Thanks for all the pretty pictures
When time has allowed over the holiday season I have been looking at the raw images, trying to grok what we are seeing. My intuition says Basaltic Tuff: fine-grained with clasts of pumice. Fracturing sometimes seems likes it is polygonal (related to cooling contraction) but there seems to be another fracturing event imposed on that. Seems to be in angular unconformity with the basaltic unit above.