seafloor spreading was involved, could it be associated with the stretching of the
continental margins located at the western end of the Ligurian Tethys oceanic basin?
(Vergés and Fernàndez 2012; Vergés et al. 2019).
The closure of the Ligurian Tethys basin is clearly linked to the subduction of the
African oceanic lithosphere northward, under Eurasia, in the Eocene (Fig. 5.13c). It
would have favored the progressive disappearance of the Atlantic-Tethys oceanographic connection. Still, the change in subduction described for the Oligocene
immediately led to the extensional collapse of the Eocene alpine orogen and opening
of the Western Mediterranean oceanic basin. A further consequence was the splitting—to the east, south, and west—of several lithospheric fragments of this orogen
(Faccenna et al. 2004; Jolivet et al. 2009; Carminati et al. 2012). This new
geodynamic scenario welcomed the maintenance of the oceanographic connection
between the Atlantic Ocean and the Western Mediterranean Sea as the Alboran
Basin was being formed, and its additional connection to the Ligurian Tethys while
this basin was gradually closed due to subduction of its oceanic lithosphere.
Westward drift of the Alboran Domain throughout the Miocene resulted in the
formation of the Betic-Rif Belt when it collided with the continental margins of
southern Iberia and northern Africa. Inside this orogen, in the back-arc region, a
marine basin developed in the wake of extensional stretching of the lithosphere
(Comas et al. 1999; Comas and Soto 1999). At this stage, several W-E oceanographic connections resisted, by means of the Northbetic area, the Alboran Sea, and
the Rif area (Braga et al. 2001, 2003; Martín et al. 2009; Do Couto et al. 2016;
Capella et al. 2017) (Fig. 5.13d). Thus, the Tortonian marine basin would have had a
much greater width (even several hundred miles wider) than the current basin
(Fig. 5.13e). This is attested to by the distribution of Tortonian coral reefs along
the main mountainous reliefs of both the Betic and Rif chains, reliefs that existed as
large islands within the Tortonian Sea (Braga et al. 2003; Galindo-Zaldívar et al.
2019).
A shift in the direction of convergence of Africa and Eurasia in the Late Tortonian
slowed the Alboran Domain’s westward drift. At the same time, tectonic stacking at
the Gibraltar Arc front (Balanyá et al. 2007), deformation related to block rotations
(Crespo-Blanc et al. 2016), and the progressive uplift of the Betic and Rif ranges
onland (Braga et al. 2003), because of increased thickness owing to the emplacement
of the Alboran Domain. The Upper Miocene also witnessed the main stage of
magmatic activity (Duggen et al. 2008): several volcanos formed in the Alboran
Basin, very likely associated with a thermal expansion of the seafloor. Furthermore,
it has been proposed that the joint action of mantle resisted slab dragging and slab
tearing also influenced the closure of these gateways (Capella et al. 2020). Given this
compressional setting, together with the generalized sea level fall in the Messinian
(Jolivet et al. 2006; Loget and Van Den Driessche 2006), an imminent consequence
was the closure of marine water corridors through which the Mediterranean Sea
communicated with the global ocean (e.g., Martin et al. 2001; Betzler et al. 2006;
Gibert et al. 2013; Flecker et al. 2015; Achalhi et al. 2016; Capella et al. 2018;
Krijgsman et al. 2018) (Fig. 5.13f). The Mediterranean Sea dried out nearly
5.9–5.5 Ma ago. A thick series of evaporites was deposited in the deepest basins,
5 A Geological History for the Alboran Sea Region
141
continental margins located at the western end of the Ligurian Tethys oceanic basin?
(Vergés and Fernàndez 2012; Vergés et al. 2019).
The closure of the Ligurian Tethys basin is clearly linked to the subduction of the
African oceanic lithosphere northward, under Eurasia, in the Eocene (Fig. 5.13c). It
would have favored the progressive disappearance of the Atlantic-Tethys oceanographic connection. Still, the change in subduction described for the Oligocene
immediately led to the extensional collapse of the Eocene alpine orogen and opening
of the Western Mediterranean oceanic basin. A further consequence was the splitting—to the east, south, and west—of several lithospheric fragments of this orogen
(Faccenna et al. 2004; Jolivet et al. 2009; Carminati et al. 2012). This new
geodynamic scenario welcomed the maintenance of the oceanographic connection
between the Atlantic Ocean and the Western Mediterranean Sea as the Alboran
Basin was being formed, and its additional connection to the Ligurian Tethys while
this basin was gradually closed due to subduction of its oceanic lithosphere.
Westward drift of the Alboran Domain throughout the Miocene resulted in the
formation of the Betic-Rif Belt when it collided with the continental margins of
southern Iberia and northern Africa. Inside this orogen, in the back-arc region, a
marine basin developed in the wake of extensional stretching of the lithosphere
(Comas et al. 1999; Comas and Soto 1999). At this stage, several W-E oceanographic connections resisted, by means of the Northbetic area, the Alboran Sea, and
the Rif area (Braga et al. 2001, 2003; Martín et al. 2009; Do Couto et al. 2016;
Capella et al. 2017) (Fig. 5.13d). Thus, the Tortonian marine basin would have had a
much greater width (even several hundred miles wider) than the current basin
(Fig. 5.13e). This is attested to by the distribution of Tortonian coral reefs along
the main mountainous reliefs of both the Betic and Rif chains, reliefs that existed as
large islands within the Tortonian Sea (Braga et al. 2003; Galindo-Zaldívar et al.
2019).
A shift in the direction of convergence of Africa and Eurasia in the Late Tortonian
slowed the Alboran Domain’s westward drift. At the same time, tectonic stacking at
the Gibraltar Arc front (Balanyá et al. 2007), deformation related to block rotations
(Crespo-Blanc et al. 2016), and the progressive uplift of the Betic and Rif ranges
onland (Braga et al. 2003), because of increased thickness owing to the emplacement
of the Alboran Domain. The Upper Miocene also witnessed the main stage of
magmatic activity (Duggen et al. 2008): several volcanos formed in the Alboran
Basin, very likely associated with a thermal expansion of the seafloor. Furthermore,
it has been proposed that the joint action of mantle resisted slab dragging and slab
tearing also influenced the closure of these gateways (Capella et al. 2020). Given this
compressional setting, together with the generalized sea level fall in the Messinian
(Jolivet et al. 2006; Loget and Van Den Driessche 2006), an imminent consequence
was the closure of marine water corridors through which the Mediterranean Sea
communicated with the global ocean (e.g., Martin et al. 2001; Betzler et al. 2006;
Gibert et al. 2013; Flecker et al. 2015; Achalhi et al. 2016; Capella et al. 2018;
Krijgsman et al. 2018) (Fig. 5.13f). The Mediterranean Sea dried out nearly
5.9–5.5 Ma ago. A thick series of evaporites was deposited in the deepest basins,
5 A Geological History for the Alboran Sea Region
141