Geoscience Reference
In-Depth Information
provides an indication of land movements since that time, relative to present-day sea
level. The net uplift of ≈250 m inland and ≈100 m around present-day Lyme Regis may
have included several downward movements, but it is unlikely that any significant ho-
rizontal movement has taken place.
The coastline of this Landscape is famous for its spectacular cliffs and abundant
fossils. From Sidmouth to Beer Head (
c1
), red Triassic sandstones are capped by Creta-
ceous Upper Greensand that slopes gently eastwards, occupying more and more of the
coastal cliff face. About 1.5 km west of Beer Head the base of the Cretaceous bedrock
passes below sea level and the New Red Sandstone disappears from view, until it is
brought back to the surface by a north-trending fault at Seaton Bay. The Late Creta-
ceous Chalk is also present in the upper parts of the cliffs in this area, forming spectac-
ular near-horizontal layers picked out by flints. The flints have been used as building
materials in Beer along with a distinctive form of Chalk known as 'Beer Stone', which
was quarried in a remarkable system of caves and tunnels.
From Seaton (
c2
) to Charmouth (
c3
), the coastal hill plateau consists largely of
Cretaceous bedrock, showing up as a yellow cap in the distance on the right of Figure
104 and resting upon gently sloping layers of New Red Sandstone and Jurassic materi-
als. Because much of this older material is made of mudstone, which tends to slip when
wet, there are numerous examples of land-slipping in this area. The Bindon landslide
of 1839 attracted widespread contemporary interest, and movements at Goat Island and
Black Ven in 1995 have greatly changed the look of the coastline.
Whereas the New Red Sandstone formed in river and lake environments and gen-
erally lacks fossils, the Lias of the Early Jurassic is marine and contains abundant
fossils that can be seen in the museums and fossil shops of Lyme Regis and Charmouth.
Ammonites are among the commonest of these fossils, but marine reptiles such as ple-
siosaurs and ichthyosaurs are probably the most famous.
FIG
104.
Black Ven landslip with Charmouth (Fig. 99,
c3
) in the foreground, and Lyme
Regis (
c6
) beyond. (Copyright Landform Slides - Ken Gardner)
