Young rifts are shaped by combined tectonic and surface processes and climate, yet few records exist to evaluate the interplay of these processes over an extended period of early rift-basin development. Here, we present the longest and highest resolution record of sediment flux and paleoenvironmental changes when a young rift connects to the global oceans. New results from International Ocean Discovery Program (IODP) Expedition 381 in the Corinth Rift show 10s–100s of kyr cyclic variations in basin paleoenvironment as eustatic sea level fluctuated with respect to sills bounding this semi-isolated basin, and reveal substantial corresponding changes in the volume and character of sediment delivered into the rift. During interglacials, when the basin was marine, sedimentation rates were lower (excepting the Holocene), and bioturbation and organic carbon concentration higher. During glacials, the basin was isolated from the ocean, and sedimentation rates were higher (~2–7 times those in interglacials). We infer that reduced vegetation cover during glacials drove higher sediment flux from the rift flanks. These orbital-timescale changes in rate and type of basin infill will likely influence early rift sedimentary and faulting processes, potentially including syn-rift stratigraphy, sediment burial rates, and organic carbon flux and preservation on deep continental margins worldwide.

This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Contents 1 Introduction and operations 5 Lithostratigraphy 9 Structural geology 13 Micropaleontology 16 Geochemistry 18 Physical properties 25 Paleomagnetism 26 Downhole measurements 30 Core-log-seismic integration 33 References

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This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Contents 1 Operations 5 Lithostratigraphy 14 Structural geology 16 Micropaleontology 22 Geochemistry 27 Physical properties 34 Paleomagnetism 38 Downhole measurements 42 Core-log-seismic integration 45 References Operations During International Ocean Discovery Program (IODP) Expedition 381, cores were recovered from one hole at Site M0079 (Figures F1, F2). In total, 18 days were spent on station, with an average core recovery of 86.65% for the site (Table T1). Drilling and coring in Hole M0079A was completed to 704.9 meters below seafloor (mbsf) using two tools in 14 days. The Fugro Corer in push mode collected the upper 67 m of sediment, and the Fugro Corer in percussive mode collected the next 81 m. The Fugro Extended Marine Core Barrel (FXMCB) was then used to complete the lowermost 556 m of the borehole.