Geophysical evidence for a newly discovered mud volcano field in the northern Moroccan continental slope, south Alborán Sea

On both sides of the Gibraltar Strait mud volcanoes (MVs) have been known since their discovery during the early UNESCO TTR expeditions in the 90s (Talukder et al., 2003). Up until now, the only occurrence of mud volcanism east of Gibraltar was reported in relation to the Ceuta contourite drift (Somoza et al., 2012), where several kilometers of rapidly deposited sediments created the preconditions for shale diapirism and fueled several expulsion structures (both MVs and pockmarks). We report here for the first time, following the investigations conducted during the STRENGTH Leg 3 expedition with R/V Sarmiento de Gamboa in April 2023, of another MVs field west of Melilla, on the Moroccan continental slope. This MVs field consists of 14 features with up to 30 m height and 300 m diameter. Both bathymetric as well as side scan sonar data (DT-1 Edgetech) suggest the features can be identified as MVs (conical shape, presence of moat, mud flows irradiating from the top). The structures seem to be in a dormant stage, with heavy colonization of various types of corals, sponges and other sessile organisms, as observed during a dive with ROV Liropus. A preliminary onboard processing and analysis of the acquired sparker data provide detailed stratigraphic information on the uppermost ~300 m below the seafloor highlighting several fluid pathways. The deep MVs’ feeder channels are clearly imaged, but interestingly, the gas-related wipeouts are situated not only below the MVs edifices themselves, but also permeate the surrounding sediments horizontally, at a specific depth. Finally, we sampled the sediments of several newly discovered MVs for future geochemical and geochronological studies

This research was supported by the grant STRENGTH (PID2019-104668RB-I00) funded by MCIN/AEI/10.13039/501100011033 and the H2020 MSCA-IF action (GA No. 101018321). This project acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S).

Peer reviewed