Understanding the complex geomorphology of a deep sea area affected by continental tectonic indentation

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

Ercilla, Gemma (Institut de Ciències Del Mar, CSIC)
Galindo-Zaldívar, Jesús (Universidad de Granada; Instituto Andaluz de Ciencias de la Tierra, Granada)
Estrada, Ferran (Institut de Ciències Del Mar, CSIC)
Valencia, Javier (Lyra, Gazteiz)
Juan, Carmen (Centro Oceanográfico de Málaga)
Casas, David (Institut de Ciències Del Mar, CSIC)
Alonso, Belén (Institut de Ciències Del Mar, CSIC)
Comas, Mª Carmen (Instituto Andaluz de Ciencias de la Tierra, Granada)
Azpiroz Zabala, M. (TU Delft Applied Geology)

2022

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.

Continental margin
Contourites
Geomorphic processes
Mass movements
Tectonic indentation
Western Mediterranean

http://resolver.tudelft.nl/uuid:44f714cb-7fb4-4b71-b10e-ed1ba97b5edc

https://doi.org/10.1016/j.geomorph.2022.108126

0169-555X

Geomorphology, 402

Institutional Repository

journal article

© 2022 Gemma Ercilla, Jesús Galindo-Zaldívar, Ferran Estrada, Javier Valencia, Carmen Juan, David Casas, Belén Alonso, Mª Carmen Comas, M. Azpiroz Zabala, More Authors