Stylolites in evaporites are very uncommon. In the Gorleben Zechstein salt
dome, stylolite horizons have been found in the so-called " Banderanhydrit"
(z3HA11) at the top of the Zechstein Hauptanhydrit (Main Anhydrite). These
pressure-solution features seems to be related to the presence of thin mag
nesite-clay interlayers. Five principal stylolite morphologies can be disti
nguished in the core sections studied. The orientation of the sutured seams
is generally bedding-parallel with the stylolite axes vertical to the bedd
ing surface. This demonstrates that pressure-solution features clearly pred
ate the formation of the salt dome and that there is no relation between th
eir formation and halokinesis. Solution rates of up to about 26% have been
calculated by measuring maximum stylolite amplitudes in certain core interv
als. Considering the bedding-parallel occurrence of the stylolites and the
fact that the stylolite seams are crosscut by anhydrite crystals that me in
terpret as pseudomorphs after gypsum, it must be concluded that the styloli
tes formed before the dehydration of gypsum to anhydrite was completed. The
lower parts of the Hauptanhydrit were excluded from these processes becaus
e they had already been converted to anhydrite by the overburden of overlyi
ng Zechstein units and by ascending compaction fluids of the underlying Zec
hstein 2 Salt. We assume that the dehydration of gypsum to anhydrite was co
mpleted before the end of Zechstein sedimentation and that the formation of
stylolites thus must be attributed to the same time interval.