PROCEEDINGS 



OF 



THE GEOLOGICAL SOCIETY OF LONDON. 



Vol. IV. Part I. 1842—1843. No. 92. 



Nov. 2. — Josiah Rees, Esq., was elected a Fellow of this Society. 



A paper was read, " On the Geology of the Western States of 

 North America." By David Dale Owen, M.D., of Indiana. 



The remarks of the author relate chiefly to that part of the west- 

 ern states Watered by the rivers Ohio, Wabash, Illinois, Rock, Wis- 

 consin, Cumberland, and Tennessee, lying between 35° and 43° of 

 north latitude, and 81° and 91° of west longitiide. It includes the 

 States of Illinois, Indiana, Ohio, Kentucky, Tennessee, and the Du- 

 buque aiad Mineral Point districts of the territories of Jowa and 

 Wisconsin. The observations recorded are the results of numerous 

 excursions in those provinces, commenced in the year 1834, and 

 continued to the present time by Dr. Owen, sometimes alone, at 

 others accompanied by Dr. Troost and Dr. Locke, the state geologists 

 respectively of Tennessee and Ohio. Though the territory under 

 consideration occupies an area of about half a million of square miles, 

 its geological features are remarkably uniform. With a few partial 

 exceptions its formations belong to the eras of the bituminous coal, 

 the mountain limestone of Europe, and the Silurian rocks of Mur- 

 chison. The exceptions are the superficial deposits which occasion- 

 ally cover these up from view, over considerable districts, and which 

 themselves must be referred to the age of the gigantic mammalia and 

 formations of a stUl more recent date ; together with a marl and 

 greensand in the v^^estern district of Tennessee, corresponding jsro- 

 bably to the greensand and other members of the cretaceous group. 



Of the tract described, the formations west of the Tennessee river 

 occupy but a small corner, and the author has had but limited op- 

 portunities of examining them in person. The upper part of this 

 group is an argillaceous marl of a light grey colour ; the lower (of 

 unascertained thickness) a greenish sandy marl. In no instance, as 

 far as known to the author, has either the greensand or marl been 

 discovered east of the Tennessee river. But it exists, according to 

 Dr. Troost, under the superficial soil in most of the countries west 

 of that river, extending probably west and south, into the states of 

 Missisippi and Alabama, Both the marl and greensand are rich in 

 fossils. In the former the most characteristic shell is the Exogyra. 

 Though it is evident, from the character of the fossils imbedded in 

 the marl and greensand beds, that these belong to the cretaceous 



VOL, IV, PART I. B 



