64 Proceedings of Indiana Academy of Science 



thickness of sandstone has been frequently mentioned by Ashley* and 

 others, with the idea that it represents a region of embayment and filling 

 in of Post-Allegheny sandstone — probably Merom — in the Coal III hori- 

 zon. Logan, however, assisted by the writer and others, traced smut 

 bands corresponding in elevation to Coal III and Ilia across the entire 

 surface of the cliff. This would indicate, of course, merely an area of 

 non-deposition of Coal III. 



A careful study of the maps in the illustrations will show an 

 irregularity in the South Prong of Little Raccoon Creek in the exti'eme 

 northeastern part of this district. My data would indicate that in pre- 

 glacial times this small stream drained directly into Troutman's Branch 

 and thence into Big Raccoon Creek. More well drillings are necessary, 

 however, to establish this absolutely. 



The middle course of Big Raccoon Creek is blocked by a very 

 definite butte near Mansfield, forming a cul-de-sac which has been 

 studied and described by Dryer.' The indications here are that the 

 Raccoon was a large tributaiy of the Wabash in preglacial times — "com- 

 parable only to the present day White River". 



These problems are interesting and woi-th further attention, but 

 cannot be discussed more fully here. The most important physiographic 

 problem of the region may be briefly stated as follows: 



Why does Raccoon Creek, flowing noi-mally in a southwesterly direc- 

 tion (until it is within 12 miles of the Wabash), forsake its wide valley, 

 which continues to the Wabash, and flow north for ten miles through a 

 narrow valley which has been carved in bed rock? 



We will attempt to answer this question. 



Lower Raccoon Creek. — In its lower course Raccoon Cieek flows 

 through the shales and sandstones of the coal measures. From Mans- 

 field it flows in a general southwesterly direction to the range line. The 

 valley is regular — averaging about one-half a mile wide with bluffs 

 60 to 80 feet high. Just south of Bridgeton the valley widens and there 

 is a pronounced terrace sloping gently from the bluffs to the valley 

 level but very flat nearest the stream. It averages about 540 feet eleva- 

 tion — 20 feet above the flood plain. The stream below Bridgeton has 

 many meanders and is constantly changing its course. This was espe- 

 cially true this spring (1922) after the heavy rains. 



South of the range line the valley continues to widen to a width 

 of two or three miles and merges with the valley of the Wabash just 

 south of Atherton. In this lower course the prairie level is reduced 

 and the valley sides are cut down to a much .smoother slope. The divide 

 between Raccoon Creek and Otter Creek below Rosedale is composed of 

 wind driven sand. There are a great many dunes stretching across 

 the valley in sections 9 and 16 of T 13 N, R 8 W. These dunes are 

 only 15 to 20 feet high but are persistent throughout the valley. All 

 along the valley there is a great abundance of sand and the merging 

 of the Raccoon and the Waba.sh valleys gives an excellent opportunity 

 for action by the west and southwest winds. 



•• Ashley, G. H., "The Coal Deposits of Indiana". Ind. Dopt. Geol., 23d Ann. Rcpt.. 

 1898, p. 300. 



= Dryer, C. R., "Wabash Studies", Ind. Acad. Sci., 1921, pp. 199-212. 



