The carbonate-evaporite lagoon of Al Dakhirah (Qatar): an example of a modern depositional model controlled by longshore transport

Abstract

The southern coast of the Arabian Gulf is considered a good example of an arid carbonate depositional system. The objective of this field investigation is to better elucidate the dynamic controls on the character and pattern of the depositional belts in a carbonate-evaporite lagoonal setting. The interpretation of this lagoon is based on combined field examination and laboratory analyses of surface samples, and this has resulted in an updated depositional model for carbonate-evaporite lagoonal settings. This study highlights the effects of sediment transport by longshore currents, with the formation of sand spits that gradually closed the lagoon during their southwards migration. The associated narrow and elongated back-barrier settings consist of tidal-dominated muddy sediments affected by a network of tidal channels. This wave-dominated high-energy system has generated several carbonate barrier and back-barrier units that migrated southwards and seawards during the last few thousands of years. This updated depositional model significantly differs from shoreline-parallel facies tracts of the classical Trucial Coast model, where the dominant wind is orientated perpendicular to the coastline. Conversely to the sediment belts of the Trucial Coast, the Al Dakhirah lagoon displays a strongly asymmetrical pattern of the sediment belts, marked by a southwards and seawards migratio

Sediment-filled karst depressions and <i>riyad</i> – key archaeological environments of south Qatar

“…The sample was washed using a centrifuge until a pH value of 6-8 was reached to avoid neutralization after the addition of 0.5N Na 4 P 2 O 7 (55.7 g L −1 ) for aggregate dispersion. Calculation of statistical parameters was performed using the GRADISTAT statistic package (Blott and Pye, 2001).…”

General considerations and highlights of low-lying coastal zones: passive continental margins from the poles to the tropics

“…Similarly, longitudinal travels from humid to more arid coastal regions within the warm climatic zones would reveal the characteristic humid coasts of eastern Central America, the sandy deposits of the desert coasts of Namibia and western South Africa and, further afield, the evaporitic landscape and deposits of the western coasts of the Persian Gulf (Billeaud et al 2013). Most similarities and differences between all these coasts have long been known and described, yet the great variety of coastal zones makes their classification not a trivial task.…”

“…This is known as the Messinian Salinity Crisis of the Mediterranean area (Cita 1982;Krijgsman et al 1999;Bassetti et al 2004;Wikipedia 2014) that occurred during the warm Miocene epoch at 5.5 Ma, and thick evaporite deposits were formed throughout the basin. An example of modern extensive evaporites occurs along the southwestern coast of the Persian Gulf (Billeaud et al 2013). …”

“…Another typical tropical coast is related to the overwhelming input of mud from major rivers; the development and alongshore migrations from the Amazon delta northwards of the numerous, very large coastal mud banks are analysed by Anthony et al (2013). Finally Billeaud et al (2013) examine evaporitic and carbonate deposits of a lagoon partially enclosed by large carbonate spits along the arid Qatar peninsula of the Persian Gulf.…”

“…To restrict the otherwise huge comparative task, the focus has been placed on Atlantic shores of the Americas. As contrast, a few outlier papers deal with coastal dunes of temperate areas of South Africa and South Australia, evaporite -carbonate settings (Billeaud et al 2013) and the effect of Late Pleistocene to Present vertical movements on Mediterranean Sea coasts (Anzidei et al 2014). Twenty-three papers have been collated that deal with global and regional reviews of coastal zones and reports of novel research in specific areas (Fig.…”