50 
FLORIDA GEOLOGICAL SURVEY—I 4 TH ANNUAL REPORT 
and the oil may be trapped and gradually accumulate until the anticlinal 
fold is filled, provided there is sufficient oil and gas to fill it. Obviously 
if the stratum contains water as well as oil, the water will accumulate in 
the synclines. If, however, the stratum contains but little or no water, 
there may be an accumulation of oil in the synclines. 
Fig. 4. Diagram representing an anticline affording conditions favorable to the 
accumulation of oil and gas. 
Folds in the rocks, both anticlines and synclines, may be either sym¬ 
metrical in form or lacking in symmetry, that is, unsymmetrical. In 
Figure 4 the fold is represented as symmetrical or essentially so. Un¬ 
symmetrical folds are more common in the earth than .symmetrical ones. 
The nature of the fold, whether symmetrical or unsymmetrical, must 
be taken into account when locating a well. 
The folds in a formation may extend in the direction of the dip or 
across the dip. If an anticlinal fold extends in the direction of the dip 
there is produced a type of structure known as a plunging anticline, by 
which is meant an anticline, the axis of which departs from the hori¬ 
zontal. If followed down the axis any given horizon in a plunging anti¬ 
cline will be found at successively lower levels. 
faults 
Not infrequently a fault in rock brings about conditions favorable to 
the accumulation and storage of oil. Such a condition is illustrated in 
