Morphogenesis of the SW Balearic continental slope and adjacent abyssal plain, Western Mediterranean Sea

Abstract

We present the seafloor morphology and shallow seismic structure of the continental slope south-east of the Balearic promontory and of the adjacent Algero-Balearic abyssal plain from multibeam and chirp sonar data. The main purpose of this research was to identify the sediment pathways from the Balearic promontory to the Algero-Balearic deep basin from the Early Pliocene to the Present. The morphology of the southern Balearic margin is controlled by a SW-NE structural trend, whose main expressions are the Emile Baudot Escarpment transform fault, and a newly discovered WSW-ENE trend that affects the SW end of the escarpment and the abyssal plain. We relate the two structural trends to right-lateral simple shear as a consequence of the Miocene westward migration of the Gibraltar Arc. Newly discovered steep and narrow volcanic ridges were probably enabled to grow by local transtension along the transform margin. Abyssal plain knolls and seahills relate to the subsurface deformation of early stage halokinetic structures such as salt rollers, salt anticlines, and salt pillows. The limited thickness of the overburden and the limited amount of deformation in the deep basin prevent the formation of more mature halokinetic structures such as diapirs, salt walls, bulbs, and salt extrusions. The uppermost sediment cover is affected by a dense pattern of sub-vertical small throw normal faults resulting from extensional stress induced in the overburden by subsurface salt deformation structures. Shallow gas seismic character and the possible presence of an active polygonal fault system suggest upward fluid migration and fluid and sediment expulsion at the seafloor through a probable mud volcano and other piercement structures. One large debris flow deposit, named Formentera Debris Flow, has been identified on the lower slope and rise of the south Formentera margin. Based on current observations, we hypothesize that the landslide originating the Formentera Debris Flow occurred in the Holocene, perhaps in historical times.

Seismic imaging of Late Miocene (Messinian) evaporites from Western Mediterranean back-arc basins

“…Evidence for this is the identification of the north-south-trending Hannibal Ridge (HR), and associated magnetic anomalies, a relict and buried spreading centre with associated volcanic centres south of Menorca Island (Mauffret et al 2004). Such direction of the Algero-Balearic basin opening is supported by the interpretation of the northern margin of the basin, marked by the Emile Baudot Escarpment (EBE), as a right-lateral strike-slip fault system generated in response to the westward migration of the Gibraltar Arc (Mauffret et al 1992(Mauffret et al , 2004Acosta et al 2001;Camerlenghi et al 2009;Driussi et al 2015). Similarly the southern margin of the Algero-Balearic basin is defined by the North African continental margin, a rifted margin with dominance of left-lateral strike-slip deformation.…”

“…The dextral strike-slip motion along the North Balearic Fracture Zone (NBFZ) allowed the Early Miocene anticlockwise rotation of the Corso-Sardinia block (Gueguen et al 1998;Carminati et al 2012). The northern margin of the Algero-Balearic basin (narrow shelf and steep slopes) is formed by a transform fault system (Emile Baudot Escarpment, EBE) (Acosta et al 2001;Mauffret et al 2004;Camerlenghi et al 2009). Oceanic crust is present below the central parts of the deep basins (within the dashed line, according to Gueguen et al 1998).…”

Messinian Salinity Crisis deposits widespread over the Balearic Promontory: Insights from new high-resolution seismic data

“…Away from the South-Menorca Block, the UU extends to the east (NE Menorca margin) and to the west (E. Baudot and Mazzaron Escarpments), where the pinch-out of the MSC unit onto the margins is sharp and apparently controlled by faults (S abat et al, 1997;Camerlenghi et al, 2009;Maillard and Gorini, 2010;Fig. 2bb' and cc').…”

The morpho-tectonic setting of the Southeast margin of Iberia and the adjacent oceanic Algero-Balearic Basin

“…As mapped by Camerlenghi et al (2009) this terrain, south of Formentera (Fig. 1), consists of concave erosional escarpments, from which a dendritic drainage system originates ( Fig.…”