TALA 2: [This is one of several pages published under this heading by LoughAllenBasin.com We endeavour to highlight what this area of NorthWest Ireland has to offer as a place to live, a place where interesting Plants and Animals may be found, and as a quiet peaceful location for Hi Tech Enterprise.]

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2. L. Allenís Carboniferous Coast
(22 March 2010)
ancient... fascinating...  intriguing and peaceful...

 

Location:  Near Corry Point, north shore of Lough Allen

 

 

Doobally Sandstone & Bellavally Shales at Corry shoreline.

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:

 

300 m. yr old Fossil on top of ShaleThe 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 galcierís 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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Bencroy Shale Formation with Ironstone beds and including the Bencroy Sandstone Member

BH BHss

Fossils are used to identify and age Strata over wide areas...

 

 

Lackagh Sandstone Formation high on the surrounding mounatins. This is the stratum in which Coal is found.

LH

 

 

Gowlaun Shale Formation. Also on the hillsides at mid altitude.

GO

 

 

Dergvone Shale Formation. These shales reach down to the shore on the south west shore of the Lake.

DE

 

 

Carraun Shale Formation. This formation occurs along the east shore of the Lake and in the north west corner also.

CN

 

 

Bellavally Shale Formation (including the Doobally Sandstone). These border the Carraun Shales on the north shore of the Lake and make up the outcrop described in this article.

BE BEdo

 

 

 

 

 

 

300 million years ago?

 

Isnít it truely weird to think that these fossils represent animals that lived and died in the Seas where these Shales were laid down about 300 million years ago. We can all pick up and examine something small and delicate that has been around for such a vast length of time. Awesome!

 

 

 

 

 

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[MORE TRIPS to come! Including some from earlier dates than this one!]

If you have any interesting records of animals or plants from the Lough Allen basin, we will be very pleased to reproduce them here.