490 G. H. Kinahan — Water Basin of Lough Berg. 



Map, because, as i^reviously stated, it could not be positively proved ; 

 but that it does exist seems probable, on account of the position of 

 the Old Ked Sandstone in the hill N.E. of the Corrao-oe Valley. 

 North of this supposed fault the deeps run nearly N. and S., till 

 they unite with the deeps of the previously-mentioned east and 

 west reach that forms part of the lake between Scarriflf and Youo;hal 

 Bays. This long reach lies in the eastern continuation of the Car- 

 boniferous Limestone valley that separates Slieve Bernagh from 

 Slieve Aughta, and the limestone seems to be brought into its 

 present position not only by a sjaiclinal curve, but also by faults. 

 On the north of the valley, a large fault with a downthrow to the 

 southward (the Scarriff valley north fault), is quite apparent; while 

 on the south of the valley one or two lines of breaks or faults 

 appear to exist. Within the valley itself they could not be posi- 

 tively proved, on account of the great accumulation of drift and bog 

 at the base of the north slopes of Slieve Bernagh, but farther east 

 in the low country, one of these, with a downthrow to the north, is 

 conspicuous, and in its strike are found the principal deeps in the 

 long east and west reach of Lough Derg. At this reach the lake 

 basin extends eastward over three miles,^ but north of the entrance 

 into Youghal Bay, the deeps extend N.N.E. to a little south of Illaun- 

 more, where they are crossed by the strike of the Scarriff valley 

 north fault. Immediately north of this strike the deeps bear N. and 

 S., but farther north, east of Goose Bay, the great deeps (over 70 feet) 

 terminate at the place where the lake basin is crossed by a line in 

 the strike of the Cloonnagro and Corra valley fault. To the north- 

 eastward of Goose Bay, the trough of the lake basin runs nearly 

 N.E. and S.W. to off Drominagh Point, where the strike of the fault, 

 supposed to run nearly E. and W. from near Lough Atorick, crosses 

 it. This fault also is not marked on the Government Maps, as it was 

 not positivel}^ proved ; but that it does exist seems suggested by 

 the sudden jump in the direction of the associated rocks and the 

 large springs along its line. Still farther northward, an east and 

 west reach extends between Gloondavaun and Terryglass Bays in the 

 line of the strike of the fault proved at Woodford (Lough Atorick 

 valley fault). North of Terryglass Bay the lake basin originally 

 extended much further in a general N.N.E. direction, and its rela- 

 tions to the other faults mentioned in connexion with Slieve Aughta 

 could be pointed out ; as, however, this part is now silted up, it may 

 be passed over. We have now mentioned the principal breaks that 

 have apparently shifted and changed the primary valley, all of which 

 are Post-Carhoniferous and jDrobaloly Pre- Glacial; there are, however, 

 others of a minor rank, many of which seem to be Post-Glacial, 

 which have more or less affected the outline of the lake. They must, 

 however, be passed over ; for as yet the Post-Glacial faults have had 

 very little attention paid to them. 



Lough Derg is one of the natural reservoirs on the Shannon, and 



_' This east and west valley might possibly shift the N.E. and S.W. valley about three 

 miles towards the eastward; but it is more probable that this second nearly north and 

 south portion of tlie lake basin was excavated along a nearly parallel fault line to 

 that along which the first portion was formed. 



