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

晚中新世（托尔顿-墨西尼亚）至更新世之间北半球冰川作用的开始和欧亚永久冻土层的形成是新生代最深刻的变化之一。关于北冰洋大范围冰川作用和冻结的时间以及气候条件的相关变化，人们仍然知之甚少。洞穴碳酸盐岩是极具价值的大陆环境条件档案，为大量古气候代用物提供了精确的辐射年表。我们从西伯利亚中部和北极地区确定了成岩未改变和可确定日期的样品材料，并提出了多代理研究U/Pb定年的洞穴主题，以详细了解10.3 Ma至8 Ma之间的热水文条件。提取碳酸盐中的流体包裹体水，研究原始中新世渗透水的同位素组成。此外，在洞穴样本中发现的层压提供了托尔顿和墨西尼亚时代季节变化的信息。我们寻求资金用于分析平行流体包裹体水同位素、碳酸盐氧和碳同位素以及元素浓度，以重建区域环境条件，以及在连续永久冻土形成之前的水分来源和温度动态。新的样本将被添加，以确定从无冰到永久冻土统治的西伯利亚变化的时间。这项研究将扩展我们对北冰洋季节性无冰条件下大气环流以及相关的水分收支和温度变化的认识。

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.