part 3] 



CHELLASTOX GYPSUM BBECCIA. 



179 



unfits it for this purpose, and when it is still more impure it verges 

 on eoarsestone. It occasionally shows signs of stratification. 



The lower bowl-shaped portion of the pillar is usually composed 

 of eoarsestone enclosing numerous ovoid or rounded lumps of white 

 gypsum, and veins of satin-spar arranged more or less horizontally 

 or in conformity with the curved outline of the pillar. The deepest 

 red colour occurs in this outer and lower layer, owing to the 

 amount of included Keuper marl. 



At this locality there are only a few relics of original cover or 

 ' cap ' left, for, as a rule, Glacial drift overlies the gypsum and fills 

 up parts of the swallowholes between the pillars ; but at one or 

 two spots traces of about 2 feet of green and red marl were found 

 resting rather unevenly upon the white alabaster. At Woodlands, 



Fig. 



3. — Diagram of a typical pillar at Chellaston, showing 

 white alabaster overlying lumps of the same set in red 

 alabaster. (Height of section = 9 feet.) 





[Fibrous gypsum in eoarsestone is shown by narrow 

 vertically shaded bands.] 



a quarter of a mile towards the south-east, the ' cap ' is exposed 

 as a bed, from 2 to 3 feet thick, of green sandy marl and green 

 gypsiferous marl resting upon a little red marl overlying the main 

 bed of gypsum. 



Sequence of Events before the Formation of the Breccia. 



We may now attempt to follow the sequence of events that led 

 up to, and finally resulted in, the formation of the breccia. 



The gypsum was apparently laid down irregularly, and conjointly 

 with the deposition of the horizontally-stratified marl, in the form 

 of basin-shaped masses, which were probably due to crystallization 

 being set up at numerous isolated points, each of which, is now 

 situated on the central axis of a pillar. The lowest mass of 

 gypsum in each case was mixed with red marl, and now forms the 

 eoarsestone of the pillar ; the next mass contained relatively little 

 marl, but was stained by the colouring-matter — this is the red 

 gypsum ; the ivpper mass was pure white gypsum, and. in all 



