DALE OWEN ON THE WESTERN STATES OF NORTH AMERICA. 433 



2. On the Geology of the Western States of North America, 

 By David Dale Owen, M.D., of Indiana, U.S.* 



[Communicated by Mr. Lyell. — Read November 2, 1842.] 



Plate XIX. 



The remarks here submitted will be confined chiefly to that part of 

 the Western States of North America watered by the rivers Ohio, 

 Wabash, Illinois, Rock, Wisconsin, Cumberland and Tennessee, lying 

 between the 35th and 4<3rd degree of N. latitude and the 81st and 91st 

 of W. longitude. The district includes the states of Illinois, Indiana, 

 Ohio, Kentucky, Tennessee, and the Du Buque and Mineral Point di- 

 stricts of Iowa and Wisconsin. This territory occupies an area of about 

 half a million of square miles, but its geological features are remark- 

 ably uniform, belonging, with a few partial exceptions, to the periods 

 of the bituminous coal and carboniferous limestone as found in Eu- 

 rope, and the Silurian rocks as described by Sir R. Murchison ; the 

 exceptions are the superficial deposits which occasionally cover up 

 these from view over considerable tracts, and these must either be 

 referred to the age of gigantic mammalia and formations of a much 

 newer date, or belong to a marl and greensand found in the western 

 district of Tennessee, probably a portion of the greensand and other 

 members of the cretaceous group. A general idea of the geological 

 formations of the whole tract may be obtained from the annexed 

 diagram. 



General Section across the Western States. 

 3 5 3 



m^mm 



5. Diluvium. 



4. Marl and greensand, probably cretaceous. 



3. Bituminous coal formation. 



2. Carboniferous limestone of Europe. 



1. Probable equivalents of the Silurian rocks. 



I now proceed to supply a ie\^ details respecting the above divi- 

 sions (except the diluvium), showing the lithological character of 

 each, together with its thickness, range, extent and bearings, its 

 organic remains, geological equivalents and mineral contents. 



The formations west of the Tennessee river occupy but a small 

 corner of the tract under consideration, and may be dismissed with 

 a few brief remarks, and the more so since I have had but limited 

 opportunities of examining them in person. 



* An abstract of this paper was given in the Proceedings of the Geological 

 Society, vol. iv. p. 1. The greater part of the memoir is now printed from the 

 author's MS. and accompanied by his Map (Plate XIX.), in order satisfactorily to 

 establish the claim of Dr. Owen to be considered the original discoverer of many 

 important points in the geology of the North-Western States of North America. 



