614 MK. E. D. VERNON ON THE GEOLOGY AND [DeC. I912, 



Measures of Leicesterslaire are very similar to those of Warwick- 

 shire, and the resemblance extends even to minor points, such as 

 the occurrence of certain coarse grits towards the summit of the 

 group near Polesworth in Warwickshire, and also near Moira and 

 Boothorpe in Leicestershire. One striking feature, which each of 

 these coalfields has in common with the South Staffordshire Coal- 

 field, is the occurrence of seams of coal of exceptional thickness 

 formed by the union of several individual seams. Prom this and 

 other evidence, it appears extremely probable that these separate 

 areas of Coal Measures were formed under similar conditions in one 

 general basin of deposition. 



In ISTorth Staffordshire and in ITottinghamshire the Keele Beds 

 are not fully developed, and the summit of the group is nowhere 

 visible ; while in South Staffordshire the top of the Keele Beds is 

 also unknown. In Warwickshire, as a result of this "work, it is 

 now possible for the first time to demonstrate the exact upward 

 limit of the Keele Beds. The Warwickshire Coalfield may 

 thus be regarded as the typical area of development of 

 the Upper Coal Measures of the Midland province, with 

 which the incomplete sequence exposed in other coalfields can be 

 compared. 



The Southerly Attenuation and Overlap of the 

 Carboniferous System. 



One other fact of general interest clearly shown by this correlation - 



table (p. 613) is the remarkable attenuation of the consecutive 



subdivisions of the Carboniferous System, along a north-and-south 



line from Nottinghamshire through Leicestershire to Warwickshire, 



just as there is also an exactly similar attenuation on a parallel line 



farther west through the jSTorth and South Staffordshire Coalfields. 



Further, this attenuation is accompanied by the successive overlap 



of each subdivision Upon the pre-Carboniferous floor of the district. 



This southerly attenuation and overlaj) of the Lower Carboniferous 



by the Upper Carboniferous, and also of the tw^o lower subdivisions 



of the Upper Carboniferous, can be demonstrated ; and it may be 



inferred that, in the unproved area south of Coventry, the Middle 



Coal Measures in turn thin away and are overlapped by the barren 



Upper Coal Measures. The southern margin of deposition of the 



Middle Coal Measures must have lain along an east-and-west line 



somewhere to the south of Coventry : therefore, we may conclude 



that the southern portion of the basin was not depressed until late 



Middle Coal-Measure times, and that the pre-Carboniferous floor 



had a general slope from south to north. 



