Friday Field Foto #57: Dish structures
A relatively common sedimentary structure found in sandstone turbidite beds are dish structures. Take a look at the photo below and you’ll see why they are called that … they are concave-up, slightly darker laminations anywhere from a centimeter to a few 10s of cm across. Sometimes they are less arcuate (platters) and sometimes the concavity is more pronounced (cups).
How do these form? If you want to learn about what these structures are, how they form, and what they can tell us about the sedimentation mechanics go check out Hindered Settling’s fantastic post on this subject. I can’t say it any better than that post, so go there. Plus, he has some beautiful photos of more exquisite examples. Check it out.
As a side note, this paper from 1972 notes the first time dish structures were recognized and reported in the literature:
Dish structure was first described by Wentworth (1967) from the Gualala Formation of northern California…
As it turns out, the photograph above is from the Gualala Formation! Maybe Wentworth went to this exact spot … that would be cool.
Happy Friday!
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Clastic Detritus 
From your recent posts, I’d say you’ve turned NorCal on us. Weeee!! Go Gualala Formation!
When I found out that dish structures were first identified here it made me want to take a little trip up there!