Mg isotope response to dolomitization in hinterland-attached carbonate platforms: Outlook of δ26Mg as a tracer of basin restriction and seawater Mg/Ca ratio

Overall, Mg isotope compositions co-vary with δ13C, Mg/Ca ratios, as well as crystal size of dolomite, which implies that variations in δ26Mg value reflect syn-depositional changes in water chemistry as a result of dolomitization in episodically restricted basins. δ26Mg tracks the fluctuating marine connection and provides a powerful tracer for the level of restriction. Furthermore, by pairing Mg isotope variability of the dolomite with a Rayleigh distillation model and elemental mass balance in aqueous solution, it is possible to constrain the Mg/Ca ratio of seawater. Based on the records from the Hevyon Formation, Mg/Ca ratio of seawater during the Albian is constrained between 1.5 and 1, which is consistent with results from other records.