The First Field Evidence of the Miocene Paleo-Tsunami Deposit in the Arabian Peninsula: Dam Formation, Qatar

Tsunami deposits are products of wave-train propagation triggered by dynamic sources and shaped by complex hydrodynamic processes. While the Arabian Gulf is traditionally characterized as a low-energy, shallow-marine environment, our findings present the first evidence of a high-energy, multi-bed tsunami succession discovered within the Miocene Dam Formation in southwest Qatar. The tsunami sequence consists of three beds (Beds 1, 2, and 3) separated by two intervening backwash horizons.Bed 1 marks the initial impact, unconformably overlying the sabkha facies, characterized by shale and evaporite alternation. This unit begins with wave-splash and traction-carpet structures, grading upward into a yellowish-gray sandy matrix containing pebbles and mollusk shells. Bed 2 represents a significant increase in wave energy, characterized by inverse grading and the presence of large, porous sandstone rip-up clasts and oversized mollusk shells. Bed 3 reflects the waning phase of the tsunami wave train, deposited as a suspension-load unit exceptionally rich in centimeter-scale echinoid fossils. Notably, the tsunami deposit exhibits a significant landward thinning geometry, tapering from a thickness of ~200 cm to only a few centimeters along an S to N transect.Paleocurrent analysis derived from sedimentary structures reveals a primary run-up direction towards the northwest, while backwash trends exhibit high variability, generally from NE to SE. Given the paleogeographic position of Qatar, these vectors possibly indicate that the active Zagros Thrust Belt was the main source of the tsunami. Despite the shallow bathymetry of the Arabian Gulf, the seismic potential of the Zagros Thrust Belt and the Makran Subduction Zone -either through direct seismic displacement or secondary submarine landslides- remains a critical threat to the region. This study provides an essential baseline for re-evaluating tsunami hazard potential in supposedly stable platform environments.Keywords: Arabian Gulf, Multi-bed Tsunami, Miocene Paleo-tsunami, Tsunami Wave-Train