Exposed Units: Aymestry Limestone
Conservation Status: Site of Special Scientific Interest (and others)
The quarries found on the Croft Castle Estate sit within Fishpool Valley. Both of the quarries display fine examples of the Aymestry Limestone Formation. The quarries are large, with the northern quarry being long and narrow at 40m long and 8m deep, with 3-4m high rock faces. The southern quarry is 30m wide, 40m deep and has rock face that reaches 5-6m.
Both quarries display bedded nodular clay-rich limestones and calcareous (calcium carbonate rich) siltstones that are typical of Aymestry Limestone Formation exposures. The nodules are more pronounced in the northern quarry, where weathering has eroded away much of the lime cement, which allows for the shapes of the nodules to be seen more clearly. Both quarries also contain thin layers (4-6cm thick) of calcareous siltstones. These thin siltstones are separated by approximately 2m of the nodular limestones. Due to their soft compositions they have weathered preferentially in comparison to the harder limestones and therefore can be easily identified.
The beds in the northern quarry are dipping (tilting) approximately 6˚ to the south-east. This dip is attributed to the fact that the rocks in this area are sitting on the southern limb of large anticlinal fold. This structure is known as the Ludlow Anticline, formed during a period of mountain building in the mid-Devonian Period (391Ma).
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Fold – A curved or angular shape of an originally planer geological structure.
Anticlinal fold – A fold closing in any direction in which the older rocks occupy the core.
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