Picking up from the astonishing first couple of outcrops we saw of strained Seine Group metaconglomerate from the boundary between the Wabigoon and Quetico sub-provinces of the Superior Craton, our group moved on down the road. It was lovely clear fall weather near Fort Frances, and shockingly warm. Our third stop of the morning was … Read more
Why are these geologists all over these rocks? Because, gentle readers, these are some seriously cool rocks. The geologists are all participants on a pre-GSA-annual-meeting field trip to the Superior Craton, a chunk of ancient crust at the “nucleus” of the North American continent. The rocks are syn-tectonic volcaniclastic conglomerates of the Seine Group. They … Read more
Wednesday, Alton Dooley put up a post about his visit to Van Hise Rock in Wisconsin. He included this photo of the famous rock with its upright (pretty much vertical) layers: Go read his description of the lithology for more detail, but essentially what you see here is an Oreo-like sandwich: pink quartzite (meta-sandstone) on … Read more
Elizabeth Eide of the National Academies shared this image with me a year or two ago, when she gave a talk on Norwegian geology for the Geological Society of Washington. Those are some bookshelfed gneiss layers sandwiched between upper-left and lower-right carbonates. The “bookshelfing” refers to the numerous parallel brittle fractures along which the gneiss … Read more
The first stop on our pre-GSA field trip to the subprovince boundaries of the Superior Craton was a place just north of Virginia, Minnesota, where the Mesabi Iron Ranges are mined (same Proterozoic banded iron formations that were portrayed as the backdrop of the mining activity depicted in the film North Country). The pull-off is … Read more
I’m on the plane home from the annual meeting of the Geological Society of America, held this year in Minneapolis, Minnesota. This annual event features a robust smorgasbord of science, with talks and posters detailing the research efforts of thousands of geoscientists from the US and other countries. It’s an amazing experience on many, many … Read more
Whilst at the JMU Field Camp in Ireland this summer, my former student Alan Pitts (author of Not Necessarily Geology), collected this lovely “pocket fold” near Derryclare Lough and brought it back to the States. A couple of weeks ago, after a graduate school advising session at a pub in Fairfax, Alan gifted me the … Read more
At the Burgess Shale this summer, it wasn’t all fun and fossils. I also saw a lovely, distinctly feather-shaped plume: This is an example of plumose structure – the subtle branching micro-topography that forms on the surface of a joint as the fracture propagates out from its origin. The more obvious “rib” that is perpendicular … Read more
Reader Jacob Langseth sent in this image of a lovely fold that he recently saw in the Blue Ridge province of Georgia. It’s located in an old CCC rock quarry, off of the Pine Log Creek Trail system, in Bartow County. You can click on that first image to make it bigger and see a … Read more
The Friday fold is a gorgeously deformed “duplex structure” in Mesozoic limestones of southwestern Montana.