72 J. A. UDDEN 



9 in the Sweetland Creek section, and the lower layers of these 

 beds may possibly all have been exposed above water at this 

 point before the railroad embankment was made. As these 

 lower layers aggregate about seven feet in thickness at other 

 places, it will be noticed that the extreme thickness of the whole 

 formation at this place is about forty-five feet. This is the 

 greatest thickness that has been seen anywhere in the county. 



Just above the wagon bridge which crosses Mad Creek near 

 the center of the northwest quarter of section 24 in Bloomington 

 township, some ledges equivalent to numbers 6, 7, 8 and 9, in the 

 Sweetland Creek section appear in the bank of a tributary from 

 the east. Again in the creek running east through the north 

 half of the northwest quarter of section 26 in the same township 

 some thin ledges of rock and some green shale corresponding to 

 numbers 3, 4, and 5 in Sweetland Creek come into view from 

 under some Coal Measure beds. 



Geographical distribution. — So far as known, the above places 

 include all the exposures of the Sweetland Creek beds in the 

 county. There is good reason to assume that they underlie 

 the Coal Measures in most of Muscatine, Bloomington, and 

 Sweetland townships, and that scattered outliers occupy the 

 same position in the east half of Montpelier township. In all 

 probability their outcrop in the river bluff is continuous from 

 Wyoming Hill to Muscatine, though mostly concealed by the 

 talus under the bluffs. 



General section. — The separate layers and ledges of the forma- 

 tion have a remarkably uniform development, varying but 

 slightly in different places. The basal layer, though only about 

 three inches in thickness, can always be recognized in its place, 

 and invariably contains the characteristic fish teeth. From six 

 inches to a foot above this layer there is a pyritiferous stony 

 seam from one-half to two inches in thickness, and this is readily 

 identified in all the creeks in Sweetland township where the lower 

 part of the section appears. The peculiar maze of green threads 

 which extend into the dark shale where this comes into contact 

 with green layers have been observed in almost every case where 





