29 May 2015
Reader Bill Mitchell contributed this week’s Friday fold, viewed here zooming in closer and closer over three photos:
Here we have a fold found along a trail in Strawberry Canyon just east of the University of California, Berkeley and the Hayward fault. It seems to be mapped (http://pubs.usgs.gov/mf/2000/2342/) as Cretaceous undivided (Great Valley sediments), but I wouldn’t be surprised if it were Claremont Chert (late to middle Miocene) or Claremont Shale (late Miocene). Superficially they are similar to the type section of the Claremont Shale, found just a canyon or two over, and perhaps too small to show on the geologic map.
Bill is on Twitter too: @i_rockhopper
Thanks for the contribution, Bill!