Radiometric age constraints for glacial terminations IX and VII

Abstract

Buried sedimentary aggradational sections deposited between 800 ka and 600 ka in the Tiber River coastal alluvial plain have been studied using borecores from around Rome. 40Ar/39Ar ages on sanidine and/or leucite from intercalated tephra layers and paleomagnetic investigation of clay sections provide geochronological constraints on the timing of aggradation of two of these alluvial sections, and demonstrate that they were deposited in response to eustatic sea level rise caused by glacial terminations IX and VII. 40Ar/39Ar age data indicate ages of 802 ± 8 ka and 649 ± 3 ka for glacial terminations IX, and VII, respectively, providing a rare test, beyond the range of U-series dating for corals and speleothems (~500 ka), of the astronomically calibrated timescale developed for oxygen isotope records from deep sea cores.