520 PROCEEDINGS OF THE ROCHESTER MEETING 



Knobstone to the overlying oolitic limestone. It is characterized by the abundant 

 crinoidal remains, the crystalline texture, and the geodes occurring in it. The 

 geodes are especially abundant in the central part of the area. There is generally 

 no sharp line between the Harrodsburg and the underlying Knobstone, but the 

 line separating it from the overlying oolitic limestone is well marked. 



The third division includes the famous Bedford oolitic limestone, one of the 

 most widely known building stones in the United States. It reaches its greatest 

 commercial importance in the central portion of the area in Lawrence and Monroe 

 counties around Bedford and Bloomington as centers, where it forms a bed twenty 

 to one hundred feet thick and is of quite uniform texture and structure. In the 

 northern extension it loses the massive structure, the bedding planes become 

 more numerous, and in many places the stone is more coarsely crystalline. It is 

 quite fossiliferous in many places. It is named from Bedford, the county seat of 

 Lawrence county, and belongs to the Saint Louis stage of the Mississippi Valley 

 deposits. 



The Mitchell limestone, named from Mitchell, in Lawrence county, consists of a 

 compact blue to drab-colored limestone containing locally much chert. The 

 chert occurs in nodular masses and irregular layers, in some places replacing a 

 large part of the limestone. Some of the layers have such a smooth, even texture 

 as to resemble lithographic stone. It is characterized topographically by the 

 numerous sink-holes and caves. It contains a great many large caves, and the 

 surface, dotted with sink-holes, shows its widespread cavernous character, which 

 is further indicated by the numerous " lost rivers," sinking streams, and large 

 springs. It is used in large quantities for burning lime and in limited quantities 

 as building stone, flagstone, and road metal. 



The Huron group, known in some of the older reports as the Chester, is in 

 some measure a transition bed between the underlying limestone and the overlying 

 sandstone. It consists of alternating beds of sandstone and limestone. In Orange 

 county there are generally three limestones and two sandstones, but farther north 

 the number and character of the layers are subject to local changes, and in places 

 shales replace the sandstone wholly or in part. There are small local deposits of 

 coal in the shale. The limestones are more coarsely crystalline than the under- 

 lying Mitchell. One of the beds frequently has a reddish tinge, and in many 

 places the limestone is in part oolitic, but differs from the Bedford oolitic lime- 

 stone in being a true concretionary oolite. 



The calcareous beds thin out to the northward along the outcrop, but not uni- 

 formly. The Mitchell is more persistent than either the underlying Bedford or 

 the overlying Huron. The Bedford loses its massive character and its chief 

 value as a building stone in southern Owen county, but extends through Owen 

 and Putnam into southern Montgomery county. The Huron thins out rapidly 

 in Owen county and does not appear north of the Big Four railroad in Putnam 

 county, except possibly in one locality. The most northern outcrop of the lime- 

 stones is in southern Montgomery county near Waveland. North of this point the 

 massive carboniferous (Mansfield) sandstone rests conformably on the Knobstones, 

 with all the limestones lacking, except a very crinoidal one, which occurs at a 

 number of localities in Montgomery county, and which is probably the chrono- 

 logical equivalent of the Harrodsburg limestone. There is quite a pronounced un- 

 conformity between the base of the Coal Measures and the Lower Carboniferous, 

 especially in the northern area, as shown (1) by the outlyers of the Coal Measures 



