the additional influence of alongshore sediment transport, instead of downslope, on
IPW development (Fig. 6.15) (Fernández-Salas et al. 2009), particularly on relatively straight coastlines with progradational coastal plains. There, IPW accretion
parallel or oblique to the coastline is usually coupled to the progradational story of
the adjacent coastal plains and seems to be favoured by significant alongshore
currents. Major changes in development of IPWs would be caused by erosional
events and/or by significant changes in the direction of prevailing winds, and then
wind-forced currents, which ultimately affect littoral drift patterns (Fernández-Salas
et al. 2009). In the particular case of the Carchuna IPW, sediment transport and IPW
construction seem to be enhanced by the role played by the Carchuna Canyon head
(Fig. 6.5a, b), which focuses wave energy during high-energy events and enhances
coastline and shoreface erosion. As a consequence of the widespread erosion,
sediments would be available in the coastal system for subsequent remobilisation,
and these would be finally entrained by along-coast hydrodynamic processes
(Ortega-Sánchez et al. 2014).
Sediment dynamics in those shelf areas where relict nearshore facies and wavecut terraces are exposed (Figs. 6.13 and 6.14), point to domains (mainly on the outer
continental shelf) with present-day low levels of sedimentation; in other words, they
are shelf areas that do not receive sediment from fluvial sources or major coastal
erosion. The ages obtained for the nearshore facies (from 21,610 Æ 350 to 1249 Æ 60
years) suggest that these facies were mainly formed during the last sea-level rise, as
the sea-level was about 110 m (Mateu 1992) below its present position at about
18,000 years, and began to transgress the entire continental shelf. The successive
coastline migration across the shelf would explain the fact these facies forms a
widespread veneer over the entire continental shelf. This migration was pulsed and
the stillstands would have favoured the formation of wave-cut terraces (Lobo et al.
2014). The occurrence of different types of bedforms, preferentially in outer continental shelf settings, where relict nearshore facies are exposed, on both the Iberian
and African shelves, could be tentatively related to the activity of reworking
processes during the course of the postglacial sea-level rise. Specifically, the dune
fields reported on the shelf around Al-Hoceima Bay have been genetically linked
with a sea-level stillstand at around 15,000 years, predating a major shelf flooding
event (Lafosse et al. 2018).
6.6.2.2 Sediment Dynamics on the Distal Continental Margin
The distal margin is dominated by marine sedimentary processes, which mainly
include the action of bottom currents and mass-movements.
Bottom Current Processes
Bottom current processes are responsible for the formation of contourite features,
both depositional and erosional. The ubiquity of these features (Fig. 6.6a) makes
bottom currents as the most important factor controlling sediment patterns in the
deep-sea areas in the Alboran Sea (Figs. 6.6b and 6.15). The effect of bottom
6 Seafloor Morphology and Processes in the Alboran Sea
189
IPW development (Fig. 6.15) (Fernández-Salas et al. 2009), particularly on relatively straight coastlines with progradational coastal plains. There, IPW accretion
parallel or oblique to the coastline is usually coupled to the progradational story of
the adjacent coastal plains and seems to be favoured by significant alongshore
currents. Major changes in development of IPWs would be caused by erosional
events and/or by significant changes in the direction of prevailing winds, and then
wind-forced currents, which ultimately affect littoral drift patterns (Fernández-Salas
et al. 2009). In the particular case of the Carchuna IPW, sediment transport and IPW
construction seem to be enhanced by the role played by the Carchuna Canyon head
(Fig. 6.5a, b), which focuses wave energy during high-energy events and enhances
coastline and shoreface erosion. As a consequence of the widespread erosion,
sediments would be available in the coastal system for subsequent remobilisation,
and these would be finally entrained by along-coast hydrodynamic processes
(Ortega-Sánchez et al. 2014).
Sediment dynamics in those shelf areas where relict nearshore facies and wavecut terraces are exposed (Figs. 6.13 and 6.14), point to domains (mainly on the outer
continental shelf) with present-day low levels of sedimentation; in other words, they
are shelf areas that do not receive sediment from fluvial sources or major coastal
erosion. The ages obtained for the nearshore facies (from 21,610 Æ 350 to 1249 Æ 60
years) suggest that these facies were mainly formed during the last sea-level rise, as
the sea-level was about 110 m (Mateu 1992) below its present position at about
18,000 years, and began to transgress the entire continental shelf. The successive
coastline migration across the shelf would explain the fact these facies forms a
widespread veneer over the entire continental shelf. This migration was pulsed and
the stillstands would have favoured the formation of wave-cut terraces (Lobo et al.
2014). The occurrence of different types of bedforms, preferentially in outer continental shelf settings, where relict nearshore facies are exposed, on both the Iberian
and African shelves, could be tentatively related to the activity of reworking
processes during the course of the postglacial sea-level rise. Specifically, the dune
fields reported on the shelf around Al-Hoceima Bay have been genetically linked
with a sea-level stillstand at around 15,000 years, predating a major shelf flooding
event (Lafosse et al. 2018).
6.6.2.2 Sediment Dynamics on the Distal Continental Margin
The distal margin is dominated by marine sedimentary processes, which mainly
include the action of bottom currents and mass-movements.
Bottom Current Processes
Bottom current processes are responsible for the formation of contourite features,
both depositional and erosional. The ubiquity of these features (Fig. 6.6a) makes
bottom currents as the most important factor controlling sediment patterns in the
deep-sea areas in the Alboran Sea (Figs. 6.6b and 6.15). The effect of bottom
6 Seafloor Morphology and Processes in the Alboran Sea
189