Luminescence dating of sediment mounds associated with shaft and gallery irrigation systems

Optically stimulated luminescence (OSL) techniques, supported by geomorphological analysis, have been applied to date the construction of shaft and gallery irrigation systems, more commonly referred to as qanats, falaj and foggara. The approach developed was tested on four hydraulic systems located in semi-arid landscape settings, three in Murcia, Spain, and the fourth in the Sus Tekna region, Morocco. Excavation of the characteristic sediment mounds that surround each ventilation shaft enabled a detailed examination of strata containing upcast deposits and their assignment to the main stages in the construction and use of the hydraulic feature. OSL techniques with single grain resolution applied to samples taken from the key strata provided age estimates for their deposition on the mound and, from these, dating of the construction and use of the system. Of the four irrigation systems analysed, the OSL dates indicated that the youngest had been constructed in the 19th century AD and the oldest, located in Murcia, was dated to the Roman period. The latter is of archaeological significance because the introduction of this particular form of hydraulic technology to Spain is widely identified as an Islamic innovation of the early 8th century AD.