50 
FLORIDA STATE GEOLOGICAL SURVEY. 
STRATIGRAPHIC GEOLOGY. 
TERTIARY. 
OLIGOCENE. 
The oldest rocks which have been recognized in Florida belong 
to the Oligocene series. They may be separated into two divisions, 
called here the Vicksburg group and the Apalachicola group. These 
two subdivisions were formerly regarded as Eocene and Miocene, 
respectively. One of the earliest attempts to fix tlie age of the rocks 
of Florida was made by Conrad 1 in 1846. In his paper Conrad re¬ 
ferred both the “silex beds” and the limestone of the Tampa forma¬ 
tion, together with the prevalent rock of the peninsula, to the upper 
division of the Eocene. For many years the rocks here included in 
the Vicksburg group continued to 'be called Eocene by various writers, 
including Bailey, 2 Tuomey, 3 Smith, 4 Dali, 5 and others. The deposits 
here called Apalachicola group were first differentiated from the 
“Vicksburg” in 1887, when Langdon 6 examined these formations 
along the Apalachicola River and classified them as probably “Mio¬ 
cene.” This name was retained for some time, but it was modified 
by the use of “Old Miocene” or “Subtropical Miocene” to distinguish 
it from the later Miocene. In 1896, Dali 7 published a brief statement 
of the reason for regarding the so-called Eocene and the so-called Old 
Miocene of Florida as Oligocene. This usage has since prevailed in 
many, but not in all, of the publications dealing with southern coastal 
plain geology. 
VICKSBURG GROUP. 
After the recognition of the “Old Miocene” there remained a con¬ 
siderable thickness of rock which was still regarded as Eocene and 
1 Conrad, T. A., Observations on the Geology of a part of East Florida, 
with a catalogue of recent shells of the coast. Am. Jour. Sci. 2d ser., Vol. 2, 
1846, pp. 36-48. 
2 Bailey, Prof. J. W., Am. Jour. Sci., 2d ser., vol. x, 1849, p. 282. 
3 Tuomey, Prof. M., A notice of the Geology of the Florida Keys, Am. Jour. 
Sci., 2nd ser., vol xi, 1850, pp. 390 et seq. 
4 Smith, E. A., On the geology of Florida, Am. Jour. Sci., 3rd ser., vol xxi, 
1881, pp. 292-309. 
5 Dali, Wm. H., Neocene of North America, U. S. Geol. Surv., Bull. 84, 1892, 
pp. 101-105. 
6 Langdon, Danl. W., Jr., Some Florida Miocene, Am. Jour. Sci., 3rd ser., 
vol. xxxviii, 1889, pp. 322-324. 
7 Dali, Wm. H. Descriptions of Tertiary fossils from the Antillean region, 
U. S. Nat. Mus. Proc., vol. xix, No. 1110, 1896, pp. 303-305. 
