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International Ocean Discovery Program (IODP) Expedition 378 was designed to recover the first comprehensive set of Paleogene sedimentary sections from a transect of sites strategically positioned in the South Pacific Ocean to reconstruct key changes in oceanic and atmospheric circulation. These sites would have provided an unparalleled opportunity to add crucial new data and geographic coverage to existing reconstructions of Paleogene climate. Following the ~15 month postponement of Expedition 378 and subsequent port changes that resulted in a reduction of the number of primary sites, testing and evaluation of the research vessel JOIDES Resolution derrick in the weeks preceding the expedition determined that it would not support deployment of drill strings in excess of 2 km. Consequently, only one of the originally approved seven primary sites was drilled. Expedition 378 recovered the first continuously cored, multiple-hole Paleogene sedimentary section from the southern Campbell Plateau at Site U1553. This high-southern latitude site builds on the legacy of Deep Sea Drilling Project Site 277 (a single, partially spot cored hole), providing a unique opportunity to refine and expand existing reconstructions of Cenozoic climate history. As the world's largest ocean, the Pacific Ocean is intricately linked to major changes in the global climate system. Previous drilling in the low-latitude Pacific Ocean during Ocean Drilling Program Legs 138 and 199 and Integrated Ocean Drilling Program Expeditions 320 and 321 provided new insights into climate and carbon system dynamics, productivity changes across the zone of divergence, time-dependent calcium carbonate dissolution, bio- and magnetostratigraphy, the location of the Intertropical Convergence Zone, and evolutionary patterns for times of climatic change and upheaval. Expedition 378 in the South Pacific Ocean uniquely complements this work with a highlatitude perspective, especially because appropriate high-latitude records are unobtainable in the Northern Hemisphere of the Pacific Ocean. Expedition 378 provides material from the South Pacific Ocean in an area critical for high-latitude climate reconstructions spanning the early Paleocene to late Oligocene. Site U1553 and the entire corpus of shore-based investigations will significantly contribute to the challenges of the "Climate and Ocean Change: Reading the Past, Informing the Future" theme of the 2013-2023 IODP Science Plan (How does Earth's climate system respond to elevated levels of atmospheric CO2? How resilient is the ocean to chemical perturbations?). Furthermore, Expedition 378 provides material from the South Pacific Ocean in an area critical for high-latitude climate reconstructions spanning the Paleocene to late Oligocene. [ABSTRACT FROM AUTHOR]