Yol. 6S.'] THE CAEBONIFEEOUS LIMESTONE AT UPPEK VOBSTEE. 69 



p. 68). Fossils are extremely abundant on the weathered rock- 

 surfaces here, and prove that the beds belong to D^. Proceeding 

 south-eastwards from this point, across the level floor of the quarry, 

 we reach a mass of limestone left by the quarrymen on the northern 

 side of the engine-shed, and against which a limekiln has been 

 built (h on the map, PL II, aud in the text-figure). Here are 

 well-bedded limestones also inclined at a high angle almost due 

 south. These limestones, which now overlie the D^ beds just seen 

 at 7i, are identical in character with certain beds near the summit 

 of the Seniinida Zone in Yobster Quarr}-. They are dark-grey and 

 black rocks, perfectly compact in texture, and occasionally brec- 

 ciated in structure. Partings and lenticles of black shale are 

 developed. Although I have failed to discover any fossils in these 

 beds, I have no doubt that they belong to the uppermost part of the 

 Seminula Zone, and that the strata of the Carboniferous Limestone 

 are here inverted. 



Slightly lovrer horizons in the Seminula Zone are exposed in cuttings on 

 the mineral-railway, close to the eiigine-slied. The sections lie (1) beside 

 the low-level rail and immediately east of the engine-shed (I on the map, 

 Ph. II); and (2) on the south side of the high-leyel rail, underneath the 

 road-wall {ni-u on the map, PI. II). The latter section extends east and 

 west of the engine-shed, and is about 130 yards long. In each section 

 the beds hare the same steep southerly inclination, so that a vei-y small 

 Tertical thickness of limestones is exposed. The limestones are, for the most 

 part, dark gx'ey, and very compact in texture. Fragments of Froductus 

 and of Seminula (!), not specifically determinable, were seen in these beds. 



This inversion of the Carboniferous Limestone, giving the 

 strata an apparent dip towards the south, appears to prevail through- 

 out that area of Yobster Old Quarry which lies east of the tramway - 

 tunnel. Westwards from the tunnel, however, the prevailing dip 

 is found to be either northerly or north-easterly in all the ex- 

 posures of limestone; aud in this western tract the observed 

 succession of lithological types, taken in conjunction with the 

 palseontological evidence, suggests that the succession of Carboni- 

 ferous Limestone beds is a normal one. 



It has been seen that, along the great fault between the Southern 

 Limestone Mass and the Grit-&-Shale Mass, which coincides 

 approximately with the northern edge of Yobster Old Quarry, the 

 disposition of the strata is variable. Thus, west of the tunnel the 

 strata dip northwards, and the beds of the Grit-&- Shale Mass 

 overlie the Carboniferous Limestone at the fault-plane with slight 

 but distinct discordance of bedding. At the tunnel itself the appa- 

 rent dip is southerly, and the succession of beds reversed : here, 

 according to Mr. AYinwood's section, there is no great discordance 

 of bedding, and no distortion of the strata, along the faulted junc- 

 tion of the two formations. 



Farther east, however, the relation of the beds along the fault is 

 evidently more complex. The eastern half of the face of Yobster 

 Old Quarry is much overgrown, and also obscured in places by the 

 presence of slipped masses of rock. Attention may, however, be 

 directed to the following features. 



