THE bowldp:ry dkift. 533 



uplift is another area of Silurian rocks extending along the northeastern 

 border of the state near the Mississippi. These are separated from the 

 Ozark uplift by the Alton fault. These also are overlain by Devonian 

 and Lower Carboniferous rocks dipping to the north and east. Surround- 

 ing these slightly elevated areas are the more horizontal Carboniferous 

 formations almost undisturbed from their original deposition in the sea. 

 The erosion of these formations, before the deposition of the Pleisto- 

 cene brought out certain topographic features. By the removal of the 

 softer shales and sandstones the firmer limestone areas were left as ridges, 

 the more notable of which are found in the western part of the state 

 and have a prevalent northeast trend. One crosses the Missouri near 

 Lexington, another at Independence, another, less elevated, crosses a 

 little west of Leavenworth, and a fourth near the mouth of the Nodaway. 



THE B WL DER Y DRIFT. 



Its Character. — The character of this dejDOsit, being of secondary im- 

 portance to our purpose, we shall but briefly describe it. It presents 

 the usual features of till or unstratified pebbly clay, and shows the usual 

 bluish appearance where it occurs to considerable depth. It nowhere 

 presents the gravelly and very stony character which it sometimes dis- 

 plays farther north. It is rarely more than forty feet in thickness and 

 more frequently is less than five, and over considerable areas consists 

 simply of a sprinkling of northern pebbles. It contains numerous crys- 

 talline pebbles and bowlders Avhich are frequently striated. The upper 

 portion becomes gradually less pebbly and acquires more of a reddish 

 color. This is more noticeable toward the west. Below it often passes 

 insensibly into an accumulation of local bowldery clay in which the 

 nodules of chert and limestone abound. Above it passes abruptly into 

 the loamy clay, which will be described further on. So far as yet dis- 

 covered, it shows no basins or knobs which so commonly occur in glaci- 

 ated regions; but, on the other hand, its surface is very even wherever 

 it is clearly undisturbed. From erosion of the country in the vicinity of 

 streams and valleys this formation has been creeping and slipping, losing 

 in great degree this horizontal position. Masses of it have in a few cases 

 even descended to the level of the present streams. It nowhere presents 

 beds of gravel or sand. In fact they are sought for almost in vain 

 through northern ^Missouri, except in the vicinity of present streams and 

 at low levels, and even in such localities are found l)ut sparingly. The 

 drift is most thickly deposited in the northwestern corner of the state, ex~ 

 tending as far south as Saint Joseph, and also along the divide between 

 the Chariton and the streams flowing into the Mississippi. It should be 

 remarked in this connection that the extreme northern part of the state 



