18 HARPER 



Bluffs on the Ocmulgee River (near the mouth of House Creek *) 

 in Wilcox County, and probable at corresponding points on the 

 Oconee and Ogeechee rivers. The Chattahoochee formation 

 seems to be rich in plant-food, and wherever it crops out there 

 is a fine growth of angiospermous trees, about which more will 

 be said later. 



6. Altamaha Grit. The formation with which this sketch 

 is chiefly concerned lies just above the Chattahoochee at several 

 places, and for this reason has been considered next to it in age 

 by some geologists. (It is not known to contain any recog- 

 nizable fossils, and its age therefore cannot be determined in 

 the usual way.) But on the other hand nothing older than 

 Lafayette has ever been seen above the Grit, and it seems more 

 reasonable to regard the latter as among the more recent for- 

 mations of the coastal plain, probably as Pliocene. There is 

 every reason to believe that the Altamaha Grit is the equiv- 

 alent of the Grand Gulf formation of the states farther west, 2 

 whose age has been equally in doubt, 3 but as the actual con- 

 tinuity of these two formations has not yet been traced it 

 seems best to retain the appropriate and distinctive name Alta- 

 hama Grit for the present, until it is proved to be a synonym 

 of the earlier (and somewhat misleading) designation, Grand 

 Gulf. 



The region in which the unmistakable exposures and char- 

 acteristic topography of the Altamaha Grit occur corresponds 

 approximately with the middle third of the coastal plain of 

 Georgia. Its inland edge is marked nearly all the way across 

 the state by an escarpment which is one of the notable features 

 of the pine-barren region. In Decatur County the Grit stands 

 200 feet or so above the soft rocks of the lime-sink region, but 

 east of the Ocmulgee River, where the Lower Oligocene rocks 

 are harder (the lime-sink phase seems to be wanting there), 

 the escarpment is not so conspicuous. 



1 Dall & Harris, Bull. U. S Geol. Surv. 84; 81. 1892. 



2 See Bull. Torrey Club 32: 144, 145. 1905. 



3 For references to a discussion of this matter see Bull. Torrey Club 32 : 

 106 (footnote). 1905. 



