GEOLOGY 



troversy, of which there are two opposing views. Some geologists, 

 following the brilliant researches of Ramsay, 1 claim a glacial origin for this 

 heterogeneous collection of rock fragments. Others 2 maintain them 

 to be scree material swept down by sub-aerial torrents from a pre-Triassic 

 hilly region situated in the south. 



TRIASSIC SYSTEM 



To whatever origin the ' Permian ' breccias of Clent and Enville be 

 attributed, the next group the unconformable Triassic rocks affords a 

 typical example of deposits laid down under continental conditions, 

 as was long ago pointed out by Ramsay and Godwin-Austen. The 

 change from the river-borne muds and silts of the Carboniferous period 

 is not only vividly contrasted in the loosely compacted red sandstones 

 and conglomerates of the Trias, but the vast interval of time intervening 

 between the close of the one set of events and the opening of another 

 is forcibly demonstrated by the newer formation reposing horizontally or 

 at gentle angles on the denuded and intensely plicated carboniferous 

 strata. This is recognized by geologists ending the Palaeozoic era with 

 the Carboniferous or Permian systems, and starting an altogether fresh 

 time epoch (Mesozoic) with the red rocks of the Trias. 



At its commencement in the Bunter period the Triassic continent 

 an elevated Carboniferous sea floor presented a very irregular rocky 

 surface fashioned out of a plane of marine denudation during upheavals 

 succeeding the Carboniferous period, and carved out by long subsequent 

 denudation. This rugged surface of pre-Triassic hill and dale and 

 possibly mountainous country became gradually levelled by dry weather- 

 ing, torrential rains and wind, while the material derived from these 

 sources was swept into and slowly accumulated in the hollows. In the 

 succeeding Keuper stage the broader depressions were further rilled with 

 sediments deposited in a great lake subjected to such intense evaporation as 

 to result in the deposition of thick beds of rock-salt and gypsum. Finally, 

 at the close of the Keuper period the area became depressed, by gentle 

 sinking movements, beneath the waters of the Rhaetic and Jurassic seas. 



The Triassic system is built up of sandstones and marls of an 

 almost universal red colour due to a thin film of oxide of iron coating 

 each particle. Traced across the district from west to east the individual 

 members show a rapid decrease in thickness : collectively, on the west 

 side of the South Staffordshire Coalfield the thickness amounts to 3,500 feet, 

 which has dwindled to about 1,200 feet on the east side of this coalfield, 

 but there is reason to believe that in the centre of the basin to the north 

 of Stafford the westerly amount is reached or even exceeded. Owing to 

 the general slight inclination of the strata the outcrops are especially 

 broad ; they are narrowest round the Carboniferous tracts in the north 



1 'On the Occurrence of Angular, Subangular, Polished and Striated Fragments and Boulders in 

 the Permian Breccia of Shropshire, Worcestershire, etc.,' <$uart. Journ. Geol. Soc. xi. 185 (1855). 



3 ' On the Permian Conglomerates of the Lower Severn Basin,' by W. Wickham King, Quart. 

 Joum. Geol. Soc. Iv. 97-128 (1899). 



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