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Solander Basin is characterized by subduction initiation at the Pacific‐Australia plate boundary, where high biological productivity is found at the northern edge of the Antarctic Circumpolar Current. Sedimentary architecture results from tectonic influences on accommodation space, sediment supply and ocean currents (via physiography); and climate influence on ocean currents and biological productivity. We present the first seismic‐stratigraphic analysis of Solander Basin based on high‐fold seismic‐reflection data (voyage MGL1803, SISIE). Solander Trough physiography formed by Eocene rifting, but basinal strata are mostly younger than ca. 17 Ma, when we infer Puysegur Ridge formed and sheltered Solander Basin from bottom currents, and mountain growth onshore increased sediment supply. Initial inversion on the Tauru Fault started at ca. 15 Ma, but reverse faulting from 12 to ca. 8 Ma on both the Tauru and Parara Faults was likely associated with reorganization and formation of the subduction thrust. The new seabed topography forced sediment pathways to become channelized at low points or antecedent gorges. Since 5 Ma, southern Puysegur Ridge and Fiordland mountains spread out towards the east and Solander Anticline grew in response to ongoing subduction and growth of a slab. Solander Basin had high sedimentation rates because (1) it is sheltered from bottom currents by Puysegur Ridge; and (2) it has a mountainous land area that supplies sediment to its northern end. Sedimentary architecture is asymmetric due to the Subtropical Front, which moves pelagic and hemi‐pelagic sediment, including dilute parts of gravity flows, eastward and accretes contourites to the shelf south of Stewart Island. Levees, scours, drifts and ridges of folded sediment characterize western Solander Basin, whereas hemi‐pelagic drape and secondary gravity flows are found east of the meandering axial Solander Channel. The high‐resolution record of climate and tectonics that Solander Basin contains may yield excellent sites for future scientific ocean drilling. 

International Ocean Discovery Program (IODP) Expedition 371 drilled six sites (U1506–U1511) in the Tasman Sea, southwest Pacific, between 27 July and 26 September 2017. The primary goal was to understand Tonga-Kermadec subduction initiation through recovery of Paleogene sediment records. Secondary goals were to understand regional oceanography and climate through intervals of the Cenozoic, especially the Eocene. We recovered 2506 m of cored sediment and volcanic rock in 36.4 days of on-site drilling over a total expedition length of 58 days. The ages of strata at the base of each site were middle Eocene to Late Cretaceous. The cored intervals at five sites (U1506–U1510) sampled mostly nannofossil and foraminiferal ooze or chalk that contained volcanic or volcaniclastic intervals with variable clay content. Paleocene and Cretaceous sections at Site U1509 also contain calcareous clay and claystone. At Site U1511, a sequence of abyssal clay and diatomite was recovered with only minor amounts of carbonate. Wireline logs were collected at Sites U1507 and U1508. Our results provide the first firm basis for correlating lithostratigraphic units across a substantial part of northern Zealandia, including ties to onshore geology in New Caledonia and New Zealand. All six sites provide new stratigraphic and paleogeographic information that can be put into context through regional seismic stratigraphic interpretation and hence provide constraints on geodynamic models of subduction zone initiation. Evidence from Site U1507 suggests the northern New Caledonia Trough formed during an early stage of Paleogene tectonic change (before 44 Ma). Paleowater depth estimates from Site U1509 indicate that the Cretaceous Fairway-Aotea-Taranaki Basin dramatically deepened (~2000 m) at a similar time. Northern Lord Howe Rise at Site U1506 rose to sea level at ~50 Ma and subsided back to bathyal depths (600–1000 m) by 45 Ma. In contrast, southern Lord Howe Rise, at least near Site U1510, experienced its peak of transient uplift at ~40–30 Ma. A pulse of convergent plate failure took place across the southern part of the region (Sites U1508–U1511) between 45 and 35 Ma. Uplift of Lord Howe Rise was associated with intraplate volcanism, whereas volcanic activity on Norfolk Ridge near Site U1507 started at ~38 Ma and may relate to subduction. Shipboard observations made using cores and logs represent a substantial gain in fundamental knowledge about northern Zealandia. Prior to Expedition 371, only Deep Sea Drilling Project Sites 206, 207, and 208 had penetrated beneath upper Eocene strata in the region. Our samples and results provide valuable new constraints on geodynamic models of subduction initiation because they reveal the timing of plate deformation, the magnitude and timing of vertical motions, and the timing and type of volcanism. Secondary drilling objectives focused on paleoclimate topics were not fully completed, but significant new records were obtained that should contain information on Cenozoic oceanography and climate in the southwest Pacific. 

International Ocean Discovery Program (IODP) Expedition 371 drilled six sites in the Tasman Sea of the southwest Pacific between 27 July and 26 September 2017. The primary goal was to understand Tonga-Kermadec subduction initiation through recovery of Paleogene sediment records. Secondary goals involved understanding regional oceanography and climate since the Paleogene. Six sites were drilled, recovering 2506 m of cored sediment and volcanic rock in 36.4 days of on-site drilling during a total expedition length of 58 days. Wireline logs were collected at two sites. Shipboard observations made using cores and logs represent a substantial gain in fundamental knowledge about northern Zealandia, because only Deep Sea Drilling Project Sites 206, 207, and 208 had penetrated beneath upper Eocene strata within the region. The cored intervals at five sites (U1506–U1510) sampled nannofossil and foraminiferal ooze or chalk that contained volcanic or volcaniclastic intervals with variable clay content. Paleocene and Cretaceous sections range from more clay rich to predominantly claystone. At the final site (U1511), a sequence of abyssal clay and diatomite was recovered with only minor amounts of carbonate. The ages of strata at the base of each site were middle Eocene to Late Cretaceous, and our new results provide the first firm basis for defining formal lithostratigraphic units that can be mapped across a substantial part of northern Zealandia and related to onshore regions of New Caledonia and New Zealand. The material and data recovered during Expedition 371 enable primary scientific goals to be accomplished. All six sites provided new stratigraphic and paleogeographic information that can be put into context through regional seismic-stratigraphic interpretation and hence provide strong constraints on geodynamic models of subduction zone initiation. Our new observations can be directly related to the timing of plate deformation, the magnitude and timing of vertical motions, and the timing and type of volcanism. Secondary paleoclimate objectives were not all completed as planned, but significant new records of southwest Pacific climate were obtained. 

Environmental and biotic responses to early Eocene hyperthermal events in the southwest Pacific are critical for global paleoclimate reconstructions during Cenozoic greenhouse intervals, but detailed multidisciplinary studies are generally missing from this time and location. Eocene carbonate sediments were recovered during International Ocean Discovery Program Expedition 371 at Site U1510 on southern Lord Howe Rise in the Tasman Sea. Part of the Early Eocene Climatic Optimum (EECO; 53.26–49.14 Ma) and superimposed hyperthermal events have been identified based on refined calcareous nannofossil biostratigraphic data and carbon stable isotope records on bulk sediment and benthic foraminifera. Four negative carbon isotope excursions (CIEs) associated with negative oxygen isotope excursions are recognized within the EECO. Comparison with a global compilation of sites indicates these CIEs correlate to the K event (Eocene Thermal Maximum 3), and tentatively to the S, T, and U events. Sediments with a high carbonate content throughout the EECO provide an excellent opportunity to examine these CIEs, as carbonate dissolution often impacts correlative records elsewhere. Benthic foraminifera and calcareous nannoplankton taxa indicative of warm waters are most abundant during the K event, the most prominent hyperthermal of the EECO. Eutrophication of surface waters during the K event did not lead to increased trophic conditions at the seafloor, whereas a coupled response is observed during smaller hyperthermals. The biotic turnover sheds new light on the paleoenvironmental consequences of hyperthermal events.