Comparative dating of recent peat deposits using natural and anthropogenic fallout radionuclides and Spheroidal Carbonaceous Particles (SCPs) at a local and landscape scale

Abstract

Abstract:Proxy records from recently accumulated peats provide valuable information about past environmental change, but they depend on high quality chronological information to calculate rates and timing of change. However, there is uncertainty in the accuracy and consistency of the methodologies used for dating recent peats. This study compares results from Spheroidal Carbonaceous Particles (SCPs) and natural and anthropogenic fallout radionuclides ( 210 Pb, 137 Cs and 241 Am) used to date three replicate cores from three contrasting sites. Data are used to test the consistency of dating techniques within and between sites, and to assess the impact of local conditions on geochronological results.There is broad consistency in results, but there is also a significant disagreement between dates in a number of cores, both within and between sites. A relatively dry site that had been affected by past burning and erosion showed the greatest consistency between methods and replicate cores. Wetter, less degraded sites showed least consistency. Using patterns of (dis)agreement between dating techniques we assess the potential causes of dating inaccuracy. The data support previous suggestions that 210 Pb is mobile in wetter conditions, and suggests that 241 Am can be considered an increasingly valuable radionuclide. Finally, our data suggest the current estimates for SCP-based ages in the region are incorrect and require further regional calibration.Using several techniques on replicate cores from three sites in the same area has provided a more robust evaluation of the likely reliability of individual techniques and the processes that may adversely affect them. We conclude that until advances are made in understanding the processes behind the variable quality of SCP and fallout radionuclide dating, using two or more dating techniques will greatly improve understanding of the validity of a peatland chronology, especially in wetter locations.

Recent environmental change in an upland reservoir catchment: a palaeoecological perspective

“…The total fallout 210 Pb inventory in the lake sediment cores (*21,000 Bq m -2 ) was considerably greater than inventories from nearby undisturbed bogs (*6,000 Bq m -2 ) (Parry et al 2013). Sediment focusing is generally cited as the main reason that inventories from lakes are larger than local fallout inventories (San Miguel et al 2003).…”

Peat bog and alluvial deposits reveal land degradation during 16th‐ and 17th‐century colonisation of the Western Carpathians (Czech Republic)

“…In comparison with these chronological markers, 137 Cs activity displays a slight discrepancy as its occurrence follows the increase in heavy metals concentrations and also the exponential growth of Picea abies curve dated to the end of 19th century. This misalignment may be explained by vertical migration of 137 Cs (Ciszewski, Czajka, & Błażej, ; Parry, Charman, & Blake, ).…”

“…In comparison with these chronological markers, 137 Cs activity displays a slight discrepancy as its occurrence follows the increase in heavy metals concentrations and also the exponential growth of Picea abies curve dated to the end of 19th century. This AD 1961-1990(Büntgen et al, 2013 and solar activity minima (Usoskin, 2017), and (c) timing of the Wallachian colonisation in Carpathian regions (after Štika, 2007, source of topographic background: SRTM3, provided by USGS; Natural Earth vector data) misalignment may be explained by vertical migration of 137 Cs (Ciszewski, Czajka, & Błażej, 2008;Parry, Charman, & Blake, 2013).…”

Using palaeoecology to advise peatland conservation: An example from West Arkengarthdale, Yorkshire, UK

“…Spheroidal carbonaceous particles (SCPs) are small spheroidal particles of carbon produced from the incomplete combustion of fossil fuels (Parry, Charman, & Blake, 2013). They are emitted to the atmosphere and dispersed over wide geographical areas and as a consequence, they have been recorded in many areas of the world including those remote from sources.…”

“…SCPs are well preserved in peat sediments and have proved useful for reconstructing atmospheric pollution histories and as age-equivalent markers for dating stratigraphic sequences covering the last 150 years (Swindles, 2010). They can provide several relative dating features: the start of the record in the mid-19th century; the postSecond World War rapid increase in concentration; and the SCP concentration peak in the 1960s (Rose & Appleby, 2005;Parry et al, 2013). The SCPs were counted alongside pollen (as the pollen preparation method used in this study does not degrade SCPs) and therefore the results are displayed on the pollen diagram (Fig.…”