The sediment dynamics of the prodeltaic systems are mainly related to settling
from the suspension of nepheloid layers, or turbid layers of sediment delivered from
rivers and streams or wave-supported gravity flows, all with a dominant cross-shelf
transport dynamic (Fig. 6.15). The settling process appears to be continuous, operating on the present-day proximal continental shelf since the installation of the
Holocene highstand (6500 years BP to present). The well-defined 2D surficial
distribution of the prodelta facies, the age of these facies (1500 years BP), and the
well-defined 3D geometry (wedge-shape) of the prodeltaic bodies identified from
seismic records indicates strong sediment progradation in the submarine environment and low sediment retention levels in the emerged domain (Fig. 6.4a, b, c, d)
(e.g. Ercilla et al. 1994; Hernández-Molina et al. 1994; Bárcenas et al. 2009; Lobo
et al. 2015). The plan-view geometries are directly related to hydrodynamic control
being greater in those with elongate patterns. In this sense, the Guadalfeo River
prodelta exhibits lateral morphological plan-view changes from lobate to elongate,
reflecting the temporal modification of the balance between fluvial supply and
sediment redistribution by the governing hydrodynamics and/or reworking of
pre-existing depocentres (Figs. 6.4a, b and 6.15) (Lobo et al. 2006; Jabaloy-Sánchez
et al. 2014).
Many prodeltas are affected by conspicuous seafloor undulations (Fig. 6.4a, d).
Morphometric, stratigraphic, and sedimentological data indicate the possible activity
of hyperpycnal flows (i.e. a particular type of turbidity current generated by river
discharge) as a plausible genetic mechanism (Fig. 6.15) (Lobo et al. 2015). The
margins of the southern Iberian Peninsula are mountainous, and the drainage basins
are small and steep; in addition, rainfall events are torrential nature in the region;
these conditions favour the generation of hyperpycnal flows. There is greater
undulation development in prodeltaic settings off river basins with high maximum
rainfalls; therefore, a genetic link between fluvial flow and undulation development
has been proposed (Bárcenas et al. 2009). In this sense, a relationship is observed
between undulation development and river basin parameters, such as river length
and basin size (Bárcenas et al. 2009). The most detailed analysis has been conducted
on the undulations off the Guadalfeo River, which could be classified as a moderately dirty river (Fig. 6.4a, b, d). There, morphometric differences between undulation fields suggest the occurrence of temporal changes in hyperpycnal flows. Higher
undulations could be indicative of intensified river flow, whereas lower and more
laterally extensive undulations could indicate their inactivity due to a change in the
course of the river (Fernández-Salas et al. 2007; Lobo et al. 2015). On the other
hand, the presence of prodeltaic channels and/or gullies would point to relatively
high-energy hyperpycnal flows, suggesting a relationship between their development and fluvial flow (Figs. 6.5c, d and 6.15).
Current interpretations also assume that inner IPWs are moulded by relatively
recent (i.e. Holocene stillstand) dynamic processes (Figs. 6.4a, c, e and 6.15). The
original conceptual model highlighted the major influence of seaward sediment
transport patterns induced by downwelling storm resuspension currents that trigger
sediment avalanching onto a depositional slope below storm base levels (Fig. 6.15)
(e.g. Hernández-Molina et al. 2000; Ercilla et al. 2010). More recent studies stress
188
G. Ercilla et al.
from the suspension of nepheloid layers, or turbid layers of sediment delivered from
rivers and streams or wave-supported gravity flows, all with a dominant cross-shelf
transport dynamic (Fig. 6.15). The settling process appears to be continuous, operating on the present-day proximal continental shelf since the installation of the
Holocene highstand (6500 years BP to present). The well-defined 2D surficial
distribution of the prodelta facies, the age of these facies (1500 years BP), and the
well-defined 3D geometry (wedge-shape) of the prodeltaic bodies identified from
seismic records indicates strong sediment progradation in the submarine environment and low sediment retention levels in the emerged domain (Fig. 6.4a, b, c, d)
(e.g. Ercilla et al. 1994; Hernández-Molina et al. 1994; Bárcenas et al. 2009; Lobo
et al. 2015). The plan-view geometries are directly related to hydrodynamic control
being greater in those with elongate patterns. In this sense, the Guadalfeo River
prodelta exhibits lateral morphological plan-view changes from lobate to elongate,
reflecting the temporal modification of the balance between fluvial supply and
sediment redistribution by the governing hydrodynamics and/or reworking of
pre-existing depocentres (Figs. 6.4a, b and 6.15) (Lobo et al. 2006; Jabaloy-Sánchez
et al. 2014).
Many prodeltas are affected by conspicuous seafloor undulations (Fig. 6.4a, d).
Morphometric, stratigraphic, and sedimentological data indicate the possible activity
of hyperpycnal flows (i.e. a particular type of turbidity current generated by river
discharge) as a plausible genetic mechanism (Fig. 6.15) (Lobo et al. 2015). The
margins of the southern Iberian Peninsula are mountainous, and the drainage basins
are small and steep; in addition, rainfall events are torrential nature in the region;
these conditions favour the generation of hyperpycnal flows. There is greater
undulation development in prodeltaic settings off river basins with high maximum
rainfalls; therefore, a genetic link between fluvial flow and undulation development
has been proposed (Bárcenas et al. 2009). In this sense, a relationship is observed
between undulation development and river basin parameters, such as river length
and basin size (Bárcenas et al. 2009). The most detailed analysis has been conducted
on the undulations off the Guadalfeo River, which could be classified as a moderately dirty river (Fig. 6.4a, b, d). There, morphometric differences between undulation fields suggest the occurrence of temporal changes in hyperpycnal flows. Higher
undulations could be indicative of intensified river flow, whereas lower and more
laterally extensive undulations could indicate their inactivity due to a change in the
course of the river (Fernández-Salas et al. 2007; Lobo et al. 2015). On the other
hand, the presence of prodeltaic channels and/or gullies would point to relatively
high-energy hyperpycnal flows, suggesting a relationship between their development and fluvial flow (Figs. 6.5c, d and 6.15).
Current interpretations also assume that inner IPWs are moulded by relatively
recent (i.e. Holocene stillstand) dynamic processes (Figs. 6.4a, c, e and 6.15). The
original conceptual model highlighted the major influence of seaward sediment
transport patterns induced by downwelling storm resuspension currents that trigger
sediment avalanching onto a depositional slope below storm base levels (Fig. 6.15)
(e.g. Hernández-Molina et al. 2000; Ercilla et al. 2010). More recent studies stress
188
G. Ercilla et al.