178 C. K. KEYES — A DEPOSITION AL MEASURE OF UNCONFORMITY 



sented in the several states occupied by this great coal field. As indi- 

 cating more clearly the various stratigraphic relationships, the sections 

 as given by the chief writers on the subject in each state have been 

 selected. In this way also the literature in general is more fully under- 

 stood in its bearing upon the special theme here presented. 



Number I is the general section of western Missouri, and includes the 

 t3^pical Missourian series** and the Des Moines t series as there repre- 

 sented. In its main features the arrangement holds good for Iowa,J 

 and also Kansas.§ The horizon of the Bethany limestone, the base of 

 the Missourian series, is indicated ; also the horizon of the Plattsmouth 

 limestone, for reasons hereafter mentioned. The top of the same series, 

 the Cottonwood limestone, is likewise a noteworthy horizon. 



In number II is given the section of southern Kansas, in accordance 

 with the observations of Adams and Haworth.|| Some of the terranes 

 ■are here thicker than farther north. 



What are called the Pawhuska (number III), the Sapula (number 

 IV), and the Poteau Mountain (number V) sections are those for north- 

 ern, central, and southeastern Indian territor}'' as generalized by Drake.^ 



Of the two Arkansas sections, the one for the western part of the state 

 (number VI) is that of Winslow, as published by Stevenson,** while the 

 more general section (number VII) is that of Branner.ft 



The course of these sections may be considered as a semi-circle ex- 

 tending around the western i)art of the northern Ozarks. It coincides 

 with the lowland belt flanking the great elevation between the Arkansas 

 and Missouri rivers. 



IOWA SECTION 



The details of the northern end of the general cross-section are to be 

 found in the reports of the Iowa Geological Survey. ;|:;|; The Iowa section 

 differs in no essential features from that given for Missouri. The sub- 

 divisions of the Des Moines series are perhaps not quite so well marked 

 as in southwest Missouri, and the lola limestone is missing, having 

 thinned out before reaching the northern boundary of the last-named 

 state. The formations, on the whole, are much thinner than farther 



* American Geologist, vol. xxiii, 1899, p. 298. 

 tProc. Iowa Acad. Sci., vol. iv, 1897, p. 22. 

 X American Geologist, vol. xxi, 1898, p. 346. 

 g Eng. and Mining Jour., vol. Ixi, 1898, p. 2r,'i. 

 II Univ. Geol. Survey Kansas, vol. iii, 1898, pi. i. 

 ^Proc. Amer. Philos. Soc, vol. xxxvi, 1898, p. :572. 

 ** Trans. New York Acad. Sci., vol. xiv, 1895, p. 51. 

 tt Am. Jour. Sci. (4), vol. ii, 1896, p. 235. 

 n Iowa Geol. Survey, vol. ii, 1890. 



