Thursday, October 20, 2016

Weird Sand Protrusions at Lilly Point, Point Roberts

I have posted before about the north bluff north of Lilly Point at Point Roberts (lilly-point-point-roberts-part-ii-north). I had another bit of a look at this spectacular bluff on my way to figure out a geohazard site further north.

The bluff consists mostly of a thick sequence of alluvial sediment that I have interpreted to be associated with a large pre-last glacial period river system possibly in some sort of delta like setting. The exposure provides a great cross-section of cut and fill structures and other alluvial deposit features.
Channel cut into layered sand with rip up silt/clay clasts overlain by a thicker sequence of silts

On the lower right of the above image there are a few protruding bumps in the sand unit that I first thought were pebbles until I actually looked at them.

I do not know what these things are or have much of an explanation. They do seem to be associated with specific layers within finely bedded sand deposit.

The bluff is eroded by combination of wave erosion and wind erosion.

As is often the case, I did not have time to linger long as I had to proceed to my main purpose and my ventures on this day had required a fair bit of hiking as well as steep bluff slope scambles.  

1 comment:

susan said...

How odd. They look like that they protrude from a similarly grain-sized deposit. Don't know what that means, though!