52 FLORIDA GEOLOGICAL SURVEY—1 4 TH ANNUAL REPORT 
Texas and Louisiana, while similar domes are found in Roumania and 
some other of the European countries. 
A remarkable feature of these saline domes is the fact that the central 
core of the dome consists usually, if not always, of a mass of salt. The 
depth to the salt core varies. In some of the domes the salt comes to, or 
practically to, the surface. In other domes the depth to salt varies from 
a few hundred to several thousand feet, while in a few domes the salt 
mass, although considered as with little doubt present, has not been 
reached in drilling. 
Overlying the salt, as a rule, is gypsum, and with or above the gypsum 
is more or less sulphur. A so-called cap rock is usually present, con¬ 
sisting of limestone or dolomite. Above these strata, where they do not 
actually reach the surface, is a variable thickness of sands, clays and 
other sedimentary rock. 
By what process these salt domes have been formed remains undeter¬ 
mined. Their importance as oil reservoirs arises from the fact that the 
salt and associated minerals have pushed up the sedimentary rocks, re¬ 
sulting in a dome structure favorable to the accumulation of oil. 
Fig. 6. Diagrammatic section through a salt dome. After Hager. 
