example. Unlike those (larger) examples of halite-shaped mud cubes, this sample shows (smaller) examples of the empty space left behind by the dissolved salt crystals: Image is scanned, and the penny is to provide a sense of scale. Here we go closer up, and annotated: Not …


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21 August 2011

The best cross-bedding you’ll ever see

Setting aside the lack of scale, it really doesn’t get any better than that. Click through to make it huge. This is the Navajo Sandstone, early Jurassic (or late Triassic?) in age. It’s in Zion National Park, Utah. Wind direction was from the right towards the left, as these preserved slip-faces of ancient dunes indicate. The beds are right-side-up, and they have been differentially eroded, causing the cross-beds to jump …


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19 August 2011

Glaciofluvial outcrop annotated

Callan’s answer to the riddle of the mystery outcrop is revealed. Spoiler: the glacier did it.


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Friday fold: One from Walcott

My man Walcott contributed a lot of images to the USGS stockpile during his travels. Today, I’ll feature one from Bishop, California, from 1894: Got it from here. Rock hammer on the left for scale. The caption reads: Plicated layers of thin bedded chert in limestone etched by erosion, Lower Cambrian (?). Hill two miles west of Big Pine. Inyo County, California. 1894. This is the one-year anniversary of the …


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18 August 2011

Try interpreting this outcrop

Here’s one you can click through to make much bigger: That’s a pretty cool outcrop that shows something amazing. Anyone want to take a stab at interpreting it?


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17 August 2011

Halite Casts from Belt argillite

I collect a lot of samples when I roam the west on my summer georoadtrips. Yesterday when I got back to my office at NOVA, I unloaded about 200 pounds of rocks from my Prius. These samples are all destined to serve as teaching aides for NOVA and GMU students in lab exercises and/or hallway displays. One of the samples I scored this summer that I am very excited to …


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16 August 2011

Hiking to the Burgess Shale

Callan visits the Burgess Shale in British Columbia’s Yoho National Park on a guided tour. This photo-heavy post discusses the depositional setting of this world-famous Cambrian fossil deposit, the landscape along the hike, and (of course) the fossils themselves.


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15 August 2011

Split concretion

Concentrically-zoned ironstone concretion in sandstone of the Morrison Formation, eastern flank of the Bighorn Mountains / western edge of the Powder River Basin, Wyoming, at the Sheridan College dinosaur fossil quarry, last week. The white stuff is caliche. A quick post to celebrate the fact that as of three hours ago, Lily & I are back home in our condo in D.C. It’s been a great summer, and I have …


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12 August 2011

Friday fold: ptygmatic granitoid dikelet

That’s from the side of route 287, somewhere between Fort Collins, Colorado, and the Wyoming border. Though I took this shot >6 weeks ago on my outward-bound trip, today I find myself back in Fort Collins on the eastward leg of my summer road jaunt. And you know what one does in Fort Collins. Happy Friday!


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