Cruggleton Bay

Site of Special Scientific Interest · 54.7753, -4.3692

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Also within

Wigtown County

Condition (NatureScot)

Favourable (1)
UnitFeatureConditionArea (ha)Assessed
F1 Caledonian Structures of the Southern Uplands Favourable — 2005-03-31

Climate exposure

This is about exposure to a nationwide pressure this habitat type carries — not a verdict on this site's own management.

Coastal

Coastal habitats are exposed to sea-level rise and storm erosion. Where hard sea defences sit behind them, there's nowhere landward to retreat to — a squeeze that keeps compressing the habitat no matter how well it's managed.

Geology & landscape

Geological Period: Silurian · Rock Type: Sandstone, Shale

Landscape processes: Coastal

Description

CRUGGLETON BAY Cruggleton Bay is a coastal geological site lying 9km southeast of Wigtown. It is divided into two sections. Outcrops of rock on the foreshore of the north side of Cruggleton Bay provide an outstanding illustration of some of the structural characteristics of the ‘Hawick Rocks’ in the Southern Uplands. The rocks consist of alternating layers of sandstone and shale, probably of mid-Silurian age (430 million years old). The layering is contorted by a series of folds formed by intense compression of the Earth’s crust during the time the Caledonian mountain-building process (orogeny) was occurring. The three-dimensional forms of a number of large folds can clearly be seen at this site. Associated with the folds is a set of cleavage planes (closely spaced parallel fractures), which show the tendency of certain minerals to break along weak lines. These can be clearly seen as they converge and diverge through the rock layers in the fold hinges, providing a classic illustration of these geological features. The cleavage surfaces run at an oblique angle to that of the folds. This is typical of this type of structure in the Southern Uplands and this site provides the clearest-known illustration of this phenomenon. The study of these structures is of great importance in understanding the nature of the Caledonian orogeny in the Southern Uplands.