Aeolian dune accommodation space for Holocene Wadi Channel Avulsion Strata, Wahiba Dune Field, Oman

Geomorphic evolution of the Wahiba Dune Field, Oman, during the Quaternary has occurred within a set of boundary conditions that include climatic forcing of fluvial, aeolian and eustatic cycles within an active tectonic basin. Because of basin down-warping and sediment transport into the basin, evolution of the geomorphic surface has been accompanied by the generation of a distinctive stratigraphic record. The coupled geomorphic and stratigraphic record of the northeastern portion of the dune field illustrates wadi-aeolian interactions, in which a channel avulsion, likely initiated during a flood, scoured through the interdune corridor between linear dunes. Interdune outcrops (7 m thick) consist of a lower interval interpreted as deposited by ephemeral fluvial flow, but an upper interval consists of six fining-upward units, each of which is interpreted to represent a flood event that culminated in ponding followed by desiccation. Luminescence dating indicates that the channel remained open for 2- 3 ka during the Holocene, but ground-penetrating radar imaging shows that dunes encroached into the channel between floods and suggests that the transition from ephemeral flow to ponding resulted from dune damming. Maximum channel width and length are unknown, but width was greater than the current interdune area, and a speculative extended channel course is identified. Subsequently, interdune strata and linear dunes were buried by crescentic dunes sourced by an influx of sand with wadi affinity. The resultant complex stratigraphic architecture illustrates the role of existing surface topography in providing local geomorphic accommodation space for short-lived, concentrated patterns of sedimentation. (C) 2020 Elsevier B.V. All rights reserved.