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Gower

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Vol. 12, 1959

The Geological history of Gower

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the British area formed part of a vast and mountainous northern
continent. To the south, a marine trough extended across Central
Europe, the northern limit of this sea being from the north of
Devon to the extreme south-east of England. Gower lay on the
southern fringe of the northern land, and powerful rivers poured
great thicknesses of sand and mud over Gower and the rest of
South Wales. These sediments were predominately red in colour,
and subsequently hardened to form the now familiar "Old Red
Sandstone", seen today on Cefn Bryn and Rhosili Down.
The foundations of Gower were beginning to be laid. On
top of the Old Red Sandstone was deposited, in early Carbon-
iferous times, some 3,000 feet of light-grey calcareous muds which
consolidated to form the Carboniferous Limestone. These deposits
were formed in a very shallow and warm sea which had spread
northwards into South Wales. This sea abounded in life-corals,
crinoids and brachiopods. The fossil remains are visible today
in almost all the limestone layers of Gower.
At the commencement of Upper Carboniferous times, im-
portant changes took place. Appreciable uplift of land to the
north resulted in rivers again pouring mud and silt over South
Wales, and great deltas were pushed out into the Carboniferous
sea. The resulting Millstone Grit is "coarse" and siliceous in areas
such as Brynamman and Glynneath, but in Gower it is mainly
shaley. As Upper Carboniferous times progressed, the vast deltas
and mud flats were periodically clothed with dense vegetation,
which accumulated on decay to form the seams of coal in these
Coal Measures. Further south, over Devon and Cornwall, violent
earth-movements were building up high mountain ranges. Rapid
erosion of these mountains resulted in great thickness of sand
and silt being carried northwards into South Wales, forming the
now familiar Pennant Sandstone (the present foundation of Town-
hill).
These earth-movements were the preliminary phases of the
Armorican Earth Storm which affected many British areas at the
close of Carboniferous times. The Devonian and Carboniferous
strata were thrown into numerous folds and the beds were also
severely upset by fractures or "faults." The displacement of beds
often amounted to many hundreds of feet. In the Gower area,
the main folds were an intense Cefn Bryn upfold and a downfold
in the Gowerton area. Other downfolds included the Oxwich
ind Port Eynon synclines, separated by an Oxwich Anticline.
Gower became part of a high mountainous mass, and a long period
)f active erosion, under mainly desert-like conditions, commenced.
[t lasted throughout Permian and much of Triassic times, and, by
ate Triassic times, the Gower surface was deeply eroded to almost
ts present form. A tremendous thickness of strata had been re-
noved from some areas. From the top of Cefn Bryn, for example,
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