358 T. E. SAVAGE ALEXANDRIAN SERIES IN MISSOURI AND ILLINOIS 



2 to 4 inches thick. Thin lenses of hard calcareous shale occur between 

 the layers of limestone; both the limestone and the shaly partings in 

 places contain numerous fossils. The total thickness of the formation is 

 35 to 40 feet. 



Detailed section. — A representative section of the Girardeau limestone, 

 exposed in the east bank of Mississippi Biver, 2% miles south of Thebes, 

 Illinois, is given below, beginning with (1) at the bottom: 



Section of Strata 2% Miles South of Thebes 



Feet In. 

 &-5. Sexton Creek (Brassfield) limestone. 



5. Red or pink mottled, fine-grained, brittle limestone, in layers 8 to 



36 inches thick, containing many fossils 8 10 



4. Light gray, 'rather fine-grained limestone, with blotches of green 

 shaly material and many nodules of chert ; containing Strick- 



landinia triplesiana and Triplecia ortoni var 1 9 



3. Chert bands, 2 to 4 inches thick, separated by 2- to 3-inch layers 



of hard, impure limestone, without fossils 5 6 



A break in sedimentation. 

 1-2. Girardeau limestone. 



2. Dark colored, fine-grained, hard, brittle limestone, breaking with 



conchoidal fracture, similar in all respects to number 1 15 



1 . Dark colored, fine-grained, hard, brittle limestone in layers 2 to 4 

 inches thick, separated by thin partings of calcareous shale, 

 and furnishing the fossils listed below, 18 



In the foregoing section the two lower members represent the Girardeai 

 limestone in its typical development, having at this place a thickness of 

 33 feet. The succeeding strata, members 3 to 5, inclusive, belong to the 

 Sexton Creek (Brassfield) limestone, the two formations being separated 

 by a sedimentary hiatus. * The Edgewood strata which, north of Thebes, 

 appear below the Sexton Creek limestone, are not present in this locality. 



The species of fossils obtained from the Girardeau limestone are listed 

 below : 



Fossils from the Girardeau Limestone in Illinois and Missouri 21 



Archceocrimi s sp. Schuchertella missouriensis (Shu- 



Ptychocrinus splendens (S. A. Miller) mard) 



Tanaocrinus cf. typus W. and Sp. Comulites incurvus (Shumard) 



A 7 ematopora alternata Ulrich Comulites tenuistriata (Meek and 



~N ematopora dclicatula Ulrich Worthen) 



Nematopora fragilis Ulrich Conradella sp. 



Nematopora retrorsa Ulrich Cyclonema concellata ? Hall 



21 The species of fossils listed from the Girardeau limestone and the Edgewood forms 

 tion are figured and described in Bulletin No. 20 of the Illinois State Geological Survt 

 Reports. 



