The Upper Palaeozoic to Mesozoic structural evolution of the North Staffordshire coalfield and adjoining areas.
The main aims of the project were to undertake a detailed
structural study of the North Staffordshire coalfield and to
assess the influence of the major structures on the subsidence
history using an extensive data set of British Coal mine plans
and bo~eholes, British Coal opencast sites and seismic
reflection profiles supplied by Fina Exploration Ltd, Hamilton
Bros Oil and Gas, Edinburgh Oil and Gas? and Shell U.K.
The extraction of over 45 coal seams over a vertical
thickness of lkm. has resulted in the detailed description of
the 3-D geometry of the folds and both small-scale faults
(down to 0.5m. throw) and large scale faults (up to bOOm
throw). This work has been supplemented by visits to opencast
coal mines? where minor structures observed include abundant
small thrusts and folds. A cored interval through a fault of
300m. throw has also been examined. This structural analysis
has been extended on a regional scale using the extensiVE
The subsidence history of the basin has been studied using
inter-seam isopach maps compiled from borehole records and
mine plans. The results of this work indicate that the
Westphalian sequence thins dramatically (up to 50%) over the
folds. The reduction in thickness is accompanied by the
amalgamation of a number of coal seams. The restoration of
detailed serial cross-sections of the anticlines compiled from
mine plans indicates that the thinning occurs in discrete
intervals that record periods of fold growth.
Late Westphalian D inversion resulted in the formation of
major (km. scale) folds with N-S and NE-SW trending axes. The
orientation of the folds was strongly influenced by the trends
of pre-existing basement lineaments. The lineaments are
oriented at high angles to the NNW directed thrusts of the
Variscan front of southern Britain.
The folds are post-dated by large NNW trending normal faults
with throws up to bOOm. The faults are predominantly planar,
hig~-angle structures and lack evidence of syn-depositional
activity. They are related to Permian/Triassic extension of
the Cheshire Basin to the NW and the Stafford basin to the S
of the coalfield.