Dating of recent sediments from Lago Maggiore and Lago di Lugano (Switzerland/Italy) using ¹³⁷Cs and ²¹⁰Pb

This paper presents the results of ¹³⁷Cs and ²¹⁰Pb dating of sediments from the northern and western basins of Lago Maggiore and the southern basin of Lago di Lugano. Vertical distributions of ¹³⁷Cs in sediment cores taken in 2017/18 were compared to those of the sediment cores taken almost two decades ago at the same positions. This comparison showed that ¹³⁷Cs peaks do not alter their shape significantly over time and ¹³⁷Cs remains a reliable time-marker for many decades. ²¹⁰Pb dating using for the first time the piecewise "constant rate supply" (CRS_PW) model constrained with ¹³⁷Cs time-markers is performed for sediment cores of Lago Maggiore and Lago di Lugano. "Event-linked" mass accumulation rates (MARs) were derived from the CRS_PW model. In combination with the dry bulk density, organic matter content, ⁴⁰K and ²¹⁰Pb activity concentrations, these "event-linked" MARs were used for the identification of one or more event layers (turbidites, detrital layers) in 1-cm thick sediment samples. "Continuous" mean MARs which are independent of the event layers were estimated: in Lago Maggiore sediment cores they are 0.066-0.090 g cm^-2 yr^-1; in Lago di Lugano they vary in the range of 0.032-0.057 g cm^-2 yr^-1 with higher values in the time interval 1963-1986 as compared to 1986-present.