Busy weeks lately; apologies for the minimal bloggery, friends. For this week’s Friday fold, I offer you a view of some of the outdoor decorations at our new house: In the lower basket there is a cut and polished block of Castile Formation rock gypsum + limestone, showing varves that have been folded, apparently by … Read more
It has been a while since I’ve reviewed any kids’ books here, but this one was so good that I just have to tell you about it. My son is now 6 and a half years old, and he’s interested in all sorts of natural history topics. Given that I’m a geologist, he’s probably more … Read more
This image graces the cover of the new report, Challenges and opportunities for research in tectonics: Understanding deformation and the processes that link Earth systems, from geologic time to human time. A community vision document submitted to the U.S. National Science Foundation: Make it bigger by clicking it The photo is of a landscape in … Read more
Yesterday I blogged the stromatolites to be seen in northeastern Islay, south along the shore from the distillery at Bunnahabhain. The sharp-eyed among you may have noticed that in this GigaPan, there’s more going on than merely Neoproterozoic carbonates: Link 1.46 Gpx GigaPan by Callan Bentley There’s also a prominent dolerite dike, weathering out recessively. … Read more
Walking along the shore east from St. Andrews, Scotland, along the seaside sandstones of Kinkell Braes, you encounter several extraordinary examples of geology. It’s a great place for the next stop on our Grand Tour of the geology of the British Isles. Here’s the scene: The first stop is a giant eurypterid trackway, potentially the … Read more
When snail shells are deposited in a bunch of sediment, they serve as tiny architectural elements, with a “roof” that protects their interiors. Any sediment mixed into the shell’s interior will settle out (more or less horizontally), and then there will be empty space (filled with water, probably) above that. As burial proceeds and diagenesis … Read more
Pisolites are large primary concretions that develop in backreef or lagoonal settings such as the Permian Tansil Formation of New Mexico, into which is cut the enormous hole called Carlsbad Caverns.
What are these Border to Beltway students up to?… Clearly, they are all immersed in their field notebooks, sketching away. This was in March, in west Texas. There must be something worth drawing at this road cut… A clue can be seen on the wall of rock behind them. There, you can find features such … Read more
The Friday fold visits the Permian basin of west Texas. There, the Castile Formation exhibits gorgeous inter- and intra-bed folding.
While in West Texas over spring break, the “Border to Beltway” students took a hike up McKittrick Canyon, in Guadalupe Mountains National Park. This is part of the famed Permian reef complex, the deep reservoir of Texas’s rich endowment of oil. Here, the reef comes to the surface. In fact, it pokes up a good … Read more
My colleague Joshua Villalobos shared this image with me the other day – it’s a thin section of fusulinid-bearing limestone of the (Permian aged) Hueco Formation, from the Tom Mays Unit of Franklin Mountains State Park, Texas. Click to enlarge Note the scale bar at lower left. The big fusulinid in the middle is 3mm … Read more
My wonderfully named e-buddy Martin Bentley recently took a field trip to a quarry in South Africa (between Grahamstown and Fort Beaufort) where the Dwyka Formation is exposed: This poorly sorted sedimentary rock (a ‘diamictite’) is usually interpreted as glacial deposits (lithified till, or ’tillite’). Alfred Wegener cited these rocks and accompanying glacial striations (and … Read more
Yesterday we examined primary sedimentary structures (including trace fossils) at an outcrop of Devonian-aged Brallier Formation turbidites between Deerfield and West Augusta, Virginia. Today, we’ll zoom in on the tectonic structures at the site: folds, faults, and joints. Remember, you don’t have to take my word for it. You can explore it for yourself in … 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.
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
Slightly annotated photo of a Permian therapsid skull on display in the Royal Tyrrell Museum in Drumheller, Alberta. Another photo of this same skull is here. This reptile needs an orthodontist.
Today, I’m going to show you some monster-sized single-celled organisms: giant fusulinid forams from the western flank of the Franklin Mountains in west Texas, beyond El Paso. I saw these critters in February when I went on a field trip there led by Josh Villalobos of El Paso Community College. Here’s the scene where we … Read more
Here’s another video, wherein I’ve made some improvements from the last one (reserved the lower right corner for the webcam “talking head” video inset, and adjusted the microphone for fewer audio blowouts). It’s still not perfect – there’s a disconnect between the audio and the webcam video that becomes more and more pronounced throughout the … Read more
One of Callan’s former students leads a field trip to examine the western edge of the Blue Ridge geologic province, attempting to answer the question of whether the Blue Ridge / Valley & Ridge contact is indeed the trace of a thrust fault. Breccias and S-C fabrics tell part of the story…
Callan visits a new outcrop of highly-sheared rocks in the basement complex of Virginia’s Blue Ridge province.