Structural and textural characteristics of surface halite crusts of a supratidal, ephemeral halite pan, South Jeddah, Red Sea Coast, Saudi Arabia

Abstract

Two saline (halite and gypsum) pans have recently developed overlying lagoonal and sabkha sediments in the Şarūm area, south Jeddah, Saudi Arabia, as a result of the construction of an asphaltic road 30 years ago. Structural and textural characteristics of the halite layers reflect their formation during flooding, evaporative concentration, and desiccation stages of the ephemeral halite pan. The flooding stage textures record partial dissolution of the halite crusts, resulting in the formation of truncation surfaces, microkarst pits, pipes, and vugs. Microbial mats can flourish within dissolution vugs, despite the ambient high salinity of the brine. The evaporative concentration stage is characterized by the formation of thick, flat, halite crusts, in addition to isolated masses resembling cauliflowers, mushrooms, and platforms. The halite crusts and isolated masses consist of cumulate rafts and pyramidal hoppers, chevrons, and cornets. Agitation of the brine by waves or currents induced by wind favors the formation of rippled and clastic halite. Desiccation stage textures are represented by polygonal fractures and ridges, chaotic mud-halite filling microkarst pits and pipes, overgrowths, and displacive and efflorescent halite crystals. Field and petrographic studies and major element geochemistry of the brine indicate that the main recharge to the halite pan is from numerous seawater seepage points without direct connection to the Red Sea water or surface drainage. The results of this study provide valuable sedimentological information that could be useful in the interpretation of similar ancient halite.