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9 December 2016

Friday fold: Machir Bay I

Friday fold: Machir Bay I

It’s Friday! Today’s fold comes to you from Neoproterozoic metasediments on the west side of Islay, at Machir Bay.

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2 December 2016

Friday fold: Dalradian kinks, crenulations, and folded crenulations on Arran

Friday fold: Dalradian kinks, crenulations, and folded crenulations on Arran

For the Friday fold, let’s travel to the northern edge of the Isle of Arran in southwestern Scotland, where near the town of Lochranza, you can find Dalradian metagraywackes that display a lovely suite of folds. There are kink bands, like this one: And this one: And these en echelon kink bands: And these: But there’s also a more pervasive structural fabric to be seen: symmetrical crenulations: And in places …

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25 November 2016

Friday fold: intrafolial folds in Eriboll mylonite

Friday fold: intrafolial folds in Eriboll mylonite

At the birthplace of the term “mylonite,” we can find Friday folds hidden in the foliation.

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18 November 2016

Friday fold: Lewisian gneiss near Tarbet

Friday fold: Lewisian gneiss near Tarbet

I tried something new this morning, and polled Twitter for their choice of Friday fold: Quick poll – What do you want for the Friday fold? 30 minutes to respond. — Callan Bentley (@callanbentley) November 18, 2016 As of the time of this posting, the first choice, “Lewisian gneiss @ Tarbet” won out with 7 / 10 votes. The people have spoken, and this time I like the result of …

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4 November 2016

Friday fold: orogeny in a cobble

Friday fold: orogeny in a cobble

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 …

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28 October 2016

Friday fold: “the eye of Sauron” at Sibubule

Friday fold: "the eye of Sauron" at Sibubule

Have a look at this week’s Friday fold – but be aware that it will be looking back!

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21 October 2016

Friday fold: a miniature ramp and flat

Friday fold: a miniature ramp and flat

Sometimes you find big ideas in small places. Here, a South African chert boulder mimics in miniature fold and thrust belts the world over.

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7 October 2016

Friday folds: Dalradian schists at St. Ninian’s Isle

Friday folds: Dalradian schists at St. Ninian's Isle

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 …

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30 September 2016

Friday fold: Torqued talc from the 2016 Biggs awardee

Friday fold: Torqued talc from the 2016 Biggs awardee

Callan’s colleague Joshua Villalobos won the 2016 Biggs Award. He also makes GigaPans of folds, like these talc-bearing rocks of the Allamoore Formation.

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23 September 2016

Friday fold: Shetland geopark rock wall at Northmavine

Friday fold: Shetland geopark rock wall at Northmavine

Can a Friday fold be a work of art as well as a source of geologic insight? The answer can be found as you enter Shetland’s Northmavine region.

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