My former student James O’Brien recently moved out to the left coast, and posted some photos earlier this week of a hike he took at Mount Diablo State Park in the mountains east of the San Francisco Bay area of California. There are some classic-looking Franciscan cherts exposed there, as these folded examples show: Seeing … Read more
The Friday fold is some crumpled sedimentary rock near the Hayward Fault in California.
Marek Cichanski (of De Anza College near the south end of San Francisco Bay) contributed this week’s Friday fold: Marek says: The locality is a place near San Francisco called Devils Slide. It is a piece of the coastal highway built along a steep mountainside above the ocean. This unstable stretch of road was recently … Read more
A guest post today for the Friday fold from my former student Naseem Naghdi, who’s now in southern California: The Ventura Avenue anticline is a fault-propogated fold and is located in the core of (Conoco’s) San Miguelito oil field, which is on the Ventura-Rincon anticlinorium. Carbon dating of seashells have indicated that the terraces range … Read more
More folds from the charismatic Noonday Dolostone in Mosaic Canyon, Death Valley National Park, California: Annotated: Happy Friday!
For the Friday fold today, let’s return to the warmth of Mosaic Canyon in Death Valley National Park, California: Can you see it there? Let’s zoom in on the dark area in the middle of that first photograph…. Ahh! Now that’s a fold to end the week on! Enjoy the weekend, everyone.
The Accretionary Wedge is a ~monthly geoblog “carnival” which elicits posts on a variety of themes. This month, it’s Maitri’s turn, and she wants to hear about our geo-injuries. Here’s my story: In 2003, I was doing field work in the high Sierra, mapping the Sierra Crest Shear Zone for my geology master’s degree. When … Read more
Following the “monster” that was the Friday fold two weeks ago, here are some more folds in the Noonday Dolostone (“Dolomite”) in Mosaic Canyon, Death Valley, California: Zooming in on this isoclinal fold: Bedding traces annotated, highlighting the “similar” style of folding (hinge thickened; limbs thinned): A very different style of folding, observed a few … Read more
While out in Death Valley with my Field Studies students last March, we encountered an extraordinary fold in Mosaic Canyon. Check this thing out: The rock is the Noonday Dolostone (“Noonday Dolomite” in mineralogically biased argot). It may be hard to make out what’s what there… So let me assist with a little annotation, tracing … Read more
Some of the dynamics of small-scale mass wasting in granular materials are captured in this animated GIF from sand dunes in Death Valley.