GEOLOGY 



the local marls continue to furnish the material for the vessels in which 

 the pottery is baked in the kilns in addition to being extensively 

 used for other purposes. The fauna indicates the conditions under which 

 the strata were deposited ; for, excepting Entomostraca, which constitute 

 three or more thin bands of impure limestone, and a few fishes, the animal 

 life consisted of the delicate thin valved mollusc Antbracomya pbillipsi, 

 met with in countless numbers in the Blackband Ironstones. The flora, 

 occasionally rich in species and numbers, partakes, according to Mr. 

 Kidston, of a transitional character between Middle and Upper Coal- 

 measures, thus further illustrating the gradual passage of one stage into 

 the other. 



The Etruria Marls, which succeed, consist almost exclusively of red 

 and mottled marls exceeding i,ooofeet in thickness in the central area. 

 Thin bands of green grits, apparently derived in great part from the 

 breaking down of igneous rocks, are interstratified at intervals. Only 

 one locally developed coal seam has been met with, and excepting two 

 thin beds of limestone containing the serpula Spirorbis the entire group 

 consists of practically unstratified red marls. 



The Newcastle-under-Lyme Series conformably overlying the Etruria 

 Marls shows, as far as the colour and nature of the material is concerned, 

 a return to the conditions of the Blackband group. Grey sandstones 

 and shales, in which lie four thin seams of coal, constitute almost the 

 entire bulk. Plant remains are numerous, including the characteristic 

 Upper Coal-measure fossil, Pecopteris arborescens, but associated with 

 others of Middle Coal-measure age. Two thin bands of limestone with 

 Entomostraca and a minute shell (Anthracomya calcifera) which are exposed 

 in the marl pits between Etruria and Longport, invariably commence 

 the sequence. 



In the Keele Series? into which these grey strata graduate upward, 

 we again find rocks of a brilliant red colour, mainly red sandstones with 

 intercalated red marls, among which at intervals thin beds of limestone 

 with Entomostraca are interstratified. The flora, though badly preserved, 

 as in most red rocks, contains species having a wide range throughout 

 the Coal-measure period. For how long the Carboniferous period con- 

 tinued beyond the record contained in these red rocks remains uncertain, 

 since the strictly unconformable Triassic rocks conceal the top beds of 

 the Keele Series or whatever strata may elsewhere succeed, and thus 

 the legend in North Staffordshire abruptly terminates. 



THE SOUTH STAFFORDSHIRE COALFIELD 



The Carboniferous strata of this coalfield are arranged in a dome 

 possessing a length of about 23 miles and a breadth of 6 miles. This 

 main anticline, broken by three subsidiary folds, constitutes the Dudley, 



1 This group was formerly placed in the Permian System. The reasons for the classification here 

 adopted will be found in a paper by the author, <%uart. Journ. Geol. Sue. Ivii. 256 (1901), and in the 

 'Geology of the Country around Stoke-upon-Trent ' (Mem. Geol. Survey), pp. 45-7 (1902). 



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