The mid-Cretaceous was marked by emplacement of large igneous provinces (LIPs) that formed gigantic oceanic plateaus, affecting ecosystems on a global scale, with biota forced to face excess CO 2 resulting in climate and ocean perturbations. Volcanic phases of the Ontong Java Plateau (OJP) and the southern Kerguelen Plateau (SKP) are radiometrically dated and correlate with paleoenvironmental changes, suggesting causal links between LIPs and ecosystem responses. Aptian biocalcification crises and recoveries are broadly coeval with C, Pb, and Os isotopic anomalies, trace metal influxes, global anoxia, and climate changes. Early Aptian greenhouse or super-greenhouse conditions were followed by prolonged cooling during the late Aptian, when OJP and SKP developed, respectively. Massive volcanism occurring at equatorial versus high paleolatitudes and submarine versus subaerial settings triggered very different climate responses but similar disruptions in the marine carbonate system. Excess CO 2 arguably induced episodic ocean acidification that was detrimental to marine calcifiers, regardless of hot or cool conditions. Global anoxia was reached only under extreme warming, whereas cold conditions kept the oceans well oxygenated even at times of intensified fertility. The environmental disruptions attributed to the OJP did not trigger a mass extinction: rock-forming nannoconids and benthic communities underwent a significant decline during Oceanic Anoxic Event (OAE) 1a, but recovered when paroxysmal volcanism finished. Extinction of many planktonic foraminiferal and nannoplankton taxa, including most nannoconids, and most aragonitic rudists in latest Aptian time was likely triggered by severe ocean acidification. Upgraded dating of paleoceanographic events, improved radiometric ages of the OJP and SKP, and time-scale revision are needed to substantiate the links between magmatism and paleoenvironmental perturbations.

When examined in plan view with side-looking sonar, the path of recent sub-sea failure events on the continental margin off Nice displays morphologic features indicative of the passage of sediment flows that interacted with the sea-bed substrate. The path begins as chutes incised on a steep prodelta slope. These chutes feed into the floor of a submarine canyon, which is covered with trains of bedforms oriented at right angles to the flow direction. The bedforms have wavelengths between 35 and 100 m and heights estimated at less than 5 m. The waves are made of coarse material ranging from sand to boulders. Giant bedforms of similar character and scale in the Channeled Scabland (eastern Washington) were produced by a sudden catastrophic flood. Near the base of the slope, where the canyon floor widens and the thalweg gradient decreases, the path becomes a scoured surface with depressions up to 70 m deep produced by the erosion of bedded sediments. As the bottom slope decreases, the width of the area scoured and the cross section of the flows increase. Along the 80 km of the path that was imaged, which was entirely upslope from the location where submarine cables were disrupted by a failure event in 1979, there is little sign of deposition, but extensive evidence of substrate reworking. Our plan-view study of a present-day surface and its bedforms offers an instantaneous picture of an unconformity in development that contrasts with the classical study of similar unconformities in cross section where the emphasis is placed on the time dimension.