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28 March 2014
Friday fauxld: the “Not a Box” at Confusion Hill
It’s Friday… that means it’s time for a fold. Let’s try this outcrop at “Confusion Hill” in the Franklin Mountains of West Texas: See it? Let’s zoom in… From the shadows to the left of the hammer, trace out the dark green layer… it may make you think of a box fold: …but it’s not. This is actually a completely planar sedimentary bed, tilted to more or less vertical, and …
26 March 2014
The Great Unconformity in the Franklin Mountains
Good morning! Let’s take a walk up the east side of the Franklin Mountains, north of El Paso, Texas, to walk across the Great Unconformity. The basement rock exposed here is the Red Bluff Granite, a 1.1 Ga felsic magma that intruded the columnar basalts of the Mundy “Breccia” and the Castner Marble. (It is unknown what substrate the Castner Marble was deposited upon.) This is what the Red Bluff …
25 March 2014
Root wedging: examples from Maryland and Texas
While I’m showing photos from last week’s Billy Goat Trail field trips (3 in total), let me share a striking example of root wedging from Olmstead Island, on the walkway out to see Great Falls: And, since I meant to get back to blogging about west Texas this week, here’s another example of the same process, seen with a different kind of tree in different sorts of rocks, in the …
21 March 2014
Friday fold: a random sample from the campus of UTEP
I know nothing about this sample, other than the fact that it was a thrown-away sample found in the rock pile next to the old geology building at the University of Texas at El Paso. Happy Friday!
20 March 2014
Montoya Group fossils and faults on the Crazy Cat landslide
Today, I initiate a series of posts based on some of the geology I saw over spring break, in west Texas and southern New Mexico, on the field exchange between Northern Virginia Community College and El Paso Community College that I helped facilitate. We spent our first morning in the field in the Franklin Mountains, due north of El Paso (and, for that matter, Ciudad Juarez). It was unseasonably cold …
9 March 2014
Off to Texas
I just wanted to let readers know that posting will be light this week, as I’m down in Texas running my field exchange course with Joshua Villalobos of El Paso Community College. Joshua’s supplying 12 students, and so am I. Together with talented colleagues, we’re aiming to give these students, many of whom hail from traditionally-underrepresented groups within the geosciences, a world-class field experience that will take them from the …
16 January 2014
Samples from Austin: another stretched-pebble conglomerate
While at the University of Texas at Austin, where the Jackson School of Geosciences was hosting the Summit on the Future of Geoscience Education this past weekend, I was impressed to see a well-developed rock garden outside the student center. Here’s an example of a stretched-pebble conglomerate from that garden: Note the nice epidote boudins running down the middle. The way the foliation “flares” at the bottom suggests another boudin …
15 January 2014
Samples from Austin: folds in the rock garden
While at the University of Texas at Austin, where the Jackson School of Geosciences was hosting the Summit on the Future of Geoscience Education this past weekend, I was impressed to see a well-developed rock garden outside the student center. Here are three boulder-sized samples of folds from that garden. Enjoy! Jackson School of Geosciences pen for scale, natch.
14 January 2014
Samples from Austin: boudinage on the wall
While at the University of Texas at Austin, where the Jackson School of Geosciences was hosting the Summit on the Future of Geoscience Education this past weekend, I was very impressed with the backdrop behind the main desk at the student center. It showed lovely meso- and macro- scale folds, and exquisite boudinage. I never found out the source or story behind this rock, but it’s certainly lovely. I’m sure …
13 January 2014
Samples from Austin: Stretched pebble conglomerate
While at the University of Texas at Austin, where the Jackson School of Geosciences was hosting the Summit on the Future of Geoscience Education this past weekend, my friend and colleague Pete Berquist snapped this image of a stretched pebble conglomerate in the structure teaching lab: Some nice examples of pressure solution evidence in there – fused pebbles; strong clasts impinging on their weaker neighbors’ boundaries… Thanks for sharing, Pete!
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.