You are browsing the archive for primary structures Archives - Page 6 of 22 - Mountain Beltway.
17 March 2016
3D virtual sample of a deep sea pillow basalt
Our local NSF geoscience education guru, Jill Karsten, is retiring. She and her husband, Rodey Batiza, are packing up their lives and moving back home, vacating the Beltway for good. This might be viewed as a shame as far as geoscience education funding is concerned: Jill has made her mark acting as an advocate of diversifying the geoscience workforce. I hope they get someone similarly awesome to replace her at …
15 March 2016
Timberville
Join Callan for a virtual field trip, as he shares dozens of photos from a recent ‘field review’ of a new geological map in Virginia’s Valley & Ridge province. Highlights: graptolites, trace fossils, geopetal structures, folds and faults.
12 March 2016
3 scenes from the Timberville VA quad field review
Explore a series of spherical photos taken on a field review of a new geologic map in western Virginia.
23 December 2015
Four new GIGAmacro images of sedimentary rocks
It’s been a week and a half since Mountain Beltway has seen any publishing action, given the overlapping timesucks of the AGU Fall Meeting and the end of the semester. But now I’m back in the Appalachian mountain belt, and my grades are all in, and I have time to think about indulgences like blogging again. Let me make up for it now with a suite of four new macro …
8 December 2015
Considering the Spechty Kopf diamictite
I have known for a long time about a diamictite in the latest Devonian part of the Appalachian stratigraphic sequence, since it is exposed in the lowermost part of the section (western end of the outcrop) at Sideling Hill, Maryland. When I led field trips there, I talked students through the multiple possible origins for diamictites (sedimentary rocks that are poorly sorted, with significantly “outsized” clasts “floating” in a finer-grained …
1 December 2015
Which way’s up? Check cavity fills.
When snail shells are deposited in a bunch of sediment, they serve as tiny architectural elements, with a “roof” that protects their interiors. Any sediment mixed into the shell’s interior will settle out (more or less horizontally), and then there will be empty space (filled with water, probably) above that. As burial proceeds and diagenesis begins, that pore space may be filled with a mineral deposit, such as sparry calcite. …
26 October 2015
Tool marks, trace fossils, and flute casts from the Brallier Formation
Another gem from Saturday’s Historical Geology field trip: the bottom of a fine sandstone bed in the Devonian Brallier Formation, showing a variety of primary sedimentary structures, including tool marks, trace fossils, and several flute casts. Current flow direction here would have been from upper left toward lower right. Here’s a version of the photo with a few of these features highlighted:
12 September 2015
New GigaPans from Team M.A.G.I.C.
Hampshire Formation outcrops on Corridor H, West Virginia: link (Marissa Dudek) link (Callan Bentley) Faults in the Tonoloway Formation, Corridor H, West Virginia: link (Marissa Dudek) Conococheague Formation, showing stromatolites and cross-bedding: link (Callan Bentley) link (Jeffrey Rollins) Tiny folds and faults, from a sample I collected somewhere, sometime… oh well, it’s cool regardless: link (Robin Rohrback) Fern fossil in Llewellyn Formation, St. Clair, Pennsylvania: link (Robin Rohrback) Cross-bedding in …
5 August 2015
Ripple marks and trace fossils in the Rose Hill Formation
An outcrop of Silurian-aged Rose Hill Formation in West Virginia reveals excellent examples of ripple marks and trace fossils.
30 July 2015
Stromatolites of the Helena Formation, Grinnell Glacier Cirque, Montana
My favorite place to have lunch in Montana is at the Grinnell Glacier cirque in Glacier National Park. This is the dining room table: You’re looking at a bedding-plane-parallel exposure of Mesoproterozoic stromatolites here. Every few years, I’m lucky enough to hike up there with motivated students and share food atop this unparalleled view into the shallow seas of more than a billion years ago. Stromatolites are sedimentary structures that …
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.