Late Quaternary aggradation of the Datong Basin in northern China revealed by OSL dating of core sediments and implications for groundwater arsenic pollution

Abstract

The Datong Basin in northern China is notorious for its geogenic arsenic (As)-polluted groundwater hosted by late Quaternary strata. Deciphering the mechanism of arsenic pollution requires an understanding of stratigraphic architecture and depositional processes, which, however, are hindered by weak chronological data. Here we utilized the optically stimulated luminescence (OSL) dating technique to obtain 15 sediment ages from the upper 20 m of core SY1 from the central basin. The dating results revealed a sedimentary hiatus covering the period of about 19–3.6 ka, which may arise from river downcutting induced by strengthened East Asian summer monsoon (EASM) and ameliorating vegetation. Ages of sediments below the hiatus demonstrated a high sedimentation rate of ~0.55 m/ka at ~39–19 ka, which might result from weakened EASM and suppressed vegetation. Above the hiatus, sedimentation resumed after 3.6 ka possibly as a result of declined strength of EASM and increasing human activities like deforestation. Overall, climate change is the most likely driving force of aggradational history recorded in core SY1 since at least 74 ka. The dating results indicate that high-As groundwater may be released from sediments accumulated within incised valleys that were sculpted at about 19–3.6 ka, or from paleolake (Nihewan)-related sediments deposited before the last glacial period.