ChahlesWorth — Glacial Geology of North-West of Ireland. 275 



exposed in many sections near the Lurganboy Bridge.^ 'I'his lalve, piiol- to 

 its extinction, was practically choked up with deltaic and lacustrine materials, 

 largely derived from the ice itself. 



The ice-margin, during part of this period, is represented by the 

 moraine curving from beyond Aghnagar to the " Tower " and Bernisk Glen. 

 'I'he latter was not yet in operation, as the drainage from " Lake Bara " was 

 at this time carried by the relatively small " Cloghfin overflow." 



During the recession to the position above Beragh and Six Mile Cross, 

 the ice rested for a brief period against the hill of Foremass. The waters from 

 " Lake Owenbrack," reinforced probably at this time by the Bernisk Glen 

 stream, swept along a wide channel (F.), which falls south-west along the 

 side of this hill. Its intake is about 550 feet, O.D. 



A lake was held up about Garvagh, in the higher reaches of the Eouting 

 Burn. Its outlet was over the wide pass across the watershed towards Sess 

 Kilgreen and Ballygawley. The melting ice, standing in the lake waters, 

 deposited great quantities of fine sand, which occur as mounds at the head of 

 the valley and are well exposed in the sides of the Eouting Burn. A series of 

 erescentic morainic ridges, curving across the valley, marks successive pauses 

 in the ice-retreat, while throughout the recession, the channel at the head of 

 the valley continued to discharge the surplus waters of the increasing " Lake 

 Garvagh." 



It has been shown above that during the withdrawal of the ice from the 

 Fintona Hills, a lobe of ice persisted in every embayment, even where such 

 recess was of comparatively small dimensions. This adjustment of the ice 

 to the smaller details of the relief suggests a relatively thin sheet. 



After the direct overflows into the Clogher valley had been thrown out of 

 action and marginal channels initiated, the whole of the waters, draining 

 from the extra-glacial lakes held up in these recesses, escaped by the " Seski- 

 nore channel " (S.). 



At the east end of the Fintona Hills the drainage was carried off by the 

 large " Pomeroy overflow " into the Lough Neagh drainage system. 



5. The Fintona and Erne Glaciers. 



The ice, which shrank ofl' the Fintona and Omagh hills, streamed eastward 

 along the Fintona Plain as a glacier some eight miles in width. That the 

 easterly direction of thrust, which prevailed during the maximum phase, 

 persisted during the later stages, is demonstrated by the form and arrange- 



' Similar lake deposits are also revealed in many river sections above and about the 

 cross-roads (495). 



