Pb210 geochronology and trace metal concentrations of sediments from Upper Klamath Lake and Lake Euwana, Oregon.

Rates of sedimentation calculated from analyses of ²¹⁰Pb activities in cores from two shallow lakes whose mean depths are 2.4m, Upper Klamath Lake and Lake Euwana (Klamath County, Oregon), indicate that they are filling at approximately 3.0mm/yr. Average sedimentation rates for compaction-corrected cores range from 0.9mm/yr to 8.5mm/yr or from 0.03g/cm²/yr to 0.48g/cm²/yr, respectively. Plots of excess ²¹⁰Pb activity versus depth show a mixing layer due to biological activity and other physical mixing that ranges in thickness from 5-20cm, and that is found below the sediment-water interface at all coring locations. Trace metal analyses performed to establish baseline levels of selected elements show very low concentrations of all metals measured in cores from Upper Klamath Lake (Cd, Cu, Cr, Fe, Pb, Mn and Zn) when compared with concentrations of these metals found in other North American lacustrine environments.-Authors