The Peninsula Emerges - Gower - page 36

thousandsofyearsduringwhichtheclimatewasmuchmilder,inmanycasesevenwarmerthanitistoday.
Most of the ice in the penultimate glaciation appears to have been derived from source areas in the moun-
tainsofcentralandsouthernWales.However,theiceinwesternGower,alongwiththatinPembrokeshire
and the Vale of Glamorgan, formed part of a very extensive ice sheet that encroached inland from the
southern Irish Sea. This is clearly indicated by the glacial debris, which north of Cefn Bryn contains a
greater amount of material originating from the South Wales coalfield while south of the ridge the rock
types suggests an Irish Sea origin.
As the ice melted during what is known as the Ipswichian interglacial period, between 130,00 and
120,000 years ago, sea levels rose about 6 to 9 metres above present levels. Subsequent falls in sea level
left behind beach deposits cemented with calcium carbonate, which are known as 'raised' beaches but
should not be confused with the true raised beaches found in Scotland. Although the beaches and their
platforms have been eroded since their formation their origin is shown by the rounded shingle and the
shells they contain. At Foxhole, near Southgate, for example, at the foot of the low cliff, there is an el-
evated platform on the Carboniferous Limestone. On this wave-cut platform is preserved one of the best
examples of the 'Patella beach', which is composed of sand, rounded limestone fragments and fossils of
the common limpet Patella vulgata , held together by calcareous cement (Fig. 18). In Gower this deposit
of shelly shingle (in which periwinkles and dog-whelks Nucella lapillus are also very common) is wide-
spread and is normally cemented into a hard conglomerate, which rests on a narrow, wave-cut platform.
ManyoftheGowercaves openontotheplatform oftheraised beach, anditisprobable that theywere
enlarged by wave action at the same time as the platform was created. Associated with the beach depos-
its are the well-known cave deposits, which have yielded bones of animals such as straight-tusked ele-
phant Palaeoloxodon antiquus ,hippopotamus Hippopotamusamphibius andsoft-nosedrhinoceros Dicer-
orhinus hemitoechus, showing that the climate was much warmer than that of today. The importance of
these deposits lies in their relationship to the raised beaches and the information this provides on the cli-
matic changes in the late Devensian. Minchin Hole at Pennard contains a particularly important sequence
of deposits and is regarded as the 'type site' for the Patella beach, which has been commonly used as a
'marker horizon' throughout southwest Britain. The cave is also unique in South Wales in containing two
raised beaches of different ages superimposed in a single section. Investigations in the 1980s suggested
that these beaches represent two separate interglacial periods, and because of this Minchin Hole is a na-
tionally important site for studies of the Pleistocene (Fig. 19).