The ENE-WSW-trending North Solway Fault acted as a northern marginal fault to the Solway Basin during Dinantian sedimentation. Structural, sedimentological and diagenetic relationships suggest syn-sedimentary Dinantian movement was dip-slip and normal. A later Carboniferous phase of dextral transtension is also indicated. Allokinetic deformation features increase in abundance and intensity towards the North Solway Fault, their presence and nature being strongly facies dependent. Syn-sedimentary fault deformation of the hanging wall sediments also increases towards this fault. Both distributed and localized shearing characterizes these early faults and is thought to be related to the water content of beds at the time of deformation. Local minor thrusting and reverse fault movement also occurred within the sediments during basin extension, due to dextral transtensional movement on the North Solway Fault. N–S– and NW–SE–trending faults appear to show no evidence for syn-sedimentary Dinantian movement and are interpreted as the products of 'Hercynian' basin shortening and Mesozoic basin formation.