geologic history of the Bailey Peninsula (Seward Park)?

[Paul Shannon]

The Bailey Peninsula is an anomaly: a north-facing peninsula in a ribbon lake (Lake Washington), in which the lake was cut by southward flowing subglacial river flow.

I am untrained in the field (as you will quickly detect...) but I nonetheless find myself wondering, and speculating.  I am posting here in hopes that my speculations can be brought down to earth, corrected by those who really know some local geology.

Derek Booth's 1994 paper, 'Glaciofluvial Infilling and Scour...' suggests that the peninsula had to withstand 'locally intense linear scour'.  Is it plausible that the more resistant elements of the Blakeley Formation  -- which can today be seen in the peninsula, especially on the north facing cliff on the west side of Andrews Bay -- provided this resistance?

Even more speculatively, I wonder whether, during the period of highest subglacial river flow, the Bailey Peninsula was actually an island, with some flow to the east across what is now the isthmus, as well as through the stronger, deeper channel to the west, on the Mercer Island side.

I will be grateful for any comments, even the most deflating!

Cheers,

 - Paul Shannon
   Institute for Systems Biology
   Seattle