Wright — Palaeozoic Floor of North-East Ireland. 641 



lake. Failing this, it is necessary to select sites as near this ideal as possible, 

 that is, along its shores; and before doing so it is desirable to consider 

 the faulting of the area. 



Consideration of the effects of faulting. 



The northern limit of the Coal Island field is an E.N.E. fault having an 

 upthrow to the north of 2000 feet, and bringing the Carboniferous Limestone 

 into juxtaposition with the Coal Measures. This fault is continued to the 

 north-east into the Mesozoic rocks, in which, however, it has a much smaller 

 throw, probably not more than some 1000 feet, it is clear, therefore, that 

 there has been movement along it at, at least, two periods, the main displace- 

 ment being pre-Mesozoic, and the posthumous post-Mesozoic displacement 

 being relatively slight. The realization of this fact is of the greatest 

 importance, for, the greater part of the displacement having taken place 

 previous to the pre-Mesozoic denudation, the Coal Measures will be preserved 

 over a much wider area to the south of the fault, as indeed we see to be the 

 case at Coal Island. 1 We should then in the first trials keep to the south of 

 this fault. For instance, on the west side of the lake, Washing Bay is a 

 better site for boring than Arboe Point, although the latter is a little nearer 

 the centre of the trough. This is more especially the case as, on this side of 

 the lake, there are, to the north of the Coal Island boundary fault, two other 

 faults parallel to it, both with an upthrow to the north, so that we might 

 expect the coal-basin to be progressively contracted towards the north. 



Now, coming to the eastern side of the lake we find only one such fault, 

 or at any rate only one has been recognized. This is the Templepatrick fault, 

 which has a north-easterly course and an upthrow to the north of about 

 500 feet. This fault is in a direct line with the Coal Island boundary fault, 

 and is believed to be a continuation of it. It should therefore, as at Coal 

 Island, have a much greater throw in the Palaeozoic rocks beneath, and Coal 

 Measures are more likely to be preserved to the south of it. For exploration 

 purposes, therefore, Lennymore Bay is, for instance, a better site than 

 Ardmore Point. If coal should be found here and at Washing Bay, the 

 exploration of the rest of the district will follow in logical sequence, which 

 need not be elaborated at present. 



1 I am indebted to Mr. Ernest Williams, Engineer to the Department for the Develop - 

 ment of Mineral Resources, Ministry of Munitions, for bringing home to me the vital 

 importance of this fault ; and indeed the discussion of the problem as a whole owes much 

 to his criticism. 



