I can always count on Dan McShane to provide me some local yum, and he had me drooling over the Orcas Chert the other day. I’ll let him ‘splain and filch one of his pictures:
The Orcas Chert is part of a suite of rocks belonging to the Northwest Cascades System (NWCS). The NWCS is not a simple assemblage and taking a walk along the the Orcas Chert exposed on the west side of San Juan Island is a good reminder. Lappen (2000) assembled the Geologic Map of the Bellingham 1:100,000 Quadrangle that includes much of the San Juan Islands. The accompanying report provides only a brief description of the geologic setting but I think it sums up the NWCS rather well as “This structural system is a thrust stack of mainly oceanic lithologic packages (terranes) of varying age, structure and metamorphic history.” I would emphasize “varying” as an understatement. When I get asked about these rocks or other assemblages of metamorphic rocks in the San Juans or Northwest Cascades I often say these rocks have had a long hard life.
There’s schist in that thar chert! How does he know I’m a sucker for schist? Argh, now I want to go to the Islands, mon!
And thanks to Anne, who tweeted the following, I’ll always have clean underwear out in the field. I am not giving away the secret here. You will have to click this link. Do not do so with your mouth full of food or beverage, because I refuse to be responsible for what happens if you do.