140 



ally oolitic, 6 to 21 feet ; (e) Upper sandstone, ferrugiuous, reddish brown 

 to white, laminated sandstone, 40 feet; (f) Upper limestone, grading from 

 limestone at the bottom to shale at the top, 25 feet thick.^ The limestones 

 of the Chester are not unlike those of the Mitchell and Salem (Oolitic) 

 formations. They are usually rather pure carbonate of lime, and hence 

 soluble, as in the case of the limestones already discussed. Springs often 

 occur at the base of the limestone beds. The sandstones are coarser 

 grained than those of the Knobstone formation, and are cross-bedded and 

 pervious, and conspicuously jointed, the joints often being widely opened 

 by weathering. Springs occur at the base of the sandstone strata, where 

 they rest on shale. The shales of the Chester formation vary from strongly 

 bituminous to argillaceous or even arenaceous. The bituminous bands are 

 very fine grained and impervious. The argillaceous shales are more per- 

 vious and grade into coarse grained pervious sandstones. 



The Mansfield sandstone, forming the basal member of the Coal Meas- 

 ures of Indiana, and resting unconformably on the Mississippian forma- 

 tions, is a ferruginous, soft cross-bedded, rather coarse grained, some- 

 times conglomeratic pervious rock. It varies greatly in thickness. Where 

 it is thick, as at Shoals, it produces a rugged topography, with cliffs and 

 pinnacles. The deejily weathered joints and honeycombed weathered sur- 

 faces give it a very characteristic appearance. Small springs abound in 

 the area of the Chester and Mansfield formations. 



The soil of the Chester-Mansfield region varies from red residual clay, 

 such as characterizes the limestone region, through sandy clay to almost 

 jiure yellow sand. In the more rugged portions of the region the soil is 

 thin and poor, and the vegetation scanty. Some of the worst gullying 

 seen in Indiana is to be found in this area. The rain water runs off very 

 rapidly, carrying with it quantities of sediment. Greene and Martin 

 Counties afford many excellent examples of this. 



From the standpoint of the water-supply engineer this region is to 

 be consideretl as intermediate in character between the Knobstone region 

 and the limestone region. It is topographically similar to the former, but 

 the greater permeability of the formations, and especially the presence of 

 beds of cavernous limestone, and the fact that the deeper valleys are 

 floored by the leaky Mitchell limestone, are all charactoristics connecting 



' Greene, F. C, The Huron Group in Western Monroe and Eastern Greene 

 Counties, Indiana. Pror. Ind. Acad. Sol. for 1910, p. 270. This paper contains a, 

 full dlsciis'^ion of tho rhfslpr formation of tbo aroa nndor discussion. 



