. . "CREN"@en . . . . . . "stable"@en . . "468.0"^^ . "Conformably overlain by the felsic tuffs and conglomerate of the Brithion Formation in the north of the Cadair Idris district, and by pillowed basaltic lavas and mafic tuffs of the Llyn y Gafr Volcanic Formation elsewhere within the district."@en . . . "Moelyn Slates [Obsolete: use CREN]"@en . . "Cregennen Formation"@en . "Conformably overlies the felsic tuffs and tuffites of the Offrwm Volcanic Formation."@en . "Bifidus Slates [Obsolete: use CREN, BFDS]"@en . "Crogenen Slates [Obsolete: use CREN]"@en . "Dark grey or black graptolitic mudstones interbedded with felsic acid and mafic tuffs and tuffites in places; sandstones and conglomerates occur locally."@en . . . "461.25"^^ . "To 350m"@en . "Mudstone with subsidiary felsic tuff, mafic tuff and tuffite and trace conglomerate and sandstone. Stratified bedrock. Occurs onshore. Deposited during the Abereiddian Stage (Ordovician Period) (468-461.25 Ma BP)."@en . "Cregennen Formation"@en .