2l8 EXPLANATION OF THE CLAXHEUGH SECTION. 



Another important point is that pieces of Compact Lime- 

 stone, not in situ, and to the east of the termination of this 

 bed, occur lying between the Shell Limestone and the Yellow 

 Sands (b in Section L). The junction of these Sands with 

 the overlying limestone is very irregular all the way from 

 the ending of the divisions, and the surface of the Sands 

 has evidently been much disturbed and denuded. 



EXPLANATION. 



The details of this section can be entirely explained by 

 supposing denudation to have gone on in a cavern the roof 

 of which afterwards settled down, thus bringing the Shell 

 Limestone in contact with the Yellow Sands, with the excep- 

 tion of the places where the breccia intervenes. It appears as 

 if denudation had gone on in a cavern until nearly the whole 

 thickness of the Compact Limestone and Marl Slate lying to 

 the east had been removed, and the top of the Yellow Sands 

 a little denuded, its upper surface being thus rendered very 

 irregular. The western end of the cavern probably, before 

 the settling down of the upper strata, presented somewhat the 

 appearance shown in Section 3. 



The roof of the cavern after a time gradually settled down, 

 and a slight sliding movement along the crack S Si possibly 

 took place. During this movement in order to relieve the 

 strain the large cracks C i, C 2, C 3 with their associated 

 smaller ones were formed. The broken masses and layers of 

 limestone lying on the floor of the cavern were pressed along 

 it eastwards, the two layers A and B being wedged in between 

 the floor and the roof, and some of the limestone was ground 

 to powder and filled F and G, Section 11. This powdered 

 mass is now firmly cemented together and is very tough and 

 hard. The banding of the Yellow Sands at D, and the 

 forcing of some of it over the brecciated mass was due to this 

 eastward movement ; while the breccia is evidently the loose 

 portions of limestone that were lying on the floor of the 

 cavern, and further to the east (b in Section I.) portions of 

 the limestone lying on the floor of the cavern would be 

 enclosed between the Yellow Sands and overlying limestone, 



