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 jointing, oxidizing and reducing fluid flow, and the emplacement of ore veins.
The Boulder Batholith outside of Butte, Montana, is actively weathering, and shedding off grus. In the third installment of the Transitions of the Rock Cycle series, we watch an igneous rock turn to sediment.
Concentric ribs with hackles on a joint face, quartzite (metamorphosed fine-grained quartz sandstone stained with hematite) from Waterton Lakes National Park, southern Alberta.
Grab your coffee and join Callan & Lily for a stroll along the quartzite cliffs of Hermanus, South Africa. Bedding, cross-bedding, joints, faults, veins, folded veins, and faulted veins all await you there in the morning light.
Here’s a cool outcrop of the Neoproterozoic Miette Group. Most of the Miette is classified as “slate” and “gritstone,” through these particular exposures, on the Icefields Parkway south of Jasper, are fine-grained and lacking in slaty cleavage. They don’t seem to have been too metamorphosed at all right here, as Sebastian shows in this photo: … Read more
Yesterday, I introduced percussion marks to this blog space. Here are some other shots of this distinctive “shatter” structure, but in a vein of hydrothermal (milky) quartz exposed on Bear Island, between the C&O Canal and the Potomac River (about right here, just west of the trail): Sometimes percussion marks are accompanied by radial fracture … Read more
To recap the week so far here on Mountain Beltway: On Monday we looked at some sweet vertical boudinage along the plane of tectonic cleavage (not to mention those folds in a (formerly) horizontal granite dike, now bearing vertical axial planes), and then on Tuesday we looked at a horizontal cut through that same outcrop, … 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…
Returning to his February field trip in west Texas, Callan examines the contact zone where the Red Bluff Granite intruded into a group of surficial rocks, including columnar-jointed basalt.
In December, Callan found an outcrop of Neoproterozoic-aged turbidites in South Africa, on the eastern shore of False Bay.