Trench floor depositional response to glacio-eustatic changes over the last 45 ka, northern Hikurangi subduction margin, New Zealand

ABSTRACT

Glacio-eustatic cycles lead to changes in sedimentation on all types of continental margins. There is, however, a paucity of sedimentation rate data over eustatic sea-level cycles in active subduction zones. During International Ocean Discovery Program Expedition 375, coring of the upper ∼110 m of the northern Hikurangi Trough Site U1520 recovered a turbidite-dominated succession deposited during the last ∼45 kyrs (Marine Isotope Stages (MIS) 1–3). We present an age model integrating radiocarbon dates, tephrochronology, and δ¹⁸O stratigraphy, to evaluate the bed recurrence interval (RI) and sediment accumulation rate (SAR). Our analyses indicate mean bed RI varies from ∼322 yrs in MIS1, ∼49 yrs in MIS2, and ∼231 yrs in MIS3. Large (6-fold) and abrupt variations in SAR are recorded across MIS transitions, with rates of up to ∼10 m/kyr occurring during the Last Glacial Maximum (LGM), and <1 m/kyr during MIS1 and 3. The pronounced variability in SAR, with extremely high rates during the LGM, even for a subduction zone, are the result of changes in regional sediment supply associated with climate-driven changes in terrestrial catchment erosion, and critical thresholds of eustatic sea-level change altering the degree of sediment bypassing the continental shelf and slope via submarine canyon systems.

KEYWORDS:

• Hikurangi subduction margin
• sedimentation
• gravity flows
• tephra
• radiocarbon date
• age model
• glacio-eustatic cycles
• IODP

Acknowledgements

We would also like to extend our thanks to Michael Underwood and Atsushi Noda for useful discussion on the manuscript, Alan Orpin for assistance with radiocarbon calibrations, and Francisco Saldana-Monroy for interpretation of bioturbation structures. We thank Lionel Carter, Fabien Paquet, and two anonymous reviewers for constructive and insightful reviews of the manuscript.

Disclosure statement

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

Data availability statement

The supplementary information, ten supplementary figures, and six supplementary tables that support the findings of this study are openly available in figshare at https://doi.org/10.6084/m9.figshare.19391531.v3.

Additional information

Funding

This research used samples and data provided by the International Ocean Discovery Program (IODP). Funding for this research was provided through UK IODP by the Natural Environmental Research Council (NERC Grant NE/S008853/1), the New Zealand Ministry for Business Innovation and Employment (MBIE) Contract CO5X1605, NIWA Science Core funding Programme COPR, and the Marsden Fund Contract 20-UOA-099. K. Pank and S. Kutterolf have been supported by the German Research foundation, DFG, within the project KU2685/11-1. L. LeVay and K. Petronotis were supported by IODP-JRSO NSF Award 1326927.