QUATERNARY FORMATIONS THE DRIFT. 225 



westward slope of the valley, and runs north, parallel to its axis, until 

 it crosses the Menomonee into Michigan. Its highest observed ele- 

 vation is about 200 feet, in the vicinity of Lake Winnebago. Its sec- 

 tion, as shown on Lake Michigan, may be seen on Plate YIII of this 

 volume, and its surface distribution on Plate IY of the accompanying 

 atlas. 



IY. UPPER RED CLAY. 



The description that has been given of the Lower Red Clay applies 

 almost completely to this deposit, the only grounds for separating 

 them being the intervention of the beach deposit which has just been 

 described. The similar character of the clay, the angularity of the 

 imbedded fragments of limestone, and their un weathered nature, the 

 high color of the clay, the large content of magnetite, are likewise 

 characteristic of this formation. It covers the northeastern corner of 

 Manitowoc county, the eastern portion of Kewaunee county and the 

 adjoining portion of Door county. It doubtless originally covered 

 the entire Green Bay peninsula and was apparantly swept away by the 

 action of the lake as it gradually retired. 



Its thickness is nowhere considerable. Along the lake shore where 

 it is best exposed, and possibly thickest, it rarely exceeds 20 feet. 



In Racine and Kenosha counties, there is a yellowish clay deposit 

 quite similar in most of its characteristics to the Red Clays, except 

 in its color and the more frequent presence of bowlders. In addition to 

 the evidence drawn from the nature of the deposit itself, the configur- 

 ation of the country indicates the modifying action of water. It 

 seems probable that this was more immediately connected with the 

 melting and retreat of the glacier than the formations above con- 

 sidered. 



Y. BEACH FORMATIONS C AND D, AND THE MODIFIED RED CLAY. 



Along the eastern border of Racine and Kenosha counties, extend- 

 ing on the average about one mile back from the lake shore, we find 

 at the surface a deposit of sand and gravel, with a varying but subor- 

 dinate admixture of clayey and marly material. The gravel is usually 

 fine and thoroughly waterworn, and is interstratitied with the sand 

 and occasionally with clay, and almost everywhere presents beautiful 

 examples of oblique lamination. It rarely exceeds twenty feet in 

 thickness, and on the average is about half that amount. At its base, 

 along the lake shore, numerous springs issue, the water being pre- 

 vented from descending farther by the impervious clay that lies below. 

 Wis. SUB. 15 



