Friday, December 12, 2008

Friday Field Photo #4

Gateway to Northumberland Canyon; photo looking east.

The entrance to Northumberland Canyon, coming in from Big Smoky Valley in central Nevada, is marked by a sentinel of Northumberland Tuff overlooking a dry wash that was in high flash-flood conditions on August 7, 1979, while I was doing field work in the area.

Well, that's a great lead in, but what I really wanted to do was post a field photo before Friday was completely over, and it looks like I've just barely made it. I took the photo a couple weeks ago while out driving around.

The cliff of strongly welded Tertiary ash-flow tuff looks like it may be capped by some black chert, and that would be Ordovician Vinini Formation chert on top of Tertiary ash-flow tuff. If that's what it is, it's pieces of chert and slide blocks the size of trucks, and larger, that slid into the caldera, forming an intracaldera breccia and slide-block formation that we called Unit 1, way back when.

A bit more on that later.

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