The Lower–Middle Miocene Lagos-Portimão Formation at Portimão, southern Portugal, consists of three main heterozoan carbonate facies: mollusc-rich rudstone in a matrix of skeletal packstone/grainstone (MR), fine-to-medium skeletal packstone/grainstone (SPG), and quartz-rich skeletal packstone (QSP). These facies occur in different arrangements and indicate deposition on a wave-dominated open shelf with a well-established heterozoan fauna, most likely related to increased trophic resources where continent supply and upwelling contributed nutrients. These facies form belts inferred to have lain roughly parallel to the strike lines of the shelf, with the MR occupying the more landward, shallower areas and the SPG and QSP extending progressively offshore on the open shelf. Bryozoan abundance in the QSP facies indicates a deep setting on the middle/outer shelf, whereas the absence of rhodalgal components is attributed to a combination of temperature decrease and seafloor eutrophication during the late Langhian and Serravallian, coeval with the “Middle Miocene climatic cooling”. The large photosymbiont-bearing foraminifers and the absence of calcareous algae and zooxanthellate corals point to deposition under warm-temperate conditions. Two main orders of cyclicity are present. Small-scale sequences, 40–60 cm thick, may represent minor sea-level changes related to fifth-order sequences modulated by (~ 100-kyr) eccentricity forcing. Six large-scale sequences, 3–9 m in thickness, are recognized. Based on LAD and FAD of planktic foraminifers and the occurrence of two erosive surfaces related to major sea-level falls (Lang2/Ser1 and Ser4/Tor1), five Miocene sequences (Bu, L1, S1, S2, and S3) are correlated with third-order eustatic cycles.

This chapter deals with the two Alpine Foreland Basins of the Iberian Peninsula. The first part of the chapter refers to the South Pyrenean Foreland Basin and its westward prolongation, the Basque-Cantabrian Paleogene Basin. It includes: (1) the introductory concepts about the basin extend, margins, sedimentary systems, basin evolution and segmentation, and terminology; (2) the impact of PETM; (3) the stratigraphy and geometry of foreland carbonate margin with special emphasis on the recent advances in its chronology and evolution, (4) the stratigraphy and geometry of the siliciclastic basin fill reflecting the recent advances in chronology and provenance; (5) and finally, discusses on the sedimentary imprints of the orogenic evolution. The second part of this chapter is focused on the Guadalquivir Basin, which developed in the southern Iberian margin at the foreland of the Betic orogenic front during the last stages of foreland basin development. An introduction to the overall geology of the basin is given before an updated view on the chronostratigraphy of its sedimentary infill is outlined. Such an updated framework provides the basis for disentangling the geodynamic processes that are encoded in the sedimentary record of the basin.

The Gibraltar Arc is a complex tectonic region, and several competing models have been proposed to explain its evolution. We studied the sedimentary fill of the Guadalquivir Basin to identify tectonic processes that were occurring when the reopening of the Strait of Gibraltar led to the reestablishment of Mediterranean outflow. We present a chronostratigraphic framework for the Lower Pliocene sediments from the lower Guadalquivir Basin (SW Spain). The updated chronology is based on magnetobiostratigraphic data from several boreholes. Our results show that the studied interval in the La Matilla core is in the early Pliocene section, providing better constraints on the sedimentary evolution of the basin during that period. Migrating depositional facies led to a younger onset of sandy deposition basinward. At the northwestern passive margin, a 0.7 m.y. period of sedimentary bypass related to a sharp decrease in sedimentation rates and lower sea levels resulted from the tectonic uplift of the forebulge. In contrast, high sedimentation rates with continuous deep-marine sedimentation are recorded at the basin center due to continuous tectonic subsidence and west-southwestward progradation of axial depositional systems. The marginal forebulge uplift, continuous tectonic basinal subsidence, and southward progradation of clinoforms in the early Pliocene can be explained by the pull of a lithospheric slab beneath the Gibraltar Arc as the Strait of Gibraltar opened. These findings are, to our knowledge, the first reported sedimentary expression of slab pull beneath the Betics related to the opening of the Strait of Gibraltar after the Messinian salinity crisis.

Trabajo presentado en el XI Convencion Internacional sobre Medio Ambiente y Desarrolllo, celebrado en la Habana (Cuba) del 3 al 7 de julio de 2017.

The Malaga basin contains an important geological record documenting the complex paleogeographic evolution of the Gibraltar Arc before, during and after the closure and desiccation of the Mediterranean Sea triggered by the "Messinian Salinity crisis" (MSC). Proxy paleo-elevation data, estimated from the stratigraphic and geomorphological records, allow the building of quantitative paleogeoid, paleotopographic and paleogeographic models for the three main paleogeographic stages: pre-MSC (Tortonian-early Messinian), syn-MSC (late Messinian) and post-MSC (early Pliocene). The methodological workflow combines classical contouring procedures used in geology and isobase map models from geomorphometric analyses and proxy data overprinted on present Digital Terrain Models. The resulting terrain quantitative models have been arranged, managed and computed in a GIS environment.The computed terrain models enable the exploration of past landscapes usually beyond the reach of classical geomorphological analyses and strongly improve the paleogeographic and paleotopographic knowledge of the study area. The resulting models suggest the occurrence of a set of uplifted littoral erosive and paleokarstic landforms that evolved during pre-MSC times. These uplifted landform assemblages can explain the origin of key elements of the present landscape, such as the Torcal de Antequera and the large amount of mogote-like relict hills present in the zone, in terms of ancient uplifted tropical islands. The most prominent landform is the extensive erosional platform dominating the Betic frontal zone that represents the relic Atlantic wave cut platform elaborated during late-Tortonian to early Messinian times. The amount of uplift derived from paleogeoid models suggests that the area rose by about 340 m during the MSC.This points to isostatic uplift triggered by differential erosional unloading (towards the Mediterranean) as the main factor controlling landscape evolution in the area during and after the MSC. Former littoral landscapes in the old emergent axis of the Gibraltar Arc were uplifted to form the main water-divide of the present Betic Cordillera in the zone. (C) 2016 Elsevier B.V. All rights reserved.

Eight sites with geological (including palaeontological and geomorphological) interest (geosites) representative of the Lower and Middle Miocene carbonate deposits near Albufeira in central Algarve (southern Portugal) have been selected based on our extended working experience. The sites can be visited by hiking in a 1-day field trip. A virtual 3D tour of the georeferenced sites was produced using augmented reality technique and geoinformatic tools which integrate thematic digital layers such as geological maps and orthophotos. Every stop in the tour includes descriptive and graphic elements that can be viewed in free virtual globes (e.g. Google Earth) combined with diagrams, photographs and information sheets that quantitatively assess the cultural-touristic, educational and scientific value of the geosites. A virtual flight itinerary compatible with video formats in the new free technologies (smartphones, tablets and iPads) is also presented.

The Piedras River marshland and El Rompido spit bar is a Natural Site in close proximity to two of the most polluted rivers in the world: the Tinto and Odiel Rivers. The aim of this study is to determine the degree of contamination of this Natural Site using a variety of pollution indices. At this site the Holocene infilling sequence is recorded and applied to a study of the pollution history and the possible impacts of human activity. The depositional history of the Piedras River estuary during the Holocene recorded open marine conditions at ca. 6500 calBP when sea-level was at its Holocene maximum. To study the pollution of the estuary during the Holocene, catchment background geochemistry was established using samples that pre-date human activity (agriculture and mining). Additionally, the sedimentary environment was reconstructed throughout the Holocene; comparison of pollution levels is interpreted to be more reliable if the sedimentary environment has remained similar throughout the depositional record. Results show that, despite being located nearby very polluted estuaries, the Piedras River marshland contains unpolluted sediments mainly because of the small catchment area relative to that of neighbouring more polluted rivers, and thus has not been affected by human activity such as mining.

We present a new high-resolution cyclostratigraphic age model for the Messinian sediments of the Montemayor-1 core. This core was drilled in the Guadalquivir Basin in southern Spain, which formed part of the marine corridor linking the Mediterranean with the Atlantic in the Late Miocene. Tuning of high-resolution geochemical records reveals a strong precessional cyclicity, with maximum clastic supply from river run off coinciding with maximum summer insolation. We recognize a gradual change in the nature of the typical cyclic fluctuations in elemental compositions of the sediments through the core, which is associated with a gradual change in depositional environment as the basin infilled. After applying the new age model, the upper Messinian glacial stages and deglaciation are clearly identified in the oxygen isotope records of the Montemayor-1 core. Reinterpretation of existing planktonic and benthic oxygen isotope records for the core and comparison with equivalent successions in the Rifian Corridor in northern Morocco allow the re-evaluation of the influence of the different water masses in the region: North Atlantic Central Water and Mediterranean Outflow Water. We observe no direct influence of MOW immediately before or during the Messinian Salinity Crisis.

Virtual fieldtrips in palaeontology and geology offer an expanded environment to make field sites more accessible for a broader audience. Based on extensive experience working in upper Neogene deposits in the province of Huelva, on the western edge of the Guadalquivir Basin, we have selected 10 sites for their regional palaeontological-geological interest (geosites). By applying geoinformatic tools, we have produced a virtual 3D tour of the georeferenced geosites, integrating multiple thematic digital layers (including geological maps, topographical maps, a digital terrain model and orthophotos). Each stop in the tour contains descriptive and graphic elements that can be viewed in free virtual globes (e.g., Google Earth), combined with diagrams, photographs and information sheets that quantitatively assess the cultural tourism, scientific and educational value of the geosite. From this digital 3D geodatabase, we propose a virtual flight itinerary that can be displayed in compatible video formats and using new technologies, such as smartphones, tablets or iPads.

Although recent studies have revealed more widespread occurrences of magnetofossils in pre-Quaternary sediments than have been previously reported, their significance for paleomagnetic and paleoenvironmental studies is not fully understood. We present a paleo- and rock-magnetic study of late Miocene marine sediments recovered from the Guadalquivir Basin (SW Spain). Well-defined paleomagnetic directions provide a robust magnetostratigraphic chronology for the two studied sediment cores. Rock magnetic results indicate the dominance of intact magnetosome chains throughout the studied sediments. These results provide a link between the highest-quality paleomagnetic directions and higher magnetofossil abundances. We interpret that bacterial magnetite formed in the surface sediment mixed layer and that these magnetic particles gave rise to a paleomagnetic signal in the same way as detrital grains. They, therefore, carry a magnetization that is essentially identical to a post-depositional remanent magnetization, which we term a bio-depositional remanent magnetization. Some studied polarity reversals record paleomagnetic directions with an apparent 60-70 kyr recording delay. Magnetofossils in these cases are interpreted to carry a biogeochemical remanent magnetization that is locked in at greater depth in the sediment column. A sharp decrease in magnetofossil abundance toward the middle of the studied boreholes coincides broadly with a major rise in sediment accumulation rates near the onset of the Messinian salinity crisis (MSC), an event caused by interruption of the connection between the Mediterranean Sea and the Atlantic Ocean. This correlation appears to have resulted from dilution of magnetofossils by enhanced terrigenous inputs that were driven, in turn, by sedimentary changes triggered in the basin at the onset of the MSC. Our results highlight the importance of magnetofossils as carriers of high-quality paleomagnetic and paleoenvironmental signals even in dominantly terrigenous sediments.

The stable isotope composition of planktic and benthic foraminifera and the distribution of selected benthic foraminiferal species from a Messinian record of the lower Guadalquivir Basin, northeastern Atlantic Ocean, show that regional productivity changes were linked to glacioeustatic fluctuations. Glacial periods were characterized by poorly ventilated bottom waters as a result of weak Atlantic Meridional Overturning Circulation (AMOC), and by phases of high productivity related to intensified upwelling. In contrast, well-ventilated bottom waters owing to strong AMOC, the presence of degraded organic matter in the upper slope, and high input of degraded terrestrial organic matter derived from fluvial discharge to the outer shelf were recorded during interglacial periods. Before closure of the adjacent Guadalhorce Corridor at 6.18 Ma, which was the final active Betic Atlantic–Mediterranean gateway, the study area was alternately influenced by well-ventilated Mediterranean Outflow Water (MOW) and poorly ventilated Atlantic Upwelled Water (AUW). Following closure of the corridor, cessation of the MOW reduced the AMOC and promoted glacial conditions in the northern hemisphere, resulting in the establishment of local upwelling cells.

Se estudiaron ciento quince piezas dentarias de Rajiformes provenientes de ocho localidades del Neogeno de Huelva. Existe una riqueza de restos de selaceos en la Formacion Arenas de Huelva, Plioceno inferior del suroeste de la cuenca del Guadalquivir, Espana. Se registraron Rhinobatos sp., Raja olisiponensis y Raja sp. Se observo un predominio de restos de Raja sp. Las asociaciones de selaceos indican que estos sedimentos fueron depositados en un ambiente litoral-neritico, con una temperatura de aguas subtropicales a templadas. Los taxones de selaceos encontrados en la Formacion Arenas de Huelva son compatibles con una edad Plioceno s.l. Se registra por primera vez para el Neogeno de Espana la especie Raja olisiponensis.

The Messinian salinity crisis (late Miocene) is one of the most fascinating paleoceanographic events in the recent geological history of the Mediterranean Sea, defining a time when it partly or nearly completely dried out. However, the relative roles of tectonic processes and sea-level changes, as triggers for restriction and isolation of the Mediterranean Sea from the open ocean, are still under debate. In this study, we present a detailed pollen, dinoflagellate cyst (dinocyst), and magnetic susceptibility analysis of a sequence of late Neogene (between ca. 7.3 and 5.2 Ma) marine sediments from the Montemayor-1 core (lower Guadalquivir Basin, southwestern Spain), which provides a continuous record of paleoenvironmental variations in the Atlantic side of the Betic corridors during the late Miocene. Our results show that significant paired vegetation and sea-level changes occurred during the Messinian, likely triggered by orbital-scale climate change. Important cooling events and corresponding glacio-eustatic sea-level drops are observed in this study at ca. 5.95 and 5.75 Ma, coinciding with the timing and duration of oxygen isotopic events TG32 and TG22-20 recorded in marine sediments worldwide. It is generally accepted that the onset of the Messinian salinity crisis began at ca. 5.96 +/- 0.02 Ma. Therefore, this study suggests that the restriction of the Mediterranean could have been triggered, at least in part, by a strong glacio-eustatic sea-level drop linked to a climate cooling event occurring at the time of initiation of the Messinian salinity crisis.

The desiccation of the Mediterranean during the Messinian salinity crisis (MSC) is one of the most intriguing geological events of recent Earth history. However, the timing of its onset and end, as well as the mechanisms involved remain controversial. We present a novel approach to these questions by examining the MSC from the Atlantic, but close to the Gibraltar Arc, analysing the complete Messinian record of the Montemayor-1 core of the Guadalquivir Basin (SW Spain). Flexural backstripping analysis shows a tectonic uplift trend that would have reduced the depth of the Rifian Corridors considerably. Nonetheless, the rate of tectonic uplift was insufficient to account for the close up of the corridors. At 5.97 Ma, a global cooling and associated glacioeustatic sea-level drop, estimated in 60 m, is observed. This would have been sufficient to restrict the Rifian Corridors and to trigger the MSC. The later flooding of the Mediterranean occurred during a sea-level rise associated with global warming during a stable tectonic period. We postulate a two-step flooding event: 1) A glacioeustatic sea-level rise during interglacial stage TG 11 (5.52 Ma) led to subtropical Atlantic waters entering the west-central Mediterranean through pathways south of the Gibraltar Strait, probably the Rifian Corridors. 2) A global sea-level drop at 5.4 Ma, that might have favoured intensification of regressive fluvial erosion in the Gibraltar threshold, along with the subsequent global sea-level rise would have generated the Gibraltar Strait leading to complete Mediterranean refilling during the earliest Pliocene.

Trabajo presentado en el 3rd INQUA-IGCP 567 International Workshop on Active Tectonics, Paleoseismology and Archeoseismology, celebrado en Morelia (Mexico), del 18 al 22 de noviembre de 2012