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12 September 2014

Friday fold: Quartz vein in Catoctin Formation, Point of Rocks, Maryland

Friday fold: Quartz vein in Catoctin Formation, Point of Rocks, Maryland

I took this image in 2005, when I was working up a geologic history of the C&O Canal National Historical Park. It’s a vein of quartz, gracefully folded within the Catoctin Formation. The exposure is along the railroad tracks at Point of Rocks, Maryland, easternmost extent of the Blue Ridge province on the north shore of the Potomac River. The Culpeper Basin begins about 100 meters to the east of …

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5 September 2014

Friday fold: Kink banding in the Arran Islands

Friday fold: Kink banding in the Arran Islands

This one is in my folder of ‘structure’ images on my computer, but it’s not one of mine. I’m not sure where it came from. A TinEye search turns up nothing. Perhaps one of  you can tell me? Lovely subparallel kink bands… such gorgeous structure. Happy Friday!

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29 August 2014

Friday fold: Pleistocene glacial folding of Cretaceous sedimentary rock?

Friday fold: Pleistocene glacial folding of Cretaceous sedimentary rock?

The Friday fold is found in Cretaceous rocks of eastern Alberta – but far beyond the tectonic influence of the Canadian Rockies. So what’s responsible for the folding?

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8 August 2014

Friday fold: Buckle vs. passive folding in the Chancellor Group slates

Friday fold: Buckle vs. passive folding in the Chancellor Group slates

The Friday fold is an outcrop in Yoho National Park that showcases differences between buckle folding and passive folding.

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1 August 2014

Friday fold: Contorted Rome Formation next to the Max Meadows Fault

Friday fold: Contorted Rome Formation next to the Max Meadows Fault

My student Mercer Parker shot this one over to me the other day: Click to enlarge Those are the slim strata of the Rome Formation (a.k.a. Shady*), strongly deformed in the region adjacent to the Max Meadows (“M&M”?) Fault. Thanks, Mercer! _____________________________________________ * Will the real slim Shady please stand up?

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4 July 2014

Friday fold: Warspite Anticline

Friday fold: Warspite Anticline

A final guest Friday fold from reader Howard Allen, who I’m pleased to be meeting up with in Banff late next week… Howard writes the following in describing this lovely scene: Warspite Anticline, Peter Lougheed Provincial Park, Alberta. Photo is a telephoto shot (hence the strong blue alpine haze–the colour cast is an accurate rendition of the original daylight Kodachrome slide), looking southwest at an angle to regional strike. The …

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27 June 2014

Friday folds: Acadian metamorphics and pegmatite from coastal Maine

Friday folds: Acadian metamorphics and pegmatite from coastal Maine

Some folds this week from coastal exposures in western Boothbay Harbor, Maine, where I’m on vacation for one more day… Acadian metamorphics (schist, gneiss), with injected granite pegmatite that has also been folded (and boudinaged): Happy Friday!

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20 June 2014

Friday fold: the Castile Formation at the State line outcrop

Friday fold: the Castile Formation at the State line outcrop

The Friday fold visits the Permian basin of west Texas. There, the Castile Formation exhibits gorgeous inter- and intra-bed folding.

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13 June 2014

Friday fold: tortured turbidites at Devil’s Slide

Friday fold: tortured turbidites at Devil's Slide

Marek Cichanski (of De Anza College near the south end of San Francisco Bay) contributed this week’s Friday fold: Marek says: The locality is a place near San Francisco called Devils Slide. It is a piece of the coastal highway built along a steep mountainside above the ocean. This unstable stretch of road was recently (finally!) replaced by some tunnels. And, amazingly, the old roadbed finally got converted to a …

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6 June 2014

Friday fold: differential weathering of carbonate intraclasts in mudstone

Friday fold: differential weathering of carbonate intraclasts in mudstone

Howard Allen is the documentarian of this week’s fold: Howard writes that this is: Middle Cambrian Chancellor Formation rock with recessive weathering intraclasts(?). Hamilton Lake trail, Yoho National Park, British Columbia. My interpretation of this one is a little shaky–it was raining when I took the photo (in 1982) and I was hiking with a non-geologist friend, so I didn’t linger at the outcrop or record the precise location. I …

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