Heat flow profile HF1625 across Hikurangi Margin, New Zealand during SONNE cruise SO247 (SlamZ)

A transect of seafloor heat probe measurements on the Hikurangi Margin shows a significant increase of thermal gradients upslope of the pinchout of the base of gas hydrate stability. We attribute these anomalously high thermal gradients to a fluid pulse leading to advective heat flow while endothermic cooling from gas hydrate dissociation may arrest temperature gradients in the hydrate stability field. Double-bottom simulating reflections in the study area are likely to be caused by uplift based on gas hydrate phase boundary considerations. Previous studies predict a seamount on the subducting Pacific Plate to cause significant overpressure beneath our study area, which may be the source of the fluid pulse. We suggest this seamount may also cause the inferred uplift. Transient expulsion of warm fluids may lead to gas hydrate dissociation with potential implications for seafloor stability.