Luminescence dating approaches to reconstruct the formation of plaggic anthrosols

Summary

Plaggic anthrosols demonstrate the significant and widespread influence of agriculture on the landscape of northern Europe and testify to increased land-use intensity over the last millennium. However, a lack of established chronologic methods to interrogate these soils has hindered research on their formation history, so the timing and process of plaggic anthrosol development remain poorly quantified. Recently, luminescence dating methods have emerged as a tool for tracing the past movement of grains, including within the soil column. This study combines two primary luminescence methods - single-grain feldspar infrared stimulated luminescence (IRSL) along with post-infrared infrared stimulated luminescence (pIRIR) measurements and small-aliquot (or multi-grain) quartz optically stimulated luminescence (OSL) - to reconstruct the formation of a plaggic anthrosol at Braakmankamp (eastern Netherlands). Toward this aim, we present a new method to identify well-bleached single grains of feldspar using the ratio of the grain's IRSL and pIRIR signals as a filter. The results provide both methodological and applied archaeological insights. Both small-aliquot quartz OSL and single-grain feldspar pIRIR ages yield reliable ages for plaggen deposits when the new filtering approach is used to remove poorly bleached feldspar grains from the analysis. Single-grain pIRIR feldspar has the added benefit of revealing complex soil formation histories for naturally bioturbated deposits, including those at the base of the plaggen layer. Augmenting this information with conventional quartz OSL dating builds confidence in the geo-chronologic record and allows us to reconstruct the timing and processes of plaggic anthrosol formation in Braakmankamp. According to the luminescence dating results, land clearance occurred around 900-1000 years ago, and accumulation of plaggen material began around 700-800 years ago. The average accumulation rate of plaggen material is estimated at ∼ 1.1 mm yr^-1.