HR: 13:55h
AN: H23J-02    [Abstracts]
TI: Sediment Accumulation and Mixing Rates in Clinton River and Lake St.Clair using Excess Pb-210 and Cs-137
AU: * Jweda, J
EM: jweda@comcast.net
AF: Wayne State University, 0224 Old Main Building, Department of Geology, Detroit, MI 48202 United States
AU: Baskaran, M
EM: Baskaran@wayne.edu
AF: Wayne State University, 0224 Old Main Building, Department of Geology, Detroit, MI 48202 United States
AU: Schweitzer, L
EM: schweitz@oakland.edu
AF: Oakland University, Department of Chemistry, Rochester, MI 48309 United States
AB: Sediment cores were utilized to reconstruct historical contamination in freshwater and coastal marine systems and require a precise chronology. Seven cores were collected and analyzed for ¹³⁷Cs and ²¹⁰Pb from the Clinton River and Lake St. Clair in southeastern Michigan. A comparison of the expected inventories of ²¹⁰Pb_xs and ¹³⁷Cs to measured values enable us to quantify the importance of sediment focusing and erosional input to the study area. The sediment inventories of ²¹⁰Pb_xs and ¹³⁷Cs varied over an order of magnitude. The ²¹⁰Pb_xs/¹³⁷Cs activity ratios in the cores varied from 0.5 to 22. This large range is likely due to differences in erosional input and sediment focusing to the sampling sites. Sediment accumulation rates based on the ¹³⁷Cs fallout peak (corresponding to 1963) were compared to ²¹⁰Pb_xs-based accumulation rates. The linear and mass accumulation rates based on ²¹⁰Pb_xs and ¹³⁷Cs varied from 0.36 to 1.29 cm y^-1 and 0.44 to 1.01 g cm^-2 y^-1, respectively. Two commonly used sediment age calculation models viz., Constant Rate of Supply (CRS) and Constant Initial Concentration (CIC), were applied to establish a chronology for the sediment cores. A sediment mixing model was also utilized to determine the sediment mixing coefficient. The causes for the discordancy in ages obtained using ¹³⁷Cs and ²¹⁰Pb_xs and the effect of sediment focusing on the chronology will also be discussed.
DE: 1115 Radioisotope geochronology
DE: 1120 Isotopic disequilibrium dating
DE: 1165 Sedimentary geochronology
DE: 1861 Sedimentation (4863)
SC: Hydrology [H]
MN: Fall Meeting 2005