Sedimentary and Microfossil Record of the 2013 Typhoon Haiyan Deposit from the Leyte Gulf, Philippines

The uncertainty surrounding typhoon hazards for the Main Development Region (MDR) in the North Pacific, the most active tropical cyclone region in the world, was tragically underscored on 7 November 2013 when Typhoon Haiyan made landfall on the Philippines as a Category 5 super typhoon. The short observational record of land-falling typhoons was insufficient in preparing the Philippines for such a rare, intense storm. Examining the sediments deposited by typhoons assists the understanding of the long-term spatial and temporal variations in typhoon frequency and intensity. We describe the microfossil assemblages contained within overwash sediments deposited by Typhoon Haiyan when it made landfall on the Philippines. The microfossil assemblages from four transects were assessed less than two months following the typhoon’s landfall.

Along each transect, Typhoon Haiyan deposited sediment up to 1.5 km inland, blanketing low-lying grassy plains and rice paddies. The Haiyan deposit is patchy and variable in thickness (ranging from <1 cm to 7 cm) as a result of inherited topography. In general, the Haiyan deposit thins landward and could be discriminated from underlying sediment by its light beige color and allochthanous microfossils. Foraminiferal assemblages contained within Haiyan sediments reveal important data regarding the typhoon that cannot be discerned from sedimentologic and stratigraphic analysis alone. At the relatively low energy carbonate environment, the Haiyan assemblage was dominated by intertidal species (e.g., Ammonia parkinsoniana), with deeper-dwelling species (e.g., Eponides repandus), and planktics present in lesser amounts. Foraminifera within the deposit at this site were both pristine and abraded, indicating that overwash sediment was sourced from depth as well as from shallow, intertidal environments. However, at transects near Tacloban along the higher energy clastic environment, foraminifera were less abundant and dominated by planktics, hindering provenance assessment. Testate amoebae, which originate in grass and rice paddy soils are present in the Haiyan overwash deposit and indicate backwash from the receding storm surge. This study serves as an important modern analogue for future paleotempestology studies in the Philippines and at other tropical locations.