Radioisotopic age constraints for Glacial Terminations IX and VII from aggradational sections of the Tiber River delta in Rome, Italy

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 geochronologic constraints on the timing of aggradation of two alluvial sections, demonstrating that they were deposited in response to glacio–eustatic sea level rise caused by Glacial Terminations IX and VII. 40Ar/39Ar age data indicate ages of 802±8 ka (1σ full errors) and 649±3 ka (1σ full errors) 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.