320 



PALAEOZOIC TIME — CARBONIFEROUS AGE. 



specimens, and numerous other remains of fishes, are found in a fish-bone bed in 

 the mountain limestone at Bristol, England, and also in the same rock at Armagh, 

 Ireland. The British and European species, although numerous and often large, 

 do not exceed in either respect those which have been already found in con- 

 nection with the Subcarboniferous beds of the United States. 



DISTURBANCES PRECEDING THE CARBONIFEROUS 

 PERIOD. 



It was remarked on page 305 that the Devonian beds are very 

 generally conformable with the Subcarboniferous, and therefore 

 afford in but few places indications of uplifts before the Subcar- 

 boniferous period and its formations began. There is the same con- 

 formability for the most part between the Carboniferous and Sub- 

 carboniferous ; yet the examples of the absence of it are more 

 numerous, and cover some wide regions. Through the investiga- 

 tions of Norwood, Daniels, Foster, and Hall, it is now known that 

 the Coal measures of Iowa, Missouri, and Illinois rest unconform- 

 ably upon the strata beneath, and Hall observes " that this is so 

 whether these strata be the Subcarboniferous, Devonian, Upper 

 Silurian, or Lower Silurian." The want of conformability is very 

 distinct in certain parts, and but slight in others ; and in some cases 

 it is apparent only in the marks of extensive surface-denudation 

 which took place at some time preceding the Coal period. 



In the annexed sections, the coal beds rest on tilted Silurian 

 strata. Fig. 558 is a section in northern Illinois. The Coal mea- 

 sures here overlie the Lower Silurian ; a, calciferous sandrock ; b, 



Fig. 558. 



Fig. 558 A. 



St. Peter's sandstone (Chazy?) ; c, Trenton and Galena limestone ; d, 

 Coal measures. (J. W. Foster.) Fig. 558 A was taken at Port Biron, 

 Rock Island co., Illinois, and shows the Coal measures A, resting 

 •unconformably on the Niagara lime- 

 stone B. (Worthen.) In this region, 

 the strike of the uplift is parallel to 

 the course of the Rocky Mountains, 

 or nearly northwest. A portion of 

 these uplifts directly preceded the Coal period. But others may be 

 of earlier date; for where the tilted rocks underneath are Silu- 

 rian or Devonian instead of Subcarboniferous, it is not yet certain 



