Looking for the Pavey Arc Member

 I've always loved these volcanic rocks on the top of Pavey Arc. There seem to be huge lumps encased in volcanic ash. 

I'm trying to learn the vocabulary and to understand what went on to form them. In this wonderful document there a diagram on page 5 which shows the "Pavey Arc Member". Page 4 also has what I've been looking for: a map that shows the extent of the Scafell Caldera. It's even bigger than I'd suspected. So I'm guessing that my rock might well be the Pavey Arc Member. I'm inferring that the rock is particles from an explosion that flowed into the caldera lake along with ash so they are sedimentary in a sense. The document calls the rock a "breccia". Now I'd only understood that to refer to rocks shattered on fault lines and cemented by solidifying solutions but it does seem to mean any rock made of large fragments in a matrix of small particles. https://en.wikipedia.org/wiki/Breccia I also looked up "clasts" and found that this is not just to do with volcanic rocks but also sedimentary https://en.wikipedia.org/wiki/Clastic_rock