ANNUAL REPORT—GEOLOGY. 
21 
abundant and characteristic are small foraminifera of the 
genus OrMtoides. From the predominance of these small 
fossils the formation has come to be known commonly as 
the Orbitoides Limestone. The formation contains in 
places large masses of flint. These flint masses seem to 
have been formed by replacement of calcium carbonate 
by silica carried in solution by the underground water, 
which circulates freely through the limestone. Locally, 
this originally porous and fossiliferous limestone has 
become compact and more or less perfectly crystallized. 
Apparently this change is also to be attributed to the 
effect of underground water. The Vicksburg Limestone 
doubtless underlies the entire State. It is a part of an 
extensive formation which encircles the Gulf of Mexico 
from Florida to Louisiana. In Alabama it makes up 
apparently the middle part of the St. Stephens or White 
Limestone, and has there, according to Smith, an esti¬ 
mated thickness of between two and three hundred feet. 1 
In Mississippi, Casey recognizes two faunal horizons in 
the Vicksburg Bluffs 2 , the upper of which contains OrM¬ 
toides as a characteristic fossil. Upon this basis Dali has 
proposed tentatively for the Orbitoidal phase of this ex¬ 
tensive formation the term “Peninsular Limestone”, from 
its typical occurrence in the peninsula of Florida. 3 
In Florida this limemstone lies at the surface in limited 
areas but is, for the most part, buried beneath later 
deposits. Good exposures are seen in the central portion 
of Alachua and in the southern part of Columbia Coun- 
lReport on the Geology of the Coastal Plains of Ala., Geological 
Survey of Ala. Eugene Allen Smith, State Geologist. 1894, pp. 107- 
122. The Underground Water Resources of Ala. Eugene Allem 
Smith, Geological Survey of Ala. 1907. The Ala. Survey has not 
found it practicable, however, to separate any part of the Whit* 
Limestone as it occurs in that State from the Eocene. (Coastal 
Plains, p. 109.) 
2Proceedings Academy Natural Science of Philadelphia, pp. 
513-518, 1901. 
3Trans. Wagner Free Institute Sci. Vol. Ill, pt. YI, p. 1554, 
1903. 
