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Indiana University Studies 



next to the Beech Creek limestone in this respect in the 

 ''American Bottoms" region. It has a wall-Hke appearance 

 along the streams, whether it be next to the valleys or high 

 up the valley slopes. Since it is overlaid by shale it gives 

 rise to rather sharp local benches, often of considerable 

 breadth where erosion has removed the overlying material 

 down to its resistant top. These benches have been mistakenly 

 interpreted as local peneplains developed in the region where 

 the sandstone is to be found. They are seen prominently 

 above the abrupt slope produced by the sandstone where it 

 rises above the ''American Bottoms". To the west the benches 

 become considerably lower on account of the dip of the strata. 

 Such benches are conspicuously developed on the north side 

 of the "American Bottoms" in section 23. The streams of 

 the "American Bottoms" pass into cavern-like openings de- 

 veloped in this sandstone, owing to the undermining of the 

 sandstone by the weathering and solution of the underlying 

 limestone, and the corrasion by the inflowing v/aters. The 

 cave-like openings of these stream inlets are among the most 

 striking phenomena of the entire region (Figs. 5, 6, and 7). 

 On the ridges in the eastern part of the area, a number of 

 broad, fairly extensive sags are developed on the Cypress 

 sandstone between the gentle summits of the ridges. Ex- 

 amples of these are to be seen at Cincinnati and Tanner. 



GolcGuda Limestone and Shale, Overlying the Cypress 

 sandstone are about 20 feet of olive shales. This shale forma- 

 tion is seldom seen except beneath the overlying limestone, 

 where it is protected from erosion. It may be considered as 

 part of the Golconda limestone and shale unit. The Golconda 

 limestone is poorly developed in the "American Bottoms" 

 region. It usually consists of several ledges with intercalated 

 thin shale bands, especially at the top ; but occasionally the 

 shale between the layers makes up as much of the thickness 

 as the limestone. The Golconda limestone has been called 

 the Upper Huron limestone, or the "Third" limestone of In- 

 diana. The latter name refers to its position in the succes- 

 sion of limestones above the Mitchell limestone. Farther 

 south it has a characteristic thickness of 30 feet, with thin 

 shale members in the upper portion. It is a coarse, semi- 

 crystalline limestone, often beautifully oolitic, and contains 

 large numbers of crinoid stems, blastoids, and several species 



