Sunday, April 15, 2012

Port Williams

This is a beautiful stretch of steep, wonderfully layered bluffs north and west of the entrance to Sequim Bay. I'll have to go back and check the maps, but I believe the geology is late glacial -- till on the bottom, overlain by river gravels, and capped with glacial marine drift (?).  The stratigraphy changes slightly along these bluffs, painting an interesting picture of complex goings on right as the glacier retreated from this area and both sea level and perhaps the Dungeness River were doing something very different than they are today!

(NOTE:  Well, I was right about till on the bottom and glacial marine drift on top, but better geologists than me report that the till at the bottom is Possession, suggesting this sequence covers two glaciations, not just the end of the last one.  And there is a lot of interesting sedimentary detail in here, too, from rip-ups to cross-bedding.)

The bluffs are steep, consistent with higher erosion rates and fairly coherent units.  The fluvial gravels are strongly cemented at the south end, resulting in a near vertical bluff.  Farther north, the gravels are less consolidated and are a distinct slope-forming unit mid-bluff, above the steep till and below the steep upper drift unit. They were so unconsolidated that they were raveling as I walked the beach, cascading over the till and forming beautiful cones on the beach.


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