﻿574 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



Alum Bluff occur between 12 and. 17 feet above the top of the Chipola 

 marl. He says regarding this flora: "It is thus apparent that the 

 Alum Bluff flora can be considered either Aquitanian or Burdigalian, 

 with a slight preponderance of the evidence in favor of the Aquita- 

 nian, * * * jf ^\^Q Alum Bluff formation is of Aquitanian or 

 Burdigalian age — and one or the other alternative seems certain — 

 the more or less academic question is raised whether it shall be 

 classed as Oligocene or Miocene." 



The floral evidence at least does not contradict considering the 

 Alum Bluff as Burdigalian. 



The matrix of the Chipola marl is particularly suited for the 

 preservation of Foraminifera, and they are very abundant; but there 

 are no orbitoid Foraminifera, neither Lepidocyclina nor Hetero- 

 steginoides. 



The Bryozoa of the Alum Bluff formation, according to Messrs. 

 Canu and Bassler, are of distinctly Burdigalian affinities. The 

 fauna is particularly characterized by the introduction of certain 

 species that persist until the present time. Two of these species are 

 Cupularia umhellata Defrance and C. canariensis Busk, both of 

 which occur in the Chipola marl at its type locality, and both were 

 collected by Doctor MacDonald on Banana River, Costa Rica, in 

 deposits correlated with the Gatun formation, and both occur in the 

 Bowden marl of Jamaica. 



The evidence of the fossil corals and of the fossil vertebrates has 

 been discussed on pages 219, 220 of this volume. 



MARKS HEAD MAKL AND CALVERT FORMATION. 



The Marks Head marl at Porters Landing, Savannah River, 

 Effingham County, Georgia, has been correlated by me with the 

 Calvert formation of Maryland and Virginia.^ The most recent 

 discussion of the age equivalence of the Calvert with European 

 horizons is that of Berry in a paper aheady mentioned.^ He says, 

 regarding the probable age of the formation: ''Seven of the Calvert 

 plants, or 26.9 per cent, are common to the Tortonian of Europe, 

 and ten others, or 38 per cent, are represented in the Tortonian by 

 very similar forms. In view of the fact that these floras spread 

 into both regions from a common and equally accessible source, the 

 evidence that the Calvert flora indicates a Tortonian age is as 

 conclusive as intercontinental correlations ever can be." 



According to this correlation of Berry, there is no Helvetian in 

 the Atlantic and Gulf Coastal Plain of the United States. 



1 Vaughan, T. W., The Miocene horizons at Porters Landing, Georgia, Science, new ser., vol. 31, pp. 

 833, 834, 1910: and in Veatch, O., and Stephenson, L. W., Preliminary report on the geology of the Coastal 

 Plain of Georgia, Georgia Geol. Survey Bull. 26, pp. 362-369, 1911. 



» U. S. Geol. Survey Prof. Paper 98 (F), pp. 61-73, pis. 11, 12, 1916. 



