 It is defined to the south by the Stublick and Ninety Fathom faults, which separate the trough from the Alston Block.To the north, where its depth is least, the trough's boundary with the Cheviot Block is less well-defined; nevertheless, the south-easterly down-throwing Featherwood and Alwinton faults can be identified along this margin.To the west, the trough is continuous with the Solway Basin.