The Southwest Region - Southern England - page 78

The youngest bedrock in Area 2 is the clay, sand and lignite near Bovey ( d8 ),
between Dartmoor and the New Red Sandstone area. Bovey and Petrockstowe in Area
3 lie on the Sticklepath Fault that runs northwest to southeast across the whole of
Devon (Fig. 78). The fault was active about 40 million years ago, at the same time as
the Alps were forming as a major mountain belt much further south. It seems likely
that this fault formed along the direction of earlier fractures in the bedrock left by the
Variscan mountain building and described more fully in Area 1. The Bovey and Pet-
rockstowe basins must have grown as areas of surface subsidence linked to movements
of the Sticklepath Fault, and sediment must have been carried into the newly subsiding
low ground by streams. The basin sediment is now mined for ball clay, which has been
an important source of clay for pottery and many other purposes. There are also layers
of lignite and sand which have been used as a fuel and in the making of glass.
FIG 78. Slope map of the eastern part of Area 2, showing the distribution of slopes great-
er than 5 degrees (coloured red). The Dartmoor granite bedrock area is indicated (or-
ange), as are the Bovey Basin (green) and the Sticklepath Fault (dashed line).
AREA 3: NORTH DEVON AND WEST SOMERSET
This Area (Figs 79 and 80) divides neatly between the high ground of Exmoor in the
north, where the bedrock consists of sediments of Devonian age, and an area of Car-
boniferous bedrock to the south (Fig. 37). The bedding slopes generally southwards,