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a reduction of 9%. The effect of this on the whole sedimentary column will
be very small, but sustained for a great length of time - and perhaps reinfor-
cing a general diapiric tendency - its effect may be real.

DISCUSSION

Salt diapirism is a process that is relatively well understood: it can be
modelled satisfactorily, and the features of the models correspond qualita-
tively, at least, with geological observations. Conversely, geological analysis of
areas of diapirism can reveal in some detail the evolution of the diapirs.
A particularly good example of this is the beautiful work of Trusheim
(1957, 1960; the name is Trus-heim, not Trush-eim) and Sannemann (1968)
in northern Germany (Fig. 15-8). Here, up to 1 km of Zechstein salt (Permian)
accumulated, and was followed by Triassic clastic sediments that also accu-
mulated to a thickness of about 1 km. The development of the salt diapirs is

I- - - ._ - __ - - ~ -
Fig. 15-8. Zechstein (U. Permian) salt-stock area, north-western Germany. (Reproduced
from Sannemann, 1968, p. 262, fig. 1, with permission.)