MIDDLE AND UPPER ORDOVICIAN. 165 



In these systems there are included the Rome (MontevaUo) formation and the Conasauga 

 (Coosa) limestone, both of known Cambrian age; the overlying Knox dolomite, the lower part 

 of which is regarded as Cambrian and the upper part Ordovician, though the plane of division 

 between the Cambrian and Ordovician is unknown; and the Chickamauga (Pelham) limestone, 

 of known Ordovician age. 



The lowest Cambrian rocks exposed in this area are limestone and shale, possibly 1,000 to 

 1,500 feet thick, so far as can be judged from the width of outcrop in Opossum Valley. These 

 rocks have been designated the Conasauga limestone by the United States Geological Survey 

 and the Flatwoods or Coosa formation by the Alabama Geological Survey. They consist of 

 thin-bedded blue limestone interbedded with shale, which in some sections, as in the vicinity of 

 Bessemer, carries considerable chert in thin layers. This limestone is underlain by a mass of 

 shale of great thickness, which to the east is known as the Rome formation. Locally it has 

 been called the Montevallo shale. In this report it is called the Rome formation. 



The Kjiox dolomite includes the rocks between the Conasauga and the Chickame,uga 

 (Pelham) limestone. In the Birmingham region and other parts of Alabama the lower part of 

 the formation is almost free from chert, and on account of both this lithologic difference and its 

 economic importance it has been separated out as a member from the mass of the Kiiox and 

 named the Ketona dolomite member. The name Ketona is chosen because of the extensive 

 quarry in this member at Ketona. The Ketona dolomite overlies the Conasauga (Coosa) lime- 

 stone with apparent conformity and is 500 to 600 feet thick along Opossum Valley east of 

 Birmingham. It is a nearly pure dolomite, with but little chert. It is thick bedded, crystalline 

 in texture, and of prevailingly light gray color. From it is drawn most of the fluxing rock used 

 in the Birmingham furnaces. * * * 



The rest of the Knox dolomite, 2,700 to 2,800 feet thick, overlies the Ketona dolomite, 

 member conformably. It is composed of dolomite with chert layers, which ia places reach a 

 thickness of 10 feet or more. Possibly one-fourth of the formation is chert. 



Overlying the Knox dolomite unconformably is the Chickaniauga limestone, of Ordovician 

 age. It is the same as the Trenton or Pelham limestone of the Alabama Geological Survey. 

 In Birmingham Valley this is a thin-bedded bluish to dove-colored limestone ranging generally 

 from 200 to 500 feet thick. It has been used for flux to some extent. 



I- J 16-17. OHIO, KENTUCKY, AND TENNESSEE. 



The well-known areas of Ordovician strata exposed on the Cincinnati and 

 Nashville domes in Ohio, Kentucky, and Tennessee are mapped from the respective 

 State geologic maps. The terranes comprise the oldest sediments exposed, namely. 

 Middle Ordovician limestones of the Stones River group and others of Trenton age 

 and the overlying Cincinnatian series (Upper Ordovician), consisting of strata of 

 Utica, Lorraine, and Richmond age. They are thin limestones and shales, which 

 are inconstant in thickness and faunal content. 



In Ohio Orton *^° distinguished the following beds : 



Cincinnati group of southwestern OTiio. 



Feet. 



Lebanon beds - 293 



Cincinnati beds proper: 



Hill Quarry beds 125 



Eden shales 250 



River Quarry beds 50 



— 425 

 Point Pleasant beds 50 



The Point Pleasant formation was subsequently, by Winchell and Ulrich,***^ 

 shown to be of Trenton age and to be "terminated above with a heavy current- 

 formed crinoidal layer, which includes large pebbles and disturbed masses of the 



