232 Proceedings of the Royal Irish Academy. 



of the district would have been understood. Indeed Du Noyer saw that there 

 was inversion of the strata on the south, as his notes on the field-map show 

 and he alludes to it in the Memoir, pp. 18, 22, 38. 



A great number of pre-Old Eed Sandstone faults and overthrusts exist 

 in the Dingle district. The boundary between the " Dingle Beds " and 

 " Annascaul Beds " lying to the south of them, is evidently an overthrust fault 

 that extends the whole way, and probably along, or close to, the original zone 

 of unconformability between the two series of rocks. Du Noyer notes that 

 this line is either a fai;lt or an unconformability, and that the " Dingle Beds " 

 are inverted close to their junction with the Annascaul rocks.' 



As already stated, I consider the line to be an overthrust fault-boundary 

 along or near the zone of unconformability. The junction zone shows evidence 

 of great crushing and movement wherever the two sets of rocks come in 

 contact or close together, as north of Annascaul, at Bull's Head, and at 

 Minard Bay, and elsewhere along the line of junction. 



As already mentioned, the conglomerates of the " Dingle Beds " to the 

 north, at the Smerwick Harbour, being so exactly like those of Parkmore 

 Point, and containing similar derived pebbles of fossiliferous limestone and 

 grit, points to their being in their proper position, towards the base of the 

 series. Du Noyer mentions this in the Survey Memoir, pp. 20, 29. It will 

 be seen in the diagrammatic section how the conglomerates with derived 

 pebbles come in both on the north and south of the fossiliferous Wenloek and 

 Ludlow beds. Many minor folds and faults are proved amongst the Wenloek 

 and Ludlow rocks, striking generally east and west, as well as others ranging 

 northwards. The line of boundary between the fossiliferous Silurians and the 

 " Dingle Beds," a little south of Dunquin, on the west, is a fault or overthrust. 



On the coast to the east of Clogher Head, a small area of Old Eed Sand- 

 stone, resting unconformably on the Ludlow Beds, has been faulted down 

 amongst the Ludlow rocks. This Old Eed Sandstone has been noticed by 

 Professor Eeynolds and Mr. Gardiner, who also allude to the abundant evidence 

 of over thrusting and overfolding throughout the Silurian inlier. Du Noyer 

 alludes to this Old Eed Sandstone in the Survey Memoir, p. 22, but refers to 

 it as being a " portion of the Dingle Beds, resting unconformably on the 

 Ludlow rocks." I agree with Professor Eeynolds and Mr. Gardiner, that it 

 belongs to the Old Eed Sandstone formation, faulted into its present position. 



Folding and contortion have also occurred amongst the " Dingle Beds " as 

 well as in the Silurians above them. A well-defined synclinal fold is notice- 

 able along the coast from near Slea Head to Yentry Harbour, and was traced 



' Geol. Survey Stemoir to sheets 160, IBl, 171, and 172, p. 33 (1863). 



