118 THE CAMBRIAN AND ORDOVICIAN DEPOSITS OF MARYLAND 

 Formations of Stones River Group in the Type Area, Central Tennessee 



Fee 



Lebanon limestone, flaggy, dove and shaly limestone 120 



Ridley limestone, massive subgranular, often cherty limestone 80 



Pierce limestone, shaly limestone crowded with bryozoans 27 



Murfreesboro limestone, heavy bedded cherty limestone (base not ex- 

 posed) 125 



In the gorge of Kentucky Kiver at and above Highbridge, Kentucky, 

 which cuts through the oldest rocks to be seen in the state, the lower 

 200 feet of the bluffs are made by massive limestone strata representing 

 Lebanon and Ridley members of the Stones River. In the Appalachian 

 Valley, rocks corresponding in age, and also very closely in lithologic 

 character with the typical Stones River, outcrop in periodically inter- 

 rupted bands from Alabama to New York. In the valley of East Ten- 

 nessee, where they attain a maximum thickness of more than 1200 feet, 

 the lithologic facies and sequence that agrees best with the typical expres- 

 sion of the formation is confined almost entirely to the western side of 

 the valley. Here a twofold division may be recognized a lower division 

 of massive, mainly pure, dove limestone and an upper division of more 

 argillaceous strata. The limestones in northern Virginia, Maryland, and 

 Pennsylvania referred to the Stones River agree in all essential respects 

 with these representatives of the group in the south. Here, however, the 

 formation is divisible into three parts, of which the lower and upper 

 thirds are of solid, massive, dove limestone and the middle third of more 

 granular often cherty blue rock holding the fauna of which the large 

 gastropod Maclurites magnus is the most characteristic member. The 

 lower part is essentially equivalent to the Murfreesboro limestone, the 

 middle division to the Pierce and Ridley beds, and the upper third to the 

 Lebanon limestone of the type section. In the eastern half of the Appa- 

 lachian Valley in Virginia and Tennessee the Maclurites magnus fauna 

 occurs and attains its best development in a formation of argillaceous 

 limestone the Lenoir limestone. In this part of the valley the upper 

 member is not present, so that here the Lenoir lies at the top of the beds 

 that are strictly of the age of the Stones River. Beneath the Lenoir is a 

 massive dove limestone formation, the Mosheim limestone, which is either 



