140 



SUMMARY OF THE SALOPIAN COAL-FIELDS. 



These beds, however, pass down in two localities, into bands of true mountain lime- 

 stone, containing exclusively fossils of marine origin. 



3rdly. The Clee Hill coal-fields consist of only the lower carbonaceous masses, re- 

 posing upon millstone grit and carboniferous limestone. These, therefore, were probably 

 accumulated in a bay of the sea. (See Map, next Chapter.) 



4thly. In the northern extremity of the Forest of Wyre, where the passage upwards 

 into the New Red Sandstone is clearly marked, no volcanic eruptions having there 

 burst forth to obscure the succession of the stratified deposits, a large portion of car- 

 bonaceous masses is thus proved to belong to the younger zone of coal measures ; but 

 the order of succession beneath them is not complete, for the carboniferous limestone 

 being absent, the coal reposes directly upon the Old Red Sandstone or Silurian rocks. 



5thly. The fields of Shrewsbury and Coal Brook Dale were originally deposited 

 upon rocks of all ages, from the slates of the Cambrian system to the carboniferous 

 limestone included, the latter case being the exception and not the rule, as in other 

 parts of England. 



Lastly. Wherever the carboniferous limestone is interpolated between the bottom coal 

 grits and the Old Red Sandstone, it is invariably perceived to thin out in a small range 

 of horizontal extension. This disappearance of the limestone is not occasioned by faults 

 and subsidences, but in all cases, whether at Lilleshall, Steeraway, Oreton, or on the 

 south of the Clee Hills, it can be traced tapering away from a central mass to thin ex- 

 tremities, which really wedge out between the coal grits and the older deposits. Since, 

 therefore, we have the clearest testimony that it has been deposited only at wide in- 

 tervals and in small quantities, it is obviously unnecessary to call in the aid of convulsions, 

 to account for its absence. 



These phenomena are in perfect accordance with the views already partially exposed, 

 of the probable distribution of land and sea during the formation of the Salopian coal- 

 fields, great part of which were doubtless accumulated in lakes and brackish estuaries, 

 the occurrence of deep marine bays occupied by pure salt water (in which alone the 

 animals of the carboniferous limestone could have lived,) having been of rarer oc- 

 currence in this region. A more complete elucidation, however, of these phenomena 

 will be found at the conclusion of the next chapter. 



