CENOzoic (marine). 273 
in Alabama may be placed at 30 feet to the mile, there are many- 
interruptions to the uniformity of this slope, and we have re- 
cently traced out, in part at least, the limits of two anticlinal 
folds and one fault involving at least 200 feet vertical displace- 
ment ; and the wide expanse of territory over which, in southern 
Alabama and Florida, the White Limestone remains at or near the 
surface, shows that the Tertiary strata in those parts, probably 
because of these folds, have very little or no Gulf-ward slope, 
and, in some places, even a dip away from the Gulf. 
All the strata above described have been classified as Eocene, 
without a dissenting voice, except the White Limestone, parts of 
which have been considered as of Oligocene age by Conrad, Heil- 
prin, and others ; but recently-made and extensive collections lead 
us to consider the White Limestone also as Eocene. On this 
point the following quotations are made. Mr. T. H. Aid rich, 
who has recently devoted much time to the collection and study 
of the fossils of the Alabama Tertiary, says : ^* I cannot find any 
good reason for calling the Vicksburg, or White Limestone, Oligo- 
cene; the presence of Venericardia planicosta in it near Clai- 
borne is enough to put it into the Eocene, but outside of that the 
fossils are not similar to the Oligocene of Europe in any way 
whatever. Oligocene of Europe is much more recent in its forms, 
more like Miocene in this country." 
Dr, E. W. Hilgard writes: "As to 'Oligocene,' I can see no 
possible use in such a subdivision in the S. W. Tertiary ; I hold 
that the Vicksburg and Jackson are so closely interconnected, 
and also — as your Alabama exposures show — so closely related 
with the Claiborne, that if the latter is called Eocene the other 
two must be." 
L. C. Johnson says: " But the Jackson, Vicksburg, and Red 
Bluff having some differences, have yet so much in common, 
that I put them in one division — the White Limestone formation 
— and, unless my recollection is at fault, we agreed upon this 
before, and also that it is truly Eocene, as Tuomey and Hilgard 
were of opinion." 
At this point, though probably out of the proper order, we 
had perhaps best speak of a fresh-water formation of somewhat 
wide distribution in Mississippi, viz., the Grand Gulf formation 
of Hilgard, made up of sandstones, sands and clays, in which 
organic remains are extremely rare ; the few fossils which have 
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