Devil’s Quoits 15
Image by ginger tt

I think 'local conglomerate' seems to be the answer, though I was hoping for something more specific.

That's a great article by Gill Hey.

I think it's just 'Conglomerate', a term which includes puddingstone. It sounds crazy and I may have seen some on a beach in Wales about thirty years ago! Bet it makes crap drystone walls.