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).

Chert, porcelainite, and other siliceous phases are exceptionally common in Atlantic sedimentary records of the early Eocene, but the origins of these facies remain enigmatic. The early Eocene was also the warmest interval of the entire Cenozoic Era, punctuated by numerous discrete warming events termed “hyperthermals,” the largest of which is termed the Paleocene‐Eocene Thermal Maximum (~56 Ma). Here we present new and published lithologic and carbon isotope records of silica‐bearing lower Eocene sediments and suggest a link between the ubiquitous Atlantic cherts of that time period and hyperthermal events. Our data demonstrate that many of these Atlantic siliceous horizons coincide with negative carbon isotope excursions (a hallmark of hyperthermal events), including a previously unrecognized record of the Paleocene‐Eocene Thermal Maximum in the South Atlantic. Hyperthermal‐associated silica burial appears to be focused in the western middle to high latitudes of both the North and South Atlantic, with no association between siliceous facies and hyperthermal events found in the Pacific. We also present a new model of the coupled carbon and silica cycles (LOSiCAR) to demonstrate that enhanced silicate weathering during these events would require a rapid increase in total marine silica burial. Model experiments that include previously suggested transient reversals in the pattern of deep‐ocean circulation during hyperthermals demonstrate that such a mechanism can explain the apparent focusing of elevated silica burial into the Atlantic. This combination—a silicate weathering feedback in response to global warming along with a circulation‐driven focusing of silica burial—represents a new mechanism for the formation of deep‐sea cherts in lower Eocene Atlantic sedimentary records and may be relevant to understanding chert formation in other intervals of Earth history.

Introduction 4 Scientific background 7 Scientific objectives 7 Drilling strategy 8 Site summaries 19 Summary of scientific results 27 References

This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Contents 1 Background and objectives 3 Operations 5 Lithostratigraphy 12 Biostratigraphy and paleoenvironment 16 Paleomagnetism 20 Petrophysics 22 Geochemistry 26 Stratigraphic correlation 28 Age model and sedimentation rates 29 References 206