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Photo shows an example of the thickly bedded sandstones from the north shore of Lough Allen, intact on top of the much softer Shales, and as loose seperated hunks to the left. This area is often flooded and the action of water and other erosive agents (sun and frost) quickly cause the softer Shale to crumble and release its fossils.
The strata are very thin very flat, and only exposed for about 200 metres at the north end of the lake on the shoreline of the bay between Corry Point and Corry Strand. Lough Allen is surrounded by rocks of the Upper Carboniferous. Not limestones as in many part of Ireland but mainly Shales with occasional Sandstones included. The names of the main Strata (and their Map codes) are listed below, with the oldest deposits at the bottom and the newest at the top:
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 The Geology of an area, the rocks and surface deposits, the effect of erosion and glaciation, very much condition an environment. It both gives it its shape, governs its water flow, and provides the soils and nutrients that cater for the differing needs of various plants and animals. As Lough Allen is conspicuous in having a good collection of extremely rare plants and animals we were wondering could its history of landscape derivation have contributed to the variety of rare plants and animals we now see in the area.
One obvious example might be the Pollan (a rare salmon type fish present in Lough Allen). This is not present outside Ireland as a landlocked fish population but is present in northern Russia as an anadromous population (running to the sea) like our own Salmon. So was this species isolated in Lough Allen (and Lough Neagh) through glacial action blocking its access to the sea?
Anyway, based on these thoughts we decided to get out our geological map and have a hunt around Lough Allen. Immediately you are struck by one salient fact... there are very few outcrops of bedrock around Lough Allen. Many will regard the lake as having a stony shore and many small hills and islands, but the stones are loose boulders and the hills are mainly glacial deposits (drumlins) full of large boulders, gravel and till carried, down the valley from surrounding hills and deposited wherever the galcier’s flow was obstructed. But we knew of some bedded rocks in a very restricted area at the north end of the lake and this report is based on a study of them.
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