Dating dikes with luminescence

Dikes are important human-made earthworks of lowland environments which have been used for flood control, land reclamation, and water management for thousands of years. Determining the robust age of dike construction and development based on traditional dating methods (e.g., historical records, archaeological finds, and radiocarbon dating) is challenging due to the paucity of sources and suitable dating materials. Luminescence dating may provide a solution as it uses ubiquitous quartz or feldspar minerals to directly determine the burial age of sediments. In this study, we applied quartz optically stimulated luminescence (OSL) and feldspar single-grain post-infrared infrared stimulated luminescence (pIRIR) dating on two dikes: the Waal dike near Wolferen in the Netherlands and the Scheldt dike near Bornem in Belgium. Results indicate that OSL and pIRIR ages are in good agreement, and the reliability of results is further corroborated by comparison with independent age control (e.g., radiocarbon dating, archaeological finds, and historical records). Chronological results from the Waal dike indicate that dike construction started in the late 11 th or 12 th century CE, and the dike was reinforced in several phases during subsequent centuries. For the investigated Scheldt dike, construction started in the 16 th century CE, and the dike was raised to about 2.7 m soon after. Additionally, equivalent-dose distributions, especially for quartz OSL signals, indicate that sediments were generally well bleached. We suggest that coeval flood deposits were used for dike construction and that bleaching occurred during sediment transport and upon deposition in the floodplain rather than during dike construction. This seems logical in an area that is prone to flooding and receives regular supplies of fresh flood deposits as construction materials. • We present the first luminescence-based dike ages. • Luminescence dating provides reliable dike chronologies and construction-method insights. • Coeval surface deposits were the primary source of materials for dike construction.