Stable lead (Pb) isotopes and concentrations – A useful independent dating tool for Baltic Sea sediments

The prehistory of the Baltic Sea has for a long time suffered from imprecise dating, due to the large uncertainties associated with bulk radiocarbon dating of Baltic Sea sediments. To constrain the timing of environmental changes in the Baltic Sea it is critical to apply new dating approaches. This study identifies lead pollution isochrones in Baltic Sea sediments, which have previously been recorded in lake sediment and peat deposits in northern Europe and ice cores from Greenland. These isochrones have formed through the deposition of atmospheric lead associated with historic lead production and silver mining in Europe, and more recently with the increased industrial emissions that peaked in the 1970’s. Lead concentration and stable lead isotope analyses (206Pb/207Pb ratios) reveal three distinct lead pollution horizons in the Baltic Sea, i.e. a Roman peak at 1 AD, a Medieval peak at 1200 AD and a peak in the 1970s. The new data will improve the chronological accuracy and precision of paleoenvironmental studies in the Baltic Sea, and for the first time, allow synchronization of Baltic Sea geological records within the basin and across Europe and the North Atlantic region (including Greenland).

► Three Pb-isochrones have been identified in the Baltic Sea.
► These occurred at 1 AD, 1200 AD and in the 1970s.
► Pb-isochrones will improve the chronological control in the Baltic Sea.