The excellent sea-cliff exposures of Sully
Island provide an insight into the environment of the area in
Triassic times, approximately 200 million years ago. Red mudstones,
sandstones and breccias (rocks made from angular pebbles) indicate
that this area was a beach situated on the margin between steep
semi-desert land and a large shallow lake or marine lagoon. These
Triassic rocks were deposited on top of much older Carboniferous
limestone which can be seen at the base of the cliffs. Sully Island
additionally provides a roost site for waders feeding in winter in
the local area.
© This orthophotography has been produced by COWI A/S from
digital photography captured by them in 2006. Licensed by the Welsh
Assembly Government's Department for Environment, Planning and
Managing this site
The site is in 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
There is no public access to this site.
Sully Island is situated opposite the eastern extremity of the
parish, offshore, and joined to the mainland at low tide by a
causeway. Sully : Sili means ‘place associated with (de) Sully’.
Sully is a personal name. The origin of the name is obscure. The de
Sully family held the manor from the last decade of the 12 cent.
but it is difficult to establish whether they derived their name
from the place, or whether the place was named after them. It has
been suggested that the name was transferred directly from Sully or
Silly in Normandy.