Reconstructing Late Holocene Sea-level Change and Impacts on Prehistoric Settlements in the Lofoten Islands, Norway

Integrated archaeological and paleoenvironmental investigations provide a long-term perspective on human-environment interactions that can address questions about how people have relied on, modified, or adapted to past environments. This project examines human-environment interactions at the prominent prehistoric settlement of Borg in the Lofoten Islands of northern Norway. In this region, people relied on a mix of agricultural and maritime economies that were susceptible to climate and sea-level changes during the late Holocene. We are developing sedimentary records from 4 lakes around Borg using bulk organic geochemistry (%sulfur, %carbon, C_org/N_total, δ¹³C_org), scanning XRF, and molecular biomarkers to reconstruct sea-level and landscape changes. Here we present results from two isolation basins, which improve constraints on sea-level variations over the last 3.5 ka. We show how changes in salinity and water column conditions influenced the Viking-Age harbor of Borgpollen as the lake isolated in response to isostatic uplift. There were 3 distinct changes in marine influence including a marine phase (3.5 - 1.6 ka), brackish phase (1.6 - 0.6 ka), and freshwater phase (0.6 ka to present). These intervals are defined by decreases in salinity interpreted from shifts in δ¹³C_org values, marine-derived elements such as Ca, Sr, Br, and water column stratification. Restriction in the connectivity of this basin to the ocean, and therefore usefulness of the harbor, are linked with local cultural changes during the Iron Age. These data will also be coupled with results from two other lakes draining prehistoric agricultural areas where we infer landscape changes starting c. 2.5 ka, possibly coinciding with the establishment of the first permanent settlements. Together these findings provide an improved perspective on human-environment interactions at the Borg settlement and contribute to the relative sea-level history of northern Norway.