The present database is composed of a polygon shape file (.shp) dedicated to GIS applications. This seafloor surface represents the area within which (sub-)outcropping methane derived authigenic carbonates were identified based on ship-borne multibeam bathymetry and seafloor backscatter data; as displayed in Figs. 4 and S1a of Dupré et al. 2020 (Dupré S, Loubrieu B, Pierre C, Scalabrin C, Guérin C, Ehrhold A, Ogor A, Gautier E, Ruffine L, Biville R, Saout J, Breton C, Floodpage J, Lescanne M (2020) The Aquitaine Shelf Edge (Bay of Biscay): A Primary Outlet for Microbial Methane Release. Geophysical Research Letters 47 (7):e2019GL084561. doi:10.1029/2019gl084561). The presence of (sub-)outcropping methane-derived authigenic carbonates at the seafloor was confirmed by remotely-operated-vehicle dives during the GAZCOGNE2 marine expedition.

The acoustic data were acquired in 2013 on board the R/V Le Suroît during the GAZCOGNE1 expedition with two ship-borne multibeam echosounders, the Kongsberg EM302 and EM2040, with transmission frequency of 30 and 200 kHz, respectively. Details on multibeam data acquisition, processing and interpretation of sub-outcropping methane-derived authigenic carbonate structures are presented in Dupré et al 2020 (including a Supporting Information section).

Cited from Dupré et al 2020: “The carbonates are exclusively located along the shelf edge with the majority (98%) between 140 and 220 m water depths. The (sub-)outcropping carbonates are spread over a 375 km² area that extends over a distance of 80 km between the Cap Ferret and Capbreton canyons. The western spatial limit of the methane-derived authigenic carbonates coincides with the shelf break.”