I misremembered this stop... I recalled that we were looking at bedrock outcrop, but this is clearly a loose boulder. However, it does look lithologically similar to the outcrop across the road, which we couldn't get at for reasons of safety and rockfall controls. What we're seeing here is probably deltaic or near-deltaic facies of the Tyee Formation. I've never seen such coarse-grained Tyee before, and that by itself was pretty exciting to me. The other feature that was particularly thrilling is the piece of coalified (as opposed to mineralized or permineralized) wood that Dana is looking at in the photo.
I have a workshop and field trip up Marys Peak tomorrow, and while I've got the photo picked out, if I don't get that post written up and scheduled, it may not go up until Sunday. So if day 530 doesn't show up tomorrow, don't worry. I'll be out beating up on rocks. More distal facies of the Tyee, in fact.
Photo unmodified. March 9, 2012. FlashEarth location. (This is probably accurate to within 10-20 miles. Sorry, no clue.)