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Sedimentary and mineralogical analyses were performed in the Neogene Agost Basin (External Domain, Betic Cordillera) to reconstruct relationships between tectonics and sedimentation, and source areas evolution over time. The sedimentary analysis allowed defining two sedimentary sequences: (1) Lower Stratigraphic Unit, Serravallian p.p. and (2) Upper Stratigraphic Unit, post Lower Tortonian (Upper Miocene p.p.) separated by an angular unconformity. They consist of marine (lithofacies L-1 to L-3) and continental (lithofacies L-5 to L-8) deposits respectively. The analysis of mineralogical assemblages and some XRD parameters of the sedimentary sequences and older formations allowed recognizing a sedimentary evolution controlled by the activation of different source areas over time. In particular, the Ill+Kln±Sme+Chl clay-mineral association characterizes the supply from Triassic formations; the Ill+Kln+Sme association from Albian formations; the Sme+Ill±Kln+(I-S) and Sme+Ill±Kln associations from Upper Cretaceous p.p. formations; and the Sme+Ill±Kln+(I-S) association from Paleogene formations, testifying a tectonic mobility of the basin margins differentiated over time. This reconstruction leads to propose detailed relationships between types of deposits and provenance and not a classic "unroofing", as follows: (i) the lithofacies L-1 (lithofacies L-2 and L-3 were not analysed) is characterized by the Ill+Kln+Sme mineralogical association indicating an origin from the Albian formations; (ii) the lithofacies L-4 shows a mixture of Ill+Kln+Sme and Sme+Ill+Kln associations sourced from the Albian and Upper Cretaceous formations; (iii) the lithofacies L-5 is characterized by the Sme+Ill±Kln+(I-S) association indicating a provenance from the Upper Cretaceous and Paleogene formations; (iv) the lithofacies L-6 to L-8 are characterized by the Ill+Kln±Sme+Chl association indicating a supply mainly from Triassic deposits. The evolutionary sedimentary model reconstructed for the Agost Basin, which improves a previous contribution about the same area, has been correlated with those reported in other intramontane Neogene basins in the Betic-Rifian Arc studied with similar resolution, so obtaining useful information for regional reconstructions.
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Source areas evolution in the Neogene Agost Basin
(Betic Cordillera): implications for regional reconstructions
Manuel Martín-Martín (1), Francesco Guerrera (2), Francisco J. alcalá (1) (3), Francisco serrano (4)
& Mario traMontana (5)
ABSTRACT
Sedimentary and mineralogical analyses were performed in the
Neogene Agost Basin (External Domain, Betic Cordillera) to reconstruct
relationships between tectonics and sedimentation, and source areas
evolution over time. The sedimentary analysis allowed defining two
sedimentary sequences: (1) Lower Stratigraphic Unit, Serravallian p.p.
and (2) Upper Stratigraphic Unit, post Lower Tortonian (Upper Miocene
p.p.) separated by an angular unconformity. They consist of marine
(lithofacies L-1 to L-3) and continental (lithofacies L-4 to L-8) deposits,
respectively. The analysis of mineralogical assemblages and some XRD
parameters of the sedimentary sequences and older formations allowed
recognizing a sedimentary evolution controlled by the activation of
different source areasover time. In particular, the Ill+Kln±Sme+Chl clay-
mineral association characterizes the supply from Triassic formations; the
Ill+Kln+Sme association from Albian formations; the Sme+Ill±Kln+(I-S)
and Sme+Ill±Kln associations from Upper Cretaceous p.p. formations;
and the Sme+Ill±Kln+(I-S) association from Paleogene formations,
testifying a tectonic mobility of the basin margins differentiated over
time. This reconstruction leads to propose detailed relationships
between types of deposits and provenance and not a classic “unroofing”,
as follows: (i) the lithofacies L-1 (lithofacies L-2 and L-3 were not
analysed) is characterized by the Ill+Kln+Sme mineralogical association
indicating an origin from the Albian formations; (ii) the lithofacies L-4
shows a mixture of Ill+Kln+Sme and Sme+Ill+Kln associations sourced
from the Albian and Upper Cretaceous formations; (iii) the lithofacies
L-5 is characterized by the Sme+Ill±Kln+(I-S) association indicating a
provenance from the Upper Cretaceous and Paleogene formations, and
(iv) the lithofacies L-6 to L-8 are characterized by the Ill+Kln±Sme+Chl
association indicating a supply mainly from Triassic deposits. The
evolutionary sedimentary model reconstructed for the Agost Basin,
which improves a previous contribution about the same area, has been
correlated with those reported in other intramontane Neogene basins in
the Betic-Rifian Arc studied with similar resolution, this obtaining useful
information for regional reconstructions.
Key words: clay-mineral assemblages, source areas, tectono-
sedimentary evolution, Neogene strike-slip faulting,
Betic Cordillera.
INTRODUCTION
The Agost Basin (SE of Spain) is located in the External
Domain of the Betic Cordillera that together with the Rif
Chain constitute the Betic-Rifian Arc representing the
westernmost Mediterranean Alpine orogenic belt (Fig. 1A)
originated by a Miocene tectonics (Guerrera et alii, 1993,
2005; Michard et alii, 2002; di staso et alii, 2009; handy
et alii, 2010; carMinati et alii, 2012; Guerrera & Martin-
Martin, 2014; Perrone et alii, 2014). Due to well preserved
sedimentary record and previous stratigraphic findings
(Martín-Martín et alii, 2018) this basin can be considered
a local key case useful for large-scale reconstructions.
The reconstructed sedimentary model and source areas
evolution contributed to better delineate the geodynamic-
paleogeographic evolution of the eastern External Betic
Zone.
The External Betic Domain was the Mesozoic to
Tertiary sedimentary cover (Fig. 1B) of the South margin
of the Paleozoic Iberian Massif. This passive Alpine margin
started to develop during the Mesozoic rifting of the
western Tethys producing deep and shallow pelagic blocks
separated by normal faults. The evolution of the resulting
faults and blocks controlled the successive Mesozoic
sedimentary evolution of the margin.
In the region, a tectonic inversion from extension
to compression took place close to the K/T boundary
(Guerrera et alii, 2006, 2014; Guerrera & Martín-Martín,
2014). The Neogene tectonic evolution of this crustal sector
is highly controversial and its evolution is still discussed by
the international scientific community (see discussions in
sanz de Galdeano & Vera, 1992; and Vera, 2000). The most
accepted models consider that the Mesozoic previously
formed normal faults in many cases evolved during the
compressive Miocene deformation as strike-slip faults.
Bending of strike-slip faults with respect to the direction
of movement determined the lateral divergent (in releasing
bends) or convergent (in restraining bends) motion of blocks
(allen & allen, 2005). Moreover, a strike-slip fault single
segment could show a successive behavior from releasing
bend to restraining bend, caused by changes of the stress axes
orientation over time. In the case of the Betic Cordillera and
in particular in the Alicante area a progressive reorientation
of the convergence during the Miocene is mostly accepted
(sanz de Galdeano & BuForn, 2005). From the Serravallian,
the Betic Cordillera experienced a horizontal maximum
compression with a rotation of the principal axis of stress
from E-W to N-S and the resulting deformation gave rise
to a strike-slip fault deformation in the whole chain. The
development of a net of interconnected intramontane
basins characterized the Neogene evolution of the eastern
Betic Cordillera (sanz de Galdeano & Vera, 1992; sissinGh,
2008).
Ital. J. Geosci., Vol. 137 (2018), pp. 433-451, 8 figs., 4 tabs. (https://doi.org/10.3301/IJG.2018.14)
© Società Geologica Italiana, Roma 2018
(1) Departamento de Ciencias de la Tierra y Medio Ambiente,
University of Alicante, Alicante, Spain.
(2) Ex-Dipartimento di Scienze della Terra, della Vita e
dell’Ambiente, Università degli Studi di Urbino, Urbino, Italy.
(3) Instituto de Ciencias Químicas Aplicadas, Facultad de
Ingeniería, Universidad Autónoma de Chile, Santiago, Chile.
(4) Departamento de Geología y Ecología, University of Málaga,
Málaga, Spain.
(5) Dipartimento di Scienze Pure e Applicate (DiSPeA), Università
degli Studi di Urbino Carlo Bo, Urbino, Italy.
Corresponding author e-mail: manuel.martin.m3@gmail.com.
Author’s personal copy
M. MARTÍN-MARTÍN ET ALII434
In the study area, the faults of this system generated a
subsiding area called the Agost Basin by Martín-Martín et
alii (2018). Terraced sidewall faults and graben subzones
developed in the Agost Basin in the context of a dextral
stepover with a dextral movement of blocks. This subsiding
area is characterized by a Neogene shallow marine and
continental infilling controlled by the evolution of several
curvilinear faults involving salt tectonics related to
basement Triassic rocks (Martín-Martín et alii, 2018).
The aim of this paper is to reconstruct the sedimentary
evolution of the Neogene Agost Basin (Betic Cordillera,
SE Spain) on the basis of mineralogical data that allows
the improvement of previous structural knowledge
(Martín-Martín et alii, 2018). The identification of the
mineralogical associations present in the pre-Neogene
sedimentary succession of the area (cfr. Cycles of Vera,
2000) allowed recognizing the possible source areas
activated in different times. The obtained data enabled to
reconstruct a detailed tectono-sedimentary model.
The space-time distribution of detrital clay minerals
in sedimentary successions may provide additional
information on the environmental conditions and lithology
of the source areas (GinGele et alii, 1998; Bolle & adatte,
2001; ruFFell et alii, 2002; liu et alii, 2008; dou et alii, 2010;
Moiroud et alii, 2012; alcalá et alii, 2013b), as well as on the
influence of tectonics on the sedimentary record (enu, 1986;
Martín-Martín et alii, 2001; JaMoussi et alii, 2003) regarding
the most classical provenance studies based on coarser
grained sediments analyses. In the Betic-Rifian external
domains, the typical clay-mineral assemblages from
Triassic (e.g. dorronsoro, 1978; Puy, 1979), Jurassic (e.g.
PaloMo et alii, 1985; lóPez-Galindo et alii, 1994), Cretaceous
(e.g. lóPez-Galindo, 1986; loPez-Galindo & oddone, 1990;
Plestch, 1997; Moiroud et alii, 2012), Paleogene (e.g.
Martinez-ruiz et alii, 1992; Bolle & adatte, 2001; alcalá et
alii, 2001; Guerrera et alii, 2014), and Neogene (e.g. alcalá et
alii, 2013a, 2013b; Maa et alii, 2017) terrains are relatively
well known and have been used to identify the source area
evolution of sedimentary successions (alcalá et alii, 2013a).
These relationships between the stratigraphic record and
source areas based on clay-mineral studies can be made
when the diagenetic influence on clay mineralogy remains
low (ruFFell et alii, 2002; liu et alii, 2008; dou et alii, 2010;
alcalá et alii, 2001, 2013b).
In brief the results obtained represent an integration
of previous knowledges and may constitute a resource
for the reconstruction of evolutionary models in similar
intramontane Neogene basins. This paper represents a first
attempt in this direction comparing the recognized evolution
with that of other external sectors of the Betic Cordillera,
Rif, Tunisian Tell and northern Apennines. The approach
followed can be interesting for further regional studies.
GEOLOGICAL SETTING
From the Middle Miocene, after the accomplishment
of the westward displacement of the Internal Zones, in
the Betic-Rifian Arc many intramontane basins developed
with stratigraphic architecture and geometries controlled
by re-arrangements of blocks, usually related to strike-slip
faults (sanz de Galdeano & Vera, 1992; sissinGh, 2008).
Contemporaneously to the development of intramontane
basins the opening of the Mediterranean Sea occurred
to form a back-arc basin after the subduction of the
Africa Plate under the Mesomediterranean Microplate
(sensu Guerrera & Martín-Martín, 2014; and references
therein). In the External Betic Zone during the Middle-
Late Miocene a foredeep area called the North Betic
Strait (or Proto-Guadalquivir Foreland Basin) connecting
the Atlantic Ocean with the Mediterranean Sea
(sanz de Galdeano & Vera, 1992) developed. In the latest
Miocene this connection was interrupted in the eastern
sector due to the Africa-Iberia convergence, and the North
Betic Strait evolved in the Guadalquivir Basin (marine
at first, then fluvial) with an opening only to the Atlantic
Ocean (Vera, 2000).
Similarly, in the External Rifian Zones (Morocco)
equivalent interconnected basins related to the Zoumi,
Gharb-Saiss, and Taza Intramontane Basins developed
starting from the Middle Miocene, contemporaneously to
the S-SW migration of thrust sheets. Other basins (e.g. the
Melilla Basin) developed in relation to the extension on
the mainland of faults related to the Mediterranean Sea
opening (sissinGh, 2008).
The Betic-Rifian Arc intramontane basins were
accomplished during the Middle to Late Miocene,
contemporaneously with the NW-SE to N-S Africa-
Iberia convergence. These basins were grouped by
sanz de Galdeano & Vera (1992) and sissinGh (2008) into
four types according to fault orientations and kinematics:
(1) NE-SW to NNE-SSW oriented sinistral strike-slip fault
basins as the Lorca and Vera Basins in the Betics, and Taza
and Melilla Basins in the Rif, due to the NW-SE extension
induced by the arc-normal pull of the E-NE trending slab
attached to the subducted Iberian Plate; (2) NW-SE and
NNE-SSW oriented normal fault basins as the Granada,
Guadix-Baza, Ronda, and Fortuna Basins, in the Betics,
and Zoumi, Bouhaddi Graben, and Taounate Basins
in the Rif, related to the NE-SW extension with a trend
similar to the Alboran Shear Zone; (3) N-S oriented fault
basins (usually normal faults) as the Mazarrón Basin in
the Betics and North African Flysch Trough in the Rif, due
to the E-W extension associated with strike-slip faulting;
and (4) E-W oriented fault basins (usually normal faults)
as the Almanzora and Huercal-Overa Basins, in the Betic,
and Saiss and Gharb Basins in the Rif, related to the
N-S extension due to the collapse of continental crust by
delamination of the lithosphere.
The Agost Basin is located in the Alicante province
in the SE Spain (Fig. 1C). This basin was located in the
easternmost part of the North Betic Strait in connection
with the Mediterranean Sea. Nowadays the Alicante
province is characterized by a network of curvilinear
faults (in plan view), bounding amygdaloidal, sigmoidal
or rhomboid blocks (Guerrera et alii, 2014; Martín-
Martín et alii, 2018; among others). During the Neogene
these faults formed a complex net of interconnected
subsiding areas (usually intramontane basins) separated
by structural highs. The structural highs were mainly
constituted by Cretaceous-Paleogene rocks and along the
fault traces that bound the blocks salty Triassic material
crops out. The presence of Triassic rocks and the scarcity
of Jurassic ones are related to a major early Cretaceous
extensional phase that laminated the Jurassic deposits
(de ruiG, 1992). This phase caused an initial event of
salt tectonics involving pinch-outs of Triassic clays and
gypsum. Most of the diapiric structures of the region
SOURCE AREAS EVOLUTION IN THE NEOGENE AGOST BASIN 435
were generated by extensional or transtensional faulting
in a second salt tectonic event reaching the surface
during the Neogene (de ruiG, 1995). Therefore, in this
region structural evolution and salt tectonics processes
are strongly linked and recorded by sedimentation. In the
considered area (Fig. 1C) the main faults characterizing
a central segment of the Novelda-Jijona strike-slip Fault
Zone have been selected as a key example for the study
of the control of fault activity on sedimentation and the
reconstruction both of the sedimentary infilling evolution
and the history and variations over time of the source
areas.
The Novelda-Jijona Strike-Slip Fault Zone in the Agost
Basin area consists of a narrow and deep area oriented
roughly N80°E, bounded by the “Sierra del Ventós”
tectonic sector (900 m high) southward and the “Sierra del
Maigmó” tectonic sector (1,200 m high) northward (Fig. 2).
Both these reliefs are separated by a sigmoid to rhomboid
shaped depression (about 6 km long and 2 km wide)
bounded by the “Maigmó” and “Ventós” Faults. Different
segments of these faults show orientations ranging from
about N50°E to N 90°-100°E.
The deepest central area can be considered a subsiding
area related to strike-slip faults where two tectonic sectors
can be recognized: (1) the so called Agost Basin that evolved
as a graben zone (550-600 m above the sea-level); and (2)
the “Sarganella” Range that evolved as a terraced sidewall
fault zone (a relative pushed up zone or flower structure
sensu twiss & Moores (2007), located 700-800 m above the
sea-level) and affected by a dense net of fractures arranged
to form sigmoid shaped blocks (map view). The first sector
is filled by Neogene deposits, while the second one is
mainly characterized by different faulted blocks marked by
the presence of exhumed Triassic material and Cretaceous
to Paleogene rhomboid outcrops. The two sectors are
separated by the “Barranco Blanco” Fault, a feature partly
parallel to the “Ventós” Fault whose strike changes from
about N50 to N150 and marked by the presence of Triassic
clays and gypsum (Fig. 2; plate I: photos 1 and 2).
The present structure of the Agost Basin corresponds
with an open syncline (the “Barranco Blanco” Fold) with
a 40° to 60° plunging axis (Fig. 2, cross sections). The
oldest sediments of the infilling crops out in the eastern
perisyncline closure and near the “Sierra del Ventós”, while
the youngest ones appear westward near the “Sarganella”
Range and unconformably seal the “Ventós” Fault in
several points. The basin infilling shows a progressive
and syn-sedimentary folding resulting in the Barranco
Blanco Fold that shows a westward plunging axis. In this
structural context the terrains of the Cycle I p.p. (Triassic)
show a root constituted by a squeezed “salt wall” with a
mushroom geometry at the surface (Mcdonnell et alii,
2009) that affects both the “Sarganella” Range and the
Agost Basin.
MATERIALS AND METHODS
For the purpose of the work, the following field and
laboratory analyses were performed: (i) sedimentary
Fig. 1 - A: Index map of the western Mediterranean region with the location of the study area; B: Geological sketch showing the main zones of
the eastern Betic Cordillera; C: Geological map based on the main sedimentary cycles proposed by Vera (2000, 2004).
M. MARTÍN-MARTÍN ET ALII436
analysis in four representative and correlated Neogene
stratigraphic sections of the Agost Basin (for a total of 805
m); (ii) sampling of forty-eight clay-rich samples (location
in Fig. 2) in different possible source areas on the flanks
of the basin (samples BB10 to BB100) and lithofacies of
the Neogene Agost Basin (samples BB110 to BB240); and
(iii) examination of the whole-rock and <2 µm grain-size
fraction (clay fraction hereafter) mineralogy of collected
samples by X-ray diffraction (XRD) at the Espinardo
Laboratory, University of Murcia, by using a Phillips
X’PERT MPD Systempert ® diffractometer with automatic
slit, CuKα radiation, and 2 to 6º min-1 scanning interval
from 2º 2θ to 60º 2θ.
For the non-calcareous clay fraction, four oriented
mounts on glass slides per sample were prepared following
air-drying, ethylene-glycol and dimethyl-sulfoxide solvation
for 24 h, and heating at 550ºC for 2h for expandable
clay-mineral identification (croudace & roBinson, 1983;
holtzaPFFel, 1985; Moore & reynolds, 1997). The position
of the (001) series of basal reflections, and eventually other
higher-order reflections at the low-angle diffraction region
under the diagnostic treatments, were used to identify the
clay-mineral groups: smectite and randomly interstratified
illite-smectite (15-17 Å), illite (10 Å), kaolinite/chlorite (7 Å)
on the glycolated curve taking the 3.57/3.54 Å peak areas
ratio into account (holtzaPFFel, 1985; Moore & reynolds,
1997). The reflections and reflecting powers of schultz
(1964), Biscaye (1965), and holtzaPFFel (1985) were used to
identify and quantify the mineral phases, respectively. The
XPowder ® program [http://www.xpowder.com/] was used
for the semi-quantitative estimates of the reflection peak
areas. Replicate analyses of a few selected samples gave
a precision of ±3% (2σ). Based upon the XRD technique,
the semi-quantitative evaluation of each mineral phase (in
weight percent, wt. % normalized to 100%) has an accuracy
of ~5%. The intensities ratio of characteristic reflections
Fig. 2 - Detailed geological
map of a sector of the Novelda-
Jijona Strike-Slip Fault Zone
modified from Martín-Martín
et alii (2018) including the
Agost Basin and surrounding
areas (location in Fig. 1C). In
the lower part two geological
cross-sections of the Agost
Basin are shown where the
five isochronous lines T1-T5
are also reported. BB identifies
code and location of samples
for mineralogical analyses, as
in tabs. 1 and 2.
SOURCE AREAS EVOLUTION IN THE NEOGENE AGOST BASIN 437
peak areas of quartz, smectite and illite were examined to
deduce possible diagenetic influences on the mineral phases
(hunziKer, 1986; riGhi & elsass, 1996; drits et alii, 1997).
The intensities ratio of the Qtz(001)/Qtz(101) peak areas
of quartz (Qtz(001)/Qtz(101) ratio hereafter) in the whole-
rock XRD diffractograms is a tentative index to discern
authigenic (higher values) from secondary quartz (lower
values) in the absence of a volcanic component (eslinGer
et alii, 1973). These authors proposed Qtz(001)/Qtz(101)
ratios below 0.3 for secondary quartz. The intensities
ratio of the Sme(003)/Sme(002) peak areas of smectite
(Sme(003)/Sme(002) ratio hereafter) from ethylene-glycol
solvated clay-fraction XRD diffractograms is useful for
differentiating dioctahedral and trioctahedral smectites
(Moore & reynolds, 1997). Increased Fe+MgxAl exchange
in the mineral structure due to physical weathering under
a low diagenetic influence results in decreased intensity of
some reflections, indicated by Sme(003)/Sme(002) ratios
below 1 for Fe+Mg-rich smectites. The intensities ratio of
the Ill(002)/Ill(001) peak areas of illite (Ill(002)/Ill(001) ratio
hereafter) from decomposited air-dried clay-fraction XRD
diffractograms is an approximate index of the AlxMg+Fe
exchange in the octahedral sheet as the mineral structure
transforms by physical processes (esqueVin, 1969). This
author proposed the (001) reflection width as indicator
of low diagenetic influence only when the Ill(002)/Ill(001)
ratio is below 0.3, which indicates a low Al/(Fe+Mg) ratio.
RESULTS
lithostratiGraPhic record oF the aGost Basin
The lithostratigraphic record and sedimentary features
of the Agost Basin were reconstructed by means of four
representative stratigraphic successions (logs 1-4 of Fig. 3,
and plate I; also located in Fig. 2) previously studied by
Martín-Martín et alii (2018). The succession was subdivided
into two main stratigraphic sequences separated by
an angular unconformity (plate I: photo 3): (1) Lower
Stratigraphic Unit (LSU), Serravallian p.p., consisting
of marine deposits; and (2) Upper Stratigraphic Unit
(USU), Upper Miocene p.p., characterized by continental
(lacustrine and fluvial) deposits.
The overlying sub-horizontal Pliocene deposits seal
the deformed USU and all previous tectonic structures by
a major angular unconformity (plate I: photo 6). The LSU
is preserved only in a restricted area of the basin where
it shows a thickness of about 100 m. Outside of the Agost
Basin this unit was also recognized in the Maigmó Relief
(Fig. 2), where it shows the shallowest lithofacies with
conglomerates and marly levels. This unit was defined
as Tap facies by Vera (2004) in surrounding areas where
marls prevail. The LSU is made up of three lithofacies
(plate I: photos 1, 2, and 3): L-1, whitish marls and marly
limestones (44 m thick) rich in foraminifers and spicules
of sponges; L-2, calcarenitic beds with conglomerate
intercalations (5-10 m thick) rich in benthic foraminifera
and several kinds of mollusks; L-3, calcarenitic beds (50 m
thick) rich in large foraminifera, echinoderms, corals,
briozoes, ostreids, and brachiopods. This succession
indicates a relative sea-level fall, evidenced by a regressive
evolution from open to shallow water and restricted
marine conditions. This local reconstruction corresponds
to the evolutionary trend recognized at the regional scale
(Vera, 2004; Guerrera et alii, 2006; Guerrera & Martín-
Martín, 2014), which is related to a progressive shallowing
of the environment towards the northern Prebetic sub-
Domain and the consequent deepening to the W-SW,
where several structural highs and deep areas occur.
The most extensive and preserved USU (more than 490
m thick) is made up of five lithofacies. The lower part of
USU consist of lithofacies L-4 being composed of more
than 250 m thick of conglomerates, arenites, and whitish
clays and silts showing a typical onlap arrangement (plate
I: photo 5). Furthermore, considering also grain size of
clasts, bad rounding, and position at the base of the reliefs,
this unit may indicate a continental foot-cliff depositional
environment. The L-4 is also common in the surrounding
area of the Sierra del Ventós relief and sometimes seals
the Ventós Fault so representing also a useful marker
level for tectonic reconstructions. The lithofacies L-5,
more than 50 m thick, is made of whitish clays and silts
with local black levels (lignite), arenites, and channelized
conglomeratic intercalations (plate I: photos 4, 5, and 6).
The coarse detritic supply of the channelized conglomerates
diminishes northwards (from conglomeratic to siltitic
beds); furthermore, the presence of abundant lignite may
be also interpreted as indicative of fluvial and lacustrine
realms.
Lithofacies L-6, more than 90 m thick, is mainly
characterized by reddish conglomerates (plate I: photos 3
and 5 to 8) containing blocks of Triassic gypsum (plate I:
photo 8) and with a fan shape arrangement of beds (plate
I: photo 7). The conglomerate beds decrease southwards
showing lateral variations to siltstones. In particular,
two conglomeratic bodies crop out in the northern side
of the Agost Basin (i.e. the Barranco Blanco Fault Zone;
Figs. 2 and 3). The lithofacies L-6 has been interpreted as
a progradational deposition of alluvial fan in a fluvial to
lacustrine realm.
Lithofacies L-7 consists of pinkish clays and silts with
occasional arenites and conglomeratic intercalations
deposited in the northern margin of the basin, arranged in
a great depositional body (> 45 m thick) and encompassing
the lithofacies L-6 in the central area of the basin (plate I:
photos 3, 5, and 6). The conglomerate beds of lithofacies
L-7 decrease southward with the occurrence of lateral
variations from conglomerates to siltstones.
The conglomerates of the lithofacies L-8 (more than 55
m thick), composed of Cretaceous-Paleogene calcareous
clasts and Triassic bi-pyramidal quartz and gypsum with
a matrix made up of Triassic reddish pelites, shows a
progradation and decrease of grain size southward. This
lithofacies is arranged in a fan structure sealing the Ventós
Fault (Fig. 2) and is fed by the Sarganella Range according
to the distribution of coarse deposits and the sense of
progradation.
In conclusion, the USU indicates a depositional system
consisting of fluvial and lacustrine realms in the central
area of the basin, and alluvial fans and cliff deposits in the
margins.
MineraloGy oF the Pre-neoGene ForMations
In the perspective to identify the possible source
areas (Sierra del Maigmó, Sarganella Range, and Sierra
del Ventós) feeding the Agost Basin in different times,
M. MARTÍN-MARTÍN ET ALII438
mineralogical associations and XRD parameters of the
pre-Neogene formations characterizing all these source
areas were studied. For this purpose the samples BB10 to
BB100 (located in Fig. 2) collected from the outcropping
sedimentary cycles indicated as follows: I (Triassic), IV
(Albian p.p.), V (Upper Cretaceous p.p.), and VI (Paleogene)
were examined (Tab. 1; Fig. 4).
Clays, and gypsy clays and pelites lithologies from
Triassic Cycle I include (in wt. % hereafter) phyllosilicates
(9-39%), K-feldspar (14-24%), gypsum (5-53%), quartz
(5-18%), and minor amounts of plagioclase, magnetite,
and hematite. The clay fraction includes illite (67-68%),
kaolinite (12-19%), smectite (9-16%), and chlorite (<6%),
which characterizes the Ill+Kln±Sme+Chl clay-mineral
association. The Qtz(100)/Qtz(101), Sme(003)/Sme(002),
and Ill(002)/Ill(001) ratios vary in the 0.21-0.31, 0.72-0.75,
and 0.19-0.28 ranges, respectively. Compared to the gypsy
clays and pelites, the clays lithology shows: (1) lower
amount of gypsum, K-feldspar, and smectite; (2) lower
Qtz(100)/Qtz(101) and Ill(002)/Ill(001) ratios; (3) higher
amounts of phyllosilicates, quartz, kaolinite, and chlorite;
and (4) presence of Fe-oxides (Tab. 1).
Pelites, sandy and silty marls, and marls lithologies
from the Albian Cycle IV include calcite (54-66%), dolomite
(9-18%), phyllosilicates (14-15%), quartz (7-9%),
and gypsum (<5%). The clay fraction includes illite
(39-45%), kaolinite (33-35%), and smectite (20-27%), which
characterizes the Ill+Kln+Sme clay-mineral association.
The Qtz(100)/Qtz(101), Sme(003)/Sme(002), and Ill(002)/
Ill(001) ratios vary in the 0.20-0.21, 0.84-0.90, and 0.18-0.21
Fig. 3 - Lithostratigraphy
and correlations of four
representative successions
(logs 1 to 4) of the Agost
Basin (location in Fig. 2). The
two main sequences (Lower
Stratigraphic Unit, LSU and
Upper Stratigraphic Unit,
USU) separated by an angular
unconformity are evidenced.
Depositional environments,
supplies and the isochronous
lines T1-T5 are also indicated.
SOURCE AREAS EVOLUTION IN THE NEOGENE AGOST BASIN 439
Plate I - Selected outcrops showing tectonic and sedimentary features of deposits of the Agost Basin. 1, mushroom
structure constituted by Triassic rocks (Tr) overriding the lithofacies F-1 (LSU, Lower Serravallian). This structure is also
shown in the cross sections of Fig. 2; 2, tectonic contact between the lithofacies L-1 and L-3 (USU) and the Triassic salt
wall (Tr) (see also the geological cross section A-B of Fig. 2); 3, angular unconformity between the LSU (represented by
the lithofacies L-3) and the USU (represented by the lithofacies L-6 and L-7) (see also the geological cross section A-B of
Fig. 2); 4, conglomeratic channelized body of the lithofacies L-5; 5, folded USU succession (Barranco Blanco) involving
the lithofacies L-4 and L-5 and the lateral change of the lithofacies L-5 to L-6 and L-7; 6, alternating lithofacies L-5 and
L-7 (USU) topped by the Pliocene deposits by means of an evident angular unconformity; 7, deformed fan deposits of the
lithofacies L-6 (USU) showing a downlap geometry; and 8, conglomeratic channelized body of the lithofacies L-6 (USU)
containing gypsum clasts.
M. MARTÍN-MARTÍN ET ALII440
TABLE 1
Average whole-rock and <2 µm grain-size fraction mineralogy (in wt. %)
of samples from the Sedimentary Cycles I to VI (source areas)
Sedimentary Whole rock <2 µm grain-size
fraction
Cycle Age Sample (a) Lithology Qtz Phy Cal Dol Kfs Pl Gp Mag Hem Sme Ill Kln Chl I-S Qtz(100)/
Qtz(101)
Sme(003)/
Sme(002)
Ill(002)/
Ill(001)
Cycle VI Paleogene p.p. BB100 marls <5 10 89 46 28 24 <5 0.20 0.85 0.26
BB96 pelitic
marls <5 9 90 45 29 25 <5 0.21 0.86 0.27
BB95 marls <5 9 90 43 30 24 <5 0.19 0.85 0.24
BB90 silty marls <5 9 90 46 29 23 <5 0.20 0.84 0.25
Cycle V Senonian p.p. BB80 marly
limestones <5 <5 95 38 30 32 0.30 0.94 0.30
BB75 marls <5 <5 96 37 32 31 0.30 0.95 0.34
BB71 silty marls <5 <5 96 41 30 29 0.32 0.87 0.29
BB70 marly
limestones <5 <5 97 41 28 31 0.33 0.86 0.33
Cenomanian-
Turonian p.p. BB60 marly
limestones <5 7 90 61 32 <5 <5 0.27 0.81 0.27
BB59 silty marls <5 6 91 63 30 <5 <5 0.28 0.82 0.25
BB57 marly
limestones <5 6 91 63 29 <5 <5 0.25 0.84 0.26
BB50 marly
limestones <5 5 92 61 31 <5 <5 0.25 0.85 0.22
Cycle IV Albian p.p. BB40 pelites 9 15 54 18 5 27 39 34 0.20 0.89 0.16
BB34 sandy
marls 9 14 57 15 5 27 40 33 0.21 0.90 0.19
BB33 silty marls 7 14 64 10 5 20 45 35 0.20 0.85 0.21
BB30 marls 7 14 66 9 <5 22 44 34 0.21 0.84 0.18
Cycle I Triassic p.p. BB20 gypsy
pelites 5 10 24 <5 52 7 16 68 12 <5 0.31 0.75 0.28
BB18 gypsy
clays 5 9 23 <5 53 8 16 67 13 <5 0.30 0.74 0.24
BB12 clays 17 39 14 <5 7 16 6 10 67 19 <5 0.24 0.73 0.21
BB10 clays 18 39 15 <5 5 17 5 9 67 18 6 0.21 0.72 0.19
(a) Location of samples in fig. 2. (b) (Qtz, quartz; Phy, phyllosilicates; Cal, calcite; Dol, dolomite; Kfs, K-feldspar; Pl, plagioclase; Gp, gypsum;
Mag, magnetite; Hem, hematite; Sme, smectite; Ill, illite; Kln, kaolinite; Chl, chlorite; I-S, mixed layer illite-smectite). Intensities ratio of the
Qtz(001)/Qtz(101) peak areas of quartz, and Sme(003)/Sme(002) peak areas of smectite and Ill(002)/Ill(001) peak areas of illite under ethylene
glycol solvation are included.
Fig. 4 - Mineralogical results concerning the source areas given as the average value from the set of samples (n) in each Sedimentary Cycle
included in Tab. 1 for the whole rock and the <2 µm grain-size fraction (in wt. %). Ranges and average values of the intensities ratio of the
Qtz(001)/Qtz(101) peak areas of quartz, and Sme(003)/Sme(002) peak areas of smectite and Ill(002)/Ill(001) peak areas of illite under ethylene
glycol solvation are included. Acronyms for mineral phases as in Tab. 1.
SOURCE AREAS EVOLUTION IN THE NEOGENE AGOST BASIN 441
ranges, respectively. Mineral phases and XRD parameters
are quite homogeneous among the analyzed lithologies
(Tab. 1).
Marly limestones, silty marls, and marls lithologies
both from the Cenomanian-Turonian and Senonian
(Cycle V) include calcite (90-97%), phyllosilicates (<7%),
and quartz (<5). The clay fraction includes smectite
(38-63%), illite (28-32%), kaolinite (<32%), and random
mixed layer illite-smectite (I-S hereafter) (<5%). The
clay-mineral associations are Sme+Ill±Kln+(I-S) and
Sme+Ill+Kln for Cenomanian-Turonian and Senonian,
respectively. The Qtz(100)/Qtz(101), Sme(003)/Sme(002),
and Ill(002)/Ill(001) ratios vary in the 0.25-0.33,
0.81-0.95, and 0.22-0.34 ranges, respectively. The
Cenomanian-Turonian shows differences regarding
the Senonian lithologies as: (1) higher amounts of
phyllosilicates and smectite; (2) lower amounts of calcite
and kaolinite; (3) lower Qtz(100)/Qtz(101), Sme(003)/
Sme(002), and Ill(002)/Ill(001) ratios; and (4) presence of
random mixed layer I-S (Tab. 1).
Marls, and silty and pelitic marls lithologies from
the Paleogene Cycle VI include calcite (89-90%),
phyllosilicates (9-10%), and quartz (<5%). The clay
fraction includes smectite (43-46%), illite (28-30%),
kaolinite (23-25%), and random mixed layer I-S (<5%),
which characterizes the Sme+Ill±Kln+(I-S) clay-mineral
association. The Qtz(100)/Qtz(101), Sme(003)/Sme(002),
and Ill(002)/Ill(001) ratios vary in the 0.19-0.21, 0.84-
0.86, and 0.24-0.27 ranges, respectively. Mineral phases
and XRD parameters are quite homogeneous among the
analyzed lithologies (Tab. 1).
MineraloGy oF the neoGene aGost Basin succession
The mineralogical associations and XRD parameters
found in the Neogene sedimentary record of the Agost
Basin (lithofacies L-1 to L-8) were examined from samples
BB110 to BB240 (Tab. 2; Fig. 5), stratigraphically located
in Fig. 3.
The marls lithology in the lithofacies L-1 (LSU) includes
calcite (62-65%), phyllosilicates (16-18%), quartz (6-11%),
K-feldspar (9-10%), and minor amounts of plagioclase.
The clay fraction includes illite (37-53%), kaolinite
(29-45%), and smectite (18-19%), which characterizes
the Ill+Kln+Sme clay-mineral association. The Qtz(100)/
Qtz(101), Sme(003)/Sme(002), and Ill(002)/Ill(001) ratios
vary in the 0.18-0.28, 0.88-0.89, and 0.15-0.20 ranges,
respectively. Mineral phases and XRD parameters are quite
homogeneous (Tab. 2).
Silty marls, marls, and pelites lithologies in
the lithofacies L-4 (USU) include calcite (76-85%),
phyllosilicates (9-10%), quartz (6-8%), and minor
amounts of dolomite. The clay fraction includes illite
(39-56%), smectite (30-31%), and kaolinite (14-30%), which
characterizes the Ill+Sme+Kln clay-mineral association.
The Qtz(100)/Qtz(101), Sme(003)/Sme(002), and Ill(002)/
Ill(001) ratios vary in the 0.15-0.25, 0.79-81, and 0.29-0.30
ranges, respectively. Mineral phases and XRD parameters
are quite homogeneous (Tab. 2).
Marls, pelites, and clays lithologies in the lithofacies
L-5 (USU) include calcite (80-91%), phyllosilicates
(5-9%), dolomite (<7%), and quartz (<5%). The clay fraction
includes illite (28-52%), smectite (24-40%), kaolinite (11-
32%), and minor amounts of random mixed layer I-S,
which characterizes the Sme+Ill±Kln+(I-S) clay-mineral
association. The Qtz(100)/Qtz(101), Sme(003)/Sme(002),
and Ill(002)/Ill(001) ratios vary in the 0.18-0.22, 0.82-0.88,
and 0.22-0.29 ranges, respectively. Mineral phases and
XRD parameters are quite homogeneous (Tab. 2).
Clays and pelites lithologies in the lithofacies L-6 (USU)
include dolomite (33-34%), calcite (29-30%), gypsum
(17-18), phyllosilicates (11%), and quartz (8-9%). The clay
fraction includes illite (48-49%), kaolinite (20%), smectite
(13%), and chlorite (18-19%), which characterizes the
Ill+Kln±Sme+Chl clay-mineral association. The Qtz(100)/
Qtz(101), Sme(003)/Sme(002), and Ill(002)/Ill(001)
ratios vary in the 0.24-0.25, 0.79-0.80, and 0.22 ranges,
respectively. Mineral phases and XRD parameters are quite
homogeneous (Tab. 2).
Marls, silts, and pelites lithologies in the lithofacies
L-7 (USU) include calcite (35-68%), phyllosilicates
(12-21%), dolomite (8-25%), quartz (7-15%), and minor
Fig. 5 - Mineralogical results of the Neogene sedimentary record of the Agost Basin (LSU and USU, given as the average value from the set of
samples (n) in each lithofacies L-1 to L-8 included in Tab. 2 for the whole rock and the <2 µm grain-size fraction (in wt. %). Ranges and average
values of the intensities ratio of the Qtz(001)/Qtz(101) peak areas of quartz, and Sme(003)/Sme(002) peak areas of smectite and Ill(002)/Ill(001)
peak areas of illite under ethylene glycol solvation are included. Acronyms for mineral phases as in Tab. 2.
M. MARTÍN-MARTÍN ET ALII442
amounts of gypsum. The clay fraction includes illite
(49-52%), kaolinite (17-30%), smectite (13-20%),
and chlorite (17-20%), which characterizes the
Ill+Kln±Sme+Chl clay-mineral association. The Qtz(100)/
Qtz(101), Sme(003)/Sme(002), and Ill(002)/Ill(001) ratios
vary in the 0.18-0.19, 0.75-0.80, and 0.20-0.26 ranges,
respectively. Compared to the marls and silts, the pelites
lithology shows: (1) lower calcite, smectite, and kaolinite;
(2) lower Sme(003)/Sme(002) and Ill(002)/Ill(001) ratios;
(3) higher amount of quartz, phyllosilicates, and dolomite;
and (4) presence of chlorite (Tab. 2).
Clays, silty pelites, pelites, and marls lithologies
in the lithofacies L-8 (USU) include calcite (57-63%),
phyllosilicates (17-21%), dolomite (10-13%), and quartz
(7-11%). The clay fraction includes illite (64-66%), kaolinite
(17-18%), chlorite (12-14%), and minor amounts of smectite,
which characterizes the Ill+Kln±Sme+Chl clay-mineral
association. The Qtz(100)/Qtz(101), Sme(003)/Sme(002),
and Ill(002)/Ill(001) ratios vary in the 0.17-0.18, 0.70-0.74,
and 0.20-0.25 ranges, respectively. Mineral phases and XRD
parameters are quite homogeneous (Tab. 2).
DISCUSSION
MineraloGical eVidences For source areas eVolution
Distinctive clay-mineral associations and XRD pa-
rameters from sedimentary successions allows identify-
ing the evolution of supplies from possible sources are-
as (GinGele et alii, 1998; Bolle & adatte, 2001; ruFFell
et alii, 2002; liu et alii, 2008; DOU et alii, 2010; Moiroud
et alii, 2012; alcalá et alii, 2013b), as well as to clarify
associated isochrones induced by tectonics (enu, 1986;
Martín-Martín et alii, 2001; JaMoussi et alii, 2003). A low
diagenetic overprint is a prerequisite for using the tem-
poral distribution of clay-mineral assemblages (ruFFell
TABLE 2
Average whole-rock and <2 µm grain-size fraction mineralogy (in wt. %) of samples from the lithofacies L-1 to L-8
(Neogene sedimentary record of the Agost Basin)
Sedimentary Lithofacies Whole rock <2 µm grain-size
fraction
Stratigraphic
Unit association Sample (a) Lithology Qtz Phy Cal Dol Kfs Pl Gp Sme Ill Kln Chl I-S Qtz(100)/
Qtz(101)
Sme(003)/
Sme(002)
Ill(002)/
Ill(001)
USU L-8 BB240 pelites 7 18 63 12 5 64 17 14 0.18 0.71 0.21
BB236 silty pelites 9 17 61 13 <5 65 18 14 0.18 0.73 0.20
BB232 clays 11 20 59 10 <5 65 18 13 0.17 0.70 0.22
BB230 marls 10 21 57 12 <5 66 18 12 0.17 0.74 0.25
L-7 BB195 pelites 13 21 35 25 6 13 50 20 17 0.18 0.75 0.20
BB190 pelites 15 19 35 25 6 14 49 17 20 0.19 0.76 0.22
BB175 marls 7 12 68 8 5 20 50 30 0.18 0.79 0.26
BB170 silts 7 13 65 9 6 20 52 28 0.19 0.80 0.24
L-6 BB204 pelites 8 11 30 33 18 13 48 20 19 0.25 0.80 0.22
BB200 clays 9 11 29 34 17 13 49 20 18 0.24 0.79 0.22
L-5 BB220 pelites <5 8 82 6 50 38 11 <5 0.18 0.85 0.23
BB219 marls 5 8 81 6 47 38 12 <5 0.18 0.85 0.25
BB218 pelites 5 8 81 6 45 39 16 0.18 0.85 0.23
BB210 pelites <5 9 80 7 46 38 15 <5 0.18 0.86 0.26
BB185 clays <5 5 84 <5 30 40 30 0.21 0.82 0.25
BB180 clays <5 6 85 <5 28 40 32 0.22 0.82 0.24
BB160 pelites <5 6 91 51 24 25 0.22 0.88 0.22
BB152 pelites <5 6 90 52 25 23 0.21 0.87 0.25
BB151 marls <5 7 90 52 28 20 0.21 0.87 0.29
BB150 pelites <5 8 90 50 28 22 0.20 0.88 0.28
L-4 BB140 pelites 6 9 85 31 39 30 0.25 0.81 0.28
BB138 silty marls 7 10 83 30 40 30 0.25 0.80 0.30
BB137 marls 6 8 81 5 31 55 14 0.15 0.79 0.29
BB130 silty marls 8 10 76 6 30 56 14 0.16 0.81 0.30
LSU L-1 BB120 marls 6 17 65 10 <5 18 53 29 0.18 0.88 0.20
BB116 marls 8 18 64 9 <5 18 52 30 0.19 0.89 0.19
BB111 marls 10 16 63 10 <5 19 36 45 0.27 0.89 0.14
BB110 marls 11 17 62 9 <5 18 37 45 0.28 0.88 0.15
(a) Location of samples in fig. 3. (b) (Qtz, quartz; Phy, phyllosilicates; Cal, calcite; Dol, dolomite; Kfs, K-feldspar; Pl, plagioclase; Gp, gypsum; Sme,
smectite; Ill, illite; Kln, kaolinite; Chl, chlorite). Intensities ratio of the Qtz(001)/Qtz(101) peak areas of quartz, and Sme(003)/Sme(002) peak
areas of smectite and Ill(002)/Ill(001) peak areas of illite under ethylene glycol solvation are included.
SOURCE AREAS EVOLUTION IN THE NEOGENE AGOST BASIN 443
et alii, 2002; liu et alii, 2008; dou et alii, 2010; Moiroud et
alii, 2012; alcalá et alii, 2013b).
In addition, the clay-mineral associations indicating
source areas in the Subbetic zone are well-known (Tab. 3):
(1) Ill+Kln±Sme+Chl for Triassic formations (dorronsoro,
1978; PUY, 1979); (2) Ill+Sme±(I-S) with additional variable
amounts of Chl±Kln for Jurassic formations (PaloMo et alii,
1985; lóPez-Galindo et alii, 1994); (3) Ill+Sme±(I-S)+Kln for
TABLE 3
Clay-minerals associations of the local source areas (Cycles I to VI) and the Neogene sedimentary succession
(lithofacies L-1 to L-8). Some clay-mineral associations compiled from the literature for Triassic to Lower Miocene
formations in different Subbetic sectors of the Betic Cordillera have been included for comparisons.
Sedimentary Cycles, local source areas (this paper) Clay-mineral association
Cycle VI, Paleogene Sme+Ill±Kln+(I-S)
Cycle V, Senonian (S) Sme+Ill+Kln
Cycle V, Cenomanian-Turonian (C-T) Sme+Ill±Kln+(I-S)
Cycle IV, Albian Ill+Kln+Sme
Cycle I, Triassic Ill+Kln±Sme+Chl
Lithofacies, Neogene Agost Basin (this paper) Clay-mineral association Main local source area
L6 to L8 (USU) Ill+Kln±Sme+Chl Cycle I
L5 (USU) Sme+Ill±Kln+(I-S) Cycle V (C-T); Cycle VI
L4 (USU) Ill+Sme+Kln Cycle IV; Cycle V (S)
L1 (LSU) Ill+Kln+Sme Cycle IV
Regional source areas Clay-mineral association Reference
Age Location (a)
Lower Miocene (1) Alta Cadena Sme+Ill+(I-S)±Kln ALCALÁ et alii, (2013a, 2013b)
Lower Miocene (2) Tajo Almarado Sme+Ill+(I-S)±Kln ALCALÁ et alii, (2013a, 2013b)
Lower Miocene (3) Argüelles Sme+Ill±(I-S)+Kln ALCALÁ et alii, (2013a, 2013b)
Paleogene (4) Alta Cadena Sme+Ill±Kln+(I-S) ALCALÁ et alii, (2001)
Paleogene (5) Tajo Almarado Sme+Ill±Kln+(I-S) ALCALÁ et alii, (2001)
Paleogene (6) Alamedilla Sme+Ill±Kln BOLLE & ADATTE (2001)
Paleogene (7) Pila-Carche Sme+Ill±Kln+(I-S) GUERRERA et alii, (2014)
Paleogene (8) Agost Sme+Ill±Kln+(I-S) MARTINEZ-RUIZ et alii, (1992)
Upper Cretaceous (9) Puerto del Viento Sme+Ill LÓPEZ-GALINDO (1986)
Upper Cretaceous (10) Alamedilla Sme+Ill±Kln LÓPEZ-GALINDO (1986)
Upper Cretaceous (11) Cerrajón Sme+Ill±Kln LÓPEZ-GALINDO (1986)
Upper Cretaceous (12) Guadalupe Sme+Ill±Kln LÓPEZ-GALINDO (1986)
Upper Cretaceous (13) Agost Sme+Ill+Kln MARTINEZ-RUIZ et alii, (1992)
Lower Cretaceous (14) Río Argós Ill+Sme±(I-S)+Kln MOIROUD et alii, (2012)
Lower-Middle Jurassic (15) Colomera Ill+Sme±(I-S)+Chl PALOMO et alii, (1985)
Lower-Middle Jurassic (16) Zegrí Ill+Sme±(I-S)+Chl+Kln PALOMO et alii, (1985)
Lower Jurassic (17) La Cerradura Ill+Sme±Chl PALOMO et alii, (1985)
Triassic (18) Moraleda Ill+Chl±Sme+Kln DORRONSORO (1978)
Triassic (19) Huelma Ill+Chl±Sme+Kln PUY (1979)
Table 4
Stratigraphic units
(Agost Basin)
Age
Lithofacies
Cycles of VERA (2000) eroded
in different times
Mineralogical features (a)
Upper Stratigraphic
Unit
Upper Miocene
p.p. (post-Lower
Tortonian)
L-6 to L-8
Cycle I
(Diapiric intrusion, Triassic)
Ill+Kln±Sme+Chl Triassic clay-mineral association. Tracers:
Gp and Chl. Sme(003)/Sme(002) ratios <0.75
L-5
Cycles V and VI
(Upper Cretaceous to Paleogene
p.p.)
Sme+Ill±Kln+(I-S) Upper Cretaceous (Cenomanian-
Turonian) and Paleogene clay-mineral association. Tracers:
Dol and mixed layer I-S
L-4
Cycle IV to Cycle VI
(Albian p.p. to Paleogene p.p.)
Ill+Kln+Sme Albian and Sme+Ill+Kln Upper Cretaceous
(Senonian) clay-mineral associations. Tracers: Dol.
Ill(002)/Ill(001) ratios >0.25
Lower Stratigraphic
Unit
Serravallian p.p.
L-1
Cycle IV
(Albian p.p.)
Ill+Kln+Sme Albian clay-mineral association. No tracers.
Ill(002)/Ill(001) ratios <0.2
(a) Acronyms for mineral phases as in tabs. 1 and 2.
MEDITERRANEAN S EA
IBERIA FO RELAND
Balearic Islands
Málaga Alm ería
Granada
Jaén
Sevilla
Cádiz
Gibraltar
Córdoba Alicante
Murcia
1619
18
17
3
9
6,10
2,5
7
8,13
11
12
15
1,4
14
External ZoneInternal Zone Foreland Basin
Maghrebian Flysch Basin Units
M. MARTÍN-MARTÍN ET ALII444
Lower Cretaceous formations (Moiroud et alii, 2012); (4)
Sme+Ill and Sme+Ill±Kln for Upper Cretaceous formations
(lóPez-Galindo, 1986; Martinez-ruiz et alii, 1992; Moiroud
et alii, 2012); (4) Sme+Ill±Kln+(I-S) and Sme+Ill±Kln for
Paleogene formations (Martinez-ruiz et alii, 1992; alcalá et
alii, 2001; Bolle & adatte, 2001; Guerrera et alii, 2014); and
(5) Sme+Ill±(I-S)+Kln and Sme+Ill±Kln+(I-S) for Lower
Miocene formations (alcalá et alii, 2013a, 2013b)
For these purposes, both mineralogical assemblages
and XRD parameters of the possible source areas from
neighboring Triassic-Paleogene successions (Fig. 4) of the
Maigmó Massif, Sarganella Range, and Ventós Massif,
and the Neogene Agost Basin succession (Fig. 5) were
examined (Fig. 6).
Relative changes in the clay-mineral shape (height and
width) peaks on XRD diffractograms have been widely used
for tentative evaluations of the exchange or uptake of cations
and/or the removal of hydroxide interlayers of inherited clay-
mineral phases induced by physical weathering under a low
diagenetic influence (hunziKer, 1986; riGhi & elsass, 1996;
drits et alii, 1997; Moiroud et alii, 2012). The Sme(003)/
Sme(002) ratio is useful for differentiating dioctahedral
and trioctahedral smectite, as basic criteria to identify the
diagenesis degree. This ratio is < 1 in all the studied samples
from Cycles I to VI (source areas) and lithofacies L-1 to
L-8 (Neogene sedimentary successions), thus suggesting
a low abundance of Al-rich phases like nontronite and
saponite, whose ratios are > 1 (Moore & reynolds, 1997),
indicative of low diagenesis (drits et alii, 1997; liu et alii,
2008). Sme(003)/Sme(002) ratios < 1 in lithofacies L-1 to
L-5 could indicate the predominance of Mg-rich phases like
montmorillonite and beidellite from Cycles IV to VI (Fig. 6A).
The chemical data according to alcalá et alii (2013a)
showed the predominance of Mg-rich smectite in other
Neogene Betic-Rifian external sectors including inherited
clay-mineral assemblages from neighboring Jurassic (e.g.
lóPez-Galindo et alii, 1994), Cretaceous (e.g. lóPez-Galindo,
1986; loPez-Galindo & oddone, 1990; Plestch, 1997;
Moiroud et alii, 2012), and Paleogene (e.g. Martinez-ruiz
et alii, 1992; Bolle & adatte, 2001; alcalá et alii, 2001)
successions. Sme(003)/Sme(002) ratios < 1 in Lithofacies
L-6 to L-8 could nevertheless indicate the predominance of
Fig. 6 - (A) Comparative plots
of XRD parameters, traceable
mineral phases, and clay-
mineral associations of the
Neogene sedimentary record
of the Agost Basin (LSU and
USU, including the lithofacies
L-1 to L-8) and source areas
(Sedimentary Cycles I to VI as
Triassic p.p., CI; Albian p.p.,
CIV; Cenomanian-Turonian
p.p., CV-CT; Upper Cretaceous
p.p., CV-S; and Paleogene
p.p., CVI); purple, green, and
orange dotted lines identify
supplies from predominant
Triassic, Cretaceous, and
Upper Cretaceous-Paleogene
source areas, respectively. The
ternary plots for the whole-
rock (B) and the <2 µm grain-
size fraction (C) mineralogy,
given as the average value (in
wt. %) from the set of samples
in each Sedimentary Cycle
(Tab. 1, Fig. 4) and lithofacies
(Tab. 2, Fig. 5), show
three compositional fields
corresponding to predominant
Triassic like (TR), Albian like
(AL), and Upper Cretaceous-
Paleogene like (CP)
mineralogical associations
mixing in variable proportions
to determine the mineralogical
associations from L-1 to L-8.
Samples with gypsum and
chloride as typical Triassic
mineral phases to identify the
Triassic influence in L-1 to L-8
are indicated. Acronyms for
mineral phases as in tabs. 1
and 2.
SOURCE AREAS EVOLUTION IN THE NEOGENE AGOST BASIN 445
inherited Fe-rich phases from the Triassic Cycle I, whose
samples provided similar ratios (Fig. 6A). The Ill(002)/
Ill(001) ratio is useful for differentiating the progressive
AlxFe+Mg substitution in the octahedral sheet as the
mineral structure transforms by physical weathering in Fe-
and Mg-rich media, such as in the study area in particular,
and other Betic-Rifian external sectors in general (alcalá et
alii, 2013a; Maa et alii, 2017). Al/(Fe+Mg) ratios below 0.3
are documented under weak burial diagenesis (esqueVin,
1969; hunziKer, 1986). Comparable values in the lithofacies
L-1 and Albian Cycle IV, in the lithofacies L-4 and Upper
Cretaceous (Senonian) Cycle V, in the lithofacies L-5 and
Upper Cretaceous (Cenomanian-Turonian) Cycle V and
Paleogene Cycle VI, and in the lithofacies L-6 to L-8 and
Triassic Cycle I are observed (Fig. 6A), thus the Ill(002)/
Ill(001) ratio being useful to distinguish the source areas
that supply each lithofacies over time. The (Qtz(001)/
Qtz(101) ratio has not provided clear relationships between
source areas and lithofacies, although a decreasing general
trend from L-1 to L-8 is observed, perhaps due to secondary
reworking processes (Fig. 6A).
The presence (and sometimes absence) of some clay-
mineral phases in sedimentary successions provides
additional criteria to qualify the diagenetic influence
and identify the source area evolution. For instance the
smectite, which has been found in all Cycles and lithofacies,
is quite sensitive to temperature rise with burial depth, and
tends to disappear above 200°C, after an exponential rate
of illitisation between 120°C and 150°C giving transient
abundances of mixed-layer I-S (nadeau & Bain, 1986;
lanson et alii, 2009), as described by Moiroud et alii (2012)
in other Subbetic sectors. However, random mixed layer
I-S has always been identified in traces in some samples
from Cycles V and VI, and Lithofacies L-5. There is not
compositional information about mixed layer I-S in this
sector, although variable abundances of smectite sheets
in R0 mixed layers I/S can be assumed from the 15-17 Å
range explored and data reported by alcalá et alii (2001,
2013a) in other Subbetic sectors, thus indicating weak
burial diagenesis at most. Despite clays, marls, pelites,
and silts lithologies from lithofacies L-6 to L-8 are illite-
and chlorite-rich, no mixed-layer chlorite-smectite has
been identified. The presence of this mineral phase could
indicate a diagenetic influence, as reported by deconincK
(1987) in Cretaceous marly sediments in southern France.
The presence of traceable dolomite, K-feldspar,
plagioclase, gypsum, Fe-oxides, chlorite, and mixed layer
I-S in Cycles I to VI can help to identify a given source area
(Fig. 6A). However, the origin of some of these mineral
phases may be controversial. For instance, dolomite may
come from neo-formation processes in lacustrine realms
under certain thermodynamics conditions and abundance
of base cations, detrital supplies from a given source area,
or by a combination of both processes in variable (usually
unknown) proportions. Based on the described lacustrine
influence in lithofacies L-4 and L-5, a combination of neo-
formation and minor detrital supplies could have taken
place, while a predominant inherited origin is proposed in
the continental (alluvial) lithofacies L-6 to L-8.
Two ternary plots for the main (end-members) whole-
rock (Fig. 6B) and clay-fraction (Fig. 6C) mineral phases
have been built to show the compositional field of Cycles
I to VI and lithofacies L-1 to L-8 (LSU and USU). These
plots allow interpreting mixtures in varying proportions
of mineralogical assemblages from Triassic to Paleogene
source areas identified in lithofacies L-1 to L-8, as basic
criteria to deduce changes in the supply and erosion of
source areas over time.
The Ill+Kln+Sme clay-mineral association identified in
the Albian Cycle IV was also found in the lithofacies L-1
(LSU) and the beginning of lithofacies L-4 (USU) (Figs. 6A
and 6C). Also, the Sme(003)/Sme(002) and Ill(002)/Ill(001)
ratios are quite similar (Fig. 6A). In addition, the presence
of K-feldspar and traces of plagioclase in the lithofacies
L-1 could suggest a minor supply from the Triassic
deposits (Fig. 6B). A main supply from the Albian Cycle IV
is proposed for lithofacies L-1.
The Ill+Sme+Kln clay-mineral association identified in
lithofacies L-4 (USU) seems to be the result of the variable
mixing of clay-mineral associations Ill+Kln+Sme from
the Albian Cycle IV and Sme+Ill+Kln from the Senonian
Cycle V, respectively (Figs. 6A and 6C). The presence of
dolomite (Fig. 6B) could suggest combined processes of
neo-formation in lacustrine realms and a minor supply
from Albian deposits. The higher Ill(002)/Ill(001) ratios
would identify the Senonian supply (Fig. 6A).
A combined supply from the Cenomanian-Turonian
Cycle V and the Paleogene Cycle VI is proposed as source
areas for the lithofacies L-5 (USU), as deduced from the
same Sme+Ill±Kln+(I-S) clay-mineral association, where
mixed layer I-S is the most distinctive clay-mineral phase
(Fig. 6A and 6C). Also the main whole-rock mineralogy
is quite similar (Fig. 6B). The presence of dolomite in
some samples could suggest neo-formation and a minor
supply from the Albian deposits (Fig. 6A). The Ill(002)/
Ill(001) ratios seem to confirm a preferential supply from
Cenomanian-Turonian and Paleogene terrains (Fig. 6A).
The Ill+Kln±Sme+Chl clay-mineral association
identified in the Triassic Cycle I is systematically found
in lithofacies L-6 to L-8 (USU), where chlorite is the
most distinctive clay-mineral phase (Fig. 6A and 6C). The
presence of gypsum in lithofacies L-6 and L-7 corroborates
this source. Lithofacies L-8 does not contain gypsum (Fig.
6A), thus suggesting a long alluvial transport that would
have caused its dissolution. Reworking of neo-formed
dolomite in previous lacustrine realms (lithofacies L-4 and
L-5) may be also considered. The absence of K-feldspar,
plagioclase, and Fe-oxides suggests reworking and
weathering. These lithofaces show the lower Sme(003)/
Sme(002) and Ill(002)/Ill(001) ratios, distinctive of the
Triassic Cycle I (Fig. 6A).
The source-area history described suggests a complex
erosional evolution. Deposits were initially fed by Albian
terrains, later by Late-Upper Cretaceous-Paleogene
successions, and finally by Triassic terrains probably with
a minor supply from the Neogene sedimentary infilling
reworking. This unroofing record relates the timing of
tectonics (uplift and subsidence) which determines the
areas of the basin to be eroded. So, not a classic “unroofing”
with a linear inverse record in ages of terrains eroded (from
youngest to oldest) is evidenced. In the following section
the mapping of sedimentary bodies is combined with the
stratigraphic data to explain better this reconstruction.
tectono-sediMentary eVolution
The strike-slip faults affecting the Agost Basin were
studied by Martín-Martín et alii (2018) proposing a
M. MARTÍN-MARTÍN ET ALII446
geodynamic evolution characterized by several stages
(see below). Contemporaneously to this evolution a
depositional regressive trend has been evidenced because
marine sediments of the LSU are followed by lacustrine
and alluvial deposits in the USU. This regressive trend is
related to regional factors and not to the local tectonics
because it is recorded in the entire Betic Cordillera and Rif
(Vera, 2000; sissinGh, 2008).
From the Middle Miocene the study area was
characterized by the presence of faults showing lateral
(horizontal) movements (Martín-Martín et alii, 2018). The
N50E trending “Novelda-Jijona” Fault Zone, the stepover
of faults, and the clock-wise bending of Agost Basin
segment allowed a dextral transtensile motion of blocks
developing the incipient basin as a subsiding graben (a
terraced sidewall fault subzone) located between the Sierra
del Maigmó and Sierra del Ventós reliefs, and also the
“Sarganella” Range as a relative raised area. The closure
of the Agost Basin was related to a tectonic inversion
due to a N-S oriented main stress occurring close to the
Latest Miocene-Pliocene boundary and allowing a pure
compressive motion of blocks that caused the deformation
and squeeze of the basin (Martín-Martín et alii, 2018).
The marine sedimentation of the LSU occurred in the
lower Serravallian and the mineralogical data suggest a
supply mainly from Albian succession (Tab. 4). According
to the field data (Fig. 2) the more reasonable source area is
the Sierra del Maigmó where the Albian terrains crops out;
see the arrows 1 in the paleogeographic map and the time-
line T1 from the paleogeographic cross section in Fig. 7A.
The deposition of the LSU was coeval to the regression
recorded by a sedimentation change from marine marls
and calcarenites to channellized deltaic conglomerates.
This regression favored the erosion and exhumation of
reliefs when the strike-slip faulting began to develop
(mainly in the Maigmó Fault Zone). A central deepening
area became the incipient Agost Basin as a part of a net of
intramontane basins (Fig. 7A).
The continental deposition of the Upper Miocene p.p.
USU started as a consequence of the regression above
an unconformity showing a marked erosive surface. The
tectono-sedimentary evolution of the USU is modeled in the
paleogeographic sketch map and cross-sections of Fig. 7B
where four isochronous-lines (T2-T5) are also outlined to
follow easily the sediment progression. Changes over time
of the mapped coarse clastic bodies coming from opposite
areas (lithofacies L-4 and L-5 from south and lithofacies
L-6 to L-8 from north) were probably related to alternating
activation of fault zones (Tab. 4).
According to the mineralogical findings during the
deposition of the lithofacies L-4 (USU) Albian but also Upper
Cretaceous and probably some Paleogene terrains were
eroded (Tab. 4). The position of the deposits of lithofacies
L-4 in the Sierra del Ventós surroundings indicates such
sector as a source area due to the activation at that time of
the Ventós Fault (see arrow 2 in the paleogeographic map
and time-line T2 in the paleogeographic cross section
in Fig. 7B). From this period the incipient Agost Basin
should probably developed disconnected from the net of
intramontane basins with activation of the border faults
and the change to continental realms. The following
deposits belong to lithofacies L-5 with mineralogical
features indicating erosion of Upper Cretaceous to
Paleogene terrains probably also derived from the Sierra
del Ventós (Tab. 3). In this lithofacies the presence of
resedimented microfossils also gave details concerning
the erosive history of the Upper Cretaceous-Paleogene-
Neogene successions, including the Langhian-lowest
Serravallian stratigraphic interval of the LSU.
Successive alluvial fans developed in the northern
margin of the basin, close to the Barranco Blanco Fault.
These sedimentary bodies were arranged in a southward
downlap and are characterized by deposits that vary
laterally (lithofacies L-6 and L-7) close to time-lines T3
and T4 and that were supplied by the Sarganella Range
(Fig. 7B). These alluvial fans constitute the first clear
evidence of a Triassic source area in the northern margin
of the basin as corroborated also by the typical Triassic
mineralogical association found (Tab. 4). The proposed
source area is the Sarganella Range, according to the
present outcroppings of Triassic bodies, which should
be tectonically active in that moment; see arrows 3-4 in
the paleogeographic map and time-lines T3-T4 in the
paleogeographic cross section in Fig. 7B. This northern
supply produced localized sedimentary bodies that quickly
but progressively migrated westward (Fig. 7B).
The end of the deposition in the Agost Basin coincided
with a third wide alluvial fan (lithofacies L-8; USU). This
fan invariably coming from the northwestern margin
is characterized by clasts originated from Cretaceous-
Paleogene terrains and by Triassic materials from northern
sources areas or associated with reworked lithofacies L-6
and L-7, as the mineralogical findings indicated (Tab. 4).
This prograding basinward sedimentation was also related
to the erosion of the uplifting reliefs of the Sarganella
Range where all the above-mentioned terrains crop out;
see arrow 5 in the paleogeographic map and time-line T5
in the paleogeographic cross section in Fig. 7B.
The recognition of different supply-areas, located
mainly in the northern margin of the Agost Basin, suggested
strong tectonic activity of the Barranco Blanco Fault in
the upper part of the USU. This activity caused a push-up
and the erosion of tectonic blocks in the Sarganella Range,
and probably the reworking of the lithofacies L-6 and L-7.
Furthermore, this tectonic activity allowed the exhumation
of Triassic bodies (mainly clays and gypsum) that reaching
the paleo-surface assumed the mushroom shape visible
nowadays (Fig. 2; plate I, photos 1 and 2), extending
both over the Sarganella Range and the margin of the
Agost Basin (Fig. 7B). The rapid erosion caused a quick
unroofing and the progradational deposition (lithofacies
L-6 to L-8) of a great amount of Triassic clays and gypsum
on the northern margin of the basin.
The deposition of the lithofacies L-8 alluvial fan sealed
the Ventós Fault in the western part of the Agost Basin
(Fig. 7B), while the Pliocene deposits evidence the end of
sedimentation in the basin and the beginning of erosion
(Fig. 2; plate I, photo 6).
reGional PaleoGeoGraPhic considerations
In the External Betic Zone the intramontane basins
(Fig. 8) were related to the North Betic Strait (or Proto-
Guadalquivir Foreland Basin) connecting during the
Middle and the beginning of the Late Miocene the Atlantic
Ocean with the Mediterranean Sea (sanz de Galdeano
& Vera, 1992). The Agost Basin was located in the
easternmost part of this North Betic Strait in connection
SOURCE AREAS EVOLUTION IN THE NEOGENE AGOST BASIN 447
Fig. 7 - Tectono-sedi-
mentary evolutionary
model with location
of source areas of the
Agost Basin and sur-
rounding areas. A:
Middle Miocene stage
(Lower Stratigraphic
Unit); B: Late Miocene
stage (Upper Strati-
graphic Unit).
M. MARTÍN-MARTÍN ET ALII448
with the Mediterranean Sea during Middle Miocene. The
Africa-Iberia convergence led to the North Betic Strait
closure in the eastern Betics, that would have caused the
isolation of the Agost Basin and the sedimentation change
from marine to continental.
The Agost Basin, that is related to the Novelda-Jijona
strike-slip fault (NE-SW oriented), has a bending reaching
an orientation close to E-W (Figs. 1 and 8). This basin
could be comprised in the NE-SW oriented strike-slip
fault basins of the Betic-Rifian belt but contrary to what
has been proposed by sanz de Galdeano & Vera (1992),
the strike slip fault has a dextral kinematics during the
Middle Miocene. The E-W orientation of the Agost Basin
is a local feature being not correlable with the E-W fault
basins since it represents a clear case of strike-slip basin
and for its location so far from the Internal Betic Zones is
not geometrically compatible with the N-S extension due
to collapse by delamination of thickened lithosfere (Vera,
2004). The above reported informations could indicate
that although the basins can be grouped according to sanz
de Galdeano & Vera (1992), in detail some basins could
be the expression of a more complex paleogeographic-
geodynamic evolution.
The general stratigraphic successions of the Betic-
Rifian intramontane basins reflect their complex tectonic
and depositional history and the relative sea-level changes.
A general regressive deposition developed during the
Middle Miocene by deep turbiditic to shallow marine
platform deposits that evolve during the Late Miocene from
shallow marine platform to fan delta deposits, followed by
continental lacustrine and fluvial sediments deposited in the
Latest Miocene to Quaternary. A similar evolution can be
reconstructed also for the Agost Basin. All the Betic-Rifian
successions are affected by numerous unconformities and
gaps (sissinGh, 2008). A common feature in most of the
intramontane basins is the appearing of resedimented
Triassic rocks at different stratigraphic levels. These deposits
are well documented in the eastern External Betics during
TABLE 4
Main sedimentary and mineralogical data, and source areas concerning the infilling of the Agost Basin.
Stratigraphic units
(Agost Basin) Age Lithofacies Source areas
Cycles of Vera (2000)
eroded in different
times
Mineralogical features (a)
Upper Stratigraphic Unit
Upper Miocene
p.p. (post-Lower
Tortonian)
L-6 to L-8
Sarganella Range
(northern margin of the
basin with migration of
supply areas westward)
Cycle I
(Diapiric intrusion,
Triassic)
Ill+Kln±Sme+Chl Triassic
clay-mineral association.
Tracers: Gp and Chl. Sme(003)/
Sme(002) ratios <0.75
L-5
Ventós Massif
(southern margin of the
basin)
Cycles V and VI
(Upper Cretaceous to
Paleogene p.p.)
Sme+Ill±Kln+(I-S) Upper
Cretaceous (Cenomanian-
Turonian) and Paleogene clay-
mineral association. Tracers:
Dol and mixed layer I-S
L-4
Cycle IV to Cycle VI
(Albian p.p. to
Paleogene p.p.)
Ill+Kln+Sme Albian and
Sme+Ill+Kln Upper Cretaceous
(Senonian) clay-mineral
associations. Tracers: Dol.
Ill(002)/Ill(001) ratios >0.25
Lower Stratigraphic Unit Serravallian p.p. L-1
Maigmó Massif
(northern margin of the
basin)
Cycle IV
(Albian p.p.)
Ill+Kln+Sme Albian clay-
mineral association. No tracers.
Ill(002)/Ill(001) ratios <0.2
(a) Acronyms for mineral phases as in Tabs. 1 and 2.
the Middle-Late Miocene appearing usually embedded in
marly platform sediments and interpreted as olithostrome-
like or “salt glacier” deposits (wenKert, 1979; tent-Manclús
et alii, 2000; estéVez et alii, 2007; sissinGh, 2008). In the
eastern External Zones of the Betic Cordillera the “salt
glaciers” are related to overflow of Triassic clayey and salty
materials from the basal level of stacked superficial nappes
or diapirs, similarly to what interpreted by Martín-Martín
et alii (2018) for the Agost Basin. Also the study presented
in this paper, reflects the existence of such type of Triassic
deposits in the Agost Basin, but the approach used allowed
to reach further and detailed information concerning the
source area in any moment of the sedimentary record.
Similar studies are missing in much of the basins mentioned
in this section making it impossible to deepen these regional
considerations.
FINAL REMARKS
The Agost Basin is a subsiding area related to a NE-
SW to E-W oriented strike-slip fault. A dextral transtensile
motion of blocks generated a graben structure (a terraced
sidewall fault subzone) between the Sierra del Maigmó and
the Sierra del Ventós reliefs with the “Sarganella” Range as
a relative raised area.
The stratigraphic succession of the Agost Basin is
subdivided into two main sequences separated by an
angular unconformity: (1) Lower Stratigraphic Unit/LSU
(marine deposits, lowest Serravallian), and (2) Upper
Stratigraphic Unit/USU (continental lacustrine and fluvial
deposits, post-lower Tortonian-pre Pliocene).
The LSU (about 100 m thick) shows a regressive trend
from open to restricted marine conditions, within which
three lithofacies (L-1 to L-3) rich in benthic foraminifera,
echinoderms, corals, briozoes, ostreids, and brachiopod
are described. The lithofacies L-1 (lithofacies L-2 and L-3
were not analyzed) is characterized by the Ill+Kln+Sme
SOURCE AREAS EVOLUTION IN THE NEOGENE AGOST BASIN 449
Fig. 8. - Paleogeographic
reconstruction showing the
Neogene basins of the Betic-
Rif chain at the Serravallian-
Tortonian boundary (modified
from sanz de Galdeano & Vera,
1992; Vera, 2000; sissinGh,
2008).
clay-mineral association probably fed by the Albian
succession from the Sierra del Maigmó. The presence of
K-feldspar and traces of plagioclase could suggest a minor
supply from the northern Triassic deposits.
The more extensive and preserved USU (more than
490 m thick) represents continental realms (fluvial and
lacustrine deposits in the depocentral area and alluvial
fans and cliff deposits in the margins) depicted by five
lithofacies (L-4 to L-8). The changes over time of the coarse
clastic bodies coming from opposite areas (lithofacies L-4
and L-5 from south and lithofacies L-6 to L-8 from north)
are probably related to the alternating activation of fault
zones. The lithofacies L-4 consists of a variable mixing of
Ill+Kln+Sme and Sme+Ill+Kln clay-mineral associations
interpreted as nourished by the erosion of Albian and
Upper Cretaceous (Senonian) and minority Paleogene-
Miocene terrains. The presence of dolomite and the higher
Ill(002)/Ill(001) ratios could corroborate these two main
source areas, respectively. The location of the lithofacies
L-4 around the Sierra del Ventós indicates such sector as
the source area related to the contemporaneous activation
of the Ventós Fault. The Sme+Ill±Kln+(I-S) clay-mineral
association of the lithofacies L-5 suggests a supply derived
from the erosion of Upper Cretaceous (Cenomanian-
Turonian) to Paleogene terrains from the Sierra del Ventós.
The Ill(002)/Ill(001) ratios corroborate these two main
source areas. The increasing amount of dolomite upward
is probably due to neo-formation processes in lacustrine
realms and a minor detrital supply. The more recent
alluvial fans developed in the northern margin of the basin
close to the Barranco Blanco Fault are the lithofacies
L-6 to L-8, characterized by a southward downlap. The
Ill+Kln±Sme+Chl clay-mineral association indicates a
Triassic source located in the northern margin of the basin.
The presence of dolomite, gypsum, and chlorite, as well as
the lower Sme(003)/Sme(002) and Ill(002)/Ill(001) ratios,
are other distinctive features of the Triassic deposits. The
end of the deposition in the Agost Basin corresponds with
the third wide alluvial fan (lithofacies L-8) coming from
the northern margin of the basin and sealing the southern
margin of the Ventós fault. The above record of source
areas evidences a complex “unroofing” controlled by a
complex tectonic activity of uplifting and subsiding blocks
alternating in time.
The origin of most of intramontane basins in the
Betic-Rifian Chain is related to local extensional processes
in the general framework of the NW-SE to N-S Africa-
Iberia convergence. The origin and evolution of the Agost
Basin was thought to be related to the orientation and
bending of the Novelda-Jijona strike-slip fault producing
a context of dextral displacement of blocks. This basin
could be included in the NE-SW oriented strike-slip fault
basins defined by sanz de Galdeano & Vera (1992) but
with a different kinematics (i.e. dextral) during the Middle
Miocene.
The mineralogical evidences corroborate the usefulness
of detrital clay minerals and their XRD parameters for
detailed reconstruction of sedimentary evolutions, adding
a better resolution to the classical provenance studies
based on coarser grained sediments. This study allowed
reconstructing the tectono-sedimentary evolution of
a small basin with a good resolution of its time/space
(vertical and lateral) evolution. So, this basin can be also
useful for wide-scale regional reconstructions for instance
the Betic-Rifian Arc.
acKnowledGMents
Research supported by: Research Project CGL2016-75679-P,
Spanish Ministry of Education and Science; Research Groups and
M. MARTÍN-MARTÍN ET ALII450
Projects of the Generalitat Valenciana, Alicante University (CTMA-IGA);
Research Group RNM 146, Junta de Andalucía; Grants from University
of Urbino Carlo Bo, responsible M. Tramontana. The revision of a
previous version of the manuscript by P. Alfaro is also acknowledged.
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Manuscript received 30 November 2017; accepted 10 April 2018; published online 13 March 2018;
editorial responsibility and handling by D. Cosentino
... Vera [16,17] provided a general framework of the Mesozoic to Cenozoic sedimentation of the EBZ, dividing the stratigraphic record into eight main sedimentary cycles. Recently, detailed multidisciplinary studies carried out in the eastern EBZ suggested the following remarks about the tectono-sedimentary evolution of the area: (1) the definition of a new and earlier Paleogene deformation stage [15,18,19], (2) the Paleogene deformation was related to the Internal Betic Zone (IBZ) tectonics paleo-geographically close to the IBZ, as proposed by Guerrera et al. [15], Guerrera and Martín-Martín [18] and Guerrera et al. [19], (3) the importance of strike-slip Miocene fault systems [20,21] and (4) the influence of salt tectonics also during the Miocene evolution [22][23][24]. Therefore, the knowledge of these Cenozoic basins has been considerably improved because these papers show their tectono-sedimentary evolution. ...
... According to the lateral-vertical distribution of the lithofacies and the thicknesses of the stratigraphic formations, the migration of the foredeep has been better specified, highlighting a complex tectono-sedimentary evolution. The same authors (Martín-Martín et al. [21,22]) studying the Cenozoic basins in the Alicante province recognized that the Miocene-Quaternary shallow marine and continental infilling has been controlled by the evolution of several curvilinear faults involving salt tectonics. These authors also specified that the occurrence of Triassic shales and evaporites played a fundamental role in the tectonic evolution of the study area since the salt material flowed along faults, generating salt walls in root zones and salt push-up structures at the surface. ...
... Differently, the EBZ of the Alicante sector is characterized by a net of strike-slip fault systems ( Figure 3) roughly oriented as follows: N70E (Cadiz-Alicante Accident system), N155E and N120E. These faults, which were active from the Early-Middle Miocene onwards [21,22], are recognizable nowadays through the presence of outcrops of Triassic clays with gypsum. Neogene deposits also appear associated to subsiding areas linked to the strike-slip faulting [23,24]. ...
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Four main unconformities (1–4) were recognized in the sedimentary record of the Cenozoic basins of the eastern External Betic Zone (SE, Spain). They are located at different stratigraphic levels, as follows: (1) Cretaceous-Paleogene boundary, even if this unconformity was also recorded at the early Paleocene (Murcia sector) and early Eocene (Alicante sector), (2) Eocene-Oligocene boundary, quite synchronous, in the whole considered area, (3) early Burdigalian, quite synchronous (recognized in the Murcia sector) and (4) Middle Tortonian (recognized in Murcia and Alicante sectors). These unconformities correspond to stratigraphic gaps of different temporal extensions and with different controls (tectonic or eustatic), which allowed recognizing minor sedimentary cycles in the Paleocene–Miocene time span. The Cenozoic marine sedimentation started over the oldest unconformity (i.e., the principal one), above the Mesozoic marine deposits. Paleocene-Eocene sedimentation shows numerous tectofacies (such as: turbidites, slumps, olistostromes, mega-olistostromes and pillow-beds) interpreted as related to an early, blind and deep-seated tectonic activity, acting in the more internal subdomains of the External Betic Zone as a result of the geodynamic processes related to the evolution of the westernmost branch of the Tethys. The second unconformity resulted from an Oligocene to Aquitanian sedimentary evolution in the Murcia Sector from marine realms to continental environments. This last time interval is characterized as the previous one by a gentle tectonic activity. On the other hand, the Miocene sedimentation was totally controlled by the development of superficial thrusts and/or strike-slip faults zones, both related to the regional geodynamic evolutionary framework linked to the Mediterranean opening. These strike-slip faults zones created subsidence areas (pull-apart basin-type) and affected the sedimentation lying above the third unconformity. By contrast, the subsidence areas were bounded by structural highs affected by thrusts and folds. After the third unconformity, the Burdigalian-Serravallian sedimentation occurred mainly in shallow- to deep-water marine environments (Tap Fm). During the Late Miocene, after the fourth unconformity, the activation of the strike-slip faults zones caused a shallow marine environment sedimentation in the Murcia sector and a continental (lacustrine and fluvial) deposition in the Alicante sector represented the latter, resulting in alluvial fan deposits. Furthermore, the location of these fans changed over time according to the activation of faults responsible for the tectonic rising of Triassic salt deposits, which fed the fan themselves.
... In the region a Cretaceous tectonic inversion from extension to compression occurred, similarly to what was observed in the western Mediterranean Alpine chains (Guerrera et al., 2014;Guerrera & Martín-Martín, 2014a; and references therein). In the EBZ the Mesozoic normal faults evolved during the Tertiary under compressive deformation as strike-slip faults, and later as thrusts (Sanz de Galdeano & Buforn, 2005;Martín-Martín et al., 2018a;Martín-Martín, Guerrera, Alcalá, Serrano, & Tramontana, 2018b;Sissingh, 2008). In the Miocene many intramontane basins developed whose geometry and stratigraphic architecture were controlled by re-arrangements of blocks and faults. ...
... This paper tries to fill the current gap concerning the Miocene stratigraphic evolution of the eastern EBZ through an interdisciplinary study taking advantage both from the good quality of outcrops and the continuity of the stratigraphic record in the Sierra del Carche-Pinoso Corridor-Sierra de la Pila sector. The results were compared and completed with the previous studies concerning the EBZ (Sanz De Galdeano & Buforn, 2005;Guerrera et al., 2014;Martín-Martín et al., 2018a, 2018b; and references therein). ...
... The crystalline-powder technique was used for mineral identification in the wholerock. For the non-calcareous clay fraction, oriented mounts on glass slides were prepared and analyzed as described in Alcalá, López-Galindo, and Martín-Martín (2013a) and Martín-Martín et al. (2018b). ...
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An interdisciplinary study of Miocene successions in the eastern External Betic Zone (South Iberian Margin) was carried out. Evidences of syn-sedimentary tectonic activity were recognized. The results enabled a better reconstruction of the stratigraphic architecture (with an improved chronostratigraphic resolution) in the framework of the Miocene foredeep evolution of the eastern EBZ. Two main depositional sequences were dated as uppermost Burdigalian-upper Serravallian p.p. and middle-upper Tortonian. p.p., respectively. The vertical and lateral diversification of lithofacies associations and thicknesses resulted from the syn-depositional tectonic complexity of the area. A great variety of sedimentary depositional realms is due to different subsidence rates, and the growing of anticlines and synclines during the Langhian p.p.-Serravallian. After a regression with an early Tortonian erosional gap, platform to hemipelagic realms developed during the middle Tortonian. The end of the sedimentation coincided with the emplacement of an important olisthostrome-like mass consisting of Triassic material related to either the development of thrust systems or diapirs emerged in the middle-late Tortonian, during the nappe emplacement. Correlations with other external sectors of the Betic Chain, and the external domains of the Rif, Tell, and northern Apennine Chains highlighted a similar Miocene foredeep evolution during the building of these orogens.
... The Sierra Espuña succession shows similarities to coeval units defined by Martín-Chivelet (1999, 2005), Martín-Chivelet and Chacón (2007) and Pujalte et al. (2010) in the Prebetic located at about the latitude 30°N and in the westernmost Tethys, between longitude 10°-15°W (Fig. 11A: 2 and 3; B). The lower Eocene shallow marine deposits are represented in the Prebetic (SE Spain) ( Fig. 11A: 2, B) about at latitude 33°N (Martín-Martín et al., 2018a, 2018b, at about longitude 10°W (Geel, 2000). In this case the sedimentary trend indicates a middle to inner ramp environment, in good agreement with the lower Eocene deposits of the Sierra Espuña. ...
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The External Tanger Unit represents one of the most complete Cretaceous-Miocene successions in the central areas of the Internal Intrarif sub-Domain (External Rif Zones, Morocco). An interdisciplinary study has been carried out to propose a new characterization of this unit which would allow a better comprehension of the confused and complex relationships among different units of the same sub-domain. The results achieved can be summarized as follows: (1) redefinition of the stratigraphic (litho-, bio-, and chrono-) record and introduction of a new, informal lithostratigraphic terminology; (2) recognition of two main depositional sequences (lower-middle Eocene p.p. and lower Oligocene p.p.-lower Miocene p.p.) separated by extended gaps (latest Cretaceous-early Eocene p.p. and middle Eocene p.p.-early Oligocene p.p.); (3) reconstruction of the evolution of the sedimentary realm, and of the relationships between tectonics and sedimentation; and (4) comparison between the upper Cretaceous-Miocene stratigraphic record and tectonic events of the Intrarif, which is located in the western external portion of the Maghrebian Flysch Basin, and the equivalent sedimentary record of the eastern portion of this basin in the Tunisian Tell. More in general, our results allowed (i) a first reconstruction of the Cretaceous-Miocene main tectono-sedimentary events; (ii) a more detailed location of the sedimentary suite in the external African Margin in the context of a wider palaeogeographic framework; and (iii) the definition of the main stages of the geological evolution of the area.
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We have studied the clay assemblages found in the different palaeogeographic domains located at the several Tunisian margin basins, ranging in age from Palaeozoic to Neogene. This study has allowed us to characterize and highlight the relationship between the clay distribution in time and space and the geodynamic and eustatic events. Marine regressions, with the intensification of erosion, seem to be responsible for illite increases, whereas transgressions, in concordance with a warm and dry climate, coincide with the smectite dominance. The minimum marine level coincides with the abundance of palygorskite. Mineralogic changes in the clay assemblages as well as in the proportion of the different clay minerals will tentatively be related to erosive tectonic events and/or to subsiding and rifting events, marked by the inheritance or the neoformation of the several clays.
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The influence of tectonic stress on the initiation and development of evaporite diapirs is of great importance in the interpretation of diapiric structures and associated sediments. The eastern Prebetic foldbelt in southeastern Spain contains many diapirs that provide excellent examples of tectonically controlled diapirism. These diapirs are mainly composed of Triassic evaporite and shale that have pierced their overburden along extensional faults and in releasing oversteps along strike-slip faults. They occur as highly elongated diapiric walls or as large, fault-bounded bodies that can cover several tens of square kilometers at the center of grabens. Most of these diapirs reached the surface in Neogene times, constituting local depocenters for Miocene sediments. Outcrop and well data suggest that their source layer consists mainly of interbedded shale and anhydrite, which are denser than their carbonate overburden and thus preclude piercement diapirism driven by buoyancy. The external geometry of these diapirs and a variety of kinematic indicators in surrounding overburden suggest that their location and initiation was primarily controlled by (trans)tensional faulting. It is therefore concluded that the Prebetic diapirs formed in response to thin-skinned extension of their overburden, which induced differential loading and viscous flow of the Triassic evaporites. Regional paleostress analysis and chronostratigraphic correlation suggest that diapirism was triggered by rifting in the adjacent Western Mediterranean Basin.