Effects of Iron Cycling on 210Pb Dating of Sediments in an Adirondack Lake, USA

Abstract

In three cores from an acidic lake in the Adirondack State Park of New York, iron cycling accounted for diagenetic enrichment of up to 14% of sediment dry mass. The accuracy of the sediment accumulation rates calculated from the constant rate of supply (c.r.s.) model and the dating and sediment accumulation rates calculated from the constant initial concentration (c.i.c.) ²¹⁰Pb models were affected by post-depositional movement of iron about the sediment–water interface and through the sediment. Dating biases from iron diagenesis reached as high as 57% and biases to calculated sediment accumulation rates ranged up to approximately 15%. In general, however, the difference between the iron-corrected and uncorrected dating was not much greater than the error expected from routine analytical precision. However, under circumstances of low sediment accumulation rates and high iron enrichment, significant deviations in dating and sediment accumulation calculations for both c.r.s. and c.i.c. ²¹⁰Pb models may become noteworthy.