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The ongoing oceanic oxygen loss will have a profound impact on the distribution and density of life on Earth. However, drivers of the initiation and termination of global oceanic deoxygenation are poorly understood. Here we present a thallium isotope record that reveals three rapid (50 k.y.) global deoxygenation intervals during the mid-Cretaceous that postdate massive volcanism by at least 1 m.y. New strontium isotope data reveal gradually enhanced continental weathering under a warmer climate following volcanism. However, global deoxygenation occurred only under the combined influences of a long-term increase in weathering rates in a warmer climate and short-term orbital modulation that led to atmospheric-circulation reorganization. Interactions of multiple drivers are consistent with the abrupt termination of each deoxygenation interval. Dynamic oxygenation responses in the mid-Cretaceous highlight the role of these processes for understanding the consequences and potential termination of the current oceanic deoxygenation. [ABSTRACT FROM AUTHOR]

A giant mass-transport complex was recently discovered in the eastern Arabian Sea, exceeding in volume all but one other known complex on passive margins worldwide. The complex, named the Nataraja Slide, was drilled by International Ocean Discovery Program (IODP) Expedition 355 in two locations where it is ~300 m (Site U1456) and ~200 m thick (Site U1457). The top of this mass-transport complex is defined by the presence of both reworked microfossil assemblages and deformation structures, such as folding and faulting. The deposit consists of two main phases of mass wasting, each consisting of smaller pulses, with generally fining- upward cycles, all emplaced just prior to 10.8 Ma based on biostratigraphy. The base of the deposit at each site is composed largely of matrix-supported carbonate breccia that is interpreted as the product of debris-flows. In the first phase, these breccias alternate with wellsorted calcar enites deposited from a highenergy current, coherent limestone blocks that are derived directly from the Indian continental margin, and a few clastic mudstone beds. In the second phase, at the top of the deposit, muddy turbidites dominate and become increasingly more siliciclastic. At Site U1456, where both phases are seen, a 20-m section of hemipelagic mudstone is present, overlain by a ~40-m-thick section of calcarenite and slumped interbedded mud and siltstone. Bulk sediment geochemistry, heavy-mineral analysis, clay mineralogy, isotope geochemistry, and detrital zircon U-Pb ages constrain the provenance of the clastic, muddy material to being reworked, Indus-derived sediment, with input from western Indian rivers (e.g., Narmada and Tapti rivers), and some material from the Deccan Traps. The carbonate blocks found within the breccias are shallow-water limestones from the outer western Indian continental shelf, which was oversteepened from enhanced clastic sediment delivery during the mid-Miocene. The final emplacement of the material was likely related to seismicity as there are modern intraplate earthquakes close to the source of the slide. Although we hypothesize that this area is at low risk for future mass wasting events, it should be noted that other oversteepened continental margins around the world could be at risk for mass failure as large as the Nataraja Slide. [ABSTRACT FROM AUTHOR]