Last week, I spent two perfect days camping with family at Usal Beach, in Mendocino County, California. Along the beachside cliffs there, I spotted plenty of lovely turbidites: graywacke and shale and a little bit of conglomerate that had been scraped off the subducted Farrallon Plate to help contribute to the bulk of the Franciscan complex. That accretionary process imparted some stresses on these deep-sea deposits, and in many places they show significant deformation. Here are a dozen images to highlight some of the folds I saw:
Beautiful folds…
Note how some of the more brittle layers in the folds feature bedding-normal extension fractures, probably filled with quartz. These fractures record layer-parallel extension and must have formed before the beds were folded.