GEOCHEMICAL CHARACTERISTICS OF DEPOSITS LAID DOWN BY THE 2016 KAIKOURA TSUNAMI AT LITTLE PIGEON BAY, NEW ZEALAND

The 14^thNovember 2016 Mw 7.8 Kaikoura earthquake led to the rupture of at least three faults offshore of northeastern South Island, New Zealand, two of which triggered complex seafloor displacement that generated a tsunami. Located approximately 160 km south of the tsunami source area, Little Pigeon Bay on Banks Peninsula received the only reported severe impacts of this event, including seawater inundation and building damage.

This study records and interprets the geochemical signatures of surface sediments deposited by the Kaikoura tsunami at Little Pigeon Bay. Surface samples were taken within a month as well as four months after the event and analyzed by a portable X-Ray Fluorescence (pXRF). The concentrations of marine (shell hash) and salinity indicators, such as Ca, Sr and S as well as electrical conductivity measurements, exhibit inland decreasing trends. Grain size indicators (Rb and Al) remain constant both through time and across the ~ 230 m inland transect. The landward decreasing concentrations of Ti and Fe highlight the mineral composition of the tsunami sand deposit, while the opposite trend for K concentration reflects the mineralogy of the underlying soil. These general geochemical characteristics as well as the anomalies observed imply that the tsunami energy decreased landward from shore and away from the dry stream channel. Geochemical similarities were also examined by defining the tsunamigenic and terrestrial origins on the Ca/Ti vs. Sr/Ba diagram, which could potentially be useful for future studies on paleo-tsunami deposits at Little Pigeon Bay and the eastern bays of Banks Peninsula.