Not a silly question at all, although I am not sure we have many members on here with geological knowledge, and that includes me as a one-time resident of Dwygyfylchi (a long time ago). I hope someone will be able to help you.
Welcome to the forum, and forgive my earlier brusqueness - as a first post yours looked suspiciously like those of the people that 'try it on' periodically. A recent one got through by copying and pasting related material from elsewhere.