AND COAL - MEASURES 



OF IOWA. 



109 



Passing from Farmington to Bonaparte, there is a rapid rise of the strata. Al- 

 ready, at Dam No. 4, the cellular magnesian limestone (&') appears above the 

 water-level; and, in the quarries below Bonaparte, the shell-beds (e'), charged 

 with small Spirifer striatus, are found from fifteen to twenty feet above the water- 

 level ; while at twenty-two to twenty-three feet numerous elliptical stems of Platy- 

 crinus, such as occur on the Mississippi, at the Keokuk Rapids, present themselves. 

 These are associated also with the same species of Cyathophylhim, Ancella, and 

 Gorgonia, that characterize the rocks at the last-mentioned locality. 



Just below Bentonsport, the different members of the lower series of carboni- 

 ferous limestones rise to more than 80 feet above the river ; the geodiferous beds 

 (a') of the upper series only capping the tops of the hills under the sub-soil. 



The strata near the middle of this section (No. 11, D) are charged with Orthis 

 umbraculum, while Archimedes and Spirifers are most abundant in the upper 

 ledges. 



At fifteen feet from the base of the section, a chert^bed, eighteen inches thick, 

 separates the Orthis beds from white, crystalline, encrinital limestone (containing 

 Spirifer striatus) lying beneath. 



At several localities in Van Buren County, four or five miles from Bentonsport, 

 in Township 69 north, Ranges 8 and 9, beds of coal have been discovered, varying 

 in thickness from twenty inches to two feet. That which was esteemed the best 

 by the blacksmiths, in 1849, was the bed owned by a Mr. Jackson, and the coal 

 procured on the west side of the waters of Bear Creek, owned by Messrs. Davis, 

 Thomas, Leech, and Christian. 



At the quarry, one mile above Bentonsport, on Section 33 or 34, Township 69 

 north, Range 9 west, a gravelly sandstone is found, like that in Slaughter's Branch, 

 at an elevation of about seventy feet, underlaid by chert and marly beds. The 

 magnesian quarry rock is also seen here at a little lower level, with a band of 

 argillaceous rock (that has the appearance of hydraulic cement rock) intervening 

 between it and the marly limestones. Three miles above this quarry, the gravelly 

 sandstone is only thirty-three feet above the water-level, and separated from a 

 fragmentary limestone by eighteen inches of marlite. At two separate locations, 

 below Keosauqua, one on the west, and the other on the east side of the Des 

 Moines, the cellular magnesian limestone is twenty to twenty-five feet above the 

 river, overlaid by concretionary limestone ; as may be seen by inspecting Section 

 No. 12, D. 



At Gillis's coal-bank, on the east half of the southwest quarter of Section 32, 

 Township 69 north, Range 9 west, about two miles below Keosauqua, these same 

 beds are seen, at a little lower level ; the pebbly sandstone being near the water- 

 level. Over the upper concretionary limestone are ferruginous clays, and on these 

 rests a coal-seam, eighteen inches in thickness, as shown in Section No. 13, D. 

 This seems to be the lowest coal-bed in the Des Moines Valley, and lies about 

 twenty feet above the concretionary limestone /'. 



Beds of coal have been observed at various localities in the vicinity of Keosauqua. 

 The best, however, is said to be obtained between the Des Moines and Skunk 

 Rivers, in the neighbourhood of Fairfield, on the waters of Walnut and Cedar 



