Vol. 6^.~] THE TOADS TONES OF DERBYSHIRE. 255 



Thickness 



in feet. 



1. Limestone, with a few fragments of encrinite-stems 4 



2. Coralline limestone (big and small corals) 2 



3. Thin limestone, with lapilli 0£ 



4. Limestone, with fossil fragments, containing a bed similar 



to No. 3 4§ 



5. Limestone crowded with fossils 3 



6. Nodular limestone, with thin shaly limestone 3 



7. Black limestones at the base of the quarry 4 



8. Limestone: the lower portions nodular, and containing 



lapilli about 6 



Below the tuff in Cressbrook Dale, and separated from it by 

 about 20 feet of limestone, is a lava-flow from 10 to 20 feet thick. 

 It is seen on the eastern side of the dale, but can only be traced 

 for a short distance. 



Some years ago, in order to arrive at the horizon of the Litton 

 Tuff, I measured the thickness of the limestone-beds above it 

 which are exposed in Cressbrook Dale as far as Wardlow Mires. 

 About 125 feet of limestone were seen above the bed of tuff. 

 The Geological-Survey map shows a small patch of Yoredale 

 rocks at the top of this section, near Wardlow Mires. If this 

 mapping be correct, the tuff is at least 125 feet down in the 

 Mountain-Limestone Series. After several careful examinations of 

 the ground, I have been unable to obtain any evidence of Yoredale 

 rocks. The small patch mapped as Yoredale by the officers of the 

 Geological Survey is covered with a peaty soil containing lumps 

 of limestone, chert, and quartz-rock, and I have therefore mapped 

 it as Mountain Limestone. If I am correct, the tuff of Litton is 

 more than 125 feet below the top of the limestone. 



A reference to the map (PI. XIX) will show that the Litton and 

 Eavensdale Tuffs are both above the upper lava-flow of the district. 

 I have been unable to trace any fault between them : they are 

 apparently two distinct bands, separated by from 250 to 270 feet 

 of limestone, the upper 100 feet of which consist of thinly-bedded 

 limestones and the remainder of thick limestones. This gives 

 roughly:— FgeL 



Limestones measured 1 25 + 



Litton Tuff 



Thin limestones 100 



Thick limestones 150 to 170 



Cressbrook Tuff 



The fault south of the Ravensdale Tuff appears to be an 

 extension of that south of the Tideswell-Dale inlier, and may be 

 traced a short distance to the eastward in Hay Dale, where the 

 limestones north of it dip 40° south-eastward and 30° southward ; 

 while south of the fault the dip of the limestones is only 5°, and 

 they occur in thinner beds than those on the north. 



