DEVELOPMENT OF LAKE SEDIMENT RECORDS OF HOLOCENE PALEOCLIMATE VARIABILITY FROM THE INTERLAKE REGION OF MANITOBA

Lakes in central Manitoba contain sedimentary archives that can be used to reconstruct past climate and environmental conditions since deglaciation ~ 10,000 years ago. In this study we present a multi-proxy analysis of sediment records from two lakes situated in the boreal forest of the Interlake Region in northcentral Manitoba. Little Limestone Lake (53.783° N, 99.316° W, 270 m ASL) is a relatively large (~ 40.5 square km) and shallow (7 m max depth) open basin lake, that is reportedly the largest marl lake in the world. In contrast, Pootachikun Lake (53.334° N, 99.351° W, 258 m ASL) is a relatively small (~ 0.5 square km) and shallow (3.6 m max depth) open-basin marl lake. Overlapping 1-meter length sediment cores were collected from both lakes until refusal and composite sediment cores were developed by aligning visible stratigraphic markers common to adjacent drives. A detailed stratigraphic analysis was completed along with measurement of dry bulk density, loss-on-ignition for organic and carbonate content, magnetic susceptibility, visible reflectance, and Powder X-ray Diffraction to determine core mineralogy, with radiocarbon dating on terrestrial macrofossils for age model development. Preliminary results show the Little Limestone Lake core is 2.2-meter in length, consisting of laminated to homogeneous mixed phase calcareous sediments, while the Pootachikun Lake core is 4.4-meter in length, consisting of homogeneous organic to organic calcareous sediments. Ongoing work includes the development of a sedimentary facies model for each lake, to aid in the interpretation of lake level changes, and carbonate stable isotope analysis on the Little Limestone Lake mixed phase carbonates for quantitative paleoclimate reconstruction.