CARBONIFEROUS LIMESTONES OF IOWA. 



93 



No beds of coal have been discovered interlaminated with any of these groups. 

 The lowest bed of coal observed lies fifteen or twenty feet above the upper surface 

 of the highest member of this series. 



Subjoined is a table, contrasting the different groups that make up this series, 

 with the beds composing the carboniferous limestone, as it occurs in Yorkshire, 

 England, near Kettlewell and Great Whernside. Though the Yorkshire formation 

 appears to be more than twice as thick as that of Iowa, a striking analogy may 

 still be traced in their leading lithological features, particularly in the succession 

 composing the upper part of the series, with its nodular and concretionary limestones 

 at top and bottom. These speak of similar causes in operation during the period 

 of deposition, in both formations, though they exist four thousand miles apart. It 

 would seem that, after the deposition beneath the water of certain beds, and before 

 complete consolidation, these were brought to the surface by slight oscillatory 

 movements of the earth's surface ; that by the action of the sun and atmosphere 

 their surface became cracked and fissured; and when again depressed, and the 

 interstices filled with calcareous mud and argillaceous depositions, that the whole 

 was re-cemented. 



TABLE EXHIBITING ANALOGY BETWEEN CARBONIFEROUS LIMESTONES OF 



YORKSHIRE AND IOWA. 



LIMESTONES BETWEEN KETTLEWELL AND GREAT 

 WHERNSIDE. 



(Under grits and shales.) 



Limestone : a hard, sharp stone, in nodular beds. 

 Limestone : a hard, sharp stone, in nodular beds. 



Parting of shale. 

 Limestone : light-coloured. 



Parting of shale. 

 Limestone : light-coloured. 



Parting of shale. 

 Limestone: light-coloured. 

 Plate. 



Limestone: rather dark-coloured, forming bold scars. 



Parting of shale. 

 Limestone. 



Fine gritstone, occasionally yielding flags. 



Gray limestones, with Producta in the lower beds. 



Blue limestones, very solid, full of large Producta, 



Lithodcndra, &c. 

 Red limestones, with Encrinites and Spiri/ers. 

 Gray limestone : in bold scars. 

 Black nodular limestone. 



Gray limestone : small-grained, compact or splintery, 



white or gray. 

 Various limestones : mostly compact, to the level of 



Kettlewell-dale ; including the "dun" (or niag- 



nesian) limestone, full of ramifications, nodules, 



or hollow cells of calcareous spar. 



UPPER LIMESTONE SERIES, NEAR THE MOUTH OF 

 THE DES MOINES. 



(Under shales.) 



Limestone : compact, close-textured, brittle, white ; 

 usually concretionary, with marly earth in the 

 interstices. 



Gritstones : brown and white. 



Limestone : compact, close-textured, brittle, white, 

 concretionary; containing Lithostrotion ; becom- 

 ing more evenly bedded in its lower portion, and 

 containing Productus cora, P. Flemingi, Spiri- 

 fers, Tercbratuloe, Mdonites, Multlpora, &c. 



Sandstones : often with small pebbles. 



Magnesian limestones : buff", often cellular, or with 

 tubular perforations. 



Limestones : impure, full of Geodes, containing cal- 

 careous spar and quartz. 



