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.

CEv4BtIWEAMounF.jpg large

Awesome. Looks like a great place. Thanks, Kate!

Happy Friday!

Comments/Trackbacks (0)>>

21 May 2015

Soft sediment deformation in sandstone and shale, Bolt Mountain

Today, I’ll treat you to two examples of soft-sediment deformation from the Kanawha Formation on Bolt Mountain, West Virginia…









This cross section looks very much like the 3D “sled” shapes to the soft sediment deformation “ploudins” at Corridor H

Comments/Trackbacks (0)>>

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:






Here are some previous examples of Liesegang banding here on Mountain Beltway. It’s lovely stuff.

Comments/Trackbacks (0)>>

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.

Comments/Trackbacks (0)>>

15 May 2015

Friday fold: Crumpled Carboniferous cyclothems

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

CEvuBFCWYAAoLGz.jpg large

Thanks Bob!

Comments/Trackbacks (0)>>

8 May 2015

Friday fold: Foreknobs formation

Last one in the triumverate sent in by reader Eric Fulmer:




Happy Friday and (for many of you) happy end of the semester!!

Comments/Trackbacks (0)>>

1 May 2015

Friday fold: Tight syncline/anticline pair in Brallier Formation

Reader Eric Fulmer provided last week’s Friday fold, and this week’s too:


This is also along the banks of the C&O Canal (mile marker 159.5), showing turbiditic strata of the Devonian Brallier Formation, crunched up into a tight fold pair. The Brallier is made of sand, silt, and clay that was shed off the Acadian Orogeny into a neighboring sedimentary basin.

Annotated version:


This deformation, entirely typically of rheologically weak units in the Valley and Ridge, is inferred to have accumulated during late Paleozoic mountain building, when Gondwana (Africa) rammed into North America in an event called the Alleghanian Orogeny.

Comments/Trackbacks (0)>>

30 April 2015

Early Paleozoic fossils in Nealmont Formation, Germany Valley, West Virginia

Looking at Ordovician carbonates in Germany Valley, West Virginia, a few weeks ago on Rick Diecchio’s GMU sedimentology and stratigraphy course field trip:



Lots and lots of brachiopods…





Crinoid columnals mized with brachiopods:


A set of coarsely-infilled trace fossils:



Crinoid stem:


Nice strophomenid brachiopod:


Bryozoan? Receptaculid?


Comments/Trackbacks (0)>>

28 April 2015

Epidotized tuff, Tucson Mountains, Arizona

I was in Tucson this past weekend for a book project meeting, and my editor and coauthor and I took a hike on Sunday morning in the Tucson Mountains to Wasson Peak. Not far from the summit, we saw an epidotized tuff, where the fiamme and pumice blobs had undergone reactions to produce pods of epidote, giving the rock a look like a sick dalmatian:


This is a cool rock (in my mind) because it tells a story with two chapters –

1) explosive eruption of a volcano, and

2) later wet metamorphism/alteration.

There was an adit (mine opening) in heavily epidotized rocks a few meters away – probably a fault or other vein of mineralization that had been tapped and explored a bit, but was clearly never a ‘big time’ operation. We did see a little bit of malachite, too – so presumably it would have been copper the miners were after.

Comments/Trackbacks (0)>>

24 April 2015

Friday fold: Bloomsburg Formation at lime kilns on C&O Canal

Milepost 127.4 (High, 2001) on the C&O Canal:


…Cool if you’re into history.

…Cool if you’re into economic geology.

…Cool if you’re into Friday folds!


Reader Eric Fulmer sent me this photo (along w/ two others you’ll see in weeks to come). Thanks, Eric!

Comments/Trackbacks (0)>>