Testing foraminiferal taphonomy as a tsunami indicator in a shallow arid system lagoon: Sur, Sultanate of Oman

The tsunami produced by the 1945 Makran Trench earthquake is considered to be the second deadliest in the Indian Ocean after the 26 December 2004 Indonesian event. The tsunami struck Iran, Pakistan, India and Oman; however, historical records outside of India and Pakistan are sparse due to limited populations in those regions and little communication with larger cities. Sur Lagoon, Oman, a small microtidal lagoon, contains stratigraphic evidence of the 1945 tsunami. The goal of this study is to test the utility of foraminiferal provenance and taphonomy as an indicator of the 1945 event and examine its potential in detecting older events in the geologic record. Foraminiferal (taxa and taphonomy) and high resolution particle size analysis show that high abundances of predominantly marine taxa (Amphistegina spp., Ammonia inflata, and planktics) associated with the tsunami bed indicate an outside marine origin for the sediment. Influxes of large test sizes and fossil specimens support a shallow marine provenance. Findings indicate that foraminiferal analysis, when combined with other proxies (e.g. mollusc taphonomy, particle size distribution), can be used to delineate tsunami units from normal background sedimentation in intertidal systems. This technique holds potential for detecting older events in Sur Lagoon which are documented in historical texts, but as of yet, have not been ‘ground-truthed’.

► Tsunami overwash can be preserved along arid coastlines. ► Foraminiferal taphonomy was used to document the 1945 Makran Trench tsunami. ► Large, fragmented tests, fossil specimens and marine taxa were tsunami indicators.