Saturday, October 26, 2013

Geo 365: Oct. 26, Day 299: Devils Punchbowl Terrace

Here, as at Shore Acres, we see sandy- likely, beach- deposits over a flat terrace on Astoria Formation sediments. It's not obvious in this view, but these rocks are dipping to the northwest, so the contact between the semi-consolidated sand and the underlying Miocene rock is an angular unconformity of sorts. As I mentioned at the above link, it's not clear to me whether "angular unconformities" necessarily require both the tilted and overlying material to be fully lithified. It should be pretty clear from the ease with which the sand is eroded by spray from breaking waves that it can't really be considered "rock."

Yaquina Head photobombs the left horizon as well, another example of CRB reaching the location of the modern coastline. If you look closely, you may be able to pick out the lighthouse there.

Photo unmodified. May 6, 2013. FlashEarth location.

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