T. E. Savage — Ordovician and Silurian Formations. 511 



this area the embayment was bordered by the Ozarkian land 

 mass. On account of the proximity of the shore, the sea was 

 generally shallow, so that even minor movements were regis- 

 tered in the deposits. As a consequence of these conditions 

 there occur here a surprising number of breaks in sedimenta- 

 tion, recording a remarkable number of oscillations of level 

 during the Ordovician and Silurian periods ; and during the 

 interval, generally represented by land conditions, between the 

 deposition of the uppermost Richmond beds and the basal 

 deposits of the Clinton. 



Succession of Strata. 

 The relations of the various formations representing the 

 Ordovician and the Silurian Systems in this region are shown 

 in tabular form below : 



a 



c3 



Clinton 



Sexton Creek limestone, 16-70 feet 



3 



Alexandrian 



Edgewood limestone, 0-12*5 feet 



m 



Girardeau limestone, 18-33 feet 



S 



Cincinnatian 



Orchard Creek shale, 17-22 feet 





Mohawkian 



Thebes sandstone, 75 feet 



o 



Sh 



Fern vale limestone, 0-3*5 feet 



o 



Kimmswick limestone, 70-82 feet 



Ordovician System — Mohawkian Series. 



Kimmswick Limestone. 



The name Kimmswick was applied by CTlrich* to a bed of 

 gray, thick-bedded, subcrystalline limestone exposed in the 

 vicinity of Kimmswick, in Jefferson county, Missouri. These 

 beds correspond in their lithology and fauna with those appear- 

 ing in the railroad cut and river bank a short distance south of 

 Thebes, which Worthen referred to the Trenton. The above 

 name is retained for these strata in southwest Illinois which 

 contain the fossils Receptaculites oweni, Dalmanella testudi- 

 naria rogata, Blatystrophia biforata, Rafinesguina alternata, 

 ParoMrophia hemiplicata, Strophomena trentonensis, Rhyn- 

 chotrema incequivalve, Zygospira recurvirostra, Bronteus 

 lunatics, Bumastus trentonensis, lllmnus americanus, Isotelus 

 cf. maximus, Platymetopus cucullus and Remopleurides 

 striatulus. 



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



