Understanding the complex geomorphology of a deep sea area affected by continental tectonic indentation: the case of the Gulf of Vera (Western Mediterranean)

This research has been funding by the Spanish projects: DAMAGE ( CGL2016-80687-RAEI/FEDER ) and FAUCES ( CTM2015-65461-C2-1-R ); and the Junta de Andalucía projects: RNM-148 (AGORA) P18-RT-3275 and PAPEL ( B-RNM-301-UGR18 )
We thank the UTM-CSIC technicians and the crew of the RV Sarmiento de Gamboa for their help in collecting data. We are grateful for the multibeam data we received from the Secretaria General de Pesca of the Ministry of Agriculture, Fisheries and Food (Spain). We also thank IHS for providing the Kingdom Suite™ licence. This work acknowledges to IGCP 640 - S4LIDE (Significance of Modern and Ancient Submarine Slope LandSLIDEs), and to the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S).
We present a multidisciplinary study of morphology, stratigraphy, sedimentology, tectonic structure, and physical oceanography to report that the complex geomorphology of the Palomares continental margin and adjacent Algerian abyssal plain (i.e., Gulf of Vera, Western Mediterranean), is the result of the sedimentary response to the Aguilas Arc continental tectonic indentation in the Eurasian–Africa plate collision. The indentation is imprinted on the basement of the margin with elongated metamorphic antiforms that are pierced by igneous bodies, and synforms that accommodate the deformation and create a complex physiography. The basement is partially covered by Upper Miocene deposits sealed by the regional Messinian Erosive Surface characterized by palaeocanyons that carve the modern margin. These deposits and outcropping basement highs are then covered and shaped by Plio-Quaternary contourites formed under the action of the Light Intermediate and Dense Deep Mediterranean bottom currents. Even though bottom currents are responsible for the primary sedimentation that shapes the margin, 97% of this region's seafloor is affected by mass-movements that modified contourite sediments by eroding, deforming, faulting, sliding, and depositing sediments. Mass-movement processes have resulted in the formation of recurrent mass-flow deposits, an enlargement of the submarine canyons and gully incisions, and basin-scale gravitational slides spreading above the Messinian Salinity Crisis salt layer. The Polopo, Aguilas and Gata slides are characterized by an extensional upslope domain that shapes the continental margin, and by a downslope contractional domain that shapes the abyssal plain with diapirs piercing (hemi)pelagites/sheet-like turbidites creating a seafloor dotted by numerous crests. The mass movements were mostly triggered by the interplay of the continental tectonic indentation of the Aguilas Arc with sedimentological factors over time. The indentation, which involves the progressively southeastward tectonic tilting of the whole land-sea region, likely generated a quasi-continuous oversteepening of the entire margin, thus reducing the stability of the contourites. In addition, tectonic tilting and subsidence of the abyssal plain favoured the flow of the underlying Messinian Salinity Crisis salt layer, contributing to the gravitational instability of the overlying sediments over large areas of the margin and abyssal plain.
DAMAGE CGL2016-80687-RAEI
FAUCES CTM2015-65461-C2-1-R
PAPEL B-RNM-301-UGR18
UTM-CSIC
Indian Health Service CEX2019-000928-S
European Regional Development Fund
Junta de Andalucía P18-RT-3275, RNM-148
Ministerio de Agricultura, Pesca y Alimentación