Dating Celtic fields with luminescence

Celtic fields are prehistoric field systems characterised by rectangular plots enclosed by earthen banks, which are widespread across northwestern Europe. They are assumed to have emerged between the final stages of the Middle Bronze Age and the Early Iron Age in continental Europe, but firm chronologies based on radiometric dating (e.g., 14C, luminescence) are sparse, hampering the interpretation of age and formation process. This leads to contrasting interpretations and unexploited potential of the systems to inform on societal transformations. This study focuses on luminescence dating and aims to develop a suitable luminescence dating procedure that can provide robust dates for the construction and raising of Celtic field banks. To achieve this, we sampled two banks in two Celtic fields in the Netherlands (Vaassen and Zeijen) in a systematic manner with high-resolution. We applied small-aliquot quartz optically stimulated luminescence (OSL) and single-grain feldspar post-infrared infrared stimulated luminescence (pIRIR) measurements. The systematic high-resolution sampling proved to be an effective sampling strategy that can provide detailed chronological information. Both quartz OSL and single-grain feldspar pIRIR provided consistent and reliable reliable dates for the time of construction and raising of the banks. Single-grain feldspar pIRIR analysis provided additional information about the formation process of the banks and bleaching history of the deposited material, but also demonstrated potential limitations in universal application. The dating results demonstrated that both investigated Celtic field banks were constructed in the Dutch Middle Bronze Age and have been gradually raised until the Dutch Roman Age. At Zeijen we documented a period of rapid raising of the bank in the Dutch Late Iron Age.