re: Home Plate - Wow!
That finely layered stuff on top looks reasonably well cemented together -- not hard, you're right, but cemented enough in discrete layers to form those thin fins and sheets sticking out now and then. Is that likely from dry ashfall? Plus the layers look awfully even for ash falls.
The lower sequence looks more plausible as ashfall or some other pyroclastic deposit.
Maybe a sequences of ash falls, then a period when fine dust from the ash formed seasonal aeloian deposits?
Well, if it's all basalt compositionally that'll tell us one thing. If it's highly altered, that's something else. I'd imagine we should have some APXS answers to that soon enough.