Makenny

Also within

Tyrone County

Habitats

Fast flowing river and stream

Geology & landscape

Geological Feature: Rock Outcrop · Geological Period: Carboniferous, Devonian · Rock Type: Mudstone, Sandstone

Landscape processes: Fluvial

Description

Makenny Carboniferous stratigraphy The area is of special scientific interest because of its important geology, which is found at outcrop in a stream section in Makenny townland. The rocks expos.ed are of Carboniferous age, some 320 million years old. The outcrop consists of interbedded sandstone and mudstone of the Ballinamallard Mudstone Formation from the Kilskeery Group. Mudstones at Makenny contain fossil miospore and other plant remams. The dominant lithology in the section is grey-red mudstones and mud-flake breccias with occasional thin beds of fine-grained sandstone. Exposure in the stream is good and the whole section is believed to contain approximately 40m of strata, inclined So_ 6° to the north-west. The section is cut by a vein ofbarytes 0.5m thick that appears to follow a fault line. The uppermost 15m of strata, at the northwest end of the section, is dominated by red-brown mudstones at the base but grey and green-grey calcareous mudstones become equally common towards the top. These grey mudstones contain filmy impressions of irregular thin plant fragments and more importantly, well-preserved miospores. The miospore assemblage includes: Densosporites anulatus, Knoxisporites stephanephorus, Lycospora pusilla, Punctatisporites sp., Convolutispora cf.jlorida, Cyclogranisporites sp., Reticulatisporites carnosus, Savitrisporites nux and Vallatisporites sp. Rocks of the Kilskeery Group were originally deposited as sediment in a subsiding, non marine sedimentary basin. There is evidence that two basins developed at the same time, separated by a topographic high composed of metamorphic and Lower Palaeozoic sedimentary rocks. The Ballinamallard Formation, exposed in the stream section at Makenny, was deposited in the southern of these two basins. Increased uplift during the early Brigantian Stage of the Carboniferous led to increased erosion of the central high, producing alluvial fans that prograded south depositing the fine grained sandstones and mudstones of the Ballinamallard Formation. The Kilskeery Group was originally thought to be of Devonian age, part of the Lower Old Red Sandstone Fintona Group. Sites such as Makenny have yielded plant material which allowed the age of the rocks to be accurately determined as younger than first thought and belonging to the Carboniferous period. https://www.daera-ni.gov.uk/publications/makenny-assi

Plant communities