. . "Helsby Sandstone Formation [Duplicate: use HEY]"@en . . "246.7"^^ . . . "Helsby Sandstone Formation"@en . . "Sandstone. Stratified bedrock. Occurs onshore. Deposited during the Early Triassic Epoch (Triassic Period) (251.9-246.7 Ma BP)."@en . "Helsby Sandstone Formation [Duplicate: use HEY]"@en . "251.9"^^ . . "HBSF"@en . "stable"@en . "[Duplicate: use HEY]"@en . .