Wright — Palceozoic Floor of North- East Ireland. 637 



does not maintain a constant direction throughout its course, is approxi- 

 mately parallel to the axis of the Ayrshire coalfield, and should be taken as 

 the line along which the greatest thickness of Carboniferous strata is to he 

 expected. 



The nearest exposed Carboniferous strata, moreover, afford confirmatory 

 evidence that there is a dip inwards towards the axis. This is apparent along 

 the whole western border of the basalt plateau in the Lower Carboniferous 

 Eocks, and, of course, in the trough-valley itself there are the Coal -Measures 

 of Dungannon and Coal Island dipping steadily towards the Lough, and, as 

 far as they can be seen, continually taking on higher beds in this direction. 



The courses of this transverse synclinal trough and of the flanking anticlines 

 are surprisingly well defined throughout the whole of the basaltic plateau, but 

 more especially outside the limits of the trough-valley to the north. On the 

 northern edge of the trough-valley the schist hills of Knocklayd and Torr 

 Head limit it to the east, these schist hills owing their elevation and 

 consequent exposure to the eastern limiting anticline. Similarly on the west 

 we have the schist hills of Coolcoscreaghan and Moneyoran, the eastern 

 outliers of the Sperrin Mountains. These hill- masses are the points wheie 

 the transverse anticlines intersect the schist-ridge of the Highland loider; 

 and in the intervening synclinal basin of the Eann this ridge is depietscd, and 

 sinks beneath the lavas and Mesozoic rocks. 



Course of the Western Anticline. 



The western limiting fold appears to be somewhat isoclinal in character, 

 the clip off its eastern flank being much more pronounced than that on the 

 west, at least as regards its effect on the Carboniferous rocks. In a broad 

 way it appears to be responsible for the elevation of the Sperrin Mountains, 

 which are flanked on the north-east and south-west by Carboniferous rocks, 

 and also within the normal limits of the rift-valley itself for the exposure of 

 the ancient gneissose axis of Tyrone and the anticlinal area of Silurian rocks 

 at Pomeroy. All along its eastern side, from the north coast of Antrim to 

 the Silurian rocks of' Armagh, the Carboniferous strata are brought in rapidly 

 by the dip and accompanying faulting in the direction of the Bann Valley 

 depression. Above them follow the Mesozoic rocks and the Tertiary Lavas, 

 with a similar but less pronounced descent in the same direction. In the 

 southern part of the rift- valley we have on the one hand the nearly horizontal 

 strata of the Millstone Grit forming the hills around Slievebeagh, and on the 

 other the steeply dipping rocks of similar age in the neighbourhood of 

 Dungannon. The further course of the fold in the Silurian strata to the south 

 is not readily traceable. 



SCIENT, PROC. K.D.S., VOL. XV., NO. XI4V. 5 g 



