282 T. O. MABRY 



formity with its base, elsewhere well within the Lafayette 

 The gravels of this western belt were all evidently first trans- 

 ported to this region and deposited during the Lafayette epoch, 

 and towards its close, though in many places they have been 

 subsequently moved locally and redeposited at the base of the 

 brown loam. On the principle of homogeny, the gravels of the 

 eastern belt are thought to have been brought down originally 

 at the same time with, and in the same manner, as those of the 

 western region ; but owing to the complete, or almost complete, 

 removal by erosion of the Lafayette in the eastern region, these 

 gravels have been shifted from their original positions and rede- 

 posited within the Brown Loam, and by the same waters (for I 

 hold the Brown Loam to be essentially an aqueous deposit) which 

 deposited the finer materials of the brown loam. These waters 

 need not have been swift in order to transport pebbles, for these 

 were probably only locally shifted and let down from higher to 

 lower levels. On the other hand, the fineness of the materials 

 of the bulk of this formation gives evidence that the formation, 

 as a whole, was deposited by sluggish currents overloaded with 

 fine sediment. 



And so an application of the principles of homogeny, as 

 defined by McGee (12th Ami. Rep. U. S. Geol. Surv., p. 381 et 

 seq.) to the Brown Loam of the whole of north Mississippi, 

 together with the fact that undoubted erosion remnants of the 

 Lafayette are to be found as far east as the Pontotoc Ridge, 

 would seem to demand the former extension of the Lafayette 

 over the whole of the area in question. A comparison of the 

 hypsographic distribution of existing patches of the Lafayette 

 with the hydrography of the region strengthens this conclusion, 

 since remnants of the Lafayette are to be found on the highest 

 hills, while on lower lands near by, the Lafayette may be entirely 

 absent. As to the original thickness of the Lafayette, we have no 

 way of determining this ; but the evidence, direct and indirect, 

 just presented, indicates a considerable erosion interval between 

 the Lafayette and the Brown Loam during which a large part of 

 the former had been removed prior to the deposition of the latter. 



