The calcian crypto- to microcrystalline dolomites (Mogila Formation) origin
ated in a mild arid peritidal depositional environment through complete ear
ly diagenetic replacement of lime sediments, at low Mg/Ca ratio of the dolo
mitizing fluids and salinity closer to normal marine water. The preservatio
n of their non-stoichiometry was mainly controlled by a closed diagenetic s
ystem with a low water/rock ratio. The fine crystalline dolomites from dolo
mitic limestones (Babino Formation) are also calcian but the process of par
tial dolomitization took place in the late diagenesis, within a closed diag
enetic system, at short reaction time and probably through autochthonous su
pply of magnesium cations. The nearly stoichiometric crypto- to microcrysta
lline dolomites (Svidol Formation) were also formed as an early diagenetic
replacement phase in a peritidal setting but at elevated Mg/Ca ratio of the
dolomitizing solutions and a hypersalinity of the water milieu which both
have been controlled by highly arid climatic conditions. The nearly stoichi
ometric medium to very coarse crystalline late diagenetic dolomites from pu
re dolostones (Mogila and Babino Formation) show a higher degree of order c
ompared to the early diagenetic dolomites. Complete replacement of limeston
es at slow crystallization rates by diluted fluids at elevated temperatures
is suggested, but neomorphism of earlier metastable dolomite phases may ha
ve proceeded as well.