Evaluating evaporative peritidal dolomite formation and its potential as seawater archives with subrecent (younger than 7 ka) records

Early marine diagenetic dolomites in peritidal settings are geologically abundant and regarded as promising seawater archives, yet their application is hindered by the still-enigmatic processes governing their formation. We investigate subrecent (<7 ka) dolomites extracted from classical evaporative peritidal carbonates near Abu Dhabi, United Arab Emirates, one of the few settings documenting (sub)recent dolomite formation. The results are inconsistent with direct seawater precipitation or reflux dolomitization. Instead, we identify syndepositional dolomitization linked to organic-driven manganese redox cycling within a very shallow, hydrologically open system. Such dolomites as seawater archives are favored by the formation conditions, but they exhibit negative shifts of δ13C and δ18O relative to bulk carbonates and large deviations of δ26Mg from that of coeval open seawater. This paradox may be attributed to ineffective seawater−pore water exchange in the peritidal setting, where tidal forcing drives pore-water oscillation rather than efficient seawater replenishment. Together with previous studies, this subrecent case provides more direct and detailed insights into syndepositional dolomitization. It highlights the complex interplay among early diagenetic redox zones, seawater connectivity, and pore-water circulation that influences peritidal dolomites as seawater archives.