Analysis of a 80 000 year old Arctic faunal deposit from Norway

The Early and Middle Weichselian are characterised by major re-distribution of flora and fauna during periods of extreme climatic fluctuations, with periods of warming, glacial advances and retreats, isostatic and eustatic changes and shifting sea ice and sea level. The Marine Isotope Stage 5a (Odderade; MIS 5a) was a period of significant warming, with possible temperatures in Fennoscandia equal or higher than today. Nevertheless, at these high latitude regions, we lack a comprehensive understanding of the faunal biodiversity during this warm period due to extreme rarity of preserved organic remains. Here, we present a remarkable sediment deposit with a diverse, faunal diversity preserved in a unique bone bearing layer that is sealed in the high-latitude Storsteinhola cave system (68°50' N 16°22' E) in northern Norway. Using a combination of sedimentology, osteological analyses and palaeogenomics, we confidently date the faunal assemblage to MIS 5a and identify 49 taxa including mammals, fish and birds with several species and genetic lineages not previously found in Fennoscandia. We do not obtain any evidence for hominin occupation. The marine and terrestrial faunal assemblage reveals an Arctic community that agrees with a close proximity to sea-ice and sediment analyses reveal changing proximity to the ice margin, consistent with advancing and retreating glacial ice. Our observations of a colder than expected environment reveals spatially distinct climatic conditions in Fennoscandia during MIS 5a, highlighting how this faunal assemblage fills a distinct knowledge gap within the natural history of the far north.