Tuesday, June 3, 2014

Geo 730: June 3, Day 520: Inland On 42 & GDB

I thought I had taken Route 42 across the Coast Range before, but I was mistaken. For the most part, until we got near Roseburg, it was entirely new to me. In consequence, I couldn't anticipate interesting spots to stop, my sense of location, which is generally pretty good, was pretty much shot, and my knowledge of what we were looking at was tentative. All that said, though, the primary thing I was after was a look at the deltaic facies of the Tyee Formation, and we did have a chance to see that, as well as some other neat stuff I hadn't anticipated. We also stumbled across a couple of long-lost spots I probably would've had a heck of a time finding if I'd set out with them in mind as targets. So all in all, it was a very good late morning and afternoon.

Above, I'm sort of half guessing (but pretty confidently) that we're looking at Roseburg Volcanics, which are correlative and equivalent to Siletz River Volcanics. Though they are not connected in surficial exposures, they almost certainly are at depth. This was the first of a number of "impulse, because we can" stops. Generally I wouldn't bother pulling off the road for basalt (which I affectionately refer to as GDB, for, ahem, "gosh-darned basalt") unless I know there's an interesting feature to see. However, it was interesting to see basalt here. I was uncertain where or if we'd traveled off of Klamath bedrock, which is what we were on at Bandon. The above was not metamorphosed at all though, as far as I could tell, so we were back on Coast Range bedrock. Dana had several firsts this day; at this outcrop she found her first slickenside on her own. Anybody who's done geology knows how exciting it is to recognize something independently for the first time, and have it confirmed by someone with more experience. A number of possibly striated surfaces are apparent to me in the above, but I'm not confident enough to call them slicks.

Photo unmodified. March 9, 2012. FlashEarth location (speculative).

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