Environmental Engineering Reference
In-Depth Information
FIG
15.
Geological map of Gower. (Gower Society)
Royal Commission on the Ancient and Historical Monuments of Wales for Figures
THE RECORD OF THE ROCKS
The oldest rocks exposed in Gower are characteristically red in colour and are known as Old Red Sand-
stone. They were laid down in the Devonian period, from 390 to 360 million years ago (although there
appears to have been a lengthy gap in deposition) and occur only in the cores of major anticlines. The
nature of any underlying 'basement' rocks is not clear. At this time the area lay in a region of sediment-
laden rivers that crossed a wide plain between mountains to the north and the sea to the south, which lay
over what is now Devon, the county giving its name to this period of the earth's history. The climate at
this time was tropical, with monsoon weather, and vast rivers carried sediment resulting from the intense
erosion that was taking place in the mountains. These rivers deposited large amounts of material as they
flowed to the sea and this eventually formed the sandstone rocks. A period of uplift and erosion in mid-
Devonian times temporarily stopped this sedimentation. Although the Devonian is sometimes referred to
as 'the Age of Fishes', other animals were present too, including insects, sharks, lungfishes and amphibi-
ans,thelatter beingthefirstvertebrates towalkontheland.Theylookedlikelargenewtsorsalamanders.
