STRATIGRAPHY OF FOSSILIFEROUS MEMBERS 



9 



Between the Mississippian and Pennsylvanian systems, or at the 

 base of the Pottsville formation, there exists everywhere a great uncon- 

 formity, as is shown by the extremely irregular upper surface of the 

 Mississippian rocks. The basal members of the Pottsville formation 

 rest sometimes on varying thicknesses of Maxville limestone and some- 

 times directly upon the Logan formation which occurs below the Max- 

 ville. The Maxville limestone is found in patches, which, as shown 



Map showing outcrop of Pottsville formation in Ohio 



by W. C. Morse, are undoubtedly 'the remnants of a once continuous 

 deposit laid down at the end of Mississippian time. 1 Uplift, however, 

 caused the withdrawal of the sea, and for a long period the region was 

 subjected to erosion. The duration of this period was great enough 



'Morse, W. C., Geol. Surv. Ohio, Fourth Ser., Bull. 13, p. 99, 1910. 



