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rim sink, or peripheral sink. A well-developed salt dome may therefore have
a profile as depicted in Fig. 15-1A and 15-2.
Structurally, salt domes are important for two reasons. First, the deforma-
tion of the overlying sedimentary rocks and the rocks through which the
dome has penetrated may lead to traps for petroleum either in the overlying
anticlinal form or by the truncation of potential reservoirs by the relatively
impermeable salt. Accumulations in such traps may also be affected by fault-
ing that resulted from the deformation. Secondly, three or more salt domes
in a group may form an anticlinal trap by virtue of their rim synclines. The
structure of the sedimentary rocks over and around a salt dome is usually ex-
tremely complex. Strata tend to be variably inclined, and faulted with pre-
dominantly radial faults that die out away from the dome (Fig. 15-3). There
is no means of knowing whether lateral continuity of particular rock units
existed prior to their penetration by salt; but local hiatus are common in the
strata overlying domes, and they are commonly associated with features that
suggest that the growth of the dome affected the accumulation of sediment.
Some salt diapirs in the Gulf Coast province of North America are also in-
timately associated with mudstone diapirs, both as a single structure and as
separate structures.

Fig. 15-3. Stratum contour map on Wilcox sand, just above salt of Clay Creek dome, Texas.
Contours in feet; contour interval, 500 ft (150 m approximately). (After Parker and
McDowell, 1953, p. 2085, fig. 8.)