Limited warming of middle Miocene arid low-latitude climates: Application of clumped isotopes in sabkha environments

Abstract

Reconstructing past climates in hot, arid regions is challenging due to scarce archives and proxies. Clumped isotopes (Δ47) on sabkha calcite-aragonite minerals might alleviate this situation. We apply the Δ47 technique to modern and middle Miocene sabkha samples yielding temperatures of 25.2 ± 2.8 °C to 32.1 ± 3.0 °C. Results show that sabkha calcite-aragonite minerals mainly reflect summer half-year temperatures, when most precipitation occurs. Reconstructed δ18Owater (SMOW) (SMOW—standard mean ocean water) values (3.2 ± 1.0‰ and 5.2 ± 1.2‰) scale with the intensity of evaporation in these intertidal, supratidal, and lagoonal settings. Despite higher middle Miocene atmospheric CO2, reconstructed sabkha temperatures are similar to modern values, suggesting a low climate sensitivity. Thus, sabkha Δ47 is a valuable tool for paleotemperature reconstructions in low-latitudes continental settings.