^^1* 57-] UPPER COAL-MEASURES OF THE MIDLANDS. 253 



productive series in North Staffordshire is one of strict conformity ; 

 and that the evidence is in favour of the post-Carboniferous 

 age of the chief movements which have affected the Midland 

 Coalfields. 



The Pottery Coalfield of N'orth Staffordshire, comprising one of 

 these areas, has been surveyed by Mr. Wedd and myself. The 

 southern portion of the South Staffordshire Coalfield, described in 

 this paper, had been partly mapped by me in connection with 

 the field-class of the Birmingham University, and the typical sections 

 were revisited last year. With the object of comparing the upper 

 series in Denbighshire with that of Korth Staffordshire, the sections 

 exposed in the Dee Valley to the east of Chirk, and between 

 Ruabon and Wrexham, were visited last year. I have also had the 

 opportunity of examining, from time to time, the cores from the 

 boring at Thurgarton (Nottinghamshire). 



II. North Staffordshire. 



Before dealing with the Upper Coal-Measures of the Pottery 

 Coalfield it will be necessary to say a few words about the pro- 

 ductive series. For convenience of description, the base may be 

 taken at the Winpenny Coal, the lowest workable seam, and the 

 summit at the Bassey Mine Coal. Grey is the prevalent colour ; 

 but on two horizons at least, notably above the Yard Coal (516 

 yards below the Bassey Mine), and again a short distance above 

 the Knowles or Winghay Coal (128 yards below the Bassey Mine), 

 red sandstones and shales from 30 to 50 feet thick are developed, 

 and can be traced throughout the eastern district. At Western 

 Sprink, red shales and calcareous nodules above the Yard Coal have 

 yielded to Mr. John Ward a marine fauna including cephalopoda 

 and brachiopoda, and also Carhonia Rankiniana, an entomostracan 

 common at several horizons in the higher Coal-Measures. At other 

 stages, but mainly associated with bands of ironstone, entomostraca 

 and Spirorbis are common, and at Adderley Green Mr. Ward 

 pointed out to me a grey limestone with Spirorbis as low down as 

 the Bowling Alley Coal (167 yards below the Yard Coal). It 

 is seen, therefore, that red strata and bands of limestone with 

 Spirorbis are not confined to the higher barren measures. 



The change from the grey measures, with numerous and thick 

 seams of coal and a prolific fauna, into the barren (mainly red) strata 

 above the Bassey Mine Coal, is very gradual. The coal-seams 

 deteriorate slowly in quality and thickness, and the fauna becomes 

 poorer in number and species as the sequence is traced upward. 

 This is particularly the case with the mollusca, which become rare 

 in the upper part of the productive measures, and thus foreshadow 

 the sparse fauna of the barren series. The character, fossil contents, 

 and thickness of the beds succeeding the Bassey Mine Coal are shown 

 in descending order in the appended table (p. 254). 



