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
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? [gigapan id=”129425″] link [gigapan id=”129426″] link … 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
At the eroded gully known as Devil’s Coulee in Alberta, you can find armored mudballs, dinosaur fossils (including eggshell), and even marine clams at higher levels in the sequence. Check out these lovely beasts: They lived and died on the western shore of the Western Interior Seaway during the Cretaceous period of geologic time. My … Read more
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) … Read more
Archaeology meets geology in this visit to the Piney Branch valley of Rock Creek Park in Washington, D.C. Cretaceous deposits of cobbles of Cambrian quartzite were quarried by Native Americans and modified into tools thanks to the fact that they break with a conchoidal fracture.
The Friday fold comes from the Texas – New Mexico – Chihuahua triple point, on the flanks of Cristo Rey mountain.
Callan and two colleagues find a “textbook” unconformity on a field trip in Virginia’s westernmost Blue Ridge.