After my cousin Brad caught up with us after our Pinkham Notch roadcut excursion, we started up the trail at Tuckerman Ravine, and then detoured to go via the Lion Head. Immediately, we began to see some freaking awesome metamorphic porphyroblasts. During the Acadian Orogeny (in the late Devonian), the original muds and sands (deep … Read more
Okay, a final post (for now, anyhow) sharing some images from last Friday’s field trip to the Billy Goat Trail, in Potomac, Maryland. Yesterday we looked at lamprophyre dikes, but there are other dikes on the Billy Goat Trail, too. Like this granite pegmatite: What’s interesting to me about this is that the joint set … Read more
The Friday fold takes us to some high-grade metamorphic rocks in the Piedmont of northern Virginia.
The Friday fold visits the French Broad Massif of North Carolina’s Blue Ridge province.
Merry Christmas! Along with the red cherts of last Tuesday, enjoy today’s green rocks — serpentinite and serpentinite mélange of Marshall Beach, west of the Golden Gate Bridge in San Francisco.
The geological tour of San Francisco continues with an examination of the graywacke deposits of the
One other thing that I noticed during my visit last weekend to the Virginia Museum of Natural History in Martinsville, Virginia, was this fold. As soon as I saw it, I squealed “Oooh! That’s going to be the Friday fold!” It says something about the crowd I was traveling with that everyone (a) knew what … Read more
Part 6 of the Tavşanlı Zone field trip had us looking at some blueschists and eclogites. Today we conclude the terrific field trip with a brief look at a couple more stops.
Lately, this blog has been focusing a lot on a subduction zone complex in Turkey, the Tavşanlı Zone. Much of the geologic appeal of that complex is its profusion of high-pressure, low-temperature metamorphic rocks, those in the blueschist metamorphic facies. From the last location visited on the Tavşanlı Zone field trip, I collected this fine … Read more
Part 5 of the Tavşanlı Zone field trip left us eating lunch amid some fine blueschists. Of course, nothing tops off a blueschist lunch like… more blueschist. So after our meal, we took another stroll through the countryside in search of more interesting subduction zone rocks… I’;ve got a bunch more photos for you today. … Read more
After our mind-boggling encounter with the limestone strata turned lurid pink by their high-pressure encounter with subduction, our band of merry geologists set off for a stroll: We began the walk in greenschist + blueschist mélange, as seen here with a Turkish 1-lira coin (26 mm diameter; about the same size as a U.S. quarter) … Read more
Picking up where we left off… I was telling you about the field trip I took through Turkey’s Tavşanlı Zone, a tectonic suture zone between fragments of continental crust that accreted during the closure of the Tethys Ocean. Day 2 of the trip dawned and we broke fast, and then headed out to a bizarre … Read more
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).
Picking up where we left off last time, we were in some partly-serpentenized peridotite, part of the Burham Ophiolite in Turkey’s Tavşanlı Zone, an ancient tectonic suture. Our next stop on the field trip allowed us to visit some diabase dikes: Here’s a close-up of the right contact of the dike with the host peridotite: … Read more
Yesterday, I shared a few thoughts about the first couple of stops on the field trip I took earlier this month from Istanbul to Ankara, prior to the Tectonic Crossroads conference. Today, we’ll pick up with some images and descriptions from the next few stops. After lunch, our next stop brought us to a relatively … Read more
Before the Tectonic Crossroads conference two weeks ago, I had the good fortune to participate in a Istanbul-to-Ankara geology field examining the Tavşanlı Zone, a tectonic suture zone where a portion of the Tethys Ocean basin closed. This paleo-convergent boundary is marked by a suite of interesting rocks, including blueschists, ophiolites, and eclogites. I’d like … Read more
For the second year in a row, more exotic travel plans meant that I wasn’t able to attend the superb Virginia Geological Field Conference. I see that they have now posted some photos on the group’s Facebook page, so go check them out to see what we both missed last weekend. Here’s a taste: Sheared … Read more
Today I’m in the air, on my way back to Turkey for the Tectonic Crossroads conference being held in Ankara next week. Before the meeting, I’m joining a field trip to examine a subduction zone complex. Over three days, we will drive from Istanbul to Ankara by way of ophiolites and blueschists and other geologic … Read more
Over the summer, when my blogging access was limited to my iPhone, I uploaded a photo (taken with the iPhone) of a metamorphosed graded bed on the summit of Mount Washington, New Hampshire. Here’s another one that I saw, further down on the mountain, on the Auto Road (famous for its iconic bumper sticker): Lens … Read more