PETROLEUM POSSIBILITIES OR PLORIDA 
51 
the accompanying sketch. (Fig 5.) A porous stratum through 
which oil and gas may migrate as shown in this sketch is caused by 
faulting to terminate abruptly against an impervious stratum. Under 
these conditions oil and gas may accumulate in the porous stratum adja¬ 
cent to the fault. 
Fig 5. Diagram illustrating a fault affording conditions favorable to the ac¬ 
cumulation of oil and gas. 
DOMES 
In its simplest form an anticline, as already stated, is an upfold or 
arch in the rock strata. A dome in its simplest form may be thought 
of as a bulging up of the strata. Anticlines are usually accompanied 
by compensating structures known as synclines. Domes may be, but 
are not necessarily, accompanied by compensating structures, which are 
basins. Domes serve as an ideal trap for oil and gas, since, being closed 
on all sides, the oil and gas entering them is retained. As seen in cross- 
section, a dome does not necessarily differ from a cross-section of an 
anticline.- In fact, a dome may be regarded as an anticline, the axis of 
which is reduced to zero in length. 
SALT DOMES 
A very exceptional type of structure, often oil-bearing, is that known 
as salt domes. These domes are known near the Gulf of Mexico in 
