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17 February 2017
Garnetiferous beds from the aureole of the Leinster Granite east of Baltinglass, County Wicklow, Ireland (Declan De Paor’s senior thesis mapping area, 1973). Manganese-rich metasediments. The prominent ‘elasticas’ or fan folds (folds with a negative inter-limb angle) are superimposed on isoclinal folds: so the brownish layer at top and bottom are the same, though that is not obvious from the image. This is a sample from the structural geology collection …
26 January 2017
The scenic arch of Dore Holm (“Door Island”) in Shetland shows off the most efficient way of breaking a slab of rock. The island’s shape is a reflection of the parsimonious nature of natural deformation.
16 January 2017
A quest to visit the “first shear zones” described in the scientific literature leads to an alternate location, and some GIGAmacro images of samples from the real, original spot.
30 December 2016
As noted previously, my colleague Declan De Paor recently retired from Old Dominion University, and I was lucky enough to inherit some of his rock samples. I’ve been making super-high resolution images of the samples ever since. Here’s a particularly striking fold, weathered out differentially. Enjoy exploring it – and have a happy final Friday of 2016! Link 2.04 Gpx GIGAmacro by Callan Bentley (If the embedded GigaPan doesn’t work …
12 December 2016
Don’t you hate it when plate tectonics ruins a perfectly good fossil? This is a sketch of a belemnite from the Swiss Alps: The thing has been broken into segments, with calcite filling the gaps between the segments. What a bummer! Now we’re going to have a much harder time reconstructing the life habits of the organism that left this fossil behind… It was a squid-like thing, with an internal …
25 November 2016
At the birthplace of the term “mylonite,” we can find Friday folds hidden in the foliation.
8 November 2016
Funzie Bay in eastern Fetlar, Shetland, is the place with a stretched-pebble metaconglomerate that triggered the development of the Flinn Diagram. Join Callan on a pilgrimage of structural geology to this special place.
4 November 2016
Happy Friday. Thank goodness it’s the last one before this horrible election season finally concludes. Let’s celebrate with two cobbles from the beach at Papil Water, Fetlar, Shetland. They show small-scale folds in metasedimentary and metavolcanic rocks of Ordovician or Silurian age, part of the ophiolite complex that makes up most of Fetlar. Each is a nice little sliver of mountain-building, small enough to hold in a hand. “Time in …
21 October 2016
Sometimes you find big ideas in small places. Here, a South African chert boulder mimics in miniature fold and thrust belts the world over.
7 October 2016
Remember St. Ninian’s Isle? It is connected to Mainland Shetland by a tombolo. But it has rocks there, too. Here are some outcrops on the beach: If you visit these schisty fins, you’ll find they are populated by a cavalcade of small folds. Some of the folds are crisp things known as kink bands: Annotated version: And finally, as a lagniappe, here’s a bit of boudinage. This quartz vein has …