AbstractThis magnalithofacies, which forms the bulk of two formations, the Bunter Pebble Beds and the Lower Keuper Sandstone, is described and interpreted as the deposits of former low‐sinuosity, largely braided, streams which flowed across a regional palaeoslope inclined to the north‐west. Arid blocks of the Welsh and Pennine Massifs lay to the west and east. Lithofacies A, conglomerate breccia and gravel, is interpreted as a deposit of former channel floors and sometimes bars. Lithofacies B crossbedded pebbly coarse sandstone, formed from large‐scale ripples developed on channel (? braid) bars of flood courses, whilst lithofacies C, argillaceous finer sandstone, represents the large‐scale ripples of quieter channels at lower stage and discharge. Lithofacies D, interbedded fine sandstone and shale, formed a riverplain topstratum deposit and, rarely, a levee. Lithofacies E is similar to D except that the sandstone is coarser and injects the mudstones repeatedly. Lithofacies F, red shales and mudstones (largely the ‘marl’ bands of former authors), may be laterally restricted or extensive. The former bands represent deposits of bar swales and abandoned cut‐off channels of varying stage: the latter suggest the development of a riverplain topstratum. Lithofacies X, soft fine sandstone, is aeolian. These lithofacies are arranged in vertical repetitions of varying thicknesses which are often asymmetric. Allocyclic climatic influence, reflected in varying discharge and sediment load under conditions of net accretion and steady subsidence, is regarded as a dominant factor in the origin of miocycles, megacycles and magna‐cycles, though in smaller repetitions the possibility of channel wandering, and in magnacycles the influence of tectoni