C.—GEOLOGY 73 
from Wrexham, and along the Dee estuary, they diverge somewhat to the 
westward, but east of Hawarden they bend as if to complete beneath the 
Trias the encircling fractures of the Cheshire Plain. ‘The continuation 
of the Bala or Llanelidan Fault tears across the whole Carboniferous 
outcrop, as does the east-west fault through the Vale of Llangollen. 
North-south faults trail into or branch from these old deep-seated fractures, 
by whose repeated movements the wedge of ground between them may 
have been subjected to horizontal torsional stress. The ring of fractures 
round the slab of Ruabon Mountain is not matched in any British coalfield. 
Further to the south, longitudinal faults bend south-westwards, and the 
Denbighshire Coalfield ends at east-west cross-fractures which also cut 
the Trias. 
Within the Cheshire Basin faulting is recorded only in broken outcrops 
of Triassic sandstones. The known pattern follows that in neighbouring 
outcrops of Carboniferous rocks. At the Staffordshire border the Red 
Rock Fault is at once marginal to the basin and longitudinal in the flank 
of the Rearers anticline. Across it both folding and fault movements 
have been renewed since the deposition of the Trias. 
Between the Red Rock Fault of Cheshire and the plateau of the Peak, 
fractures which gather from East Lancashire die in the lower flanks of 
the steep upfold. Along the crest of that main Pennine fold in Yorkshire 
and Cheshire, longitudinal displacements replace the narrow folds con- 
verging to it from the south, and form the Pennine anticlinal fault. Out 
of this across the Millstone Grit moors, minor branch fractures, cross- 
connected, curve away to the eastward in a wide half-circle, to join the 
longitudinal series of the Yorkshire and Derbyshire Coalfield. 
_ The triangle of country which lies between the Peak of Derbyshire, 
the Longmynd and Charnwood, has longitudinal faults which branch as 
they diverge southwards in the middle limbs of folds. As boundary 
faults in the edges of the exposed coalfields of the Midlands, some of 
these are associated with great change of stratigraphical level. They 
range with slight obliquity to the strike of pre-Carboniferous structures, 
and are in the flanks of late Carboniferous upfolds, which have completed 
perhaps the last third of their movements during or since the deposition 
of the Trias. Faults developing in the limb of the western anticline of 
Staffordshire turn and cross the Potteries syncline obliquely, their 
considerable throw reducing the effect of southward pitch. Numerous 
adjustment faults, often in pairs, traverse the crests of anticlines in the 
North and the South Staffordshire coalfields, and also the coalfield 
synclines of South Derbyshire and Leicestershire. Only east-west faults 
of the arcuate group in the northern margin of the Staffordshire-Trent 
Valley Basin are recognised as breaking across both anticlines and 
synclines, or as having direction unrelated to Carboniferous and older 
structures. 
In his studies of structure in the country between the Longmynd and 
_the Berwyns, Wedd has discussed the development of faults by resolution 
of horizontal stress to lateral shear or spiral torsion, where compact rocks 
have met obliquely an advancing Hercynian crustal wave. Possibly 
Structural disposition along other ribs of reinforcement in the pre- 
D2 
