International audience Deep-sea fans are favoured settings for the formation of gas hydrates, due to high sedimentation rates and organic matter content that promote the upwelling of methane-rich fluids. Gas hydrates have not been sampled on the Nile fan, but geophysical evidence of their presence is known to the Egyptian hydrocarbon industry. Here we use academic data to document a bottom-simulating reflection (BSR) on the central Nile fan, and examine its relationship to evidence of seabed fluid seepage. We use reprocessed multi-channel seismic profiles acquired from 1973-2002, of varying offset (0.3-4 km) and peak frequency content (10 1-10 2 Hz), together with sonar imagery and subottom profiles (10 3-10 5 Hz). The regional methane hydrate stability zone (RMHSZ) is modeled using a phase boundary for methane hydrate in equilibrium with bottom water of 3.86% salinity (Mediterranean average) and gridded inputs for bathymetry, bottom water temperatures and geothermal gradients. A BSR is observed across the central Nile fan in water depths of 2000-2500 m, as a discontinuous reflection of negative polarity at depths of 220-330 ms below seabed. BSR 'patches' vary in extent and character, but are mainly of low amplitude and, on higher frequency data, may be associated with reduced amplitudes or blanking in the overlying succession. The BSR is observed both in stratified intervals and within interbedded unstratified mass-transport deposits (MTDs, up to 200 ms thick). The depth below seabed of the BSR is comparable to the base of the modeled RMHSZ (converted to travel-time at sediment velocities of 1.6-1.8 km/s). The presence of gas hydrates in the lower part of the RMHSZ is indicated by published resistivity logs from two exploration wells, here located in areas lacking a BSR. We infer that on the central Nile fan gas hydrates are present within a sub-seabed interval up to 250 m thick, that is in places associated with a weak BSR recording basal accumulations of free gas. Previous work shows the central Nile fan is also characterised by widspread phenonema of fluid seepage, expressed at seabed as sonar backscatter anomalies that correspond to authigenic carbonate pavements, developed over timescales of at least 10 3 years, some associated with hydroacoustic flares at their edges recording ongoing gas venting to the water column. The carbonate pavements lie within stratified sediments up to 110 m thick that, in most areas, have been affected by post-depositional deformation of underlying MTDs. Seismic profiles across seepage areas show the stratified sediments to contain pipes linked to faults rooted within the MTDs; the latter are offset in places by more deeply-rooted faults, but the seeps do not correspond to vertical structures rising beneath the RMHSZ. These observations suggest that seabed seeps across the central Nile fan record the long-term rise of gas-rich fluids rich from sources within the hydrate stability zone, in places facilitated by faults rooted in MTDs. Different mechanisms have been suggested to explain gas migration through the stability zone : one is the rise from depth of hot and/or saline fluids in focused flows capable of locally displacing the phase boundary upwards to seabed; an alternative involves the diffuse upwelling of methane-rich fluids over wider areas to drive salt-exclusion at the base of the stability zone, a process proposed to lead to the rise of the 3-phase boundary to seabed within hydrate-choked chimneys. We note that the diffuse upwelling of fluids rich in dissolved methane could also account for the weak and discontinuous BSR, in terms of an upward flux of dissolved methane at rates high enough to limit gas accumulation beneath the stability zone, assuming there to be a minimum in the gas solubility curve. Our calculations of gas solubility show that a minimum is present below the RMHSZ, despite low geothermal gradients on the Nile fan, due to downward-increasing pore water salinities (as recorded at DSDP/ODP sites). We hypothesise the central Nile fan to contain a gas hydrate system driven by the upwelling of pore fluids rich in dissolved methane, at rates that result in: a) a discontinuous BSR beneath gas hydrate deposits; b) salt exclusion at the basal 3-phase boundary which rises to seabed along hydrate-choked vents (chimneys and/or faults). This model of a stability zone containing widely distributed phase-boundary vents is of interest as it implies a system in which temporal fluid fluxes, and perhaps pore pressures, may be regulated by seepage. A gas hydrate system containing vents that connect the basal phase boundary to seabed has been argued to be more sensitive to climate forcing from above. The abundance of seeps on the central Nile fan raises the question whether, by facilitating fluid venting to seabed, it might also be less likely to to result in slope failures? This is of particular interest on the Nile fan as it contains a stratigraphic record of recurrent large-scale failures and has experienced large changes in bottom water temperatures during glacial-interglacial climate cycles that imply basin-wide changes gas hydrate stability. Modeling of the RMGHZ for the last glacial maximum (LGM : -140 m sea level, -4˚C bottom waters) suggests that since deglaciation the stability zone on the Nile fan has reduced in thickness by 160 m (30%) at all water depths below about 800 m. Thus if gas hydrate dissociation during glacial to interglacial transitions can trigger slope failures, the Nile fan is an ideal location for it to take place. The question is whether it has occured, or if transient fluid fluxes were instead relieved by fluid venting? We aim to address the above questions during a forthcoming Franco-Brazilian campaign, focused on understanding the nature and dynamics of the gas vents. The Nile fan contains a gas hydrate system that is associated with widespread gas venting and has experienced large temporal changes, making it an ideal location to explore the linkages between gas hydrate stability, fluid flux and sediment failure over glacial-interglacial timescales.