Cheshire Basin
The Cheshire Basin is a late Palaeozoic and Mesozoic sedimentary basin extending under most of the county of Cheshire in northwest England. It extends northwards into the Manchester area and south into Shropshire. The basin possesses something of the character of a half-graben as its deepest extent is along its eastern and southeastern margins, where it is well defined by a series of sub-parallel faults, most important of which is the Red Rock Fault. These faults divide the basin from the older Carboniferous rocks of the Peak District and the North Staffordshire Coalfield. In terms of its architecture, the basin is sometimes considered to be divided into two sub-basins: the more southerly Wem–Audlem Sub-basin and the Sandbach–Knutsford Sub-basin to its northeast. The basin fill is mainly Permian and Triassic sandstones and mudstones, but it also incorporates economically important halite beds. The sequences referred to the Sherwood Sandstone Group and the overlying Mercia Mudstone Group are the thickest in England. An isolated outlier of Jurassic rocks occurs within the basin at Prees in north Shropshire. The basin is just one part of a wider complex of basins that includes the Worcester Basin, the Stafford Basin and the East Irish Sea Basin.