Limited warming of Middle Miocene arid low-latitude climates: application of clumped isotopes in sabkha environments

Reconstructing past climatic conditions in arid and hot environments is challenging due to a scarcity of climate archives. However, this task is crucial for assessing the sensitivity of these areas to climate change. The lack of reliable proxies currently prevents precise and absolute temperature and moisture reconstructions. Clumped isotopes on sabkha calcite might alleviate this situation. In this study, we apply the clumped isotope technique (∆47) to both modern and Middle Miocene fossil sabkha samples and we report temperatures between 26.2±5.4 to 33.6±6.3ºC. Our results suggest that sabkha calcite-aragonite minerals primarily reflect summer half-year temperatures, corresponding to the dry season when most calcite-aragonite precipitation occurs in these environments. Reconstructed  18Owater values range between 3.2±0.9 and 5.3±0.8‰, scaling with the intensity of evaporation in these intertidal, supratidal and lagoonal settings. Despite higher atmospheric CO2 levels during the Middle Miocene, reconstructed temperatures are similar to modern ones, suggesting a reduced climate sensitivity at low latitude. Overall, sabkha clumped isotopes offer a valuable tool for bridging the latitudinal gap in continental paleotemperature reconstructions near the horse latitudes.