Foraminiferal evidence for the provenance and flow history of turbidity currents triggered by the 2016 Kaikōura Earthquake, New Zealand

ABSTRACT

The 2016 Mw 7.8 Kaikōura Earthquake triggered simultaneous turbidity currents down ten submarine canyons along a 200 km stretch of the continental slope, east of New Zealand. Some discharged into the Hikurangi Channel which flows >1500 km northwards along the abyssal trench floor. To better understand provenance continuity in deep-sea sedimentary records, foraminiferal samples from the 2016 turbidites from 17 canyon and channel cores were used to investigate the source histories of these submarine gravity flows. Cluster analyses suggest the canyon provenances for most 2016 turbidite faunas should be determinable using a combination of the relative abundance of key benthic genera, planktic foraminiferal index (dissolution), absolute test abundance and planktic % of the foraminiferal faunas. Two ordinations (PCA, PCO) based on these parameters were used to infer provenance and flow history. One hundred kilometres down the Hikurangi Channel, faunas in the 2016 turbidite confirm a Kaikōura Canyon source. Further downstream, 200–500 km north of the confluence with Campbell, Cook and Opouawe canyons, faunas indicate that the 2016 turbidite in the northern Hikurangi Channel is a composite deposit, from an initial Opouawe-Cook canyon-sourced turbidity current over-ridden and partly mixed with, a Kaikōura Canyon-sourced flow that arrived sometime later.

KEYWORDS:

• Foraminiferal faunas
• turbidity currents
• provenance
• Kaikōura Earthquake
• Hikurangi Channel
• Kaikōura Canyon
• Campbell Canyon
• Cook Canyon
• Opouawe Canyon

Acknowledgements

We thank Lisa Northcote and Grace Frontin-Rollet, both of NIWA, for assistance in coping with Biosecurity issues, for helping to sample and sanitise the samples before they could be removed from the biosecure laboratory. Laura Wallace and Kate Clark, GNS Science, for their skills in obtaining the funding for this research and for coordinating our contribution to the much larger Endeavour Programme ‘Diagnosing peril posed by the Hikurangi subduction zone’. We thank the captains, crew and scientific party on board the NIWA research vessel RV Tangaroa during research cruises TAN 1613, 1701 and 1705 during which these cores were obtained. We are indebted to reviewer Michael Hannah and editor Kyle Bland for their improvements to the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Measured foraminiferal data for 2016 Kaikōura turbidite samples used in analyses is openly available in zenodo at https://doi.org/10.5281/zenodo.6482596. It contains information on all the foraminiferal samples studied from the 2016 turbidite in cores at bathyal and abyssal depths down the canyons and abyssal Hikurangi Channel, test size distribution, planktic percentage, absolute number of tests, planktic foraminiferal fragmentation index and census counts on key benthic foraminiferal genera.

The interview protocol for the elicitation of community preferences that support the findings of this study is openly available in zenodo at https://doi.org/10.5281/zenodo.6821332. This is the standardised protocol based on the Swing method that was used to elicit weight preferences for first-level and second-level management objectives with the overall goal of developing a collaborative management plan for Blueskin Bay estuary (Aotearoa New Zealand) together with the local community.

Additional information

Funding

Many of the authors received funding support for this work from a New Zealand Government Ministry of Business, Innovation and Employment (MBIE) Endeavour programme ‘Diagnosing peril posed by the Hikurangi subduction zone’ [grant number CONT-46722-CRFRP-GNS, contract C05X1605]. Research voyages in 2016 and 2017 were funded by the New Zealand (MBIE) Tangaroa Reference Group and the MBIE Endeavour programme and co-funding from a MBIE Strategic Science Investment Fund in the Marine Geological Processes programme in NIWA’s Oceans Centre. Funding for core analysis was provided by an EQC biennial research grant (No 18/756) and Royal Society of New Zealand Marsden 'Testing the veracity of turbidite paleoseismology using the Kaikōura earthquake’ grant (19-NIW-027, contract MFP-NIW1902).