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6 December 2017

My GSW Presidential address

I can hardly believe it but tonight I wrap up my tenure as the 2017 President of the Geological Society of Washington. In our Society, it’s a tradition for the President to give the final talk of the year, a Presidential Address that takes up the entirety of the final regular meeting. I’ll be talking tonight about the art of geology. Specifically, my title is “Visualization in geology: A brief …

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14 November 2014

Friday fold: GSW fall field trip

Last Saturday was the Geological Society of Washington’s fall field trip. Dan Doctor, Alan Pitts, and I led a team of ~20 geologists out to the great new exposures along Corridor H in West Virginia. Here’s the team in front of some of the parasitic anticlines and synclines that decorate the larger structure of the Patterson Creek Mountain Anticline: The strata here are Silurian-aged tidal flat carbonates of the Tonoloway …

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9 November 2014

Silurian mudcracks in cross-section

Spotted these cross-sectioned mudcracks yesterday on Corridor H, on the GSW fall field trip: They are in the Tonoloway Formation, a batch of tidal flat carbonates with lots of evidence of shallow arid conditions.

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28 October 2012

Geology and wine in northern Virginia, part I: the Blue Ridge

Callan attends the Geological Society of Washington’s fall field trip, examining the relationship between grape-growing and the underlying geology of two provinces in northern Virginia: the Blue Ridge and the Valley & Ridge. With GSW compatriots, Callan visits Hume Vineyards in the Blue Ridge basement complex and North Mountain Winery in the Shenandoah Valley. This is part I.

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19 October 2011

Bookshelfed mullions from Norway

Elizabeth Eide of the National Academies shared this image with me a year or two ago, when she gave a talk on Norwegian geology for the Geological Society of Washington. Those are some bookshelfed gneiss layers sandwiched between upper-left and lower-right carbonates. The “bookshelfing” refers to the numerous parallel brittle fractures along which the gneiss slabs have slid down the face of their neighbors, like a set of encyclopedias tilted …

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22 October 2010

Friday fold: twice-folded turbidites at Black Pond

Today’s Friday fold comes to us courtesy of Gary Fleming, botanist extraordinaire and brother of Tony Fleming, geological Jack of All Trades. Together, the Fleming brothers led a field trip for the Geological Society of Washington. While I was on that field trip, the topic of polyphase deformation came up, which led a couple of weeks later to Gary sending me this photograph. He took this photo in the Black …

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24 March 2010

Transect debrief 4: transgression, passive margin

…So where were we? Ahh, yes: an orogeny, and then some rifting. What happened next to Virginia and West Virginia? Let’s consult the column… After the rifting event opened up the Iapetus Ocean, seafloor spreading took place and tacked fresh oceanic crust onto the margin of the ancestral North American continent. As North America (“Laurentia”) moved away from other continental fragments (Congo craton, Amazonia craton), it got a little bit …

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20 February 2010

GSW spring field trip

A few photos from last May’s spring field trip with the Geological Society of Washington… Here’s the group at Chain Bridge Flats (far westernmost-Washington, D.C.), looked at the metamorphic rocks there — a metagraywacke melangeĀ  known as the Sykesville Formation. Another group shot, with field trip leaders Tony (khaki shirt) and Gary (red jacket) Fleming in the foreground: Euhedral metamorphic pyrite crystals (porphyroblasts): An elusive bedding plane in the Sykesville …

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