104 ME. L. M. PAR soys OX THE CARBOXIFEEOrS L^'ol. Ixxui, 



Main Midland Area. 



Leicestershire. 



Typical Eastern South-Western 



District. 



District. 



D, 



Cyathaxonia Limestone and black Limestones and 

 nishiana. shales. shales. Chert 



Thinl^-'bedded dark in the lime - 

 limestones and stones. 



shales AA-ith chert. 



Mainlv thinly -bedded Variable Ume- 



D,. 



Lonsdalia 

 Jioriformis. 



limestones with 

 chert. 

 Thickly-bedded 

 Avhite limestones 

 in the lower part. 



stones, dark 

 shaly partings, 

 and some chert, 



Xo typical 

 development. 



Thinly-bedded'^ 

 dolomites 

 succeeding 

 moderately 

 thick beds | ^ 

 of yellow }>^ 

 dolomite | q 

 with a 

 variable 

 quantity of j 

 chert. i 



I'pper Toadstone. ^Massive white or Fairly thickh- 



Thin dark lime- 

 stones. 



Thickly-bedded 

 white limestones 



Lower Toadstone. 



Massive white 

 limestone. 



grey Kmestones 

 poorly fossiH- 

 ferous. 



bedded yellow 

 dolomites. 

 Xo igneous 

 material. 



YI. The Oeigix of the Dolomites. 



The dolomites of the Leicestershire area exhibit characters 

 indicating two distinct sources of origin which are believed to be 

 referable to (1) the influence of salts in waters of pre-Triassic age, 

 probably in the Carboniferous Sea itself, upon rocks that were 

 deposited as normal organic limestones ; and (2) the influence of 

 waters associated with the Trias upon beds which were seemingly 

 crinoidal limestones previously undolomitized. 



The dense yel'ow dolomites forming the bulk oE the 

 sequence at Bi'cedon, Breedon Cloud, etc. 



The greater portion of the dolomites of the eastern inliers is 

 composed of yellow material, the chemical composition of which 

 does not di"ffer greatly from that of a ])ure dolomite. Analyses of 

 typical sj^ecimens from Breedon yield the following average 

 percentages : — 



Calcium carbonate .5 8*2 



Magnesium carbonate 39*6 



Iron compounds I'o 



Insoluble residue 0' 7 



100-0 



