LACUSTRINE RECORDS OF MID TO LATE HOLOCENE CLIMATE AND ENVIRONMENTAL CHANGE FROM THE LOFOTEN ISLANDS, NORWAY

Lake sediments are useful paleoenvironmental archives; however their sensitivity depends on lake and catchment-specific characteristics. Here we analyze lacustrine records from two contrasting lakes on Vestvågøy in the Lofoten Islands, Norway to investigate region-specific influences of Holocene climate changes and human-driven landscape evolution. Sediment cores spanning the last c. 7.5 ka were collected from Lauvdalsvatnet, a small lake (~0.17 km²) with a steep-sided catchment and large catchment to lake area ratio (~18.8), and Ostadvatnet, a larger lake (~1.2 km²) with a smaller catchment to lake area ratio (~5.2) and lower slope catchment. Sediment analyses include magnetic susceptibility, organic matter content, bulk density, biogenic silica, carbon to nitrogen ratios and scanning X-ray fluorescence data. Chronologies are based on radiocarbon dating of terrestrial macrofossils. In Lauvdalsvatnet, which contains frequent high-density laminations throughout the record, increases in organic matter content and downward shifts in biogenic silica and clastic sedimentation indicators occur synchronously c. 3 ka. Peaks in clastic sedimentation, heightened organic matter flux, and lows in biogenic silica appear c. 3-3.6 ka. In the late Holocene portion of the Ostadvatnet record, high-amplitude fluctuations in organic matter concentration begin c. 2.5 ka, followed by decreasing C/N and increasing magnetic susceptibility since c. 1.7 ka. In the Lauvdalsvatnet record, we observe a large peak then abrupt, lasting decline in organic matter content c. 2 ka, followed by fluctuations in magnetic susceptibility and increased sedimentation rates starting c. 500 BP. We attribute late Holocene changes in Lauvdalsvatnet to reflect cooling temperatures beginning c. 3 ka associated with regional termination of the Holocene Thermal Maximum, and a possible period of heightened storminess c. 3-3.6 ka. Ostadvatnet was not sensitive to this transition, however both lakes record changes starting c. 2.5 ka, which are likely due to the onset of local agriculture and early human population expansion. Our results have implications for understanding how the Lofoten region responds to global climate changes, and the spatial extent of human landscape impacts on Vestvågøy through time.