CALLAWAY LIMESTONE. 31 



W., Callaway outcrops in patches. Its maximum thickness is 

 about 40 feet, and occurs south of Shiel in section 20. In this 

 section its contact with the Mineola is exposed on the roadside. 

 It is a sandstone or a sandy limestone at the bottom and con- 

 sists of alternating beds of sandstone and limestone. Twenty 

 to thirty feet from the bottom a limestone bed is made up 

 largely of Acervularia davidsoni Edwards and Haime and Favo- 

 sites sp. undet. A sandy bed about ten feet from the bottom 

 contains Spirifer euryteines Owen, Chonophyllum ellipticum Hall 

 and Whitfield, and Atrypa reticularis (Linnaeus) in abundance. 

 The fossils are all silicified. 



In the eastern part of section 29 about 80 feet of Devonian 

 is exposed. The Callaway rests on the Mineola, and the two 

 formations are of about equal thickness. 



An unusual exposure occurs in section 33, about one mile 

 south of the exposure in section 29. The Mineola consists of 

 sharply truncated limestone and sandstone beds. The lime- 

 stone seems to have been pushed over the sandstone when the 

 folding took place. See Plate D, fig. b. 



Exposures in Pike County.— In southeastern Pike County, 

 near Paynesville, Rowley has mapped several patches of Devon- 

 ian that seem to be Callaway though the identification is un- 

 certain. They may be Mineola. Spirifer euryteines Owen is 

 common in the beds. The writer has not studied the outcrops. 



Exposures in Lincoln County. — In a belt extending from 

 Winfield northwestward to near Briscoe, Devonian occurs in 

 small outliers and most of it seems to be Callaway. It outcrops 

 in the bluffs of the Mississippi west of the railroad about one 

 mile north of Winfield and its outcrops were examined in four 

 other places between there and Briscoe. It is absent more 

 frequently than present in this area. The rocks have a mono- 

 clinal dip ranging from 25 degrees to 80 degrees and a thick 

 section is exposed along the belt which has been truncated by 

 erosion. In most places basal Mississippian rests on the Maquo- 

 keta shale of the Upper Ordovician but here and there the 

 Devonian, ranging up to 20 feet thick, comes in between. 



The best section studied is in Sec. 34, T. 50 N., R. 1 E, on 

 Bobs Creek. At this place it rests disconformably on the Maquo- 

 keta shale and is overlain disconformably by the Grassy Creek 

 shale of basal Mississippian, 



