23 November 2010
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 tectonic, structures (i.e., those that formed as a result of the rock being strained under tectonically-imposed stresses).
One student found this sample, which made me go all ga-ga because of the wealth of different structures it displays:
How many different structures can you identify here? Start naming them in the comments! I’ll post an annotated version of the diagram tomorrow so you can compare your structure-o-vision to mine…