98 ilK. SARDINEE AND PEOF. EETXOLDS ON THE [Feb. I912, 



YII. General Summary and CoNCLrsioxs. 



The stratigraphical succession in Arenig times is not nearly so 

 complete in the Kilbride area as at Tourmakeady and Gleusanl, 

 neither the coarse conglomerate towards the base of the Arenig 

 deposits nor the Shaugort Beds near their summit being seen. The 

 lowest Arenig bed at Kilbride is a spilite-flow with some accompany- 

 ing breccias, upon which rest quartzose grits, with black cherts and 

 shales containing Didymograptus extensus, these being almost the 

 sole representatives of the Arenig sedimentary deposits in the area. 

 A most extensive series of spilite-lavas accompanied by felsite and 

 spilite-breccias follows: the coarseness of the breccias indicating the 

 highly explosive character of the eruptions, and the large blocks of 

 felsite in the breccias proving the presence of an acid magma at no 

 great distance, although no acid lavas have been found in the area 

 and as yet no acid intrusioos had taken place. 



Later on, but almost certainly in Arenig times, occurred the up- 

 wellings of the acid rock which now forms the great felsite- 

 intrusion of Glenbeg and the smaller felsite-masses elsewhere in the 

 area. At what exact period the extensive fracturing of the Arenig 

 beds took place is not evident. It is probable that it occurred in 

 post-Arenig times, and was connected with the uplift which brought 

 these rocks under the influence of the Llaudeilo sea. 



The Kilbride area contains no Llandeilo rocks ; but an enormously 

 thick series of grits, with a coarse basal conglomerate containing 

 blocks of a quartz-felsite exactly like the Glenbeg rock, rests upon 

 the Arenig beds along the western margin of the Kilbride area, and 

 forms the northern shore of Kilbride Bay. These rocks are similar to 

 the grits and conglomerates to which we refer in our Tourmakeady 

 and Glensaul papers as of Bala (?) age, but according to llr. H. B. 

 Maufe and Mr. E. G. Carruthers they are of Llandeilo age. 



If these beds ever extended over the Kilbride Peninsula, they 

 were removed by erosion in pre-Llandovery times, as the Llandovery 

 Beds rest directly upon the Arenig Series. 



Llandovery Beds some 2350 feet thick, succeeded by about 

 2000 feet of Wenlock grits, occur in the area ; but no Ludlow Beds 

 are seen, JSIonograptus vomerinus being found in the verv hio-hest 

 strata. 



Probably at an early post-Silurian date came intrusions of 

 lime-bostonite and of coarse porphyrite. Then followed a period 

 of important earth-movement, connected in all probability with 

 the Caledonian movements of other regions. The whole area was 

 folded into a syncline, the axis of which trended roughly north- 

 east and south-west ; and, perhaps owing to the presence of the 

 rigid block of the Glenbeg felsite, the rocks in adjusting themselves 

 were traversed by numerous cross-faults, M'hich shifted the outcrops 

 of the lime-bostonite and coarse-porphyrite intrusions as well as 

 those of the Silurian strata. The important fault brinc^ino- the 

 Silurian deposits against the gneiss in the south-eastern part of the 

 area is probably also of this date. 



