In Shenandoah National Park, astride Virginia’s Blue Ridge, feeder dikes of Catoctin Formation (meta-)basalt cut across the Grenvillian-aged granitoid basement. Due to their mafic composition and columnar jointing, these feeder dikes generally weather more rapidly than their host rocks. I led a field trip in the park on Thursday for my son’s school, and my … Read more
The Friday fold is a guest submission from Bill Burton, who took the photo of these lovely ptygmatic folds in migmatite in a national park on the 100th anniversary of the founding of the Park Service.
An inaugural visit to an outcrop in Shenandoah National Park reveals the signature of lava flows ~600 million years old.
You could use a macro GigaPan of some pretty sand, I think. Link That’s sand from near Acadia National Park, in Maine. Exploring it, you can find both small chunks of Acadian granite, and green rods that are sea urchin spines. It’s fun – check it out.
I’ve been thinking lately about Harpers Ferry, the spot where West Virginia, Virginia, and Maryland meet, at the confluence of the Potomac River and the Shenandoah River. I’ve noted small outcrops of its overturned beddding here previously, and also described a book I read about the man who made the place infamous: John Brown. I … Read more
As longtime readers know, late summer is when my Rockies students submit their final projects – web-based explanations of key geologic sites they examined during the trip. Today, I offer you a guest blog post by student John Leaming. You’ll notice that I’m not *completely* absent from the post, however – I make a couple … Read more
After reading the post last weekend about the discordant offshoot of the Purcell Sill, Rich Gashnig (post-doc at Georgia Tech) sent me a few photos he shot at Piegan Pass (at the head of a side-canyon adjacent to the one containing Grinnell Glacier). They show the Purcell Sill leaving one stratigraphic horizon and jumping to … Read more
The Neoproterozoic Purcell Sill is a stark, obvious black stripe in the strata of Glacier National Park. Here it is emerging from behind “The Salamander” glacier, above Grinnell Glacier Cirque: Zooming in, you can see the “baked” (bleached) zones above and below this concordant intrusion. But this time, during my visit to this special place, … 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.
The coarser strata of the Neoproterozoic Miette Group in the Canadian Rockies of Alberta record changing water current strength over time, and maybe an iceberg or two.
Check out the argillite boulder in the left midground of this GigaPan, which I’ve showed here before. It was taken at the Icefields Center parking area in Jasper National Park, Alberta: link There, you’ll find some lovely orange lichens, some iron oxide staining, some graffiti, and a fair number of sub-aligned glacial striations. Also, at … Read more
The Friday fold is asymmetric, overturned, and chock full of primary sedimentary features. Join us in Glacier National Park’s Mesoproterozoic Belt Supergroup.
I love moraines, rocky beaches, gravel bars – they are like a giant smorgasbord of delicious goodies. Here, for instance, are some close-ups of a trilobite-bearing boulder on the south lateral moraine of the Athasbasca Glacier, Jasper National Park, Alberta. And what are these things? Any ideas?
Posted this morning as my “Christmas gift” to blog readers in both photo and GigaPan form, here are the exquisite stromatolites of Helen Lake, Banff National Park, Alberta. link link link link link link link Finally, three other non-stromatolitic GigaPans from the site: One of Artomys Formation siltstone / shale interbeds… link …and two of … Read more
The exquisite stromatolites of Helen Lake, Banff National Park, are presented in photographic and GigaPan renditions. Enjoy unwrapping them as your “Christmas gift” from Callan.
For those inclined toward trace fossils… …This is from Banff National Park, Alberta, Canada. I saw it on the trail to Consolation Lakes from Moraine Lake. I do not recall rock type – could be dolostone, could be Gog quartzite. It’s float (loose; not in situ), but I infer the photographed surface is the underside … Read more
I saw this large, chunky stylolite this summer somewhere along the trail from Takkakaw Falls to the Walcott Quarry of the Burgess Shale (in Yoho National Park, British Columbia). I like the way weathering has highlighted its form.
Good afternoon! Here are a few photos, both plain and annotated, showing the relationship between primary sedimentary bedding and tectonic cleavage in the “tectonised Stephen” Formation atop the Cathedral Escarpment (in Yoho National Park), just northeast of the Walcott Quarry where the (thicker, basinward) Stephen Formation hosts the Burgess Shale. Weathering exploits both these planes … Read more
Over the weekend, I ran a 1-credit field course for NOVA, on the geology of Shenandoah National Park. I was about eight minutes early getting to the meet-up location, so that allowed me to check out a promising new outcrop of rock along the road (route 33, ~100 m west of Swift Run Gap). Here … Read more
Here’s an outcrop of Miette Group slate, seen at the intersection of the Icefields Parkway with the Trans-Canada Highway, just north of Lake Louise, Alberta: There’s a lovely anticline just to the right of Zack, who obligingly provided a sense of scale. Also note how cleavage which is subparallel to bedding on the far left … Read more