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The Monviso metaophiolite complex (W. Alps) is an almost intact fragment of Tethyan oceanic lithosphere metamorphosed to eclogite-facies peak metamorphic conditions during Alpine subduction. This 1:20.000 scale geological map encompasses, in an area of ∼35 km2, the Monviso Unit (MU) and the Lago Superiore Unit (LSU). Major focus was given to the Lower Shear Zone sub-unit (LSZ), where in the strongly deformed serpentinite-rich matrix are embedded blocks of variably brecciated metagabbros. Here, the occurrence of eclogite-facies mylonitic foliation (paragenesis: omphacite + rutile + garnet ± ex-lawsonite ± quartz) cut by breccia planes (cemented by omphacite + garnet ± ex-lawsonite) indicates brecciation at pristine eclogitic conditions. This map (i) provides new lithological, structural and morphological insights regarding the stratigraphy of the Monviso metaophiolite complex and (ii) supplies an unprecedented detail on the distribution of eclogite-facies breccia blocks inside the Lower Shear Zone that crosscuts the Lago Superiore Unit.

The Monviso metaophiolite complex (W. Alps) is an almost intact fragment of Tethyan oceanic lithosphere metamorphosed to eclogite-facies peak metamorphic conditions during Alpine subduction. This 1:20.000 scale geological map encompasses, in an area of ∼35 km2, the Monviso Unit (MU) and the Lago Superiore Unit (LSU). Major focus was given to the Lower Shear Zone sub-unit (LSZ), where in the strongly deformed serpentinite-rich matrix are embedded blocks of variably brecciated metagabbros. Here, the occurrence of eclogite-facies mylonitic foliation (paragenesis: omphacite + rutile + garnet ± ex-lawsonite ± quartz) cut by breccia planes (cemented by omphacite + garnet ± ex-lawsonite) indicates brecciation at pristine eclogitic conditions. This map (i) provides new lithological, structural and morphological insights regarding the stratigraphy of the Monviso metaophiolite complex and (ii) supplies an unprecedented detail on the distribution of eclogite-facies breccia blocks inside the Lower Shear Zone that crosscuts the Lago Superiore Unit.

The Oran earthquake of 9th October 1790 in NW Algeria caused heavy damage in that city, and originated a tsunami observed in Almeria and Cartagena, SE Spain. It occurred in a region of low seismicity in comparison with other regions east of Algeria. The abundant contemporary documentation analysed in the present study, some of it not used previously, confirms a maximum intensity of IX–X (EMS-98) for Oran city. The estimated focal parameters are: origin time 01 h 15 m or 01 h 30 m UT, duration 1-to-2 min, a macroseismic offshore epicentre at 35.9°N, 0.6°W to explain the generation of the tsunami, and estimated magnitude 6.0–6.5. The rupture is complex, formed by two events, and may have been associated with NE-SW oriented thrust faults present in the area.