Vol. 54.] LIMESTONE OF THE COUNTKY AROUND LLANDUDNO. 



395 



down, the limestone is covered with plantations and fields as it 

 reaches the valley below. It continues along the strike and forms 

 the terraced hill of Mynydd Pentre, where the exposures are con- 

 tinuous, and the general dip about 20° to the south-east. On the 

 north there is a depression of the surface, traversed by an important 

 fault between Mynydd Pentre and Little Orme's Head, and running 

 north-west and south-east. The Middle White Limestone then rises 

 again, and forms the bold and precipitous headland 400 feet above 

 the sea. The occurrence of the fault is evident, as the elevation 

 of the base of the Lower Brown Limestone is 300 or 400 feet higher 

 at Mynydd Pentre than it would have been in the absence of a 

 fault. 



A large quarry has been opened in recent years, by the Little 

 Orme's Head Limestone Company, along the 100-foot contour-line 

 on the north-eastern coast of the headland. The mural face of the 

 quarry is along the dip-slope, and from 80 to 120 feet in elevation, 

 with a dip of from 20° to 25° S.S.E., but the bedding of the massive 

 limestone is somewhat obscure and varies in different places. The 

 section towards the southern end of the quarry shows two faults, one 

 of which has fractured a bed of dolomite, and the other has thrown 

 up a bed of brecciated conglomerate. The dolomite is 14 feet 

 thick, and the conglomerate 7 feet ; the latter contains quartzite- 

 pebbles. It must be below the dolomite, and probably near the 

 base of the subdivision. The two faults run nearly due east and 

 west, the principal one throwing up the conglomerate-bed at least 

 100 feet to the north. Quartzite-pebbles have been dragged down 

 the fault, and are mixed up with the limestone-breccia, which also 

 contains hard grit, sandstone, and red shale. 



Fig. 3. — Quarry at Little Ormes Read, in the Middle White 



Limestone. 



About 70 Yards between Faults 



Remains of 



50 Yards 



45 Yards 



50 Yards 



The dislocation of the dolomite by the small fault is remarkable, 

 but, as the throw is only 9 feet, this fracture may be more recent 

 than the general faulting of the Carboniferous Limestone. It is, 

 however, quite possible that the dolomitization may have occurred 

 along the bed after it was fractured. The bed probably possessed 

 some affinity for the magnesium carbonate, a condition that might 

 be expected on both sides of the fault. The dolomite is coarse- 

 grained on one side of the fault, and fine-grained on the other. 

 Mr. Robert Storey, the manager of the quarry, informed me that 



