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19 August 2015

Iron oxide sweat stains in sandstone

Iron oxide sweat stains in sandstone

What do a sweaty baseball cap and fractured sandstone have in common? Episodes of absorption of dirty liquids that pile up material such as iron oxide at the soaking front.

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21 May 2015

Soft sediment deformation in sandstone and shale, Bolt Mountain

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

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

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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24 March 2015

Martinsburg Formation outcrops in Edinburg Gap

Martinsburg Formation outcrops in Edinburg Gap

A report from the field: new outcrops of Ordovician-aged turbidites featuring geopetal indicators, fossil content, and a structural overprint imparted during Pangaea’s assembly.

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20 March 2015

Friday fold: flexed turbidites

Friday fold: flexed turbidites

Spring is almost here! As you get ready for the equinox, enjoy this gentle fold on a Friday: These are turbidites (graywacke and shale) of the late Ordovician Martinsburg Formation, seen in Edinburg Gap, western Massanutten Range, greater Shenandoah Valley, Virginia. Bedding is flexed very slightly here, from moderately-dipping to more steep, and then back to moderate again. Slickensides on the top of some exposed layers indicate the beds shifted …

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27 January 2015

Miette Group gritstone showing scours, mudchip rip-ups, cross-bedding, and dropstones

Miette Group gritstone showing scours, mudchip rip-ups, cross-bedding, and dropstones

The coarser strata of the Neoproterozoic Miette Group in the Canadian Rockies of Alberta record changing water current strength over time, and maybe an iceberg or two.

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21 January 2015

Bloomsburg Formation in GigaPan

Three images, working our way in from outcrop setting to hand sample: link link link These fine red sandstones are the Silurian-aged Bloomsburg Formation, as it crops out in Fort Valley, Virginia. What would we see if we kept zooming in? …Stay tuned…

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17 January 2015

Geology of the Acropolis (Athens, Greece)

Geology of the Acropolis (Athens, Greece)

When visiting Athens, Greece, you are drawn to the Parthenon’s grand architecture atop the hill called the Acropolis. But why is the Acropolis a hill?

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16 January 2015

Friday fold: the Ross Sandstone, Ireland

Friday fold: the Ross Sandstone, Ireland

Zoltán Sylvester has contributed today’s Friday fold, an anticline in the Ross Sandstone of Ireland: Click image to go to the source (full sized). Thanks Zoltán! Happy Friday everyone.

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