44 A UG. F. FOERSTE 



about fifty-six feet, and is underlaid by the richly fossiliferous, 

 more clayey layers, containing Platystrophia lynx. It also occurs 

 up the valley along the railroad south of Centreville, To this 

 cross-bedded, nearly unfossiliferous, Ordovician limestone the 

 name "Swan creek limestone" is here given. Judging from the 

 exposures at Swan Bluff and at the J. M. Gardner locality, it is 

 of Lorraine age, probably below the Dinorthis retrorsa horizon. 



At the quarry, a sixth of a mile up the hollow, east of the 

 home of J. D. Dean, this cross-bedded limestone has disinte- 

 grated into a brownish mass which has been quarried as brown 

 phosphate. The cross-bedded limestone which occurs at Clifton, 

 and which has there been identified as Richmond, has also disin- 

 tegrated into a brown phosphate rock immediately below the old 

 cement mill at the southwestern end of the town. It appears, 

 therefore, that waters sufficiently turbulent to produce cross- 

 bedding were present during the deposition of both the upper 

 Lorraine and of the lower part of the Richmond in western 

 Tennessee. The Leipers creek bed is often cross-bedded, as 

 well as coarse-grained. Between the cross-bedded Swan creek 

 limestone and the coarse-grained Leipers creek limestone, a thin 

 section of clayey rock, apparently of Lorraine age, intervenes in 

 places. This is probably the position of the clayey rock at the 

 base of the section at Newsom. 



D. CONCLUSIONS. 



According to the preceding observations, the Ordovician 

 exposures in the valleys of the Tennessee river, the Buffalo river. 

 Swan creek, Leipers creek, and South Harpeth creek suggest the 

 following lithologic succession, in descending order : 



Mannie shale. 



Richmond -, t • i i- 



\ Leipers creek hmestone. 



(^Warren hmestone ; clay rock at Newsom. 



/-• ^- „„,.• I Swan creek limestone. 



Cmcmnati t - t,- i i r -i-r t • ,• • , 



^ ^, ^ -< Lorrame ^ Richly rossilirerous Lorraine limestone in the 



Vjrroup. -' r 1 1- T • • 



' eastern part of the area studied, containing 

 Platystrophia lynx. 



Utica \ Saltillo limestone. 



The Lorraine appears to become thinner west of the Cincin- 

 nati anticline, so as to be represented by thinner sections or so 



