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Located in the arid basalt desert of northeastern Jordan, the settlement of Jawa is by far the largest and best-preserved archaeological site in the region. The Early Bronze Age (EBA) settlement phase of Jawa (3500-3000 BCE) is characterized by a highly sophisticated water storage system made of a series of pools, dams, and canals. In addition, recent archaeological and geoarchaeological surveys have uncovered agricultural terrace systems in the nearby vicinity.

In this study, four of these runoff terrace systems were investigated by detailed mapping. Additionally, thirteen sediment profiles from inside and outside the terrace systems were recorded and sampled. The examined samples were analyzed for bulk chemistry, texture, phytoliths, diatoms, and dung spherulites to supply information on the environmental and depositional conditions. The terrace systems were dated using optically stimulated luminescence (OSL).

Ancient terrace agriculture was practiced on slopes, small plateaus, and valleys close to Jawa through the use of surface canals, which collected and diverted floodwater from nearby wadis or runoff from adjacent slopes. The terraced fields were usually arranged in cascades and comprised a system of risers, canals, and spillways. The terrace fills investigated yield OSL ages of around 3300 BCE, indicating that the terraces were constructed in the Early Bronze Age. The terrace fill sequences are composed of mixed unstratified fine sediments of local origin, reflecting low-energy fluvial deposition regimes. The phytolith record is dominated by Pooid grasses that include the most common Near Eastern cereals, such as wheat and barley. Increased phytolith concentrations in terrace fill sediments, as compared to samples from non-terrace deposits nearby, suggest increased plant growth and water availability within the terraces. Whether the terrace systems were used for growing food crops only or whether they were additionally used for grazing cannot be ascertained. Overall, quantitative phytolith analyses in arid environments are well suited to investigate temporal and spatial distributions of plant microfossil concentrations and their relation to human activity or paleoenvironmental conditions. (C) 2016 Elsevier Ltd and INQUA. All rights reserved.