Abstract Volume Geoscience Society of New Zealand Miscellaneous Publication 151A ABSTRACT VOLUME Organising Committee Chairperson Joe Prebble (GNS Science) Organising Committee Helen Bostock (NIWA) Jenni Hopkins (Victoria University of Wellington) Cécile Massiot (GNS Science) Sarah Milicich (GNS Science) Christian Timm (GNS Science) Rose Turnbull (GNS Science) Administration Janet George (Absolutely Organised) 1 SPONSORS Gold Silver & Poster Session Silver Bronze & Icebreaker Bronze Plus Bronze Supporting Exhibitor Lanyards 2 BIBLIOGRAPHIC REFERENCE FOR ABSTRACTS Author A, Author B, Author C 2018. Title. In: Sagar M, Prebble J ed. Abstract Volume: Geosciences 2018, Napier, New Zealand. Geoscience Society of New Zealand Miscellaneous Publication 151A. p 123. Geoscience Society of New Zealand Miscellaneous Publication 151A ISBN (online): 978-0-473-45947-5 ISSN (online): 2230-4495 3 CONTENTS SPONSORS ............................................................................................................................................ 2 BIBLIOGRAPHIC REFERENCE FOR ABSTRACTS ..................................................................................... 3 CONTENTS ............................................................................................................................................ 4 PLENARY ABSTRACTS ........................................................................................................................... 5 ABSTRACTS ......................................................................................................................................... 11 4 PLENARY ABSTRACTS THE HIDDEN CONTINENT OF ZEALANDIA YIELDS NEW EVIDENCE FOR HOW SUBDUCTION STARTS R Sutherland1, J Dickens2, P Blum3 & participants of IODP Expedition 371 1School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140 2Rice University, Houston, TX 77005, USA 3Texas A&M University, College Station, TX 77845, USA [email protected] There are seven continents on Earth, but Zealandia is one of the least well known, because 96% of it lies submerged beneath the ocean. Northern Zealandia, a region about the size of India between New Zealand, New Caledonia, and Australia, was investigated during International Ocean Discovery Program (IODP) Expedition 371 in late 2017. The only previous expedition to sample this region to a similar depth was DSDP Leg 21 in 1971. Subduction zones drive plate tectonics and global geochemical cycles, but little is known about how they start. The most profound subduction initiation event and global plate-motion change since 80 Ma occurred in the early Eocene, when Tonga–Kermadec and Izu–Bonin–Mariana subduction initiation corresponded with a change in direction of the Pacific plate (Emperor–Hawaii bend) at ~50 Ma. Expedition 371 precisely dated and quantified deformation, uplift/subsidence, and volcanism associated with Tonga–Kermadec subduction initiation. Existing geodynamic models are not able to explain the range of observations we made, and a new class of model is currently under development. Our observations provide new insight into the role of subduction zone initiation as a continent-altering process. 5 OCEAN PLANET—ANZIC AND THE NEXT PHASE OF THE INTERNATIONAL OCEAN DISCOVERY PROGRAMME L Armand1 Research School of Earth Sciences, Australian National University, ACT, Australia [email protected] The International Ocean Discovery Program (IODP), turned 50 this year. The program is recognised as the global community’s longest and most successful marine geoscience program. Throughout the life of this program, the IODP scientific strategy has been to answer globally-significant research questions about the Earth’s structure, and the processes that have, and continue to, shape our planet and its climatic history. The current strategic plan (2013–2023) has been shaped and delivered through international community-driven input. It is a plan that nations and other global research bodies consider when planning their own scientific plans and strategies. With the end of the current strategic plan fast approaching in 2023, the IODP Forum has opened discussion again to look at our current four themes (Climate and Ocean Change, Biosphere Frontiers, Earth Connections and Earth in Motion) and 14 challenges to decide on where our successes have been and what globally-significant research questions will next face our Ocean Planet. The Australian and New Zealand IODP Consortium (ANZIC) will again shape this future strategy with a new workshop “OCEAN PLANET—Developing the new IODP Strategic Plan 2024–2034” on April 14–16 2019. While we may reflect on how far we have come, and the successes of the past two years due to an IODP focus in our region, it is now time to think about how our nations, with support from our Universities, Government research institutions and agencies, will continue our strong collaboration and also provide input from our community (from early and mid-career through to established researchers) to ensure the global questions include those of relevance to our nations and the southern hemisphere. 6 DRILLING AND CORING THE NORTHERN HIKURANGI SUBDUCTION MARGIN TO UNLOCK THE SECRETS OF SLOW SLIP: INTERNATIONAL OCEAN DISCOVERY PROGRAM (IODP) EXPEDITIONS 372 AND 375 P Barnes1, D Saffer2, L Wallace3, I Pecher4, K Petronotis5, L Levay5 & IODP Expedition 372 & 375 scientists 1National Institute of Water and Atmospheric Research, NIWA, PO Box 14901, Wellington 2Department of Geosciences, Pennsylvania State University, USA 3GNS Science, PO Box 30368, Lower Hutt 5040 4School of Environment, University of Auckland, Private Bag 92019, Auckland 1142 5International Ocean Discovery Program, Texas A&M University, USA [email protected] Slow-slip events (SSEs) at the northern Hikurangi subduction zone, New Zealand, are among the shallowest on Earth, and recur every 1–2 years. At depths of 2–15 km and potentially reaching the seafloor, they offer a unique opportunity to use scientific ocean drilling to investigate the processes and in situ conditions associated with SSEs. International Ocean Discovery Program (IODP) Expedition 375 (March–May 2018) together with part of Expedition 372 (November 2017–January 2018) were designed to address three broad scientific objectives: (1) characterize the incoming plate and shallow plate boundary fault near the trench, which represent the protolith and initial conditions for fault zone rocks hosting SSEs at greater depths; (2) characterize material and physical properties in the upper-plate above the primary SSE source further landward; and (3) install borehole observatories at two upper-plate sites to measure temporal variations in deformation, temperature, and fluid flow over multiple SSE cycles. Preliminary results of logging-while-drilling (LWD; Exp. 372) and coring (Exp. 375) will be presented at four sites, tied to regional seismic reflection profiles. The two upper-plate sites were located within an active thrust fault near the deformation front and in a sedimentary basin above the high- slip SSE source region, respectively. Pleistocene mudstone samples and geophysical logs from the thrust fault zone provide insights into the composition, physical properties, and structure of a shallow splay fault that potentially hosts slow-slip behaviour, as well as providing constraints on the growth of the accretionary wedge. At two sites on the incoming Pacific Plate we sampled and logged the Early Cretaceous to Holocene sedimentary succession in the Hikurangi Trough and atop the Tūranganui Knoll seamount. These first drilling data from the Hikurangi Trough tied to seismic reflection profiles provide insights into the lithological and structural assemblages that may exist in the plate boundary fault zone undergoing slow-slip and other seismic phenomena. 7 TEN YEARS OF THE NEW ZEALAND EXTENDED CONTINENTAL SHELF V Stagpoole1 & E Geddis2 1GNS Science, PO Box 30368, Lower Hutt 5040 2Harbour Chambers, PO Box 10242, Wellington 6143 [email protected] & [email protected] In September 2008 the United Nations Commission on the Limits of the Continental Shelf (CLCS) confirmed New Zealand’s rights over approximately 1.7 million km2 of seabed outside the EEZ. New Zealand now has sovereign rights over more than 5.7 million km2 of ocean floor, about 1% of the surface of the Earth. In 1996 New Zealand ratified the United Nations Convention on the Law of the Sea (UNCLOS) and set up the Continental Shelf Project. A multi-disciplinary and cross-governmental team was formed to carry out the project—including scientists, lawyers and administrators from GNS Science, National Institute of Water & Atmospheric Research (NIWA), Ministry of Foreign Affairs and Trade (MFAT), Royal New Zealand Navy (RNZN) and Land Information New Zealand (LINZ). The objective of the project was to define the outer limits of New Zealand’s extended continental shelf—the area of seabed outside the EEZ that forms the “natural prolongation” of the landmass. From 1996 to 2004 the team planned and undertook surveys, processed and analysed the data. In 2004 New Zealand resolved our maritime boundaries with Australia, paving the way for the submission to be presented to the CLCS in 2006. After two years of close analysis, and six meetings with the New Zealand delegation, the CLCS adopted recommendations confirming the outer limits of the continental shelf. Those limits have recently been adopted in New Zealand law. Tangible