ABSTRACT
This study documents the formation of distinctive, microbially induced sedimentary surface structures (MISS) in recent intertidal-supratidal and interdunal sabkhas and saline pans, a supralittoral ephemeral lake, and solar saltworks in the Red Sea and the Arabian Gulf coasts of Saudi Arabia and Egypt. MISS occur commonly during the wintertime due to submergence of the evaporation settings from inflowing of low salinity water from torrential rainfalls, continental mountainous flooding, marine flooding, seawater, and/or groundwater seepage. In the summertime, the increased salinity of surface and subsurface brines decreases the flourishing of microbial mats and favours the deposition of evaporite minerals. MISS are distinguished into (1) mat growth structures (MGS) such as photosynthetic mat layers, reticulate patterns and tufts; (2) mat deformation structures (MDS) that are induced by (a) water movement due to wind friction, such as wrinkles, detached mats, erosion pockets and remnants, and mat chips and (b) escape of gases such as gas bubbles, gypsum blisters, cones, domes, pinnacles, polygonal folds (petees) and sand volcanoes; and (3) desiccation-related structures such as microbial shrinkage cracks. The distribution of MISS is controlled by the topography of the evaporation settings, salinity, brine depth, degree of submergence and emergence, and water friction. The results of this study allow the recognition and discrimination of the environmental conditions that control the formation of MISS in saline evaporative settings.
