Pore water geochemistry and bulk sediment 14C ages at Chatham Rise, Canterbury Shelf and Inner Bounty Trough, New Zealand

The pockmarks are concentrated above the flat-subducted Hikurangi Plateau. Echosounder data identifies recurrent episodes of pockmark formation at ~100,000yr frequency coinciding with Pleistocene glacial terminations.

Here we show that there are structural conduits beneath the larger pockmarks through which fluids flowed upward toward the seafloor. Large negative Δ¹⁴C excursions are documented in marine sediments deposited next to these subseafloor conduits and pockmarks at the last glacial termination. Modern pore waters contain no methane and there is no negative δ¹³C excursion at the glacial termination that would be indicative of methane or mantle-derived carbon at the time the Δ¹⁴C excursion and pockmarks were produced.