CHARACTERISTICS OF THE LAFAYETTE. ' 169 



cies (Mactra lateralis, Say) belonging to the newer Chesapeake, it is prob- 

 able that the Pascagoula beds should also be referred to this horizon. 

 The aluminous clay was also recognized in a bed, 19 feet thick, above the 

 Chesapeake marl at Abes spring, and part of the 27 feet assigned to the 

 Chesapeake at Darlings slide is probably of this horizon, though, owing 

 to the verticality of the bluff, its face could not be closely examined at 

 this height, and the line of distinction between the two, if it exists, had 

 been so obscured by the rush of huge logs over the surface that it could 

 not be recognized from the foot of the bluff. 



This completes the summary of the Miocene section of the Apalachi- 

 cola region. It has involved some repetition of previously mentioned 

 details, but this was thought best to avoid obscurit}''. 



There was found near the top of every section studied on the Apala- 

 chicola river a bed which in general was composed of a mixture of 

 yellow and red colored sands and clays, the predominating tint and 

 composition of the material varying with the locality. The thickness of 

 this bed in each case has been shown in the descriptions of the sections. 

 It has already been noted that in the vicinity of Bainbridge this material 

 is of considerable thickness and homogeneous in texture, highly argil- 

 laceous and of a uniform red color throughout; also that in some places 

 it has the appearance of a decomposition product in situ, while in others 

 rearrangement of the material is apparent, yet each so simulating the 

 other as to make identification at times difficult. This condition of 

 affairs continues with considerable uniformity northward to Macon, but 

 it is safe to say that there is greater heterogeneity in this material in the 

 limited area studied than there is in its greater northward extension- 

 At Old Chattahoochee landing it preserves its Bainbridge characteristics 

 and rests upon an erosion surface. At Aspalaga and Rock bluff modi- 

 fication is more noticeable, and when Alum bluff is reached on the sea- 

 ward route this formation is represanted by a bed nearly 70 feet thick, 

 highly arenaceous, fine in texture ; in color, orange and white, so alter- 

 nating as to present a mottled appearance, and, while even this portion 

 of the bluff has a stratified aspect, there is some evidence of plunge and 

 flow structure. It also rests conformably upon the bed of aluminous 

 clay which immediately overlies the Chesai^eake. A little farther south 

 and 12 or 15 miles to the westward, at Abes spring and Darlings slide, 

 the sand of which it is composed is coarser, the mottlings have a marked 

 red and yellow color, plunge and flow structure is more pronounced and, 

 as at Alum bluff, it rests apparently conformably upon the aluminous 

 clay overlying the Chesapeake. From our observation we conclude that, 

 though often different in composition, structure and color, it is never- 



