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You are browsing the archive for 2015 May.

29 May 2015

Friday fold: Hayward neighbor

The Friday fold is some crumpled sedimentary rock near the Hayward Fault in California.

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22 May 2015

Friday fold: Welsh carbonates

Kate Littler sent in this Friday fold, via Twitter: lovely parasitic folds in the Carb limestone,  West Angle Bay south Wales. Awesome. Looks like a great place. Thanks, Kate! Happy Friday!

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21 May 2015

Soft sediment deformation in sandstone and shale, Bolt Mountain

Two nice new examples of soft sediment deformation structures in Pennsylvanian-aged clastic sedimentary rocks from West Virginia.

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20 May 2015

Liesegang banding in Pennsylvanian sandstones, Bolt Mountain, West Virginia

While out at the eastern section of NAGT’s annual meeting last weekend in West Virginia, I participated in a field trip to look at the stratigraphy of the Bolt Mountain section of Pottsville Group strata. One thing that was particularly eye-catching about the sandstones we saw was that many of them had been stained by rusty groundwater, producing the lovely stripey pattern known as Liesegang banding. Here are five examples: …

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18 May 2015

Spheroidal weathering in sandstone

Here’s a nice example of spheroidal weathering in a sandstone, developed using orthogonal jointing and bedding: This is one of many sites I visited Saturday near Bolt, West Virginia, on a field trip with NAGT’s Eastern Section.

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15 May 2015

Friday fold: Crumpled Carboniferous cyclothems

Twitter follower Bob J. submitted this week’s Friday fold: Carboniferous cyclothems at Scremerston, Northumberland. Thanks Bob!

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8 May 2015

Friday fold: Foreknobs formation

Last one in the triumverate sent in by reader Eric Fulmer: Annotated: Happy Friday and (for many of you) happy end of the semester!!

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1 May 2015

Friday fold: Tight syncline/anticline pair in Brallier Formation

The Friday fold shows clastic detritus (turbidites or “flysch” from the Acadian Orogeny) crumpled into tight folds due to the later Alleghanian Orogeny.

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