Climatic transitions in the Arctic as revealed by minera- logical evidence from the Upper Cenozoic sediments in the central Arctic Ocean and the Yermak Plateau

, vol. 88, pp 305-312. Trondheim 2008. ISSN 029-196X.Mineralogical characteristics of the sediments can be used to evaluate critical climate transitions in the Arctic Ocean based on a close relationship between ice-sheet initiation, ice rafting and sea-ice cover changes. Such transitions are found in the Middle Miocene (~ 13.9 Myr ago), when the Earth’s climate cooled dramatically after an extended period of relative warmth, and in the Middle Pliocene (at ~3 Myr), when average global temperatures were significantly warmer than they are at present.This study covers the Middle Miocene to Recent succession at the IODP Expedition 302 Site M0002 (Lomonosov Ridge) and provides a revision of the Middle Pliocene core data from the ODP Site 911 (Yermak Plateau). Both these sites consist of siliciclastic sediments characterised by low organic carbon concentrations. The first key transition coincides with increased, but fluctuating kaolinite occurrence in the central Arctic Ocean, probably due to continental ice generation and increased glacial erosion on land. Periodically, high smectite contents indicate changes to interglaci-als and more open marine conditions. At the same time, the increased smectite content, pyroxenes and amphiboles of the Middle Pliocene warmth sediments on the Yermak Plateau, indicate that during interglacials transport mechanisms were a combination of both sea-ice and oceanic currents reflecting also significant fresh-water input from the great Siberian rivers.