GEOLOGY 



chosen as the base of the upper sub-division. The unequal rate of 

 deposition of the Coal-measures is accentuated in the Pottery Coalfield, 

 where the strata between the Bassey Mine and Winpenny Coals approxi- 

 mate to 1,200 yards at Shelton, whereas at Apedale, 4 miles to the 

 west, they are under 800 yards thick, from which the rate of diminu- 

 tion can be calculated to be about i in 17, equivalent to a gradient of 

 over 3 degrees. 



Below the Winpenny the coal seams are of small value, but one 

 called the Crabtree Coal, a few yards above the First Grit, is well known 

 from its shale roof, yielding in all four areas abundant specimens of 

 Goniatites, Pterinopecten and Lingula. The strata below the Winpenny 

 occur in all the four areas, while they constitute the entire measures of 

 the small basin of Shaffalong and a considerable portion of that of Cheadle 

 and Goldsitch Moss. 



The strata enclosing the coals and ironstones consist of clays, marls, 

 fireclays and shales with an occasional band of sandstone very impersistent 

 and of no great thickness. The colour is generally a dull grey excepting 

 a few bands of intensely black shales or an occasional impersistent stratum 

 of a red colour. The absence of any great mass of hard rocks is reflected 

 in the scenery, which is tame and uninteresting, but whenever a ridge 

 breaks the monotony it is almost certainly found to consist of one of the 

 bands of sandstone, and inasmuch as the sandy material is more prevalent 

 in the north so the ridgy character of the coalfield, as in the Norton 

 district, becomes more pronounced. 



The numerous coal seams between the Ash and Winpenny Coals 

 constitute the chief seams of the Pottery Coalfield. They include varieties 

 suitable for house purposes, for making gas and coke, for raising steam, or 

 for use in the arts and manufactures of the district. The only ironstone 

 at present raised is the Burnwood Stone of the variety known as semi- 

 blackband. In the adjacent Cheadle Coalfield there are also several valuable 

 coal seams, but they have not been satisfactorily identified with those of 

 the Pottery Coalfield. A peculiarity in the distribution of the coals in 

 the Pottery area is the fact that certain easily recognized seams, which are 

 gas or coking coals in the western area, rapidly lose a large quantity of 

 their bituminous matter when traced eastward, until they become house 

 or steam coals. 



The commonest fossils are molluscs, of which the most abundant 

 belong to the genus Carbonicola (Anthracosia)^ regarded as a freshwater, 

 mud-loving animal. They occur in great profusion in the ironstones 

 and shales overlying the Cockshead, Ten-feet and other coals, forming 

 the so-called ' mussel or cockle bands ' of the miner. In comparison with 

 the Middle Coal-measures, fish remains may be said to be rare ; of great 

 interest are fragments of various parts of the skeleton of the amphibian 

 Loxomma, met with in the shale overlying the Cockshead Coal at Adderley 

 Green. Within recent years a number of thin bands of shales and cal- 

 careous nodules containing marine organisms have been brought to light 

 at no less than seven widely separated horizons ; the lowest, as previ- 



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