Local Geology
Solid geology
The solid geology of the English Midlands comprises up-faulted horst blocks of Palaeozoic strata of Cambrian to Upper Carboniferous age, separated by down-faulted basins containing Permian, Triassic and Lower Jurassic strata.
The Upper Carboniferous contains a condensed sequence of Westphalian A & B strata which rests unconformably on Lower Palaeozoic strata. The condensed sequence contains coal seams up to 9m thick, with the result that mining activity was intense from the 18th century onwards, leaving a legacy of unstable and potentially unstable ground. Mining activity in the region has now largely ceased.
Most of the major conurbations in the region developed just outside the coalfield areas, where barren Westphalian C & D and Triassic strata provided better foundation conditions. The centre of the city of Birmingham is underlain by Triassic sandstone upon which large structures can be founded with comparative ease at shallow depth.