Abstract

Carbonate clumped isotope paleothermometry is a promising method for paleoclimate reconstructions and understanding diagenetic processes, although clumped isotope compositions (measured as Δ47 values) can be altered by recrystallization and thermal resetting. Several studies have investigated the effects of deep burial and exhumation on Δ47 values; we present Δ47 values of samples from an ∼4500-m-long drill core from Andros Island, Bahamas, which represent the spectrum from shallow to deep burial conditions. These limestones and dolomites originally formed under near-surface temperature conditions, which are reflected by ∼27 °C Δ47 temperatures in samples buried to <∼1.3 km depth. Below this depth, calculated Δ47 temperatures increase by ∼10 °C, indicating a shift from preserved near-surface temperatures to diagenetically modified values. Importantly, this shift is not accompanied by a change in δ18O and δ13C values or cathodoluminescence, and non-uniform micrometer-scale crystallization is observed in both Δ47-altered and unaltered rocks. Similar Δ47 temperatures recorded by each carbonate phase suggest that mineral-specific differences are minor. Fine-grained dolomites and calcites are viable materials for recording surface temperature conditions, and both are susceptible to alteration of their primary clumped isotope abundances during burial diagenesis. Our results demonstrate that original Δ47 values of fine-grained carbonates can be altered under mild diagenetic conditions.

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