66 SECTIONAL ADDRESSES 
than 3,500 ft., and along the Severn Valley the Clent Breccias are also 
thick. Northwards and westwards, as the breccia beds tail out, the group 
becomes difficult to separate from calcareous Keele beds with which they 
are included in the 2,000-3,000 ft. thick Erbistock series of Denbighshire. 
The accommodation of such thickness of Upper Coal Measures over 
the Western Midlands necessitated the shifting the Pennine geosynclinal 
centre towards the south. ‘To what extent the uprising of the Derbyshire 
High Peak area was contemporaneous, is not known, but pebbles in 
Midland conglomerates have not been traced to any Pennine source. In 
the Ingleton Coalfield the highest Red Beds with bands of Spirorbis lime- 
stone are associated with brockram scree deposits, and by this stage uplift 
to the north and denudation of the escarpment of the Craven Faults had 
there exposed the Lower Carboniferous, 
In the Concealed Coalfield of Yorkshire and Nottinghamshire basal 
Permian transgresses 5,000 ft. of folded Coal Measures. The simple 
geometry of the floor on which the Permian rests shows that, following 
the storm of crustal movements, the cycle of denudation was completed. 
The regular eastward slope of that buried peneplain from Tynemouth to 
Nottingham is proof that that side of the Pennines was already con- 
solidated as a structural unit, which, rippled by gentle swelling of the 
underlying cross-folds, and cracked a little by rejuvenated coalfield faults, 
has since been tilted as a whole. Such later displacements as, east of 
Leeds and about Nottingham, have also cut the Trias, are of amplitude 
insufficient to distort the structural pattern, which, born before the end 
of the Visean, developed during the Lancastrian and Productive Coal 
Measure period, attained maturity when the Red Beds of the Midlands 
were being deposited, and was dissected and planated before tilting and 
regional settlement depressed it to receive the sediments of the Magnesian 
Limestone sea. 
West of the Pennines, the Collyhurst Sandstone rests with sharp dis- 
cordance upon the tilted Ardwick group, and westwards transgresses 
3,800 ft. of underlying Productive Coal Measures. Its thickness alters 
abruptly, sometimes by hundreds of feet, at the crossings of important 
faults, and its disposition suggests accumulation in the fault scarp hollows 
at the foot of the upraised and faulted Pennine and Rossendale anticlinal 
ridges. The Manchester Marls above it are displaced, but not otherwise 
affected by faulting which also cuts the Trias. They contain a fauna 
correlated with the Lower Magnesian Limestone, and pass up by transition 
into the Bunter Sandstone of the Cheshire Basin. 
South of the Pennines the evidence of post-Carboniferous chronology 
is mainly buried under Trias, which banks against a land surface composed 
of every kind of older rock. Each exposed Midland coalfield is a dish or 
dimple in an upraised horst, bounded by faulted folds of variable pitch, 
which are axially convergent on the Coal Measure geosynclinal centre west 
of the Peak near Manchester. In middle limbs outside the lateral crests 
are powerful but discontinuous boundary faults, flanking the Trias-filled 
deep depressions which contain concealed coalfields. ‘These boundary 
faults are late Carboniferous structures which displace alike all members 
of the Productive and Upper Coal Measures, to and including the Keele 
