518 T. E. Savage — Ordovician and Silurian Formations. 



coarsely granular limestone, four feet in thickness, which is 

 locally oolitic in the upper part. 



The dark shalemember furnished the fossils Clorinda sp., 

 Pqfinesquina mesacosta, coarsely plicate shells of Schuchertella 

 subjplanus, and Dalmanites dance. The massive upper layer 

 yielded Clathrodictyon vesiculosum, Atrypa putilla, Clorinda 

 sp., Leptama rhomboidalis, Phynchotreta thebesensis, Schu- 

 chertella subpla?ius, Spirifer cf. sulcatus, Whitfieldella 

 billingsana, Pterinea thebese?isis, Dalmanites sp., Proetus 

 determinants and Lichas clintonensis. The exposure in the 

 abandoned quarry, near Gale, furnished the following addi- 

 tional species : Calapmcia sp., Lyellia thebesensis, Atrypa 

 marginalis, Plectambonites transversalis and Phynchonella 

 janea. 



The Post-Edgewood Unconformity. 



A break in sedimentation between the Edgewood and the 

 succeeding deposits is shown at the abandoned quarry, near 

 Gale, where the Edgewood limestone is separated from the 

 basal portion of the Sexton Creek beds by a two-inch band of 

 red, residual clay. 



The Niagaran (Clinton) Series. 



Sexton Creek Limestone. 



The name Sexton Creek limestone is here proposed for 

 Silurian strata in this region, which represent some portion 

 of the Clinton time. The name is taken from Sexton creek, 

 one and one-half miles north of Gale, in Alexander county, 

 along which stream these beds are well exposed. In my 

 paper of 1908 these beds are referred to as 4a, 4b, and 4c. 



Ulrich* has proposed the name Bainbridge limestone for 

 the Silurian strata appearing in the river bluffs for some miles 

 above and below Bainbridge, Missouri. He states that it is 

 nearly the equivalent of the Clifton limestone of Tennessee 

 (later than Clinton), and that it also occurs in the vicinity of 

 Thebes, Illinois. The present studies have shown that the 

 Silurian strata in the vicinity of Thebes are of Clinton age, 

 or earlier, and hence cannot be correlated with beds in 

 Missouri 'representing the horizon of the Clifton limestone in 

 Tennessee. ♦ 



The lower part of the Sexton Creek formation consists of 

 hard, gray limestone, in layers four to eight inches thick, which 

 are separated one from another by two- to four-inch bands of 

 *Ulrich : Mo. Bur. Geol. and Mines, vol. ii, 2d series, p, 110, 1904. 



