SECOND ANNUM, REPORT—STRATIGRAPHIC GEOLOGY. 
91 
No. 2 rests unconformably upon No. 1 and is a thin but persistent 
bed. 
Section at railroad bridge—Orient ( Tampa ). 
5. Fossiliferous white sand .. 2 feet. 
4. White marl . 6 feet. 
3. Light gray sand . 1 foot 
2. Gray shell marl . 0-1 foot 
1. Gray to yellow limestone, very fossiliferous in places. 6 feet. 
No. 2 rests unconformably upon No. 1 and is evidently the same 
horizon as No. 2 in the preceding section. The limestone in both of 
these sections is what has commonly been called "Tampa limestone.” 
In the section at the railroad bridge, there is some "silex” near the 
base and this evidently represents the same horizon as the "silex bed” 
at Ballast Point. 
ALUM BLUFF FORMATION. 
The name Alum Bluff formation as here used includes those beds 
which belong stratigraphically between either the Chattahoochee for¬ 
mation or the Hawthorne formation and the marls and limestones of 
Miocene age. This usage differs from that of Dali, 1 who appears to 
have regarded the Chipola marl and the Alum Bluff as distinct for¬ 
mations. The Alum Bluff formation includes two different, though 
closely related, members which have been known respectively as the 
Chipola marl and the Oak Grove sands. To these is added a third 
member, recently discovered by Vaughan 2 in west Florida, and called 
the Shoal River marl member, from the stream where it is best 
exposed. The Chipola marl member and the sands of the type locality 
at Alum Bluff were first described by Langdon, who referred them to 
the Miocene. 3 
The type locality of the Chipola 4 marl member is at McClelland’s 
farm, near Bailey’s Ferry, on the Chipola River, and the Alum Bluff 
formation is named from a bluff on the Apalachicola River, where it was 
first examined. The fullers earth deposits which represent the Alum 
Bluff formation east of the Apalachicola River, have been mentioned 
by a number of writers, but the first comprehensive description of 
1 Dali, Wm. H., Cenozoic Geology Along the Apalachicola River; Geol. Soc. 
Am. Bull., vol. v, 1893, p. 167. 
2 Vaughan, T. Wayland. Unpublished notes. 
3 Langdon, Daniel W., Jr. Some Florida Miocene; Am. Jour. Sci., 2nd ser., 
vol. xxxviii, 1889, p. 32. 
4 Dali, Wm. H., Neocene of North America, U. S. Geol. Survey Bull. No. 
84, 1893, p. 122. 
