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
Callan’s colleague Joshua Villalobos won the 2016 Biggs Award. He also makes GigaPans of folds, like these talc-bearing rocks of the Allamoore Formation.
I’ve posted here before about the extraordinary intra-layer folds in the varved evaporite deposits of West Texas’ Permian Basin, but today I can go one better and offer a GIGAmacro look at these lovely folds: Link GIGAmacro by Callan Bentley Enjoy checking these amazing small-scale folds out. They will boggle your mind.
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
I just finished this excellent memoir by Mary Karr, mostly about her childhood, mostly in east Texas. It’s not explicitly geological but it does feature an oil town economy and a hurricane, as well as some consideration of the Rocky Mountain Front Range in Colorado. I didn’t read it out of any illusions it would … 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.
Good morning. Here are two images from last March’s “Border to Beltway” field trip to West Texas, on the north flanks of the Cristo Rey laccolith. Specifically, these are Cretaceous strata of the Anapra Sandstone, looking at the bedding plane of the rocks. Cutting across bedding are a series of fractures (joints) that have been … Read more
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.
That’s the State Line outcrop south of the Guadalupe Mountains, along the Texas / New Mexico border. Know what you can find there? Tune in tomorrow to find out…
Folks, I’m off to lead another field course – so don’t expect much on the blog this week. This is “phase 2” of the Border to Beltway community college field exchange program. In March, over spring break, I took a dozen NOVA students to Texas to team up with a dozen students from El Paso … Read more
Here’s a fold I saw in Texas, in the Mesilla Valley shale, close to the contact with the Muleros Andesite at Cristo Rey: This is a pretty wild looking fold. Let’s zoom in on the most deformed portion: Annotation: white is top of the distinctive, blocky, buckled bed, and black is its bottom side. Red … Read more
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
I saw this fault in Texas, north of the laccolith known as Cristo Rey: Click to enlarge I had a hard time making sense of the offset in my head, though, since the layers were of inconsistent thickness. Several people tried to convince me that the offset was “normal” (that is, right side down), but … Read more
Back to Texas, today. Here’s a cross-sectioned Turitella snail from the Buda Formation limestone: It’s exposed in a block of rock on the north side of Mt. Cristo Rey. You can explore these GigaPanned blocks of the Buda in search of your own Turitella… How many can you find? link link link
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
Hark! What gleams on yonder contact? Well, there’s no glaciers to polish anything ’round these here parts (southernmost New Mexico + westernmost Texas), so I reckon it must be fault polish. Let’s test that hypothesis by looking for slickensides… Sure enough! There they are! Unlike the deformation we saw yesterday, this faulting of the contact … Read more
Yesterday, I showed off a few views of the contact between the Cretaceous aged Mesilla Valley Formation shale and the hypabyssal Muleros Andesite which intruded into it during the Eocene at Mt. Cristo Rey (on the US/Mexico border where Texas meets New Mexico). Today, I’d like to look at some of the structure associated with … Read more
There are two rock units in this photo. One is igneous, one is sedimentary. Can you find the contact between them? It’s somewhere along this dashed line… The Mesilla Valley Formation is Cretaceous shale with some sandstone. The Muleros Andesite (pretty much identical to the Campus Andesite you find at UTEP) is Eocene. Here’s a … Read more
These four slabs, collected at “Fossil Hill,” north of the Cristo Rey laccolith at the Chihuahua (Mexico) / Texas / New Mexico triple point, bear positively-weathering fossils of the benthic foraminiferid called Cribratina, an index fossil for the Albian age / stage: My field notebook serves as an imperfect sense of scale. Here’s the Albian … Read more