Cwm Crymlyn is of considerable importance
since it provides the only permanent outcrop of Tremadoc rocks
anywhere in South Wales. These strata were deposited as a blanket
of mud on the sea floor some 500 million years ago. The site has
yielded a rich assemblage of fossils, some of which occur nowhere
else in Britain. The fossils described from this locality, include
a group of marine arthropods known as trilobites (which are now
extinct), graptolites (colonial organisms which were particularly
abundant in early geological times) and a variety of shelly
fossils. Some species of trilobite show a close similarity to forms
described from Argentina, the site is of importance in an
international as well as a national context.
Managing this site
The site is under private ownership. The special features of
this SSSI and CCW’s views about site management have been
summarised in a Site Management Statement, addressed to the owners
and managers of the land. The statement can be found in the
resource section below.
There is no public access to this site.
Cwm is ‘hollow, narrow valley, valley’. Crymlyn means ‘curved
pool’ from crwm ‘curved’ and llyn ‘lake, pool’.