308 GEOLOGY. 



entertained by others. The difficulties felt by those who have aban- 

 doned it are (1) the absence of marine fossils even where conditions 

 favor their preservation; (2) the presence of structural features not 

 identical with those of typical marine deposits; (3) the chemical 

 condition, particularly the high and very varying oxidation, and the 

 meager hydration, with a general absence of the reduction phenom- 

 ena connected with organic action beneath the sea; (4) the topo- 

 graphic relations of the formation, which are with difficulty reducible 

 to the requisite horizontally; and (5) the absence of characteristic 

 shore phenomena. Terraces have indeed been appealed to, but they 

 are local and doubtfully consistent with one another, and seem better 

 assignable to low gradient stream erosion through which this formation, 

 under any interpretation, must have passed, in rising from its primi- 

 tive low slope to its present higher one. 



The Mississippi portion of this formation was formerly assigned 

 to glacio-fluvial action connected with the Pleistocene ice invasions, 1 

 but this was due to its erroneous correlation with the Natchez formation, 

 which is essentially a derivative from the Lafayette, with a glacio- 

 fluvial contingent. It rests unconformably on the Lafayette, with 

 notable erosion between the two. 



Marine Pliocene Beds. 



The Atlantic coast. — If fossils be the test, Pliocene beds of marine 

 origin have but little development on the eastern side of the conti- 

 nent. In Florida only (Caloosahatchie beds) 2 have beds containing 

 marine fossils any considerable extent at the surface, though small 

 patches are known in Georgia, the Carolinas, 3 Virginia, and perhaps 

 Massachusetts. The isolated outcrops in Virginia and farther south 

 may be parts of a continuous formation, chiefly concealed by younger 

 deposits. The beds in Massachusetts which have been regarded as 

 Pliocene occur at Gay Head, 4 where they are unconformable on the 

 Miocene. Farther south also, the relations of the Pliocene beds to 

 their substratum is locally at least one of unconformity. The time 



1 Hilgard, Agr. and Geol. of Mississippi, 1860. 



2 Dall, Am. Jour. Sci., Vol. 34, 1887, p. 161, Wagner Free Inst, of Science, Vol. 14, 

 Pt. VI, p. 1604, Bull. 74, U. S. Geol. Surv. 



3 Dall, Croatan beds of N. Carolina and Wassemer beds of South Carolina. Trans 

 Wagner Free Inst, of Sci., Vol. Ill, Pt. II, pp. 201-17, 1892. 



4 Dall, Am. Jour. Sci., Vol. 48, 1894, p. 299. 



