Three new GigaPans I shot last Friday east of Staunton, Virginia, at a semi-legendary exposure behind the Sleep Inn at the 250 / 81 intersection. link link link Students: Which way is up? Which criteria did you use to make that determination?
Are you into structure? Sedimentology? Stratigraphy? Well, I’ve got some good news for you – I’ve imaged several key outcrops on the newly-discovered (to me) roadcut on South Page Valley Road, showcasing the middle Martinsburg Formation turbidites (and their Alleghanian structural overprint). link link link link link link See if you can find: an anticline … Read more
The Friday fold photo was taken this morning on a GigaPanning expedition, and shows a small syncline within turbidite strata of the Martinsburg Formation, Page Valley, Virginia.
Boudinage is such a fun structure. Here’s an example from the roadcut adjacent to the quarry featured so heavily last week. The thick limestone stratum in the center of the photo has been stretched left-to-right. It exhibits pinch-and-swell structure, the first stage of boudinage. Small extensional fractures began to form in the boudin necks, accommodating … Read more
Today, we return to my field trip from last week, for a look at an odd outcrop of the Ordovician-aged Edinburg Formation: Note the car key with green lanyard, to provide a sense of scale. It’s folded, as the yellow bedding traces show in this annotated version: But what really caught my eye about this … Read more
During Alleghanian deformation (late Paleozoic), the Cub Sandstone we looked at yesterday was tilted to near vertical at Catherine Furnace. The shale layers developed cleavage at this time, and there was evidently some flexural slip between sandstone layers, to judge from these fine slickensides: Students: Can you deduce the sense of motion from the orientation … Read more
Today, two GigaPans shot of the uppermost Martinsburg Formation, informally known as the “Cub Sandstone” since it crops out along Cub Run in the southern part of the Massanutten range. 10 or 15 meters upsection (west) of these two outcrops is the base of the Silurian-aged Massanutten Sandstone, the ridge-forming unit. Lower in the section: … Read more
Last week, the Friday fold was presented in GigaPan format only, which led to a concerned reader lamenting that he couldn’t see it on his mobile device. (GigaPans are Flash-based images; they don’t work on Apple devices in the standard GigaPan format, though there is a perfectly suitable workaround with two extra clicks.) So, for … Read more
The initials ABE might make you think of Lincoln, but that’s not what I’m talking about. Today, the letters mean something else: three subdivisions of the 5-part Bouma sequence of turbidites. I took these photos on a new (to me) outcrop of the Ordovician-aged Martinsburg Formation in Page County, Virginia. I visited the site for … Read more
Yesterday, I spent a pleasant day in the field with John Singleton, the new structural geology professor at George Mason University. I was showing John a couple of sites I’ve used as field trip locations for the GMU structural geology class, and John was showing a couple of new sites to me – places he … Read more
Here’s a terrific outcrop to start off the new year at Mountain Beltway. We’re back in the Bighorns of Wyoming here, on highway 16, traversing the southern portion of the range en route from Buffalo to South Pass City. Click to enlarge Annotated, expanded, and Easter-egg-embedded: Click to enlarge From a different perspective (uphill a … Read more
An outcrop of the Ordovician-aged Martinsburg Formation is used to illustrate the development of slaty cleavage, and hence a major transition in the Rock Cycle.
My students Alan Pitts, Chris Johnson, Robin Rohrback and I have been busy adding to the Mid-Atlantic Geo-Image Collection. Check out a few of these new GigaPan images: link link link link link link link
The Friday fold is presented in photo, annotated photo, and GigaPan formats. It’s a cleaved anticline in lower Martinsburg Formation limy slate from Page County, Virginia. See if you can spot Mr. E. coli in the GigaPan!
A sketch of the Massanutten Synclinorium is presented, made with a Wacom Cintiq stylus/monitor combination.
The Friday fold is a contribution from the Massachusetts Geological Survey. It shows a migmatite with lovely structure. An upcoming (free) field trip to this location will be part of the 2012 Structural Geology and Tectonics Forum: an event readers may be interested in attending
Riding a cable-car up the side of the Franklin Mountains, Callan checks out the local stratigraphy and structure (and igneous intrusions). Join him on an insightful cruise up several thousand feet and through a billion years of geologic time.
On the way to visit the Bighorn Medicine Wheel, in a road-bottom outcrop of the Bighorn Dolomite (Ordovician), Callan finds a lovely receptaculid fossil (colloquially known as a “sunflower coral,” though it’s not a coral at all).
Here’s a gigapan I shot yesterday, looking north at the contact between the New Market and Lincolnshire Formations at the classic “Tumbling Run” outcrop south of Strasburg, Virginia: See if you can find the E. coli plush toy I included, or the cm-scale pencil! As usual, you can see it full screen, by clicking on … Read more
The Shenandoah Valley of western Virginia records the switch in late Ordovician time from passive margin sedimentation associated with the Sauk and Tippecanoe epeiric seas, to active margin sedimentation associated with the onset of the Taconian Orogeny to the east. Higher up in the stack, a similar pattern is seen: a return to passive margin … Read more