The Clifton Down Mudstone, a mixed peritidal-fluvial sequence of Arundian (late Osagean-early Meramecian) age from southwest Britain, contains a suite of varied, cumulative paleosols. Temporal changes in soil-type within this paleosol suite provide evidence for a shift in the climatic regime during Arundian times. Calcic Vertisols, in the lower part of the sequence, developed on floodplains and are equated to a seasonally semi-arid climate in which wetter periods induced Vertisol development and promoted leaching. In contrast, a ferric Podzol and thionic Gleysols characterize the upper part of the succession and are associated with a thick fluvial sandstone interval. The ferric Podzol probably developed either in a humid-tropical or temperate climate and indicates that there was a shift to a more humid climatic regime during late Arundian times. Thionic Gleysols with dolocrete horizons represent brackish, hydromorphic marsh soils associated with marine incursions, and overprint earlier paleosols.