I've been asked by a student (Dirk Sachse,[log in to unmask]) to
forward this question to the list,
Dear list members,
I analysed d18O and d13C of a dolomite core (lagoonal, southern margin
the Zechstein basin, E-Germany). The data show quite clearly that the
values are derived from initial water isotopic composition (controlled
evaporation and freshwater inflow; correlate with lithology, high d18O
anhydrit bearing horizons, low d18O in shales; d13C shows opposite
So I'd like to calculate the initial isotopic composition of the
water (assuming a temperature range). I found several equations for the
of d18O in water vs.
dolomite (Land, 1983). They seem to give reasonable values (0 to 4 ‰
for temperatures around 30°C.
But, since the sediment was deposited as calcite first (assuming the
reflux model) these equations don't give me information about the
water but about the dolomitizing fluids.
So, what exactly happens especially to oxygen isotopes during
of calcite by hypersaline brines? Are there any references?