138 
the tertiary geology op the 
.nation I low far south the Orbitoitic limestone extends has not yet been determined, 
but there appear to be no reasons for assigning it to a limit far removed from the 
border line of the Everglades. For aught we know to the contrary it may extend 
quite or nearly to the peninsular extremity. , . 
Ib.rrimr the post-Pliocene of the coast, the only indication that we as yet have of the 
existence of any marine formation in the State newer than the Oligocene is the patch 
of limestone referred to by Dr. Smith ’"^-as occurring at Rock Spring, Orange Co., 
from which Imve been obtained specimens identified by me as belonging to the Miocene 
period— Madisoniiis, Venus alveata, Cardita gramdata, Carditamera arata, 
and doubtfully, Mgtilo<-oncJia incurva, Cardium suUineatum and Oliva litterata. Other 
Miocene areas will doubtless be discovered, and not impossibly a more or less con- 
tinuous belt will be found to unite the Rock Spring patch with the Miocene area in 
Georgia. 
Alahama. 
'ri.e 'I'ertiary formations of Alabama, which occupy a tract in the southern part 
of the State with a general width varying from about 55 to 90 miles, seemingly 
exhibit eipiivalents of all the various subdivisions that have been recognized on either 
the .\tlantic or Gulf borders as intervening between the base of the system and the 
\’icksburg IhxIs (Oligocene). The Eocene appears here clearly defined in its four 
divisions, the Eo-Lignitic (Thanetian 1), Buhrstone (Londonian ?), Claibornian 
(Parisian, or Calcaire Grossier), and Jacksonian (Bartonian), which follow each other 
in a general succession (commencing with the lowest) from north to south. Covering 
the Jacksonian, and occujiying a belt immediately to the south of it, are the Vicksburg 
iK’ds, who.se most southern exposure on the Alabama River is at or near Gainestown, 
some eighty miles north of the Gulf, where the strata pass under the beds that have 
bi'en designated by Ililgard as the “Grand Gulf Group.” Whatever the exact age of 
the deiHisits of this grouj) may be, they are the only ones of marine or fluvio-marine origin 
that indicate along the Gulf border a Tertiary formation of newer date than the Vicks- 
burg : whether they belong to the Miocene period, as has been suggested by Ililgard, or 
to the Plioeene, can only be ascertained when a more thorough examination of their 
fossil remains will have been attempted than has heretofore been practicable. For 
their entire extent the Tertiary deposits abut against those of Cretaceous age, the two 
having a very nearly equal development, and together occupying about one-half the 
area of the State. In their eastern half the outcrop or strike of the strata is more 
nearly due east and west, with a moderate dip to the south, while in the western half 
the line of outcrop is W. by N.— E. by S., with a dip S. by W. of about 10 feet to the 
mile. 
A convenient starting point in the Tertiary stratigraphy of the State is afforded 
Loc . cit ., p. 303. 
