Drumharvey ASSI

Drumharvey is of special scientific interest by reason of the geological features and is the type locality for the Shanmullagh Formation, the dominant Devonian rock series north of the Tempo-Sixmilecross fault. This Formation has been dated from other sites and is of Upper Devonian age, some 370 million years old.

The rocks here are purple-brown, fine to medium-grained sandstones. The available evidence indicates that these rocks were formed on a low-lying inland plain experiencing desert conditions but subject to periods of temporary flooding. Sand and silt material was deposited occasionally during these floods. The frequent presence of ripple marks in sandstones, with desiccation cracks in succeeding thin mudstones, indicates the intermittent nature of extensive flooding with high evaporation leading to a complete drying out of temporary lakes and other water.