Vol. 68.] PALEOZOIC ROCKS OF THE KILBRIDE PENINSULA. 81 



subsequent to the consolidatiou of the rocks with which they are 

 associated, and that the great majority of them are due to infiltra- 

 tion. One of the best spots for observing these varieties of chert 

 is near the point where the rough track to Derrypark leaves the 

 Pinny road. 



Allusion may here be made to certain large veins or masses of 

 red chert, or of quartz, which may be observed in various parts of 

 the district. The following are the most important exposures : — 



(i) A band about a quarter of a mile long and some 3 feet thick strikes in 

 a north-westerly direction between the breccia and spilite. a third of 

 a mile south-west of Lough Mweelaun. This runs parallel to the 

 dolerite-dyke (120). 

 (ii) A mass appears through the peat, a third of a mile north-east of the 

 top of Knock Kilbride. 



(iii) A jDatch surrounded by spilite is found half a mile due west of the top 

 of Knock Kilbride. 



(iv) Much red chert occurs to the west of the dolerite dyke (137), where 

 the latter traverses breccia and the basal Silurian conglomerate. 



At one point only has a variolitic structure been observed in the 

 spilites : this was at a spot (111) about a quarter of a mile north 

 of Lough Mweelaun, where the spilite rests upon the breccia. 



III. The Silurian Kocks. 



{a) The Main Outcrop. 



As has been already mentioned, except for an area of gneiss, the 

 whole of the southern and eastern part of the Kilbride Peninsula 

 is formed of Silurian strata and their associated intrusive rocks. 

 Except in the Barnarinnia area, between Bird Hill and St. Bridget's 

 Well, which requires separate treatment, the Silurian strata have 

 a general dip varying from east to south-south-east. At the 

 northern end of the outcrop, east of Knocknamuck, the dip is 

 easterly or east-south-easterly ; but, south-west of the Kilbride 

 burial-ground, it becomes south-easterly and then south-south- 

 easterly, this direction being maintained until the area ends at the 

 Finny Eiver. 



Although careful mapping shows that the outcrop is shifted by 

 numerous cross-faults, the general succession is perfectly easy to 

 ascertain, and is as follows, in descending order : — 



Thickness infect. 



Wenlock 6. Doon Eock Grits 2000 seen. 



? Tarannon Shale 5. Purple sandy shale 75 



(equivalent) . ^ ^j^^^ School Beds (calcareous flags) 600 



-r 3. Annelid-Grits 900 



Llandovery U Red sandstone 700 



1^1. Basal conglomerate 75 



The thicknesses are very variable, and the maximum observed in each case is 

 given. 



Q. J". G. S. No. 269. G 



