The reserve is comprised almost entirely of wind-blown sand. Boreholes have shown that the calcium-rich sand is up to 12 metres deep.

The underlying rock is exposed at Sker Rocks and Gwely'r Misgl in the form of Keuper Breccia from the Triassic period when desert covered this area around 200 million years ago.

The dune system to which Kenfig belongs has developed since the end of the last Ice Age, approximately 10,000 years ago. As the ice melted, the melt-water eroded the sandstone to the east and deposited large amounts of sediment in Swansea Bay. This was eventually blown ashore by the south westerly winds to form the sand dunes.

During the glaciation of the South Wales area there was considerable erosion of the hills. This resulted in the deposition of sands and gravels in the region now occupied by the Bristol Channel.

As the glacial ice melted, the land was relieved of the weight of the ice. This caused the land to rise and a forest grew on the newly formed coastal plain. The decaying forest formed a layer of peat above the glacial sands.

Erosion and sea level fluctuations resulted in the sea reaching what is now the base of Margam Mountain. In this shallow sea the clay deposit found under the dune sands was deposited.

Slow rising of the land possibly occured and this exposed a large area of the glacial sand of the Bristol Channel. Winds blew the sand inland forming the dune system. The 13th and 14th centuries were the times of main sand advance.

Bibliography:

(1) Bridgend Library & Information Services, Coed Parc, Bridgend

Webpage Author:

Mr Rob Bowen, Kenfig.org Local Community Group, 2009