"Dark grey to black mudstone."@en . . . "Faulted at the base against the Maughold Formation, which is distinguished by the loss of any sandstone/siltstone interbeds."@en . . . . . "Up to 900 m thick."@en . "Barrule Slates and Slieau Managh Slates [Obsolete: use BRUL]"@en . "Barrule Slates (Manx Slates) [Obsolete: use BRUL]"@en . . "BRUL"@en . "Barrule Formation"@en . . . "Mudstone. Stratified bedrock. Occurs onshore. Deposited during the Arenig Series (Ordovician Period) (477.1-468 Ma BP)."@en . "stable"@en . "In stratigraphical contact at the top with the Injebreck Formation, which is marked by a change from a mudstone/sandstone facies to a mudstone-dominated facies."@en . "Barrule Slates [Obsolete: use GLRN, BRUL]"@en . . . "477.1"^^ . "Barrule Formation"@en . "468.0"^^ .