Holocene dust accumulation in the southern Levant: the role of local sources and fixation processes

Initial soils covering archaeological ruins in the southern Levant include fine grain size fractions that may stem from aeolian sediments. Thus, ruins could act as effective dust traps which preserved rare Holocene aeolian records. We assessed physical parameters and chemical composition of initial soils covering archaeological ruins in the Negev and southern Jordan, including clay mineralogy and Sr- and Nd-isotopes, which we compared with modern dust from collectors installed close to the sites. A significant contribution from local weathered rocks could be observed in southern Jordan. In the Negev, the contribution of rocks was negligible, probably due to greater rock hardness and abundant biological crusts sealing surfaces. However, loessial paleosols surrounding the sampled archaeological ruins were "recycled" in the Negev. Compared to modern settled dust, archaeological soils in southern Jordan are enriched with various major and trace elements associated with clays and oxide coatings of fine silt particles. This was not due to in-situ weathering, which was found to be minimal. However, site-specific fixation processes may explain variations of dust records at the studied sites. In addition, modern dust samples associated with precipitation, in particular snow, were found associated with higher amounts of major and trace elements. Initial soils covering ruins in the southern Levant therefore suggest that the formation of soils in desert fringes may less be a function of dust supply, but more of dust deposition and fixation processes. There are multiple, local and regional dust sources and dust-generating processes active in drylands, but deep loessial soils form only when dust fixation is effective.