Speleothems from Arctic Siberia: A unique terrestrial archive for past temperature and hydrological conditions in the late Miocene.

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The onset of northern hemisphere glaciation, and build-up of Eurasian permafrost between the late Miocene (Tortonian-Messinian) and the Pleistocene is one of the most profound changes in the Cenozoic. The timing of extensive glaciation and freezing of the Arctic Ocean, and related changes in climatic conditions remain poorly understood. Speleothems (secondary cave carbonates) are highly valuable archives of continental environmental conditions and offer precise and accurate radiometric chronologies for a large array of palaeoclimate proxies.We identified diagenetically unaltered and datable sample material from central and Arctic Siberia and propose a multi-proxy study on U/Pb dated speleothems to gain detailed insights into the thermal and hydrological conditions between 10.3 Ma and 8 Ma. Fluid inclusion water, trapped in the carbonate, will be extracted to study the isotopic composition of original Miocene-age infiltration water. Additionally, lamination found in the speleothem samples offers information on seasonality changes during the Tortonian and Messinian times. We seek funding for the analysis of parallel fluid inclusion water isotopes, carbonate oxygen and carbon isotopes and element concentrations, to reconstruct regional environmental conditions, as well as moisture source and temperature dynamics, prior to the build-up of continuous permafrost. New samples will be added to determine the timing of the change from an ice-free to the permafrost-governed Siberia. This study will extend our knowledge of atmospheric circulation and associated changes in moisture budget and temperature under conditions of a seasonally ice-free Arctic Ocean.