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On the Classification of the Carboniferous Limestone Series ; 

 Northumbrian Type. By Hugh Miller, F.R.S.E., F.G.S., 

 of H.M. Geological Survey. 



[From the Report of the British Association for the Advance- 

 ment of Science, 1887. Communicated by the Author.] 



It is now twenty years since the late George Tate, of 

 Alnwick, published his completed classification of the Carbon- 

 iferous Limestone Series of North Northumberland. For mure 

 than half that period it has been set aside as of a merely local 

 value. It will be the endeavour of this paper to claim for it its 

 true place. 



Tate's classification may be summarised as in the following 

 table : — 



Carboniferous Limestone Series of North Northumberland : 

 Tate's Classification, 1856-1868. 



Upper or Calcareous group : — From the base of the Millstone Grit 

 to the Dun Limestone, ' the lowest limestone of any value.'' 

 Good workable limestones, interstratified among alternations 

 of sandstone, shale, and coal ; large number of marine 

 organisms in the calcareous strata. Thickness about 

 1,700 feet. 



Lower or Carbonaceous group : —From the base of the Dun Lime- 

 stone to the top of the Tuedian group. Distinguished by the 

 number, thickness, and quality of its coal seams ; limestones 

 thin and generally impure ; marine organisms in fewer 

 numbers than in the calcareous group. Thickness, 900 feet. 



Tuedian group : — The beds intermediate between the productal and 

 enerinital limestone* of the county and the Upper Old Red 

 Sandstone. Distinguished by coloured shales, by thin, 

 argillaceous and cherty or magnesian limestones, and by the 

 rarity of encrinites and Brachiopoda. Some Stigmarian 

 layers, but no beds of coal. Thickness about 1,000 feet. 

 In one of his papers Tate distinguishes a series of ' Tuedian 

 grits ' forming the upper part of the group. 





