channel on the lower slope that mouths directly into a channelised lobe at the base of
slope and basin. The submarine ramp model comprises a feeder system with gullies
linked downdip to amalgamated lobe deposits. Seismic facies analysis of turbidite
systems involves complex patterns of chaotic and discontinuous stratified facies with
different configurations (prograding-, divergent-, and mounded-fill) for the canyons
and channels and vertical stacking of asymmetric and roughly symmetric mound
bodies of stratified facies that stand out from the seafloor. The architecture and
dimensions of these systems suggest their sedimentary model ranges mostly from
sandy to mixed sand-mud fans, and they describe a continuum between both
end-member types from west to east.
The lone valleys are characterized by the lack of channel leveed and lobe deposits
at their mouths and because of that they are considered separately from the turbidite
systems. The valleys mapped comprise (Fig. 6.3b): the 10 km long Adra Channel,
eroding the uppermost continental slope of the western Iberian margin; the Castor
Canyon and gullies on the northeastern side of the Alboran Ridge; and the Ceuta and
Nekor canyons, on the African margin. The Ceuta Canyon is 25 km long and widens
down the valley (from 4 to 6 km); it has a curved pathway and mouths onto the
entrance of the Strait of Gibraltar. The Nekor Canyon is 3 km long and 1.3 km wide,
with a rectilinear pathway that extends down to a water depth of 300 m. Seismic
facies analysis shows valleys eroding contourite deposits, generally presenting
truncated, stratified, and prograding facies on the canyon margins, and chaotic
deposits on the canyon floors.
Isolated landslide scars as well as landslide scars with associated mass-transport
deposits have been mapped on both the Iberian and African continental slopes, in
addition to the steep walls of some seamounts (Figs. 6.6a and 6.11). Landslide scars
delineate the headscarp of the failed area, and form a relatively steep scarp (a few to
tens of km long, with tens of metres of relief) facing seaward, with concave and
amphitheatre shapes (Figs. 6.6a and 6.11). These slide scars are associated, in
attached and detached forms (Fig. 6.11a, b), to lobate bodies, from around 5 km to
<10 km in length and tens of metres in thickness, with chaotic and transparent
sediments producing a wavy and irregular seafloor area, which varies roughly in the
area from 5 to >100 km
2 . Baraza (110 km
2 ) on the Iberian slope (Figs. 6.6a and
6.11a), and the Montera slide (90 km
2 ) in the SAB, are some of the largest landslides
affecting the upper Quaternary deposits (Casas et al. 2011; Vázquez et al. 2013;
Rodriguez et al. 2017). The Alboran Ridge, Francesc-Pagès Seamount, Djibouti,
Pollux and Sabinar Banks, and Maimonides and Adra Ridges are some of the
seamounts whose recent sedimentary record, on their walls and in the surrounding
areas, are characterised by the vertical stacking of numerous landslides (Figs. 6.6a
and 6.11c) (e.g. Palomino et al. 2009; Alonso et al. 2014; Galindo-Zaldívar et al.
2018).
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G. Ercilla et al.
slope and basin. The submarine ramp model comprises a feeder system with gullies
linked downdip to amalgamated lobe deposits. Seismic facies analysis of turbidite
systems involves complex patterns of chaotic and discontinuous stratified facies with
different configurations (prograding-, divergent-, and mounded-fill) for the canyons
and channels and vertical stacking of asymmetric and roughly symmetric mound
bodies of stratified facies that stand out from the seafloor. The architecture and
dimensions of these systems suggest their sedimentary model ranges mostly from
sandy to mixed sand-mud fans, and they describe a continuum between both
end-member types from west to east.
The lone valleys are characterized by the lack of channel leveed and lobe deposits
at their mouths and because of that they are considered separately from the turbidite
systems. The valleys mapped comprise (Fig. 6.3b): the 10 km long Adra Channel,
eroding the uppermost continental slope of the western Iberian margin; the Castor
Canyon and gullies on the northeastern side of the Alboran Ridge; and the Ceuta and
Nekor canyons, on the African margin. The Ceuta Canyon is 25 km long and widens
down the valley (from 4 to 6 km); it has a curved pathway and mouths onto the
entrance of the Strait of Gibraltar. The Nekor Canyon is 3 km long and 1.3 km wide,
with a rectilinear pathway that extends down to a water depth of 300 m. Seismic
facies analysis shows valleys eroding contourite deposits, generally presenting
truncated, stratified, and prograding facies on the canyon margins, and chaotic
deposits on the canyon floors.
Isolated landslide scars as well as landslide scars with associated mass-transport
deposits have been mapped on both the Iberian and African continental slopes, in
addition to the steep walls of some seamounts (Figs. 6.6a and 6.11). Landslide scars
delineate the headscarp of the failed area, and form a relatively steep scarp (a few to
tens of km long, with tens of metres of relief) facing seaward, with concave and
amphitheatre shapes (Figs. 6.6a and 6.11). These slide scars are associated, in
attached and detached forms (Fig. 6.11a, b), to lobate bodies, from around 5 km to
<10 km in length and tens of metres in thickness, with chaotic and transparent
sediments producing a wavy and irregular seafloor area, which varies roughly in the
area from 5 to >100 km
2 . Baraza (110 km
2 ) on the Iberian slope (Figs. 6.6a and
6.11a), and the Montera slide (90 km
2 ) in the SAB, are some of the largest landslides
affecting the upper Quaternary deposits (Casas et al. 2011; Vázquez et al. 2013;
Rodriguez et al. 2017). The Alboran Ridge, Francesc-Pagès Seamount, Djibouti,
Pollux and Sabinar Banks, and Maimonides and Adra Ridges are some of the
seamounts whose recent sedimentary record, on their walls and in the surrounding
areas, are characterised by the vertical stacking of numerous landslides (Figs. 6.6a
and 6.11c) (e.g. Palomino et al. 2009; Alonso et al. 2014; Galindo-Zaldívar et al.
2018).
178
G. Ercilla et al.