Geochronology of a surface core in the northern basin of Lake Qinghai: Evidence from 210Pb and 137Cs radionuclides

摘要

The radioactivities of 210Pb and 137Cs have been measured to estimate the dates of the sediments of a surface core (QH0407-C-2) in the northern basin of Lake Qinghai. The sedimentation rate derived from 210Pb radioactivity correlates well with that inferred from 137Cs radioactivity. The dates calculated from depth sedimentation rate (cm/a) are similar to those derived from mass accumulation rate (g·cm-2·a-1) between 0-5 cm, but are significantly different below 5 cm, which has been ascribed to the compaction of surface sediments during early diagenesis. The dates derived from mass accumulation rate are consistent with those calculated from the AMS 14C dating model. The precipitation-controlled indices based on the chronology data derived from mass accumulation rate are similar in trends to the precipitation reconstructed from tree rings in adjacent region, which further verifies the reliability of the geochronology data.