Tuesday, April 22, 2014

Geo 730: April 22, Day 478: Puzzling Pillows

This is perhaps one of the nicest exposures along the waterfront sidewalk in Depoe Bay. There's a cleft in the rock, coming right up to the sea wall, near the crosswalk in the middle of town. Looking down onto the rock, you can see individual pillows and clumps of them suspended in a mixture of sandstone and breccia. I presume the latter formed by spalling off the pillows as they formed. Glassy breccia of this sort is pretty standard with pillow basalt, and can be seen in a post from last January's Geo 365 series. The sandstone, though, is a little puzzling to me. In the lower middle, there's a lighter-colored lobe with less fragmental basalt. This may represent a spot into which the pillows didn't push, or perhaps a diapir-like "intrusion," where the sand rose in one place in response to being pushed down by the denser basalts elsewhere.

Photo unmodified. July 10, 2012. FlashEarth location.

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