Geoscience Reference
In-Depth Information
FIG
117.
Oblique block view of the crustal geology, starting 10 km west of the eastern
edge of Area 5 and looking westwards.
The cross-section in Area 4 (Fig. 109), a few kilometres west of the boundary
with Area 5, is relevant to this area, since the same bedrock pattern continues eastwards
through this Landscape. The Triassic, Jurassic and Early Cretaceous layers in this sec-
tion have been cut by a number of normal faults, indicating stretching movement of the
crust in a north-south direction, linked to subsidence and increasing amounts of sed-
iment accumulation to the south. This contrasts with the folding and faulting that is
visible in the Purbeck Stepfold or Monocline, with reverse faulting that indicates con-
vergence of the crust and increased sedimentation to the north in mid-Tertiary times.
The same patterns, involving two distinct phases of movement, are also visible where
the stepfold crosses the Isle of Wight.
