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Northern Ireland Geology - Shale and Greywaches

Shale is a fine grained sedimentary rock which splits easily. It can contain fossils such as graptolites which are characteristic of the Silurian and Ordovician Periods. Some excellent shale outcrops with numerous graptolites can be found along the coast around Donaghadee.

Greywache is a hard rock which is quarried for road stone throughout County Down. They consist of sand grains enclosed in a fine grained matrix. They are formed in deep water where underwater 'avalanches' of sediments (called turbidity currents) led to large quantities of sandy sediments accumulating at the base of steep slopes.

Shale data Shale sample Greywache data Greywache sample

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