Two-Stage Dolomite Formation in Carbonate Platforms Revealed by Carbonate Clumped Isotope Thermometry

The “dolomite problem” refers to the scarcity of dolomite in Cenozoic marine environments compared with its abundance in earlier strata. This discrepancy has been attributed to changes in marine environments or to insufficient thermal maturity required for dolomite formation. We measured carbon, oxygen, and clumped isotope compositions of carbonate rocks from the Albian Nahal Me'arot reef complex (north Israel), where dolomite is confined to back-reef lagoon facies and associated with reflux-brine dolomitization, a process thought responsible for large volumes of dolomite in Phanerozoic rocks. Results show a negative trend between TΔ₄₇ (29–54°C) and δ¹⁸O_dolomite (−3.25 to −1.35 ‰VPDB), consistent with burial alteration, and support a two-stage process: (a) proto-dolomite formation near the lagoon floor, and (b) recrystallization during burial. Together with compilations of Mg/Ca ratios in Cenozoic marine carbonates predicting more dolomite than observed directly, our results suggest that insufficient thermal maturity has limited dolomite formation in Cenozoic strata.