536 J. E. TODD — PLEISTOCENP: problems in MISSOURI. 



Missouri, it is of a lightish and light gray complexion. It very closely 

 resembles, if it is not identical with, the white clays described b}^ Mr 

 Leverett as found in Indiana and southern Illinois.* This variety re- 

 sembles the residuary clays quite common in sub -Carboniferous and 

 Silurian areas, and also a clay sometimes underlying the drift in north- 

 central Missouri. Mr McGee states that the formation which he calls 

 " upper till " in southeastern Iowa is the equivalent of the loess.f I have 

 not been able to distinguish his " upper till " from this gray loamy cla\^ 



The Limit of the Loess and associated Deposits. — One of the first things I 

 discovered in studying the loess at Kansas City, where it is finely devel- 

 oped, was the fact that there is a higher loess and a lower loess. The 

 latter is the deep silt covering of a high terrace which rises 125 to 150 

 feet above the Missouri and is confined to its near vicinity. J The former 

 is that which caps the unmodified bowlder-clay where it occurs, and 

 covers in some form all the uplands north of the Missouri river, as well 

 as considerable areas to the south. The lower formation will be con- 

 sidered later, under the head of terraces. 



For several reasons, no less prominent in Missouri than elsewhere, it is 

 almost always difficult to determine the limits of the loess No beach 

 lines have been found. Topography and depth of deposit are in many 

 places the most obvious means of determining the margin. Not only 

 does the loess resemble the adjoining residuary clays and loams, but the 

 two are apparently intermingled. The loess-covered plain not only covers 

 northern Missouri, but all Iowa outside of the moraine and Nebraska' to 

 its northern boundary and as far west as Aurora, Nebraska, and Salina^ 

 Kansas. Its southern boundary in Missouri may be given as follows : 



Locality. How marked. ahovftea. 



Kansas City, Jackson county Character, depth and topoo;raphy . . 950 



South of Lake City, Jackson county. ... ^' " . . 925 



West and southwest of Sibley, Jackson 



county " .... " 



SoutliM^est of Lexington, Lafayette 



county •' " . . 918 



Near Mayview, Lafayette county " . . 890 



South of Mayview, Lafayette county *' ' . . ... 



Southwest of Brownsville, Saline county " . . 800 ? 



South of Hughesville, Pettis county ''.... " . . 850— 



Near Pilot Grove, Cooper county " . . 825±: 



Southeast of Billingsville, Cooper county ** . . 825± 



North of Prairie Home, Cooper county '* .... " . . 83 )zb 



Near Jamestown, Moniteau county " . . 850dz 



* Am. Geologist, vol. 10, p. 18. 



t Geology of Macon County, Trans. St. Louis Acad., vol. 5, p. 317. 



{(■f. R. E. Call, Crowley Ridge, Ark. Geol. Rep., vol. ii, 1889, p. 41, where he recognizes a later and 

 lower loess, though he does not find it in terrace form. 



