602 IOWA ACADEMY OP SCIENCE Vol. XXV. 1918 



ravine joins the main valley- is an excellent example of how the 

 character of glacial drift may be influenced by the original ma- 

 terial. Here a bank twenty feet high is composed of dull red- 

 dish drift clay with numerous small pebbles. The red clay was 

 no doubt derived from the red Ste. Genevieve clay shales close by. 



The beds seen in these exposures are stated by Wilder on page 

 103 of his rejjort to belong- to the gypsum series. Keyes in his 

 report on the gypsum^ also referred these beds to the same series. 

 As stated above, however, because of their character and of their 

 association with the massive gray sandstone beneath them this 

 whole assemblage of shales is here placed in the Ste. Genevieve. 

 The underlying sandstone seems to be the same as the St. Louis 

 sandstone which is well exposed near the mouth of the Lizard and 

 at the dam on Des Moines river at Fort Dodge. 



In the lower one-half mile of South Lizard valley there are sev- 

 eral exposures of the red and green shales. Only one of these, the 

 southernmost, need be described here. This one shows beneath 

 twenty or thirty feet of till a body of red clay shale tw-elve feet 

 thick. Under it is eight feet of gray sandstone and below this 

 bed a green and red shale extends fifteen feet to water level. Some 

 of the shale near the base of this exposure is finely sandy. All 

 the other outcrops are similar in the character of the beds ex- 

 posed and it is noteworthy that none of the beds carry any fos- 

 sils. 



An interesting outcrop of St. Louis limestone may be seen at 

 the point of the ridge bounding the west wall of South Lizard 

 valley, and marking the junction of the two branches. Thirty 

 feet of limestone is exposed above water level and shows a steep 

 dip to the east, that is, downstream. One hundred feet upstream 

 there is present ten feet of green sandy marl grading up into 

 gray sandstone and underljdng the limestone. Below a gap of 

 six feet there is exposed above the water a two foot bed of lime- 

 stone. Two hundred yards downstream the red and green clay 

 shales overlie the concretionaiy upper 'beds of the St. Louis lime- 

 stone, just above stream level. Taken together this series of ex- 

 posures emphasizes the irregularity of the surface of the St. 

 Louis limestone. 



B. The fossils of the maris have been known for Avell over 

 half a century. As early as 1858, Worthen,^ in his report on the 



nowa Geol. Survey, Vol. Ill, d. 279. 



t^Geol. of Iowa. vol. I, pt. I, pp. 178, 179, 1858. 



