The Magnesian Conglomerate is a geological formation in Clifton, Bristol in England (originally Avon), Gloucestershire and southern Wales, present in Tytherington, Durdham Down, Slickstones Quarry and Cromhall Quarry.

It dates back to the Rhaetian stage of the Late Triassic,[1][2] although it may be as old as the Norian stage of the Late Triassic and as young as the Hettangian stage of the Early Jurassic.

[citation needed] The Magnesian Conglomerate was first discovered in autumn 1834 and was studied in 1836 by Henry Riley and Samuel Stutchbury.

[3] The Avon Fissure Fill is often paired with the Magnesian Conglomerate.

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