Style and timing of the Tuaheni North landslide off the Hikurangi Margin

Submarine landslides are hazardous events capable of triggering deadly tsunamis and destroying costly seafloor infrastructure worldwide. Accurate landslide dating provides insights into their origins, recurrence patterns, and potential links to climate change. However, a comprehensive record of well-dated submarine landslides is currently lacking, limiting our ability to analyze past slope failures and quantify future risks.

This study investigates the morphology and timing of Tuaheni North, a significant landslide within the Tuaheni Landslide Complex on New Zealand's Hikurangi Margin. We provide insights into the timing and style of Tuaheni North’s slope failures, which may help identify their causes and recurrence patterns. Our analysis reveals a clear correlation between two major source volumes from Tuaheni North and corresponding downslope mass transport deposits (MTDs), indicating two distinct events. An intermediate layer separating the stacked MTDs suggests a significant time gap between the failures.

We introduce a novel method for dating submarine landslides that does not rely on sediment core analyses. Instead, we use seismic and bathymetry data to map bottom simulating reflections (BSRs) beneath the slide-impacted seafloor. BSRs are non-stratigraphic reflections marking the base of the temperature-sensitive gas hydrate stability zone. Submarine landslides disturb the sediment temperature field, and BSR depth serves as a proxy for dating these disturbances. Our findings suggest that Tuaheni North underwent several slope failures, displacing approximately 11.2 km³ of sediment. We estimate the ages of the two major slope failures at ~37 ka and ~23 ka, highlighting a substantial time gap between them.

New Zealand's Hikurangi Margin, known for its extensive gas hydrate and landslide activity, has over 2,200 recently identified slope failures. The 2-D age-dating method developed in this study can be applied to similar regions where gas hydrates and landslides coexist, both within New Zealand and globally. Additionally, we offer a publicly available interactive Windows application to facilitate similar studies.