Tectosedimentary Units Research Articles

Stratigraphy and sedimentology of distal-alluvial and lacustrine deposits of the western-central Ebro Basin (NE Iberia) reflecting the onset of the middle Miocene Climatic Optimum

Stratigraphic and sedimentological study of distal alluvial and lacustrine deposits in the Plana de la Negra-Sancho Abarca area (western-central Ebro Basin, NE Iberia) within the early and middle Miocene allows five main lithofacies to be characterized and mapped within two tectosedimentary units, construction of a sedimentary facies model and discussion on allogenic controls on sedimentation. In this area, the boundary between tectosedimentary units T5 and T6 appears to be conformable and is marked by the change from dominant clastics to carbonates. Correlation of the studied outcrops with nearby sections that already had magnetostratigraphic and biostratigraphic data allows the studied succession to be dated from C5Dr to C5Cn (Burdigalian-Langhian), placing the boundary T5/T6 at ca. 16.1-16.05Ma. Seven vertical facies sequences document deposition of distal alluvial clastics and palustrine and lacustrine carbonates. Sandstones and mudstones represent low-sinuosity channels and lateral and terminal splays by unconfined flows runnig across the alluvial plain, associated to the Pyrenean-derived Luna fluvial system. The carbonates contain charophytes, ostracods, bivalves and gastropods, indicating deposition in 2-4m deep lakes. Laminated carbonate facies record reworking of shore carbonates and the influx fine-siliciclastic sediment offshore. Abundant bioturbation and desiccation features indicate episodic submergence and subaerial exposure. Four main episodes of alluvial and associated palustrine/lacustrine facies belt shifts are identified. Alluvial deposition in the studied T5 unit is related to low lake level conditions, rather than to a Pyrenean uplift. The maximum extent of the freshwater carbonates occur at the base of unit T6. This is consistent with conditions of increasing humidity of the Middle Miocene Climatic Optimum.

Sedimentación fluvial y lacustre sintectónica ligada a un sinclinal de “buttressing” paralelo a una falla en el sector de Nigüella (NW Cordillera Ibérica)

En este artículo se discute la evolución sedimentaria del relleno neógeno de un área situada en la parte Noroeste de la Cordillera Ibérica que presenta depósitos fluviales y lacustres, y su relación con la tectónica alpina compresiva que afectó a una falla anteriormente extensional. Los análisis estratigráficos permiten caracterizar tres unidades tectosedimentarias, con un espesor total de 120m. Las Unidades 1 y 2 están formadas dominantemente por litofacies clásticas, y están separadas por una discordancia y su correlativa conformidad. La Unidad 3 está formada por calizas tobáceas y micríticas, y representa un salto litológico brusco con la Unidad 2 en toda su extensión. Estas unidades están involucradas en dos estructuras de escala kilométrica con dirección alpina NNW-SSE: 1) la Falla de Nigüella, que pone en contacto materiales triásicos con cenozoicos en los bloques levantado y hundido, respectivamente, y 2) el Sinclinal de Nigüella, subparalelo a la falla anterior, con buzamiento de estratos entre 19º y 70º. En las unidades 1 y 2, cuatro asociaciones de facies sedimentarias representan el depósito en áreas proximales y medias de abanicos aluviales, procedentes de relieves locales, y un sistema fluvial braided con reducida llanura de inundación, procedente del Norte. Ambos ambientes registran sedimentación carbonática fluvial y lacustre. Otras tres asociaciones de facies representan el depósito dominante de carbonatos, tanto en entornos palustre-fluvial-lacustres como en lacustres. En las tres unidades, los rudstones de oncoides y fitoclastos se formaron en canales de aguas someras, con baja sinuosidad y en zonas encharcadas, con extensas zonas palustres tobáceas, con desarrollo de plantas hidrófilas. Por el contrario, las calizas micríticas con ostrácodos y las margas corresponden al depósito de calcita en zonas lacustres de aguas tranquilas y permanentes. Por tanto, el sistema sedimentario evolucionó desde un ambiente aluvial-fluvial dominante hasta un ambiente lacustre. Este hecho, junto con el desarrollo de calcretas en las unidades 1 y 2, indica condiciones más húmedas y posiblemente el paso a un lago cerrado hidrológicamente. La falla de Nigüella funcionó a principios del Jurásico como una falla normal, y durante la compresión del Cenozoico provocó la formación de una cuenca sinclinal mediante buttressing del bloque NE contra la falla. Este contexto condicionó la distribución y extensión de litofacies miocenas a lo largo del espacio y del tiempo y la localización de depocentros. La disminución de la actividad tectónica a lo largo del intervalo estudiado favoreció la incisión fluvial, la captura del acuífero mesozoico y la salida del agua subterránea rica en Ca2+ y HCO-3, dando lugar al depósito generalizado de carbonato cálcico y, finalmente, a la expansión del lago.

Palynostratigraphy of the Middle Triassic (Anisian) Eslida Formation, SE Iberian Ranges, Spain

ABSTRACTThe Triassic record in the SE Iberian Ranges starts with two tecto-sedimentary units of continental origin in Buntsandstein facies: and Cañizar and Eslida Formations. The Eslida Formation always lies conformably on top of the Cañizar Formation and it grades upwards into overlying coastal mud flats, traditionally assigned to the Röt facies. In the past, accurate dating of the Eslida Formation was problematic because of its continental character, absence of datable fossil remains, and lithological similarities with Middle–Upper Permian rocks. Macroflora and fossilised vertebrate footprints in the Eslida Formation indicate an Anisian age (Middle Triassic). In this work, we date the Eslida Formation on the basis of a palynological assemblage. The precise dating of the Eslida Formation is essential in order to establish stratigraphical correlations with other units in the Iberian Ranges and to obtain palaeogeographical considerations on the rapid subsidence represented by the sedimentary record of this unit in the new NNE–SSE Middle Triassic rift developed in eastern Iberia.

The Effect of Drainage Reorganization and Climate On the Sedimentologic Evolution of Intermontane Lake Systems: The Final Fill Stage of the Tertiary Ebro Basin (Spain)

Abstract Stratigraphic and sedimentologic analyses and geochemical data from the middle and late Miocene record in the southwestern-central sector of the Ebro Basin have allowed the evolution of its Neogene final fill stage to be characterized and its controlling factors to be discerned. The focus of these analyses was the distinct depositional environments that occurred over time (tecto-sedimentary units T6, T7, and T8). Twelve main associations of lacustrine, palustrine, fluvial, and alluvial facies revealed that the sedimentary processes leading to the formation of the units occurred in different environments in units T6 and T7 (middle and late Aragonian, i.e., Langhian–Serravallian) and in unit T8 (Vallesian–Turolian?, i.e., Tortonian). The depositional environments of units T6 and T7 encompassed a closed, shallow carbonate lake system with wide palustrine fringes. The lake was fed by small sandy and gravelly channels flowing from the southwest (Iberian Range) and a sandy fluvial system from the north (Pyrenees). Inputs were also received from a southeastward-flowing axial fluvial system (AS). The mouths of these systems commonly formed small deltaic sandy lobes on the northern lake margins. The evolution of unit T6 and in particular that of unit T7 was greatly influenced by Pyrenean tectonics. The depositional environments of unit T8 included the occurrence of the AS, but this system was soon replaced by an open, shallow carbonate lake surrounded by wide and shallow oncoid-bearing channels and palustrine tufaceous areas on its west-southwest margin. Distinct depositional events from the south and west, which involved intra-T8 erosion, resulted in minor coarse alluvial deposits. The carbonate system of unit T8 occurred in an open depression created after local erosion of the pre-T8 deposits and subsequent northward shifting of the AS since early deposition of unit T8, the origin of which was related to late contractile deformation in the northwestern Iberian Range. Bicarbonate- and calcium-rich water from the Mesozoic carbonate rocks in the Iberian Range fed the T8 system. Sedimentologic, δ13C, δ18O, and trace-element data support the change from closed to open drainage, and strongly suggest a general climate trend toward wetter and cooler conditions, which is consistent with the middle–late Miocene climate evolution of other European regions. Despite the general timing coincidence between unit T8 deposition and the opening process of the Ebro Basin, the attributes of the T8 deposits are inconclusive to support the previous hypothesis that the fluvial–lacustrine–palustrine system could be directly connected to the emptying drainage of the basin into the Mediterranean Sea. Instead, the results of this study demonstrate the combined influence of tectonics and climate on the evolution of the final fill stage of this part of the Ebro Basin. These results may be useful for assessing the influence of such allocyclic factors on the sedimentologic, hydrologic, and geochemical evolution of other intermontane lake basins.

Magnetostratigraphy of the Miocene continental deposits of the Montes de Castejón (central Ebro basin, Spain): geochronological and paleoenvironmental implications

A detailed magnetostratigraphic study has been carried out in the early to middle Miocene distal alluvial and lacustrine sediments of the Montes de Castejon (central Ebro Basin). The study was based on the analysis of 196 magnetostratigraphic sites sampled along a stratigraphic interval of about 240 meters. Local magnetostratigraphy yielded a sequence of 12 magnetozones (6 normal and 6 reverse) which could be correlated with the Geomagnetic Polarity Time Scale (GPTS) interval C5Cr to C5AD (between 17 and 14.3 Ma.). The sampled sedimentary sequences include the boundary between two tectosedimentary units (TSU, T5 and T6) already defined in the Ebro Basin. The magnetostratigraphy of the Montes de Castejon allows to date the T5/T6 TSU boundary at 16.14 Ma, within chron C5Cn.1n. This magnetostratigraphy also allows us to analyse in detail as well as to discuss the variations in sedimentation rates through space and time between different lacustrine environments: Outer carbonate lacustrine fringes and distal alluvial plains (Montes de Castejon sections) show higher sedimentation rates than offshore lacustrine areas (San Caprasio section, 50 km east of Montes de Castejon).

Las principales discordancias del Mesozoico de la Cuenca Neuquina según observaciones de superficie

The main unconformities of the Mesozoic of the Neuquén Basin based on surface observations. A general summary of the main unconformities which produced major order break-ups during the evolution of the Mesozoic sedimentary infill of the Neuquén Basin is offered in this paper. Based on its hierarchy, they are categorized in three groups, as follows: 1) key unconformities widely spread along the whole basin; 2) «Intracuyan» unconformities related to the Dorsal de Huincul, and 3) «Intraprecuyan» unconformities restricted to isolated depocentres. Having into account tectonic, eustatic, paleoclimatic and/or paleontological aspects of the sedimentites situated below- and above of each unconformity, precisions about their ages are given. The number of the recognized key unconformities sums 10, as follows: Huarpican (Intratriassic), Rioatuelican (Intraliassic), Lotenican (Intracallovian), Araucanican (ca. Oxfordian/Kimmeridgian boundary), Huncalican (Intravalanginian), Coihuequican (Intrahauterivian), Pampatrilican (Intrabarremian), Pichineuquenican (Intraaptian), Patagonidican (ca. Albian/Cenomanian boundary) and Huantraiquican (Intracampanian). In relationship with the area realated with the Dorsal de Huincul, three «intracuyan» unconformities were identified, as follows: the Intratoarcian, only recognized at subsurface, the Seguelican (Intrabajocian 1) and the Lohanmahuidican (Intrabajocian 2). However, the influence of these unconformities diminish towards northern areas of the basin, as the distance increase with regard to the cited morphostructural element. The «intraprecuyan» unconformities recorded in the Cordillera del Viento and Chachil depocentres are of local character and less hierarchy. They are the result of short interruptions in the volcano-sedimentary infill of these halfgrabens. Given its geographical restriction to the cited depocentres, no formal names were ascribed to these unconformities. Once defined the key unconformities, a summary in three tables of genetically related formational units bounded by them, using the classical lithostratigraphic categorization in Groups, the latter ones basically coincident with the concept of tectosedimentary units (TSU), is presented. The obtained results lead to suggest some new ideas with regard to the evolution of the Neuquén Basin and to keep attention on still open nomenclatural problems.

El anticlinal y las discordancias de Pareja (Guadalajara): definición de las unidades cenozoicas de la Depresión Intermedia (provs. Cuenca y Guadalajara, España)

This paper deals with the stratigraphic units visible at the Pareja Anticline in the Cenozoic-age Depresion Intermedia. The stratigraphic section allowed us to identify three main stratigraphic units differentiated through angular unconformities and sedimentary breaks. Some subunits are also been defined from sedimentary breaks linked to minor diastrophic processes. These subunits as well as the main ones (Cretaceous-Paleogene Unit, Paleogene Unit and Neogene Unit) can be defined as tectosedimentary units being identifiable in all the Depresion Intermedia Basin extent through field sections and borehole logs where large numbers of fossil mammals have been located.

Oligocene–Miocene alluvial sedimentation in the northern Ebro Basin, NE Spain: Tectonic control and palaeogeographical evolution

The Oligocene–Early Miocene rocks cropping out in the northern Ebro Basin (central sector) comprise conglomerates at the margin of the basin gradually passing into sandstones and mudstones towards more central areas. These rocks belong to the Peraltilla and Sariñena Formations and originated in both small monogenic-conglomerate alluvial fans that fed from the South Pyrenean Sierras directly, and large polygenic-conglomerate fans which drained more internal areas of the Pyrenees. Their lithological, textural and geometrical features, in combination with sedimentary structures, reveal the existence of several lithofacies associations whose lateral and vertical relationships, and distribution throughout time have been used to establish the main features for each type of depositional system. Near the margin of the basin, the Tertiary series is folded and thrusted and several unconformities can be identified. Three tecto-sedimentary units (T3 to T5) have been characterised for the whole area. At the margin, they are bounded by angular or syntectonic unconformities. In more central areas, their correlative conformities can be registered as changes from coarsening- to fining-upward general trends or as sudden shifts in the vertical trend. Fining-upward trends are related to onlaps and record the retrogradational stages of the alluvial fans. In contrast, coarsening-upward trends record the progradation of the fans. Stratigraphic and sedimentological studies permit to establish the palaeogeographical evolution of the area during Oligocene and Early Miocene times. Also, it can be demonstrated that during periods of tectonic activity in the Pyrenees the alluvial fans prograded whereas during the stages of relative tectonic inactivity the fans retrograded.

Sequential limb rotation and kink-band migration recorded by growth strata, Almazán Basin, North Spain

Abstract The geometry of growth strata in the Almazan monocline demonstrates that limb rotation and kink-band migration can coexist as folding mechanisms. The Almazan Basin, showing an overall synclinal geometry, was one of the most actively subsiding areas during the Tertiary in the inner part of the Iberian plate, with more than 3500 m of preserved Tertiary non-marine sediments. They are arranged in five tectonosedimentary units, TSU (A1 to A5), bounded by unconformities at the basin borders. The southern basin border is defined by the WNW–ESE-trending Almazan monocline, that can be followed for 25 km along strike, with a maximum structural relief of about 2500 m. The maximum changes in thickness on both limbs of the monocline occur in units A2 and A3, which constrains the maximum deformation period to between the Middle/Upper Eocene (Headonian, top of A1) and Upper Oligocene/Lower Miocene (Agenian, base of A4). The detailed geometry of the Mesozoic, pre-growth, and the Tertiary growth strata of the Almazan monocline was determined from the analysis of six seismic reflection sections, at high angles or perpendicular with the fold axis. The average dip of the monocline changes from 15° in the east to more than 45° in the western sector, being replaced westwards by a north-verging, steeply dipping thrust. In some sections, growth strata in the dipping limb show rotational offlap–onlap syntectonic unconformities, with progressively decreasing dips from bottom to top, indicating that limb rotation took place during the first stages of folding. At the limits of the dipping limb (anticline and syncline), two kink bands appear in some of the sections, the one located on the syncline being more developed. Within each kink-band, beds show a constant dip of 30–40°. The axial surfaces of each kink band converge upwards in the third and fourth tecto-sedimentary units, being parallel in the older units. The fixed axial surface occurs in a down dip position with respect to the active axial surface. The geometry of growth strata indicates that the mechanism of folding followed a sequence of: (i) a first stage of large-scale limb rotation (wavelength larger than 5 km), with minor development of kink-bands in some sections, and (ii) a second stage of more localised kink-band migration, probably favoured by fault propagation in the basement.

Ebro Basin continental sedimentation associated with late compressional Pyrenean tectonics(north‐eastern Iberia): controls on basin margin fans and fluvial systems

ABSTRACT This contribution deals with the External Sierras and a part of the foreland Ebro Basin related to the southern Pyrenean thrust front. The structure of the External Sierras consists of a south‐verging thrust system developed from middle Eocene to early Miocene times. Since the end of the early Oligocene, a regional‐scale detachment anticline (the Santo Domingo anticline) developed, folding the original thrust system and creating new thrust units.The molassic fill in this part of the Ebro Basin (Uncastillo Formation) mainly corresponds to an extensive, composite distributary fluvial system, termed the Luna system, which drained the uplifted Gavarnie Unit to the north. Small, marginal alluvial fans originated along the External Sierras and coalesced in the proximal‐middle portions of the Luna system.Three tecto‐sedimentary units (TSU), late Oligocene to early Miocene in age, comprise the Uncastillo Formation. Lateral relationships and areal distribution of lithofacies through time have been used to establish sedimentary models for the marginal alluvial fans and the Luna fluvial system. Their sedimentary evolution was controlled by tectonics affecting the drainage basins, and based on mapping and stratigraphic relationships of the TSU, the temporal succession of the marginal alluvial fans and their relationships with each thrust system in the south Pyrenean front can be shown. Alluvial fan formation evolved through time from west to east, in accord with the progressive eastward growth of the Santo Domingo anticline as a conical fold.The fluvial network of the Luna system appears to have been mainly radial, but near the basin margin its architecture was influenced by the syndepositional Fuencalderas and Uncastillo anticlines developed within the Ebro Basin. These low‐amplitude folds originated by layer‐parallel shearing caused by rotation of the southern flank of the Santo Domingo anticline. Progressive uplift of these anticlines constrained part of the fluvial discharge to synclinal areas parallel to the basin margin; these areas where characterized by meandering sandy channels. At the peripheral tips of the anticlines the channel system flowed basinward.

Latest Oligocene–Late Miocene lacustrine systems of the north-central part of the Ebro Basin (Spain): sedimentary facies model and palaeogeographic synthesis

In the central part of the Ebro Basin (Spain), north of the Ebro River, three allostratigraphic or tectosedimentary units differentiated within the latest Oligocene–Late Miocene (upper Agenian–Vallesian) interval are sedimentologically characterized. These deposits represent carbonate and sulphate lacustrine environments fed by Pyrenean alluvial systems (Luna system and Huesca system). In each unit, several facies associations or lithofacies were mapped. These interfinger through time: gypsum lithofacies occupy the southernmost part of the study area and are surrounded by carbonate and/or detrital lithofacies to the north. Each lithofacies consists of different carbonate, sulphate and/or detrital facies, arranged in simple sequences, decimetres to metres thick. The four types of sequences characterized reflect a complex shallowing evolution involving carbonate or sulphate contexts. Thus, each lithofacies represents the sedimentation in a particular lacustrine or alluvial subenvironment. A single lacustrine system is proposed for the central part of the basin. Its evolution followed cycles of water level variations, which caused kilometre-scale migrations of the lake shoreline. In this model, two distinct situations or lakes alternated through time. (a) One represents high levels associated with a single body of dilute carbonate water, where massive carbonate facies formed influenced by organism proliferation. These lakes had wide palustrine vegetated margins, in which bioturbated facies developed. (b) The other represents low levels that correspond to a playa-lake model. Laminated sulphate deposits formed in the lake waters, while nodular gypsum originated in the surrounding saline mud flats and within the exposed, previously deposited carbonate sediments. Transitions from one situation to the other, including minor water level fluctuations within carbonate sedimentation conditions, were marked by the development of laminated and stromatolitic facies. Lake level variations were caused by climatic cycles and gave rise to the simple sequences and to the lithofacies lateral relationships recognized in this study. Correlation among tectosedimentary units in the studied Pyrenean domain and in the Iberian domain of the Ebro Basin shows that for units N1 and N2 the facies that resulted from dilute carbonate waters are rare in the lacustrine areas of the Iberian margin. This indicates that a strong hydrological contrast existed between both regions. On this basis, a theoretical asymmetrical facies model is proposed for the single lacustrine basin that extended over these regions.

The Rioja Trough (N Spain): tectosedimentary evolution of a symmetric foreland basin

ABSTRACTThe Rioja Trough is the foreland basin of the western Pyrenees (to the north) and the Cameros‐Demanda Massif (to the south). This E–W elongated trough is about 120×35 km. It was filled with Tertiary continental deposits (upper Eocene to upper Miocene), reaching thicknesses between 2500 and 5000 m. Both margins of the Rioja Trough are large thrusts with horizontal displacements of more than 20 km basinward. Rocks that fill the basin originated in alluvial fan and playa‐lake environments, with conglomerates in the proximal sectors grading into sandstones, mudstones, lacustrine limestones and evaporites in distal sectors. The Tertiary series are horizontal in the central parts of the basin, with several E–W monoclines caused by north‐verging thrusts in the basement of the basin. Near the basin margins, the Tertiary units are folded and thrusted, with several syntectonic unconformities. Calculated velocities for the Cameros‐Demanda thrust range from 0.02 to1.1 mm yr−1 (average 0.7 mm yr−1). The sedimentation rate near the southern basin margin varies between 2 and 20 cm 1000 yr−1 (average 10 cm 1000 yr−1). Deposition in the Rioja Trough was strongly controlled by tectonic activity throughout the Tertiary. Eight tectosedimentary units (R1 to R8) have been characterized. These are bounded by angular unconformities at the margins and breaks in the vertical trend of the sedimentary record toward the basin centre. Every tectosedimentary unit (except R6 and R8) shows a fining‐upward/coarsening‐upward trend, corresponding to tectonic retrogradations and progradations, respectively. The main source area during the Palaeogene was the Cameros‐Demanda Massif, whose unroofing sequence was strongly dependent on tectonic activity. During the Neogene a longitudinal WNW–ESE drainage system, with short alluvial fans in the northern and southern margins, developed. The final shape and the evolution of the Rioja Trough are the result of crustal flexure in the northern border of the Iberian plate, linked to the emplacement of the southern Pyrenean thrust system, and intraplate thrusting with basement uplift at its southern margin.

Late Oligocene - Early Miocene syntectonic fluvial sedimentation in the Aragonese Pyrenean domain of the Ebro Basin: facies models and structural controls.

This contribution deals with a part of the northern margin of the Ebro Basin (Fig. 1). The Upper Oligocene-Lower Miocene molassic infilling in that part mainly corresponds to an extensive fluvial system: the Luna system, which drained the Gavamie unit area and emerged in the basin to the west of the Sierras Exteriores Aragonesas. Small, margina] alluvial fans originated along the Sierras combined in the Luna fluvial system, as well as in the eastern Huesca fluvial system, outside the study area. TIn-ce tectosedimentary units (T.S.U.> were differentiated in the Uncastilio Formation (Figs. 2, 3 and 4), the evolution of whichwas controlled by teetonies affecting the drainage basins. The study of the different lithofacies, their lateral relationsbips and their areal distribution through time (Fig. 5) led to establish sedimentary models for the marginal fans and Luna fluvial system (Hg. 6>. The Luna system resulted from coalescence of two fluvial fans (Figs. 6 and 7). Despite the fluvial network appears mainily as radial, it was controlled by the syndepositional development of the Fuencalderas and Uncastillo anticlines, within the Ebro Basin. Syndepositional folding is shown by important thickness variations in T.S.U., as wel] as by tibe formation of wedge systems within the basin. Progressive uplift of these structures channeled part of the diseharge parallel to tibe basin margin (Figs. 6 and 7), while another portion flowed basinward from the periclinal ends. Vertical aceretion in the synclinal areas north of the anticlines compensated tibe anticlinal uplift, making the siope more genfle and originating bench terraces within tibe general fan slope. In these arcas of gentle slope meandering sandy rivers developed in proximal scctors of tibe systcm, 5.5 lun fair from the margin at present. i<ley words: Fluvial sedimentation, Syndepositional tectonics, Uncastillo Formation, Neogene, Ebro Basin, Spain. Late Oligocene-Early Miocene syntectonicJluvial sedbnentation. 279

Tectosedimentary setting and chronostratigraphy of the Neogene reefs in the Almanzora Corridor (Betic Cordillera, Spain)

The Almanzora Corridor is a narrow Neogene depression which formed part of the system of connecting channelsbetween the Atlantic and Mediterranean marine environments during the late Miocene. Its Miocene filling is siliclastic and is arranged in four tectosedimentary units (TSU). During deposition of TSU II and III, reefs developed in coastal and very shallow environments. In general, these were small, isolated reefs, built up by corals (mainly Porites and Tarbellastraea) and red algae. The reefal structures belonging to TSU-II are patch-reefs and are associated exclusively with fan deltas which developed on both borders of the basin. The basin marls of this unit contain planktonic foraminifera assemblages that can be dated to the younger part of the early Tortonian and the early part of the late Tortonian, subdividing the Tortonian by using the FAD of Neogloboquadrina humerosa (Takayanagi & Saito). Two groups of reefs can be distinguished within TSU-III: larger coastal reefs developed on a palaeorelief formed after the intra-Tortonian tectonic phase which concluded TSU-II, and patch-reefs associated to fan deltas. The deepest contemporary sediments contain planktonic foraminifera assemblages from the lower and middle parts of the upper Tortonian. In this basin, reefal development was prematurely interrupted by the upper Tortonian marine regression, which left all the basins of the central sector of the Betic Cordillera disconnected from marine waters. Marine sedimentation during the latest Tortonian — early Messinian (TSU-IV) only continued in the easternmost part of the Corridor, but no reefs related to this sedimentary unit have been observed.