Lawhorne Mill High Strain Zone
Callan attends a field trip in the Blue Ridge of Virginia, looking first at a Paleozoic shear zone that disrupts (and improves) Mesoproterozoic basement complex rocks.
proterozoic
Tillite in outwash
Hoo boy. This one made me yelp… While on the glacial geology of western Pennsylvania trip last Saturday, we visited a gravel quarrying operation. The operators were extracting gravel from a glacial lake delta deposit, and it was full of glacial outwash — sediments washed out from the melting front of the Erie lobe of … Read more
Friday fold: Jefferson River Canyon
Here’s your Friday fold, straight from the canyon of the Jefferson River, near Cardwell, Montana. Perspective is to the south. East is on the left; west is on the right. Bigger version This is right next to the outcrops of LaHood Conglomerate that I mentioned earlier this week. My Rockies course co-instructor Pete Berquist and … Read more
Outcrops of the LaHood Conglomerate
Remember the LaHood Conglomerate? Here’s a few field photos of my Rockies class visiting it last July: Amphibolite clast: Marble clast: I love how well-rounded these clasts can be — like eggs. When these grains were loose cobbles, tumbling down into the Belt Sea, the Earth was only 3 to 3.5 billion years old. The … Read more
Diamictite close-ups
Here’s three shots of the Konnarock Formation diamictite, taken with my Nikon microscope. Field of view is about 1 cm in each shot.
Friday fold: Mars Hill terrane
Today’s Friday Fold comes to us via Pete Berquist of Thomas Nelson Community College in Hampton, Virginia. Check it out: Pete explains what’s going on here: I cannot provide an exact location but this is within the Mars Hill Terrane (MHT), which is an distinctive swath of Mesoproterzoic basement extending ~50 km x 100 km … Read more
Animated laminae
More of the new scientific medium* I showed you on Wednesday: animated GIFs of super-small stuff, to give a sense of depth. This time, I included a 1 mm scale bar: These are laminations of silt and clay in the rhythmites of the lower Konnarock Formation. If the above image moves too fast for your … Read more
Reduction rims?
Another look at Konnarock Formation diamictite, showing colorful reaction “halos” around some clasts.
How many structures can you see here?
Last summer, in Bonner, Montana on my Rockies field course, I took the students to see some nice exposures of Belt Supergroup strata on the side of the road. We were keeping our eyes peeled for both primary structures (i.e., patterns in the sediment that formed at the time of their deposition) and secondary, or … Read more
Accretionary Wedge #28: Deskcrops
In honor of this month’s Accretionary Wedge (geoblog carnival; this month the theme is “deskcrops”), I recorded the following short video, showcasing some samples I have in my office: stromatolite (western Montana), conglomerate (Patagonia), schist (New Hampshire), anorthosite (New York), amygdular meta-basalt (Virginia), amphibolite (California), hematite concretions (eastern Montana), and a stretched-pebble lineated meta-conglomerate (Turkey).
Drilling: what, why, and how
As mentioned, I spent a significant part of last weekend was spent on a paleomagnetic sampling project with collaborators from the University of Michigan. On Friday, this was our field area: That’s the south slopes of Old Rag Mountain, a popular Blue Ridge hiking destination because unlike many Virginia peaks, when you get to the … Read more
Rocks of Glacier National Park
This is the second of my Rockies course student projects that I wanted to share here on the blog: it is a guest post by Filip Goc. Enjoy! -CB —————————————————————————– The Rocks around Glacier National Park, Montana: Introduction to the formations The geology around Glacier National Park is great for beginners because the area is … Read more
Transect debrief 3: Rodinian rifting
The Grenville Orogeny, responsible for Virginia’s basement complex, was one mountain-building event among many that helped put together a Mesoproterozoic supercontinent called Rodinia. But Rodinia didn’t last: it broke apart during the Neoproterozoic to form the Iapetus Ocean basin. This rifting event is recorded in Virginia’s Blue Ridge province in the Swift Run Formation and … Read more
Transect debrief 2: weathering the Grenvillian landscape
From the basement complex, the next unit up in the Blue Ridge province’s stratigraphic sequence is the Swift Run Formation. It rests atop an erosional unconformity. After the Grenville Orogeny (~1.1 Ga) added a swath of new crust along the margin of the North American continent, the landscape began to weather and erode. Eventually, an … Read more
Transect debrief 1: starting in the basement
It is time to debrief the post-NE/SE-GSA field trip that I went on, affectionately dubbed the “Transect Trip” for the past 27 iPhone-uploaded “live”-geoblogged posts. First off, I’d have to say that I enjoyed the live-field-blogging experiment overall, though I’ve got some critiques of the process and products. I think it’s amazing that I can … Read more
When the Sturtian happened
Last Friday, I spent the evening riding up to New York on a bus. To pass the time, I had my iPod and a new paper by Francis Macdonald and colleagues in Science. The paper examines the timing of one of the episodes of “Snowball Earth” glaciation. There’s some important new data in this paper, … Read more