Wednesday, April 23, 2014

Geo 730: April 23, Day 479: Transition

We're looking at a rugged, but more or less flat-lying, marine terrace here. The sedimentary component seems to becoming more sparse, and the basaltic component- both pillows and breccia- more dominant, as compared to earlier exposures farther south along the sidewalk.

Photo unmodified. July 10, 2012. FlashEarth location.

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.

Monday, April 21, 2014

Geo 730: April 21, Day 477: Muddled Mix

Some sections of the basalt/sedimentary mixture at Depoe Bay seem at least somewhat stratified- not organized, per se, but not exactly chaotic either. The above shows a disorganized muddle of pillows, breccia and sediment. It's hard to tell the finer breccia material from the sediment at this distance, so I don't have a good sense of how much there really is of the latter here, and how much is purely volcanic in origin.

Photo unmodified. July 10, 2012. FlashEarth location.