6 August 2012
What are these geologists looking at?
Posted by Callan Bentley
Photo by Sarah O.
Tune in tomorrow for the answer!
Connect with Callan:
About Callan
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.
Other geobloggers are writing about
- Arctic ice is a hockey stick 20 March 2023
- We were probably wrong about caudal pneumaticity in Ca13 of the Brontosaurus excelsus holotype YPM 1980 20 March 2023
- Arctic air mass breaking up 19 March 2023
- The Old Man and the Sea -- Ocean currents -- March 18, 2023 18 March 2023
- Shallow M6.7 earthquake in Equador 18 March 2023
Hmmm. Well, they’re standing on a knob of bedrock that’s been overrun by the Athabasca Glacier (that’s its lateral moraine in the background). The bedrock around here is carbonates of Cambrian and/or Devonian age. So, I’ll guess–in order of likelihood: 1) Glacial striations and/or polishing; 2) Devonian tabulate corals; 3) Cambrian trilobites.
Spoken like a man who knows the Canadian Rockies! But while we came for the glacial striations, we stayed for something else…
…and it wasn’t fossils!
Nuts. OK, I cheated and did some reading, so I think I know what it is now, but I’ll let someone else have a kick at it. Suffice it to say (if I’m right this time) it’s something that would be of interest to structural geologists, and the evidence is visible in the photo.
You’re right that it is of interest to structural geologists, but I’d be shocked if you could make it out in this photo, given how far away the photographer was from the cm-scale features we were discussing.
Since you’ve given the clues about it relating to structural geology and it’s cm scale, my guess would be something showing that bedding is overturned, like ripple marks, or burrows or shell beds.
Good guess — but it’s not primary structures that caught our eye…
Nuts again. Maybe I should just shut up and wait for the answer, but I’m too weak to resist. I figured your group was standing on the fault trace of the (?)Simpson Pass Thrust. Looks like the rocks to the left of your group are dipping at a very different angle than those to the right of the guy in the orange shirt, in which case you would be looking at slickensides or something closely related. But maybe that’s just a trick of the camera angle and my imagination. If this isn’t related to the fault, then I’ll just toss out a WAG and say “stylolites”.
WAG confirmed! Guess I should write the follow-up post now…