48 CRUSH-BRECCIATION IN THE MAGNESIAN LIMESTONE 



The beds in this part of the section are much folded, brecciated 

 and disturbed. The hard white layers are brecciated in places, 

 while still maintaining their original bedding planes in others. 

 This brecciation coincides with sharp folds and with thrust 

 planes. At one part of the section the soft strata have been 

 squeezed out entirely, and the hard beds have been thrust 

 along an oblique plane against a mass which has acted as 

 a Horst, crush brecciation having been developed on a large 

 scale. The effect of the thrust, as far as this particular 

 horizon is concerned, gradually dies out from this point, and 

 is soon no longer clearly observable. Vertical fissures filled 

 with breccia are also seen here. One of these, in the cliff a little 

 to the south of the "Chimney," is filled with blocks from the 

 Upper Permian, some of the pieces having a volume of nearly 

 loo cubic feet. The Upper Magnesian Limestone, which is 

 distinctly marked off from the beds below by its peculiar 

 cannon-ball and other concretionary structures, here comes in 

 at the top of the cliff, and having a steady dip to the south 

 it soon occupies the whole of the coast exposure. 



In this section, which is two miles long, there is evidence of 

 thrusting, and of brecciation both on a large and small scale 

 produced by thrust-movement ; the folding and fissuring of 

 the strata being also probably associated with the same 

 phenomena. The main direction of thrust has clearly been 

 from the north, the amount of lateral displacement and 

 folding having been considerable. The breccia forming the 

 Brecciated Limestone is /;/ situ, while that filling the fissures, 

 breccia-gashes and faults, is clearly not so. A detailed and 

 fully illustrated paper dealing with the phenomena discussed 

 in this preliminary note is in preparation. 



