560 



APPENDIX. 

 Section for Arkansas. 1 



Names of Formation! 



Thickness 

 in Feet. 



' Potea beds. 



> 



a 



Ph 



3500 



Productive beds. 



1800 



Barren beds. 



18480 



Discontinuity. 



Characteristics. 



Mainly shales and sandstones with some coal- 

 beds. 



Millstone grit. 



500 



Sandstones and conglomerates; friable to 

 hard; buff or brown, with occasional .scams 

 of limonite. 



Kessler limestone. 



3-15 



Thin-bedded. 



Coal-bearing shale. 60-90 



Shale, in places highly fossiliferous; thin coal- 

 seams. 



Pentremital lime- 

 stone. 



0-90 



Impure, dark-colored, and loose-textured; 

 sometimes interbedded with sandstone. 



Washington sand- 40-7^ 

 stone and shale. 



Varying proportions of sandstone and gray 

 shale. 



Archimedes lime- 

 stone. 



0-80 



Light-gray limestone, rich in Archimedes. 



Marshall shale. 



0-250 



Black, bituminous. 



Batesville sandstone. 



10-200 



Sometimes massive; sometimes thin-bedded. 



Spring Creek Black 

 shales and limestone. 



Wvman sandstone. 



Boone chert. 



Eureka shale. 



Sylamore sandstone. 1 

 - Unconformity -^~~^. 



a l St. Clair limestone 

 * 1 and Carson shale. 



->- Unconformity — ~^> 



300 



Shales and limestones, black to bluish or yel- 

 lowish brown in color. 



0-9 



370 



Interbedded chert and limestone ; contains the 

 St. Joe marble, 25-40 feet. 



0-50 



Thin-bedded, black. 



0-40 



80 



Hard or saccharoidal. 



Underlain by shales which locally bear man- 

 ganese ore and phosphates in commercial 

 quantities. 



1 Branner, Amer. Jour. Sci. 4th series, Vol. 2. 1896, p. 235; Hopkins, Ark. Geol. Surv. Ann 

 ReDt 1890 Vol IV, pp. 10, 90-125, 253; Penrose, Ark. Geol. Surv. Ann. Rent. 1890. Vol. I, pp. 

 113-i97 215- Williams, Ark. Geol. Surv. Ann. Rept. 1892. Vol. V. pp. 273-356; TafT, 22d Ann. 

 Reot. Ul S. Geol. Surv. Part III, pp. 389-392. Section above the Millstone grit is for the Arkansas 

 vallev region. Section below this region is for northern Arkansas. , 



2 Sylamore sandstone usually given as the Phosphate horizon, but unpublished work places tt 

 in the Carson shale. 



