KiNAHAN — A Neio Reading of the Donegal Rocks. 25 



the nortli-west, eastward of the Lurgy valley ; while it is a down- 

 throw to the south-east westward of that valley. North-westward 

 of the latter portion of this fault, in a few places, the lowest beds 

 of the quartzite are in such positions that they must be unconform- 

 able to the adjacent Older Period Rocks. These unconformabilities 

 occur in the following places, viz. about a mile west-north-west of 

 Kiimacrenan, nearly vertical micalites and argillites strike about 

 east and west, slightly obliquely to the quartzites, which dip south- 

 east at 40°. A vertical section, perpendicular to the unconform- 

 able boundary, is represented in fig. 1, Plate IV. A little to the 

 south-west, in the vicinity of Doonrock, nearly similar relations 

 exist between the Older and Later Period Rocks. 



A little more than a mile south-west of Doonrock there are in 

 several places quartzites that dip south-east at from 25" to 30" ; 

 while in their immediate vicinity are the Older Period Rocks that 

 dip north-west at from 30° to 45°. A vertical section across this 

 locality is given in fig. 2, Plate III. 



The unconf ormability at the Knockanteenbeg quartzite outline, 

 shown in the section, fig. 1, Plate III., has already been described. 

 Due south of the south-west end of Gartan Lough, at the line of this 

 section, the unconformability seems to be due to deposition ; but 

 a little to the south-west it is evident that the quartzite have been 

 thrust over the basal-bed on to the older rocks. 



In the localities that have been described the actual junction 

 between the older and later rocks cannot be seen on account of a 

 covering of either drift or bog ; but this is not so in places along the 

 south-east boundary of the Lough Keel and Kiimacrenan quartzite. 



In the area contained in sheet 16, between Glen Swilly and 

 Drumabogue, the conspicuous boundary seems to be a fault which 

 has let down the Later Period against the Older Period Rocks. But 

 on examination it is found that, in places alongside the fault, the 

 basal-bed of the newer rocks still exists, its preservation being due 

 to its lower portion being incorporated with the broken upturned 

 edges of the older. 



The Older Period Rocks are rolling in sharp curves, dipping at 

 high angles to the north and south ; while to the westward, across 

 them, lies the Later Period Rocks, which dip north-west at 75°. 

 This junction is best seen along the road near where the site of 

 the old Roman Catholic chapel is marked on the map. 



