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14 July 2017

Friday fold: chevrons in the Scaglia Rossa, Apennines

The Friday fold visits the Apennine Range of central Italy.

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23 June 2017

Friday fold: Canoeing the Célé River, France

I was in southern France last week, exploring an awesome suite of caves cut into the Causses limestone plateau. My family and I took an afternoon to paddle a canoe down 5 kilometers of the Célé River. While floating along, we spied a gentle, open fold in the limestone layers that crop out along the banks. This low-amplitude fold is highlighted with the “horizontal” reference line of the river’s edge. …

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16 June 2017

Friday fold: toothpasty Tomstown

I spent last weekend at the National Association of Geoscience Teachers’ Eastern Section meeting, based out of the Community College of Baltimore County in Catonsville, Maryland. One of the two field trips I took headed out to the western Piedmont, Blue Ridge and Valley & Ridge provinces of western Maryland. On that trip, we took a tour of Crystal Grottoes, a commercial cave south of Boonsboro. I was impressed at …

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3 October 2016

A virtual field trip to Rathlin Island, Northern Ireland

Rathlin Island lies north of mainland Northern Ireland, a few miles offshore. I spent three lovely days there this past summer, investigating the geology and appreciating the wildlife (puffins and other sea birds, and seals). The geology is pretty straightforward: Paleogene basalt overlying Cretaceous “chalk” (really not so chalky here – technically, it’s the Ulster White Limestone). Here’s a suite of interactive imagery that you can use to explore Rathlin’s …

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22 July 2016

Friday fold: The walls of Scalloway Castle

When in Shetland, one of my first stops was the museum in Scalloway, and one of the ancillary benefits of visiting there is the castle next door: Scalloway Castle includes building stones derived from the local limestone – a Neoproterozoic unit that has recently been chemostratigraphically correlated with Snowball Earth cap carbonates elsewhere in the world. But that need not concern us today. Today we are here for the folds! …

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28 June 2016

“Dunbar marble” at Barns Ness, Scotland

Thanks to the website ScottishGeology.com, run by Angus Miller, I learned of Barns Ness, a Mississippian-aged limestone fossil site on the shore not far from where we are staying at Dunbar. We ventured out there on Saturday afternoon, in search of fossils. The presence of the Dunbar Cemenet Works nearby is an indication that this is the most extensive limestone outcrop in central Scotland. I set my field assistant loose …

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9 June 2016

Storm deposits in Tonoloway Fm. limestone – a virtual sample

Our series of  virtual samples continues! This week, I’m presenting examples of a visualization combination that leverages the advantages of the GIGAmacro system with the 3D ‘virtual sample’ perspective of the Sketchfab-hosted model: the same sample presented in both formats. Today, we feature a lovely slab of limestone, chock full of fossil material, and showing both primary sedimentary structures like graded bedding and cavity fills (both geopetal indicators), but also …

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8 June 2016

Differential weathering in dolostone – a virtual sample

Our series of  virtual samples continues! This week, I’m presenting examples of a visualization combination that leverages the advantages of the GIGAmacro system with the 3D ‘virtual sample’ perspective of the Sketchfab-hosted model: the same sample presented in both formats. Today, we feature a differentially weathered dolostone. [gigapan src=”http://gigapan.org/gigapans/187111/options/nosnapshots,hidetitle/iframe/flash.html” height=”250″ scrolling=”no” width=”100%”] Link GIGAmacro by Callan Bentley [sketchfab id=”c3fe8faed09b4c7886135ce0015a67dc” start=”0″ spin=”” controls=”0″] Photoscan model by Marissa Dudek Differential weathering (i.e., …

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7 April 2016

New GIGAmacro images of rock samples

Another week, another batch of new images produced on my home-based Magnify2 imaging system from GIGAmacro. Leptaena brachiopod in (Mississippian?) limestone from Montana: [gigapan src=”http://gigapan.org/gigapans/185784/options/nosnapshots,hidetitle/iframe/flash.html” height=”250″ scrolling=”no” width=”100%”] Link Here’s the flip side of the same sample, with a lot of fenestrate bryozoans to see: [gigapan src=”http://gigapan.org/gigapans/185809/options/nosnapshots,hidetitle/iframe/flash.html” height=”250″ scrolling=”no” width=”100%”] Link Fault breccia from the Corona Heights Fault of San Francisco: [gigapan src=”http://gigapan.org/gigapans/185868/options/nosnapshots,hidetitle/iframe/flash.html” height=”250″ scrolling=”no” width=”100%”] Link Amygdular metabasalt from …

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17 February 2016

3D virtual sample of gastropod-rich Reynolds Limestone

Check this out: [sketchfab id=”2acb8b4130ad467791fa62c00d7a8b18″ start=”0″ spin=”” controls=”0″] It’s a sample of the Reynolds Limestone, a member of the Mississippian-aged Mauch Chunk Formation, chock full of gastropod fossils. The image here is a 3D model made with Agisoft PhotoScan, a 3D model rendering program. The only input was a series of ~32 photos taken of the sample at various angles and orientations. Alan Pitts then posted it to his Sketchfab …

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1 December 2015

Which way’s up? Check cavity fills.

When snail shells are deposited in a bunch of sediment, they serve as tiny architectural elements, with a “roof” that protects their interiors. Any sediment mixed into the shell’s interior will settle out (more or less horizontally), and then there will be empty space (filled with water, probably) above that. As burial proceeds and diagenesis begins, that pore space may be filled with a mineral deposit, such as sparry calcite. …

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19 November 2015

A little geologic history before breakfast

What geological stories can be read from the stone on the front of a building? Walking past some facing stone in Baltimore, Callan discovers a wealth of little clues.

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