NEOICHNOLOGY OF A MICROTIDAL CARBONATE INTERTIDAL ZONE: ABU DHABI, U.A.E.

Abstract The Abu Dhabi coast, particularly the supratidal zone known as the “sabkha”, has been a subject of geological interest in recent decades due to its relevance as an analogue for subsurface petroleum reservoirs. The intertidal zone (Al Qantur lagoon) has received less attention, especially regarding neoichnological investigations. This study addresses this research gap by combining modern sedimentological and neoichnological observations. Three recurring depositional textures are identified in the sediments examined: the bioturbated peloidal grainstone, microbially laminated bindstone, and bioclastic rudstone. Observed burrows are generally of two types; those attributed to worms (Nereis polychaetes) and those to decapod crustaceans. Crustaceans homogenize sediments in distal areas by excavating dwelling structures, while worms act as mobile deposit feeders. The relatively low complexity and diversity of burrowing morphologies in Abu Dhabi are attributed to heightened environmental stressors, including salinity, heat, and subaerial exposure, as well as upward seepage of hypersaline continental brines. Porewater analyses indicate a stabilization of salinity within burrows, suggesting the infauna irrigate their burrows to cope with elevated salinity. Crustacean burrows enhance solute advection in the lower intertidal zone by increasing substrate permeability, facilitating the penetration of less-saline surface waters to greater depths. This study provides a unique neoichnological examination of Abu Dhabi’s intertidal zones and assesses the impact of bioturbation on solute advection, an aspect often overlooked in contemporary carbonate sedimentological studies.