118 



CARBONIFEROUS LIMESTONES 



lower beds differ but little in colour from, the ordinary reddish-brown and yellow 

 sandstone of the country. On the left bank the ridges of sandstone attain the 

 height of eighty-five feet above high-water of the Des Moines. • The upper beds, 

 and those of the deepest red tint, are so soft as almost to crumble under the pressure 

 of the hand. Some of the brown sandstone, on the contrary, is hard enough to 

 strike fire with steel. There seems to be a northwesterly dip of the beds, of a few 

 degrees, but as it strikes back into the bluffs, it cannot well be observed. Some of 

 the strata are marked by cross-lines of deposition, others are banded with varie- 

 gated stripes of red and yellow. 



Though differing somewhat in colour, the sandstone of Red Rock occupies, in all 

 probability, the same geological horizon as that which forms Raven Cliff and Elk 

 Bluff. 



These cliffs of sandstone continue only for a short distance beyond Red Rock. 

 Near the mouth of Calhoun Creek, the base of the hills is composed chiefly of 

 argillaceous strata, enclosing a six-foot bed of sandstone, and an imperfect seam of 

 coal, together with crystals of selenite and bands of ironstone, in the order here 

 shoAvn : 



THICKNESS OF IiKDS. 



Feet. Inches. 



1. Bands of ironstone and crystals of selenite enclosed in shale, with a thin, 



imperfect seam of coal, ......(?) 



2. Light-gray and yellow sandstone, containing Stitpnaria, ... 6 



3. Shale, . . . . . . . . 2 £ to 3 



4. Coal, 16 



5. Fire-clay, containing Stigmaria; together with slaty clays, containing 



argillaceous oxide of iron, . . . . . 45 6 



Half to three-quarters of a mile higher up stream, the bed of sandstone, which 

 lies fifty feet above the river in the last section, is already within twelve feet of 

 the water-level. Here the eighteen-inch seam of coal can be seen underlying it, 

 reposing on fire-clay containing Stigmaria. The argillaceous shale over the sand- 

 stone contains much argillaceous oxide of iron, and includes one band of ironstone, 

 four to six inches in thickness, lying about five feet above the bed of laminated 

 sandstone. 



Two to three miles above this, in a ravine, about a quarter or half a mile from 

 the Slue, there is a wall of bituminous shale, lying in large, thinly-laminated 

 sheets. 



Near Bennington, the bluffs consist chiefly of soft, light-buff sandstones, which 

 were penetrated twenty-two feet in digging a well ; and a little above that place a 

 three-foot seam of coal is seen near high-water mark. Coal has also been found in 

 the bluffs opposite Bennington, which is preferred for blacksmiths' use to the bed 

 immediately on the river. At the foot of the bluffs, below the site of Perryville, 

 sandstone extends down to the water-level. This sandstone rises, up stream, and 

 discloses five feet of shale beneath it. A band of carbonate of iron, and a calca- 

 reous rock resembling hydraulic limestone, are associated with this shale, and 

 beneath the whole lies an eighteen-inch seam of coal, resting on marly clay. The 



