|Fallout-based radioisotopes – 137Cs and 210Pb – can be utilized for near-surface sediment dating.|
|Event-based 137Cs fallout: time markers for 1986 (Chernobyl NPP accident) and 1963 (high intensity of atmospheric nuclear weapon tests).|
|Continuous 210Pb fallout: depth distribution of ‘unsupported’ 210Pb can be used to calculate sediment accumulation rates.|
|Carbonates and micro-fossils in the sediment: radiocarbon based age-dating is available|
Radiocaesium (137Cs, t1/2 : 30.07 yr.) is originally absent in natureand has been produced and released by anthropogenic processes.Its most important global environmental source was thefallout from atmospheric thermonuclear weapon tests (from 1954to 1963) which peaked in the early 1960s and declined rapidly interms of intensity after the Nuclear Test Ban Treaty in 1963. Afterwards,the majority of Eurasia was affected by a subsequentdeposition of 137Cs due to the accident of Chernobyl Nuclear PowerPlant (26 April 1986). The depthdistributionof fallout-derived 137Cs is widely used to establishthe recent (max. 6 decades) chronology of sediment cores retrievedfrom various depositional systems.
210Pb geochronology is widely used to determine the ages of sediment layers in investigationsof a variety of environmental processes. Common applications include assessments ofmaterial fluxes to the seafloor, environmental pollution studies, and inter-calibration of multipletracers to determine event sequences in time. A 210Pb-chronology is determined for a sediment core based on the down-core activities of210Pbex (total minus supported).Profiles of 210Pbex versus depth (cm) and mass depth (g/cm2) are then used to calculatesediment accumulation rates and sedimentation rates, respectively, using various models, like CA (Constant Activity), CF (Constant Flux), CF:CS (Constant Flux, Constant Sedimentation), etc.