H. F. Bain — Limestone at Bethany, Missouri. 435 



Not far from here is the mouth of the stream which is just 

 above the falls of Big Creek. The rock forming the falls lies 

 probably 6 to 8 feet below the base of the limestone just 

 described. It is about 20 feet thick, the upper 18 feet 

 being made up of a coarse but firmly cemented limestone 

 breccia. It is marked by long dark streaks which suggest 

 corals but which fail to show structure. The only fossil col- 

 lected from it was Productus cor a. Below the breccia is about 

 two feet of fine-grained gray limestone, carrying large well- 

 formed Spirifer earner atus m with Productus cora. The brec- 

 ciated character of the limestone and the absence of marked 

 sedimentation plains has given under water action rounded forms 

 and knob and pot hole surfaces. 



The general sequence found here, with the four bodies of 

 limestone separated by shales, is the same as has already been 

 found in central Iowa. The exposures in the latter region 

 were first studied by White* and have been more recently 

 reviewed by the present survey, f In many of the minuter 

 details even, there is a close correspondence between the 

 Bethany section and that of Madison and adjacent counties. 

 The latter may be summarized as follows : 



Feet. 



8. Limestone, thick and thin-bedded, characterized by a 

 particular abundance of Fusidina cylindrical and 

 hence called the Fusulina limestone ._ 15-30 



7. Shales, predominantly dark-colored and argillaceous, 

 containing several thin bands of bituminous limestone 

 which are usually quite fossiliferous. About midway 

 of the shales is a horizon which is particularly fossil- 

 iferous. The more usual forms, including Athyris, 

 Productus and Spirifer, occur in great abundance and 

 perfection. With these forms are vast numbers of 

 Derby a crassa with Myalina subquadrata, Myalina 

 kansase?isis, Myalina swallowi, Aviculopecten occiden- 

 talism Productus nebrascensis, etc. Not far above this 

 horizon is usually a thin band of limestone literally 

 made up of Chonetes verneulianus. The whole thick- 

 ness of shale is 10-20 



6. Limestone earthy, magnesian, easily disintegrating above 



to medium grained coarse-bedded quarry rock below . . 10-20 



5. Shale, usually dark and including a black bituminous 



horizon _ -. 8-12 



4. Limestone, well shown near Karlham and hence called 

 the Earlham limestone. It carries an abundant fauna 

 which will be noted later 20 



* First and Second Ann. Repts. State Geol., pp. 71-72, 1868; Geol. Iowa, vol. 

 i, pp. 245-250, 1870. 



f Trans. Iowa Acad. Sci., vol. i, pt. iii, p. 144, 1895; Iowa Geol. Surv., vol. 

 iii, p. 137, 1895; ibid., vol. vii, pp. 446-451, pp. 491-539, 1897. 



