Data from International Ocean Discovery Program (IODP) Expedition 371 reveal vertical movements of 1–3 km in northern Zealandia during early Cenozoic subduction initiation in the western Pacific Ocean. Lord Howe Rise rose from deep (∼1 km) water to sea level and subsided back, with peak uplift at 50 Ma in the north and between 41 and 32 Ma in the south. The New Caledonia Trough subsided 2–3 km between 55 and 45 Ma. We suggest these elevation changes resulted from crust delamination and mantle flow that led to slab formation. We propose a “subduction resurrection” model in which (1) a subduction rupture event activated lithospheric-scale faults across a broad region during less than ∼5 m.y., and (2) tectonic forces evolved over a further 4–8 m.y. as subducted slabs grew in size and drove plate-motion change. Such a subduction rupture event may have involved nucleation and lateral propagation of slip-weakening rupture along an interconnected set of preexisting weaknesses adjacent to density anomalies.

lieh, obwohl der Vorgang geographisch diachron ist. Sein Verschwinden aus dem Südatlantik ist frühzeitig, grob korrelierbar mit Schätzungen aus tropischen Regionen. Kurze Intervalle starker Häufigkeit von C. reticulatum und C. protoannula können darauf hindeuten, daß ihr letztes Erscheinen (jeweils 37.86 Ma und 38.18 Ma) einen begrenzeten biochronologischen Wert hat. Für die Eozän/Oligozän-Grenze wird anhand des Hole 522 und des Aussterbens von Hantkenina ein Alter von 36.15 Ma bis 36.20 Ma vorgeschlagen. Das nächstliegende Nannofos-Silienereignis ist das erste häufige Erscheinen von E. obruta (36.07 Ma) oder, regional (?), der scharfe Umschlag im Verhältnis R. umbilicus/C. formosus (36.10 Ma).

The SW Pacific region consists of a succession of ridges and basins that were created by the fragmentation of Gondwana and the evolution of subduction zones since Mesozoic times. This complex geodynamic evolution shaped the geology of New Caledonia, which lies in the northern part of the Zealandia continent. Alternative tectonic models have been postulated. Most models agree that New Caledonia was situated on an active plate margin of eastern Gondwana during the Mesozoic. Extension affected the region from the Late Cretaceous to the Paleocene and models for this period vary in the location and nature of the plate boundary between the Pacific and Australian plates. Eocene regional tectonic contraction included the obduction of a mantle-derived Peridotite Nappe in New Caledonia. In one class of model, this contractional phase was controlled by an east-dipping subduction zone into which the Norfolk Ridge jammed, whereas and in a second class of model this phase corresponds to the initiation of the west-dipping Tonga–Kermadec subduction zone. Neogene tectonics of the region near New Caledonia was dominated by the eastwards retreat of Tonga–Kermadec subduction, leading to the opening of a back-arc basin east of New Caledonia, and the initiation and southwestwards advance of the New Hebrides–Vanuatu subduction zone towards New Caledonia.

A basic means to establish and understand variations in climate and ocean water properties is through sediment mass accumulation rates (MARs), which are quantified measurements of solid material flux to the seabed (mass Abstract Sediment mass accumulation rate (MAR) is a proxy for paleoceanographic conditions, especially if biological productivity generated most of the sediment. We determine MAR records from pelagic calcareous sediments in Tasman Sea based on analysis of 11 boreholes and >3 million seismic reflection horizon picks. Seismic data from regions of 10,000-30,000 km 2 around each borehole were analyzed using data from International Ocean Discovery Program Expedition 371 and other boreholes. Local MAR was affected by deepwater currents that winnowed, eroded, or deposited seafloor sediment. Therefore, it is necessary to average MARs across regions to test paleoceanographic and productivity models. MARs during the Miocene Climate optimum (18-14 Ma) were slightly lower than Quaternary values but increased on southern Lord Howe Rise at 14-13 Ma, when global climate became colder. Intensification of the Indian and East Asian monsoons at ∼8 Ma and ∼3.6 Ma approximately corresponds to the start and end, respectively, of the Biogenic Bloom, which had MARs at least double Quaternary values. On northern Lord Howe Rise, we recognize peak MARs at∼7 Ma and ∼5 Ma. There is no correlation between Neogene MAR and ocean pH or atmospheric CO 2 concentration. Neogene MARs are on average higher than Quaternary values. We posit that future long-term productivity in the southwest Pacific could be higher than Quaternary values, but new computer models that can fit our observations are required to test this hypothesis. Plain Language SummaryGlobal climate is likely to get warmer, and we want to know what will happen to marine life. We can study ancient warm periods to better predict the future. The ocean is a global carbon sink, because some organisms form shells by combining calcium with carbon dioxide dissolved in seawater. Once dead, their calcium carbonate shells sink to the seabed. Over millions of years, the southwest Pacific accumulated huge deposits. We used geophysical surveying and drilling to measure this history of deposition, which is a proxy for ancient biological productivity (how much marine life existed). A warm period 18-14 million years ago had high atmospheric carbon dioxide (2-4 times preindustrial levels) and slightly lower ocean productivity. In contrast, 8-4 million years ago, atmospheric carbon dioxide was similar to predicted 21st century levels and productivity was much higher: more than double recent values. Rates of calcium carbonate deposition in the past do not correlate with ocean acidity or atmospheric carbon dioxide; but they were mostly higher than today. Hence, long-term biological productivity and carbon sequestration in the southwest Pacific might increase in future, but computer models that fit our observations are needed to test this idea.