"BFMB"@en . "461.25"^^ . "Didymograptus Bifidus Beds And Didymograptus Murchisoni Beds (Undifferentiated)"@en . . . "Bifidus Slate Formation and Murchisoni Beds (Undifferentiated) [Obsolete: use BFMB]"@en . "Didymograptus Bifidus Beds And Didymograptus Murchisoni Beds (Undifferentiated)"@en . . "Siliciclastic argillaceous rock. Bedrock. Occurs onshore. Formed during the Abereiddian Stage (Ordovician Period) (468-461.25 Ma BP)."@en . . "468.0"^^ . . . . "See the Lithology descriptions for the component units."@en . "stable"@en . .