62 DS. T. p. SIBLY ON THE FArLTED INLIEE OF [Feb. I912, 



(2) It comprises (a) a jS"orthern Limestone Mass, and (5) a Southern 



Limestone Mass, separated by (c) a Grit-&-Shale Mass. 



(3) The great bulk at least of the exposed Carboniferous Limestone 



belongs to the Seminida Zone and the Lower Dihunoplnjllmn 

 Zone. 



(4) The beds of the Grit-&-Shale Mass are in faulted relation witli 



the Carboniferous Limestone, on both sides. 



(5) On the northern side of the Grit-&-Shale Mass, the immediately 



adjacent beds of Carboniferous Limestone represent part of the 

 Seminula Zone. On the southern side, in Yobster Old Quarrj^, 

 the adjacent beds belong to the Lower Dibunopliyllum Zone. 

 On both sides the limestone beds are considerably disturbed. 



(6) Tn the Northern Limestone Mass, Vobster Quarry exposes over 



500 feet of limestones belonging to the Seminula Zone. The 

 whole succession is here inverted, the beds dipping north- 

 westwards at an angle of about 135°. 



(7) In the Southern limestone Mass, where portions of the Lower 



Bihunopliylluin Zone and of the Uj)per Seminula Zone are 

 exposed, the strata are locally overfolded northwards. 



(8) The beds of the Grit-&-Shale Mass include quartzites which 



must certainly be assigned to the Millstone Grit. They also 

 comprise shales, with intercalated fine-grained sandstones, of con- 

 siderable thickness. Possibly this mass includes the lowest beds 

 of the Coal Measures, in addition to a part of the Millstone Grit. 



(9) In most of the sections of Carboniferous Limestone, signs of 



the immense stresses to which the rocks have been subjected 

 are very evident. The strata are often distorted, while 

 slickensides and calcite-veins are extensively developed on both 

 a large and a small scale. 



IV. Detailed Desceiption. 



(rt) The Northern Limestone Mass. 



A^obster Quarry. (PI. Ill & PI. IV, fig. 1.) 



(i) General features. — The Carboniferous Limestone is well 

 exposed along the western, northern, and eastern sides, where 

 quarrying is in progress ; but on the southern side, where great 

 quantities of Liassic limestone-rubble have been tipped, it is con- 

 cealed by piles of this material, except near the mouth of the 

 tramway-tunnel. 



From east to west the quarry is approximately 250 yards long, 

 and the distance from the mouth of the tunnel northwards to the 

 present northern face of the quarry is about 190 yards. If the 

 present rate of quarrying should be maintained, the northern limit 

 of the Carboniferous Limestone will probably be reached in the 

 course of a few } ears. 



At the western end the Carboniferoas Limestone comes to the 

 surface (PI. Ill); but on the eastern side and along nearly the whole 

 of the northern face it is overlain by a thm covering of yellow, 



