210Pb Dating

Abstract

During the last decade, there has been an unprecedented push to learn more about how the environment has changed over time. This interest is grounded in trying to better understand differences between natural-and anthropogenic-driven changes and how our environment may respond to such changes in the future. One of the most fundamental steps in establishing a record of environmental change is to first derive an accurate geochronology. The geochronologies generated by210Pb analysis can resolve the very recent past (last 100–200 years), with total (1s) uncertainties varying from just under 1 year to around a decade (Baskaran 2011). However,210Pb geochronol-ogies are not without inherent problems and uncertainties (Robbins and Edgington 1975; von Gunten and Moser 1993). The development of a210Pb geochronology should never become a routine exercise (Appleby and Oldfield 1992; Appleby 2008). Even some recent studies that employ210Pb as a geochronometer still fail to meet the minimum requirements identified by Oldfield and Appleby (1984). For example, some of these efforts may fail to adequately evaluate inconsistencies in competing210 Pb models, or they may forego assessing210Pb model results against independent geochronologies (e.g., other radioisotope systems or varve counting). Lastly, some210 Pb applications may ignore postdepositional mixing (Benninger et al. 1979; Berner 1980; Miguel et al. 2003) that can yield a surprisingly plausible down-core210Pb profile but which produces a geochronolog-ical model that is simply invalid (Kirchner 2011). That said, a carefully developed210Pb geochro-nology, and one substantiated in the peer-reviewed literature per recommendations outlined in Smith (2001) and Hancock et al. (2002), is invaluable in any recent environmental reconstruction. Sediment dating using210 Pb methods will continue to be refined with new improvements in analytical and model capabilities.