Workshop Reports Sci. Dril., 24, 61–70, 2018 https://doi.org/10.5194/sd-24-61-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Developing community-based scientific priorities and new drilling proposals in the southern Indian and southwestern Pacific oceans Robert McKay1, Neville Exon2, Dietmar Müller3, Karsten Gohl4, Michael Gurnis5, Amelia Shevenell6, Stuart Henrys7, Fumio Inagaki8,9, Dhananjai Pandey10, Jessica Whiteside11, Tina van de Flierdt12, Tim Naish1, Verena Heuer13, Yuki Morono9, Millard Coffin14, Marguerite Godard15, Laura Wallace7, Shuichi Kodaira8, Peter Bijl16, Julien Collot17, Gerald Dickens18, Brandon Dugan19, Ann G. Dunlea20, Ron Hackney21, Minoru Ikehara22, Martin Jutzeler23, Lisa McNeill11, Sushant Naik24, Taryn Noble14, Bradley Opdyke2, Ingo Pecher25, Lowell Stott26, Gabriele Uenzelmann-Neben4, Yatheesh Vadakkeykath24, and Ulrich G. Wortmann27 1Antarctic Research Centre, Victoria University of Wellington, Wellington, 6140, New Zealand 2Research School of Earth Sciences, Australian National University, Canberra, 0200, Australia 3School of Geosciences, The University of Sydney, Sydney, NSW2006, Australia 4Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, 27568 Bremerhaven, Germany 5California Institute of Technology, Pasadena, CA 91125, USA 6College of Marine Science, University of South Florida, Saint Petersburg, FL 33701, USA 7GNS Science, Lower Hutt, 5040, New Zealand 8Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama 236-0001, Japan 9Kochi Institute for Core Sample Research, JAMSTEC, Nankoku, Kochi 783-8502, Japan 10National Centre for Antarctic and Ocean Research, Vasco¯ Da Gama,¯ Goa-403 804, India 11University of Southampton, National Oceanography Centre, Southampton SO14 3ZH, UK 12Department of Earth Science & Engineering, Imperial College London, London SW7 2AZ, UK 13Organic Geochemistry Group, MARUM Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany 14Institute for Marine and Antarctic Studies (IMAS), University of Tasmania, Hobart, TAS 7001, Australia 15Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France 16Department of Earth Sciences, Utrecht University, Utrecht, the Netherlands 17Service Géologique de Nouvelle-Calédonie, Nouméa, New Caledonia 18Department of Earth Sciences, Rice University, Houston, TX 77005, USA 19Department of Geophysics, Colorado School of Mines, Golden, CO 80401-1887, USA 20Department of Geology & Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA 21Geoscience Australia, GPO Box 378, Canberra, ACT 2609, Australia 22Center for Advanced Marine Core Research, Kochi University, Nankoku, Japan 23School of Natural Sciences and Centre for Ore Deposit and Earth Sciences (CODES), University of Tasmania, Hobart, TAS 7001, Australia 24CSIR-National Institute of Oceanography, Dona Paula, Goa-403 004, India 25School of Environment, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand 26Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA 27Department of Earth Sciences, University of Toronto, 22 Russell Street, ON, M5S 3B1, Canada Correspondence: Robert McKay ([email protected]) Received: 3 November 2017 – Revised: 26 January 2018 – Accepted: 1 February 2018 – Published: 22 October 2018 Published by Copernicus Publications on behalf of the IODP and the ICDP. 62 R. McKay et al.: Developing community-based scientific priorities and new drilling proposals Abstract. An International Ocean Discovery Program (IODP) workshop was held at Sydney University, Aus- tralia, from 13 to 16 June 2017 and was attended by 97 scientists from 12 countries. The aim of the workshop was to investigate future drilling opportunities in the eastern Indian Ocean, southwestern Pacific Ocean, and the Indian and Pacific sectors of the Southern Ocean. The overlying regional sedimentary strata are underexplored relative to their Northern Hemisphere counterparts, and thus the role of the Southern Hemisphere in past global environmental change is poorly constrained. A total of 23 proposal ideas were discussed, with ∼ 12 of these deemed mature enough for active proposal development or awaiting scheduled site survey cruises. Of the re- maining 11 proposals, key regions were identified where fundamental hypotheses are testable by drilling, but either site surveys are required or hypotheses need further development. Refinements are anticipated based upon regional IODP drilling in 2017/2018, analysis of recently collected site survey data, and the development of site survey proposals. We hope and expect that this workshop will lead to a new phase of scientific ocean drilling in the Australasian region in the early 2020s. 1 Introduction subgroup meeting not related to the above tectonic settings. The potential proposals discussed in the breakout sessions The importance of the Southern Hemisphere in the narra- are listed in Table 1, and locations shown in Fig. 1. tives of global plate tectonics and oceanography is well es- tablished, but understudied. This is in large part due to the 2 Large igneous provinces and associated vastness of the eastern Indian Ocean, southwestern Pacific paleoceanography Ocean, and the Indian and Pacific sectors of the Southern Ocean. This is an ideal region to address many of the 14 sci- Earth’s evolution includes multiple, geologically brief ence challenges in the 2013–2023 IODP science plan. The episodes when extraordinary volcanism occurred across Australian and Indian continents have undergone the largest some surface regions. Documentation for this comes from and most rapid paleo-latitudinal shifts of any continents glob- large igneous provinces (LIPs), extensive areas covered by ally since 150 Ma. The region boasts the following: (i) ar- thick layers of mostly mafic material that was emplaced on guably the greatest diversity of subduction zones from fully million-year timescales. While LIPs have been widely ac- seismically coupled to uncoupled; (ii) extensive shallow ma- knowledged and discussed by the geoscience community for rine seas and submerged continents (e.g., Zealandia) with ex- more than two decades, major first-order questions regard- traordinary and unstudied stratigraphic records; and (iii) the ing their origin and environmental impact remain. Profound largest suite of plume-related products and the largest man- and rapid changes in biota and chemical cycling have also tle cold spot. Sampling of plateaus, ridges, and their asso- punctuated Earth’s history and many of these ”events” have ciated sedimentary strata will provide an enormous wealth been linked to the formation of LIPs. For example, mas- of information about their origin and address fundamental sive volcanic outpouring may have been coupled to large paleoceanographic and paleoclimate questions. Drilling of increases in atmospheric pCO2, which could have raised the Antarctic margin in the Indian Ocean and South Pa- surface temperatures, amplified the hydrological cycle, and cific sectors will increase our understanding of the Antarctic changed ocean circulation. Equally important is the fact that cryosphere and global climate evolution and past land and oceanic LIPs typically lie above the carbonate compensation sea ice extent from the Cretaceous through the Cenozoic. Ge- depth, thereby providing the elevated foundation on which omicrobiological questions can be addressed on a number of many outstanding records of Earth’s climate history accumu- expeditions, including targeted expeditions to study the deep late. biosphere in a variety of tectonic settings. Petrological and geochemical studies of oceanic, back-arc and arc crust, as 2.1 Manihiki-Plus: ground zero for understanding large well as uplifted mantle remain a high priority, as do those of igneous provinces and their environmental impact geological hazards. To facilitate and nurture cross-disciplinary proposals, Manihiki Plateau, in the southwestern Pacific, is a large workshop breakout sessions focused on distinct tectonic set- (770 000 km2) bathymetric high, which appears to have been tings and their associated paleo-environmental evolution. emplaced about 125–120 Ma. Five drill sites are proposed, These included (1) large igneous provinces and associated four on Manihiki Plateau and one on the older Magel- paleoceanography, (2) subduction zones and associated pa- lan Rise. Numerous hypothesis could consequently be ad- leoceanography, (3) a separate focus group on the Hikurangi dressed: (1) Manihiki Plateau was part of a much larger LIP subduction zone, (4) conjugate margin/Zealandia studies and that has been disjointed since the Cretaceous (other compo- associated paleoceanography, and (5) a biosphere frontiers nents are believed to include the Ontong Java and Hikurangi Sci. Dril., 24, 61–70, 2018 www.sci-dril.net/24/61/2018/ R. McKay et al.: Developing community-based scientific priorities and new drilling proposals 63 130 E 140 E 120 E 150 E E 110 160 E 1 53 70 E 0 E 3.1 18 9 0 E 0 E 17 8 0 E E 1 70 6 3.4 0 E E 60 5.6 PACIFIC OCEAN E 0 5 2.5 AUSTRALIA N AFRICA INDIAN OCEAN 10 3.2 2.1 5.7 0 6.1 4.4 4.20 S 0 37 4.1 1 Topography 2.2 3500 m S 20 5.5 5.8 3.3 5.2 S SOUTHERN OCEAN 5.1 Sea level 30 -2000 m 4.3 6.2 S 5.4 40 2.3 S 50 5.3 2.4 ANTARCTICA -5000 m S Drill sites 60 IODP completed sites -9000 m IODP planned sites S 0 0 1000 2000 3000 4000 km 7 PP -3 ODP 12 -3 DSDP Large Igneous Provinces Conjugate Margins and climate Subduction