Criteria for the recognition of clastic halite: The modern Dead Sea shoreline

Abstract

AbstractSedimentological studies of modern halites have focused on shallow water to subaerially‐exposed saline pans, where in‐place crystal growth, dissolution and cementation textures dominate. Clastic halite transported and deposited by waves and unidirectional currents as bedload is poorly known. This paper: (i) describes and interprets the diagnostic sedimentary features of clastic halite from a modern outcrop exposed along the north‐western coastline of the Dead Sea; and (ii) provides criteria for recognition of clastic halite in the rock record. The 2 m thick halite unit at Nahal Og was deposited within the last four decades at water depths <30 m as Dead Sea levels fell ca 30 m. Clastic halites consist of frameworks of sorted crystals with point contacts and no preferred growth fabrics. Halite cumulates, deposited as suspended load, precipitated in the water column and sank to the brine bottom. The excellent sorting and purity of halite crystal layers are unique to cumulates. Small‐scale ripple cross‐stratified thin beds and intraclast conglomerates were deposited from bedload. Halite bedload deposits (composed of halite flat pebbles, ooids, rafts, single clear crystals, cumulate crystals, mud intraclasts and rounded mudballs, foraminifera, gypsum) reflect wave transport and deposition via oscillatory flow above wave base, or by unidirectional flow in the breaker and surf zones. In addition, waves on the Dead Sea coast generate longshore currents. Thin beds produced by wave‐influenced oscillatory transport of halite are symmetrical in cross‐section. Less common cross‐stratified units with asymmetrical cross‐sections indicate unidirectional currents. Clastic halite, especially as a bedload deposit, has rarely been identified in ancient evaporites. Shoreline deposits from ancient halites, however, must contain wave‐reworked and current‐reworked layers and should be common in saline giants, given their enormous size and potential for generating waves and currents. Documentation of modern clastic halite may lead to a better understanding of ancient hypersaline environments on Earth.