Friday Field Photo #186: Coastal California Turbidites
July 12, 2013
It’s been two years since we moved from California to Virginia, time flies! We really love where we live now, but there are times where I do miss California. I especially miss exploring the outcrops along the coast. Many of these wave-washed bluffs have gorgeous exposures of bed-scale sedimentary geology, a real delight for those who like sedimentary structures.
The above photo shows some Paleocene turbidites along beach cliffs in the town of Gualala, a few hours north of the Bay Area.
Happy Friday!
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Clastic Detritus 
I was just at Montana de Oro State Park, just south of Morro Bay, which is one of my favorite spots on the coast. There are some great tidepool areas in coves off the Bluff Trail south of Spooner’s Cove. One thing that makes them such great tidepools is the rock substrate: a very thick sequence that looks a lot like that only it’s tilted so the rock layers stand very nearly vertical, and pointing straight out to sea. The softer parts form channels for water to roll in, while the harder parts stand up a little make for very good footing (except for the biological coverings, which can be slippery). The bluffs mostly made up of much younger horizontally bedded sand and gravel (a terrace) which stands on top of the layered rock.
I haven’t been to that spot, but, yes, that’s a common pattern along the central CA coast. Much older (~70-100 million year old) sedimentary rock sequences that are tilted, sometimes vertically, overlain by much younger (<1 million years old) deposits that are essentially flat. I love the tide pools.