Lisnaragh

Also within

Tyrone County Sperrin Scenic Area

Habitats

Fast flowing river and stream

Geology & landscape

Geological Feature: Moraine · Geological Period: Quaternary

Landscape processes: Glacial

Description

Lisnaragh Pleistocene The Lisnaragh area is of importance in understanding the recent glacial history of Northern Ireland. The landscape of this area has been defined by events that occurred towards the end of the last Ice Age, between 17,000 and 13,000 years ago, a period of gradual climatic warming. The area contains part of an excellent example of a moraine ridge that crosses the Bum Dennet valley, which is fronted by a section of a valley side outwash terrace. It is of importance as an example of a deglacial landform association. The Lisnaragh area demonstrates that ice in this region retreated south towards the Sperrin Mountains. Constraints imposed by bedrock topography strongly influenced the shape of the ice margins with morainic belts and meltwater, and therefore glaciofluvial deposits, focused along the axes of the main river valleys. The scale of the valley fill requires either a reduction in the rate of ice retreat at this time or a significant increase in sediment availability. The Lisnaragh moraine therefore records the position of the ice margin at a stage during its retreat. The outwash terrace immediately fronts the moraine at around 125m above sea level and slopes gently northwards. The dissection of the morainic ridge at Lisnaragh indicates that the region was subject to meltwater floods both during and following moraine deposition in the later stages of deglaciation, as the ice withdrew further south. This was possible as ice in the Foyle Valley must have also retreated to a point where meltwater could escape from the Bum Dennet valley. https://www.daera-ni.gov.uk/publications/lisnaragh-assi

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