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.
Two years ago, I posted on some interesting structures my students and I saw at Consolation Lakes, near Moraine Lake in Banff National Park. They were little concretions, “oncoids” roughly speaking, and may have indicated (thanks Howard!) that the boulders were sourced to the Peyto Formation, a Cambrian carbonate within the Gog group: The purpose … Read more
Esteemed readership, I’ve got a mystery for you. What are these white lines, inclined consistently at a high angle to bedding? I picked up this sample below the “Wall of Death,” on the trail from Wapta Lake below Mount Wapta, en route to the Walcott Quarry of the Burgess Shale. The “zebra-striped” rock is of … 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.
Driving west from Calgary, your first evidence of entering the Canadian Rockies’ Front Ranges is the startling sheer cliff of Yamnuska, north of the Trans-Canada Highway: Yamnuska’s shape is a function of differential weathering of the two rock units that make up the mountain: Cambrian Eldon Formation limestone, and Cretaceous shales of the Brazeau Formation. … Read more
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
The Friday fold is an outcrop in Yoho National Park that showcases differences between buckle folding and passive folding.
My student Mercer Parker shot this one over to me the other day: Click to enlarge Those are the slim strata of the Rome Formation (a.k.a. Shady*), strongly deformed in the region adjacent to the Max Meadows (“M&M”?) Fault. Thanks, Mercer! _____________________________________________ * Will the real slim Shady please stand up?
Howard Allen is the documentarian of this week’s fold: Howard writes that this is: Middle Cambrian Chancellor Formation rock with recessive weathering intraclasts(?). Hamilton Lake trail, Yoho National Park, British Columbia. My interpretation of this one is a little shaky–it was raining when I took the photo (in 1982) and I was hiking with a … Read more
Good morning! Let’s take a walk up the east side of the Franklin Mountains, north of El Paso, Texas, to walk across the Great Unconformity. The basement rock exposed here is the Red Bluff Granite, a 1.1 Ga felsic magma that intruded the columnar basalts of the Mundy “Breccia” and the Castner Marble. (It is … Read more
Today, I initiate a series of posts based on some of the geology I saw over spring break, in west Texas and southern New Mexico, on the field exchange between Northern Virginia Community College and El Paso Community College that I helped facilitate. We spent our first morning in the field in the Franklin Mountains, … Read more
The Friday fold series returns to Kootenay National Park in Canada for a look at some folded Cambrian limestones.
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.
Two years ago, I took a trip to the Phoebe Hall Knipling Outdoor Lab, which is Arlington, Virginia’s outdoor education facility in the Pond Mountains (southern continuation of the Bull Run Mountains), on the eastern edge of the Blue Ridge geologic province. I was invited back last week to look at some new exposures. I … Read more
Yesterday, I took five new GigaPans at Thoroughfare Gap, a water gap where Broad Run cuts through Bull Run Mountain, the eastern limb of the Blue Ridge Anticlinorium at my latitude. The rocks here are the Cambrian-aged Chilhowee Group, with bedding tilted moderately to the east during Alleghanian mountain-building in the late Paleozoic. To the … Read more
Callan and two colleagues find a “textbook” unconformity on a field trip in Virginia’s westernmost Blue Ridge.
Whoa – look at all that GREEN. You can tell this Virginia picture wasn’t taken recently. In fact, it’s another image from the field review I participated in for the Elkton East quadrangle back in May of last year. Somehow I start blogging these things, but run out of steam (or really more accurately: I … Read more
Dan Doctor of the US Geological Survey contributed this week’s Friday fold. It’s a lovely view of the asymmetric folds in the Cambrian-aged Weverton Formation (part of the Chilhowee Group, a Sauk-Sea passive margin transgressive sequence), exposed on the western flank of the western limb of the Blue Ridge Anticlinorium. It’s a LIDAR image, and … Read more
Callan continues his week-long recounting of his five-day backpacking trip from the Cape of Good Hope to Cape Town, South Africa, along the Hoerikwaggo Trail. Today, we examine the Table Mountain Sandstone.