Contrasting styles of sediment dispersal and environmental signal propagation in hyperarid mixed carbonate–siliciclastic–evaporite systems: Red Sea vs. Arabian Gulf

Aridity drives many aspects of sediment production and dispersal in mixed systems. The northern Red Sea and Arabian Gulf are both hyperarid basins located at similar latitudes within the Afro–Arabian desert belt. Despite climatic and geographic propinquity, these basins have contrasting tectonic affinities that drive mixed carbonate–siliciclastic facies arrangements. This study combines field, remote sensing, core/bottom sample, and reflection seismic datasets to highlight extrinsic drivers of sediment mixing and partitioning linked to upland catchment characteristics, Quaternary sea level changes and salt kinematics.

The northern Red Sea is a nascent ocean basin characterized by rifted margins that transition abruptly from shallow fringing reefs to >3000 m water depths across slopes that exceed 70 degrees. Ephemeral wadis drain axially to the coast and deliver pulses of sediment during flash floods, which occur once a decade or less. Siliciclastic sediment is transferred by either: 1) bypass to the basin through shore-attached canyons, 2) longshore diversion to open canyon heads, 3) retention in backreef lagoons, or 4) “hoteling” in minibasins. Quaternary sea level fluctuations have resulted in coastal knickpoint incision, accentuated synoptic relief of canyon heads by reef growth and photozoan colonization of lowstand delta-top real-estate, and diversion of minor point sources into longshore cells. The neighboring Arabian gulf is a contiguous foreland basin characterized by a flexural, load-induced asymmetric profile that shallows from the Zagros mountains to a western flexural forebulge. The main siliciclastic point source is the Shatt al Arab at the northwestern terminus of the basin, which perennially drains a catchment area of more than 800,000 km2 transversely to form a watershed nearly equal to the aggregate area of wadi catchments that drain to the Red Sea. Turbidity and temperature variance drives facies compositions near the coast, which contain few coral reefs that grow on offshore piedmonts, while the coastline is dominated by mobile ooid–peloid admixtures.

This study highlights the influence of local/regional tectonic affinity as a major driver of carbonate–siliciclastic sedimentation patterns, not just through accommodation, but as a mechanism that forces feedbacks between local orography and coastal depositional systems that potentially overprint global environmental signals.