Clare Island Survey — Geology. 7 5 



zone, which runs through the townlands of Strake, Kill, and Glen, almost from 

 end to end of the island, red argillaceous sandstone is the prevailing rock ; but 

 other varieties, as dark slate, red and green sandstone and shale, and greenish- 

 grey slate, are also represented. 



Crushed Zone. — Mr. Kilroe thinks that the rocks of the faulted area, 

 referred to as the crushed zone, are simply altered forms of the adjoining- 

 rocks lying outside the fault lines. Their extremely altered character, how- 

 ever, and their striking resemblance to the great metamorphic group of 

 Dalradian rocks, render this interpretation rather doubtful. It is, in fact, 

 extremely likely that they represent portion of the old Dalradian floor, which 

 has been brought to the surface by the faulting down of the Upper Silurian 

 trata lying to the north and south of the area. These altered rocks consist 

 of epidiorite, mica-schist, quartzite, and quartzose conglomerate. 



Harbour Series. — Occupying a small area around the harbour, in the 

 south-east of the island, may be seen another group of rocks, the Harbour 

 Series, which is obviously different from the Knockmore strata. The beds, 

 consisting of grey sandstones, and purple and chocolate sandstones and con- 

 glomerates, are apparently of Old Bed Sandstone date, and probably belong 

 to the older division of the system. 



Maum Series. — North of the great fault which runs W.N.W. across the 

 island from the northern end of the Harbour strand, a group of red sand- 

 stones and conglomerates, the latter containing large rounded pebbles of white 

 quartz, jasper, and quartzite, extends over parts of the townlands of Lecarrow, 

 Maum, and Ballytoohy. The beds are not of very great thickness, and may 

 be regarded as forming the base of the Carboniferous strata, but in keeping 

 with the principles upon which the mapping was carried out on the main- 

 land at Achill, these red rocks have been separated from the Carboniferous 

 series of the adjoining ground, and mapped as Upper Old Bed Sandstone. 



Cappnagower Series. — On the north-east of the island, in the townlands of 

 Cappnagower, Fawnglass, Lecarrow, and Maum, the Carboniferous system is 

 represented by the Cappnagower series, consisting of gre) r sandstones, shales, 

 and calcareous beds, but no limestone. The beds, which dip from 5° to 10° to 

 the east, are for the most part covered with drift ; but good exposures are to 

 be seen along the coast-line for about a couple of miles (Plate II, fig. 2). 

 The fossil forms found in this series, viz., molluscan shells, crinoid stems, 

 indistinct corals, and plant impressions, have been adjudged to be distinctly 

 Carboniferous in type, and probably belonging to the Lower Carboniferous. 



Igneous Mocks. — An interesting band of igneous rocks runs along the line 

 of the great fault north of Croaghmore and Knocknaveen. The rocks 

 contain, in places, small quantities of the minerals malachite and copper 



