600 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



feet. All of these beds have a starchlike fracture where fresh 

 faces are seen, but crumble to a marly texture on exposure. 



In the lower part of the ravine the upper red shale, or marl, 

 is overlain by residual Coal Measures material and drift. Per- 

 haps two hundred yards up the ravine twenty feet of Coal jNIeas- 

 ures shales are exposed along the hillside. They are gray and 

 fine textured below but near the top contain characteristic iron- 

 stones, concretions and coaly streaks and other matter. This up- 

 per part is probably largely residual. The beds are exposed for 

 two hundred yards or more up the ravine from their first definite 

 outcrop. There are in places some traces of the bright colors 

 w'hich are so noticeaWe in the pit of the Fort Dodge Brick and 

 Tile Company across the river. 



On the north bank of Lizard creek, about one-fourth mile 

 above the creek mouth, is a long-abandoned pit of the Fort Dodge 

 Clay Works. It shows beneath thirty feet of drift a series of iso- 

 lated blocks of gypsum about four feet thick. The gypsum lies 

 directly on a black -clay shale, fissile and tough, which by dig- 

 ging may be exposed for a thickness of seven feet. Thence there 

 is a gap of six feet, although at this level there are scattered 

 about some ironstone nodules. Below this gap are twenty-five 

 feet of red and yellow and green non-fissile shales with a starch- 

 like fracture. These lie on gray and green shales which have 

 harder fossiliferous limy bands at the top an 1 near the middle. 

 These shales are twenty feet thick and lie on heavy bedded sand- 

 stone and limestone ledges which rise ten feet above the water. 



The red and green marly shales are exposed at several other 

 places immediately upstream from this old pit, but at most of 

 these localities they seem to be barren of fossils. At the second 

 cutting along the Illinois Central railway west of the river, aibout 

 half a mile west of the yard limits, there are exposed about 

 twenty feet of gray-,green clay shales which have oxidized to yel- 

 low and red at the top. Near the middle of the exposure there 

 are one or more streaks of nodular gray limestone which is very 

 fossiliferous, while the body of shale is very sparingly or not at 

 all fossil bearing. This seems to be the exposure described by 

 Doctor Wilder on page 78 of his report. Opposite this cut on 

 the south bank of the creek and below the railroad grade there is 

 a poor exposure of the gray and gi*een shales with the fossilifer- 

 ous limy bands. Most of the fossils here are brachiopods. Below 

 the level of these shales are red and green shales in alternating 



