Regional Picture. Bala area has series of fault bot blocks wh. are sinking as sedimentation takes place - all are : shallow water deposits subtidal but not v. deep. How does this differ from F. Williams interpretation of hills on anticlinorium wh. are gently eroded as subsidence. In Bala area the volcanic intrusions (andesites) & volcanic outflows provided sediments from within the basin unlike area to S. & W. The Irish ridge was not a source of sediment. On west side of Irish Ridge there was more rapid subsidence & diff. kind of sediments. The subduction zone is from E. acc. to Dewey & to W. acc. to one of the earlier writers. Anglesey Northern section has an entirely different relation i.e. Wales Anglesey. S.E. Ireland shares some similarities w. Wales. Irish Ridge.