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2 March 2014
A chip off the ol’ charnockite
We visited the Philip Carter Winery this weekend with family. Baxter and I were pleased to see outcrops of charnockite scattered over the property (located in the middle of the Blue Ridge geologic province). As any 18-month-old will tell you, charnockite is a pyroxene-bearing granitoid. It’s a distinctive and common rock type in Virginia’s Proterozoic basement complex. Here’s a close-up: The dark green is pyroxene. The white is plagioclase feldspar. …
12 December 2013
Some folds along the Crypt Lake trail
Hiking up to Crypt Lake in Waterton Lakes National Park, Alberta, Canada, you can see some sweet stromatolites, We’ve already taken a look at the falls, but today, let’s zoom into the folds exposed in that shadowy cliff near the center… These limestone layers are Mesoproterozoic in age – they’re part of the Purcell (Belt) Supergroup. The folding likely dates to the late Cretaceous into early Paleogene “Laramide” Orogeny (as …
11 December 2013
Stromatolites along the trail to Crypt Lake
On the trail up to Crypt Lake in Waterton Lakes National Park (southernmost Alberta, Canada), there’s a ‘traditional’ hiking trail, and then an intense ledge on a glacial headwall that you must teeter along, including scaling your body up into and through a person-sized tunnel! Right at the transition between the two “phases” of the hike are some boulders of Mesoproterozoic Belt limestones (Helena/Siyeh Formation??) bearing many, many, many stromatolites. …
4 September 2013
Granite balls, boudins, and tadpoles in Archean schist, Laramie Range, Wyoming
A final post from my visit to the Laramie Range with Bob Bauer and Fred McLaughlin earlier in the summer -Recall that there is schist and granite at this site, and much of the granite shows cross-cutting or inclusive relationships indicating it is younger than the schist, while still younger mafic dikes cross-cut than the granite. Both exhibited folding. However, in other places, we observed the opposite: granite inclusions within …
9 August 2013
Friday fold: four more Proterozoic folds from the Laramie Range
To this and this, add these: Some interesting fold shapes here. Bob Bauer, who took me to this site, interprets these as interference patterns, evidence of two generations of folding: Happy Friday – for me, there’s only a week of summer break left, and then a week from today, I’ll be back at work.
2 August 2013
Friday fold: 2Z
Two Z folds from the Proterozoic rocks of the Laramie Range, Wyoming – you get two since I’ve been so delinquent about blogging over the past month.
27 June 2013
Paleoproterozoic dikes in Archean granite, Laramie Range, Wyoming
At Morton Pass, where highway 34 crosses the crest of the Laramie Range, you can see a nice set of (younger) mafic dikes cutting (older) granite/gneiss basement complex. The pink stuff is Archean; the black stuff is Paleoproterozoic; around 2 billion years old. Click to enlarge I got to check out this outcrop on Tuesday with colleagues from the University of Missouri and the University of Wyoming. Deformation in the …
24 April 2013
Native copper from the Catoctin Formation
Another new insight from last week’s visit to the Outdoor Lab was that they have several fine examples of native copper found in float of the Catoctin Formation on their property. Here are a few examples: Classic examples – a bit of malachite in there too, it looks like. I wasn’t totally shocked when I saw these items, since just a month or two ago, I was shown a similar …
17 April 2013
Four new GigaPans from an intriguing contact
Callan and his colleague Jay Kaufman (University of Maryland) go to extraordinary lengths to document an intriguing block of rock in northern Virginia’s Blue Ridge province. Great images and a lot of fun result – but what do these rocks tell us?
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.
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.