378 
EARTH-MOVEMENTS DURING CARBONIFEROUS TIMES. 
Pennine Range is a stable ridge that came into existence at a 
comparatively late period in Coal Measure time. That it acted 
as a barrier between two differentially-subsiding areas. The 
steepness on the Lancashire side is explained by the fact that 
this area was subsiding faster than the Yorkshire one, and 
obviates the necessity for calling in the assistance of a thrust 
from the east to explain the structure. The Pennines may 
be regarded as a range of the Uinta tj^pe,* formed by the 
coming into action of the deep-buried pre- Carboniferous ridge. 
VIII.— Conclusions. 
Briefly stated, the conclusions arrived at from the con- 
sideration of the limited data available of the tectonic features 
of the coalfield and its margins are as follows : — 
{a) The Charnian axis is an ancient ridge of relative stability 
dating back to at least post-Silurian time. 
(6) The Market Weighton axis was in existence as a relatively 
stable anticline during Middle Coal Measure time and 
soon after the formation of the Barnsley seam. 
(c) The Pennine Bange is of the Uinta type, and the date 
of its appearance might be fixed not later than the close 
of the Middle Coal Measure period. The difficult}^ in 
correlating the Middle Coal Measme seams on both sides 
rather suggests that it w^as exercising some influence 
a little earlier. 
(d) The present limits of the Yorkshire. Derbyshire, and 
Nottinghamshire coalfield were determined, not by post- 
Carboniferous earth-movements, but as a result of the 
operation of a sequence of complicated movements com- 
mencing with the post-Silurian tangential stresses that 
crushed the pre -Carboniferous floor, and changing, 
after equilibrium had been established, into differential 
subsidence continued into post-Carboniferous times, when 
the margins referred to were denuded, and even later. 
* Geology of Uinta Mountains, p. 201. 
