English abstract
We used petrographic, heavy-mineral, and geochronological signatures of sand-sized grains to document an exceptional case of long-distance sediment transport dominated by eolian processes in a hyperarid climate. Feldspatho-quartzo-lithic orogenic detritus shed by the Anatolia Plateau and Zagros Mountains-including carbonate, chert, volcanic, metabasite, and ultramafic lithic grains with a rich epidote-amphibole-pyroxene-garnet heavy-mineral suite-was carried to the Arabian-Gulf foreland basin via the Euphrates-Tigris-Karun fluvial system and other rivers draining the Zagros, and blown inland by dominant Shamal winds to reach well into the Arabian foreland. Sediment dispersal over a cumulative distance of up to 4000 km took place in multiple steps, involving extensive eolian reworking of older deposits during lowstand stages of the Pleistocene before final accumulation in the Rub' al Khali sand sea. The siliciclastic fraction of Gulf beaches changes southeastwards from litho-quartzose carbonaticlastic and quartzose north of Qatar to quartzo-lithic carbonaticlastic along the Trucial Coast, but invariably contains chert, volcanic, and metabasite lithics, together with epidote, pyroxene, amphibole, and garnet. Dune sand inland is progressively enriched in quartz until composition becomes feldspatho-quartzose, whereas the heavy-mineral assemblage remains virtually unchanged. Beach and dune sands of the Gulf and northeastern Rub' al Khali were derived from Arabia, Anatolia, and the Zagros in varying proportions, with only local contribution from ophiolites of the northern Oman Mountains as revealed by cellular serpentinite and enstatite grains. In all samples detrital zircons yielded mostly Cambrian to Neoproterozoic ages reflecting "Pan-African" crustal growth and amalgamation of the Arabian shield, but several upper Paleozoic, Mesozoic, and Cenozoic zircons with ages as young as 5 Ma in northeastern Rub' al Khali dunes document ultimate provenance from the Anatolia-Zagros orogen. Quartzose dune sand of the southwestern Rub' al Khali, containing a moderately poor, amphibole-rich heavy-mineral assemblage and very few young zircons, is dominantly Arabian-derived. Relatively soft carbonate grains are typically concentrated in finer sand classes, which is ascribed to both mixing with coarser quartz recycled from Arabian siliciclastic covers and selective mechanical wear during multicyclic long-distance transport in high-energy eolian environments. Understanding the complex transfer of huge detrital masses on the Earth's surface, and mixing of sediments derived from different sources along successive tracts of a composite routing system that may cover cumulative distances of thousands of kilometers across climatic and tectonic boundaries over time periods of millions of years, is essential to enhance the resolution of source-to-sink studies and avoid gross oversimplifications in paleogeographic reconstructions.
