La estratigrafía y la fauna de la sección de Francás (Tarragona)

The stratigraphy anld fossils range the Francás section (Tarragona) are given. Atter fauna1 assemblage the section can't be oilder than Tortonian

Nuevas aportaciones micropaleontológicas al conocimiento del Neógeno del Baix Llobregat (Barcelona)

Se aportan nuevos conocimientos al estudio geológico y micropaleontológico del subsuelo del área metropolitana de Barcelona, acompañándose de una lista de especies de Foraminíferos que se han encontrado en los materiales neógenos estudiados

Invertebrados y micropaleontología en la evolución de la Cuenca del Guadalquivir (España) y la Plataforma del Algarve (Portugal)

Based upon the depositional sequences in the Guadalquivir basin and the bio-events defined (foraminifera and nanoplancton) we present the synthesis of the paleontological results in correlation with the Neogene of Algarve (Portugal). We present the most representative outcrops for micropaleonlologic results, as well as paleoenvironmental correlations between Algarve and the Guadalquivir basin

La relación foraminíferos-sedimento en los niveles finos del Mioceno medio de la Depresión Prelitoral Catalana (noreste de España)

El análisis sedimentológico de las muestras procedentes de niveles de grano fino (arcillas limosas y limos arcillosos), del Mioceno medio en el Alt Penedés y el área de Tarragona, pone de manifiesto que estos niveles tienen un carácter granocreciente positivo. Estos datos están de acuerdo con la variación de la relación entre foraminíferos planctónicos y bentónicos En el diagrama C-M la mayoría de las muestras aparecen reunidas en dos grupos: 1) sedimentación por suspensión uniforme y 2) sedimentación por suspensión pelágica. El primer grupo comprende dos tipos de sedimentos. Uno con predominio de foraminíferos bentónicos, típico de condiciones marinas normales. El otro presenta claros indicios de episodios hiposalinos: abundancia de foraminíferos aglutinados y cistes de Lingulodinium marchaerophorum. En el segundo grupo se pueden distinguir dos tipos de sedimentos. Uno refleja condiciones marinas normales con abundancia y diversidad de foraminíferos planctónicos. El otro presenta una menor diversidad, con predominio de los foraminíferos bentónicos que evidencian la existencia de condiciones deficitarias de oxígeno

Las asociaciones de microfauna como indicadores de cambios paleoambientales en los ciclos fluvio-lacustres Miocenos (NE de la Cuenca del Duero, España)

The siliclastic and carbonate deposits are interbedded in the Villadiego area (Miocene, NE Duero Basin). They have been subdivided into two high-rank depositional sequences: DDS and CDS. The sedimentary analysis of these units and the study of the microfauna content, mainly ostracods, led to the identification of lacustrine-fluvial interaction systems. The sedimentary characteristics reveal the existence of fluvial systems of gravel, flood plains and lacustrine systems that were interconnected and intimately related in north-south direction. In the sedimentological analysis, thirteen types of fluvial and lacustrine lithofacies and six genetic facies associations were recognized. The top of DDS is the result of lake level risings. The CDS shows a deepening-shallowing cycle. The ostracod micropaleontological analysis of the sediments have been studied, with the aim of reconstructing the palaeoenvironmental evolution of this area. These microfauna assemblages integrated with the analysis of the sedimentary facies allowed to conclude the existence of lakes with a water-bearing level of few tens of meters. A change in the chemical conditions of the waters, which evolved from oligohaline and carbonated to mesohaline and sulphated is concluded.Los depósitos siliciclásticos y carbonatados se encuentran intercalados en el área de Villadiego (Mioceno, NE cuenca del Duero). Se han subdividido en dos secuencias de depósito de alto rango: DDS y CDS. El análisis de estas unidades sedimentarias y el estudio del contenido de microfauna, principalmente ostrácodos, condujo a la identificación de sistemas de interacción lacustre-fluvial. Las características sedimentarias revelan la existencia de los sistemas fluviales de grava, llanuras de inundación y sistemas lacustres que estaban interconectados e íntimamente relacionados en dirección N-S. En el análisis sedimentológico se reconocieron trece tipos de litofacies fluviales y lacustres y seis asociaciones de facies genéticas. La parte superior del DDS es el resultado de levantamientos del nivel del lago. El CDS muestra un ciclo de profundización-somerización. Los sedimentos se han estudiado mediatne análisis micropaleontológico de ostrácodos, con el objetivo de reconstruir la evolución paleoambiental de esta zona. Estos conjuntos de microfauna integrados con el análisis de las facies sedimentarias permiten concluir la existencia de lagos con un nivel acuífero de pocas decenas de metros. Se concluye que existió un cambio en las condiciones químicas de las aguas, que evolucionaron a partir de oligohalinos y sin gas a mesohalino y sulfatadas

Estudio palinológico de los sedimentos maastrichtienses del Barranco de la Posa (Prepirineo, Lérida, España)

El Maastrichtiense que se extiende entre Tremp y Coll de Nargó está representado por depósitos de carácter lagunar y salobre, con pequeños niveles marinos intercqlados . En la sección estudiada l a intercalación marina corresponde a un banco de Hippurites castroi al que acompañan a l g unos coral es . Los Narmapolles no son muy numerosos ni en especies ni en individuos . Entre los tipos 'que caracterizan la vegetación cabe destacar las formas de Inaperturados, ( Taxodiaceae-Cupressaceae) , Palmae y t ipo Platycarya . Localmente Cycadale~, Cupuliferoipollenites y Subtriporopollenites pueden ser abundantes. La frecuencia de Cycadales + Palmae en el conjunto esporopolínico de La Posa se aproxima al tipo de asociación polínica del Maastrichtiense de Africa pro parte. Sin embargo, Trilobospori tes ( Tuberos isporites) se encuentra en la l ocalidad tipo del Maastrichtiense, en la región boreal. Por el momento , parece que se trata de un conjunto pol ínico del r~aastrichtiense con un carácter parti cular en relación a los i ndicadosLe Maastrichtien affleurant entre Tremp et Coll de Nargó est représenté par dép8ts lagunaires et saum§tres ave e ni veaux marins i ntercalés. A la section étudiée 1 ' intercalation mar ine est determinée par un banc a Hippurites castroi avec quelques coraux . Le nombre des taxa et la quantitée des Normapolles ne sont pas tres élevées . En ce qui concerne les types qui caractérisent la végetation, les polles i na perturés ( TaxodiaceaeCupressaceae) 1 Palmae et l e type de Pl atycarya sont en premier l i eu remarquables. Localement les Cycadales , Cupuliferoipolleni tes et Subtriporopol l enites peuvent se rencontrer en quantitée remarquable . L' a bondance des formes Cycadal es + Palmae se révéle au type d'association pollin i que du ~1aastric h tien en 1' Afrique pro parte . Mai s Trilobospori tes ( Tuberosisporites) se trouve dans la l ocal i tés type de Maastricht 1 dans la région boréale. A notre avis il s'agit d 'un type d'association pollinique du Maastrichtien particulier 1 par rapport aux précédent

Paleomagnetic and paleoenvironmental implications of magnetofossil occurrences in late Miocene marine sediments from the Guadalquivir Basin, SW Spain

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.This study was funded by the Guadaltyc project (MINECO, CGL2012–30875), ARC grant DP120103952, and NSFC grant 41374073

Impact of restriction of the Atlantic-Mediterranean gateway on the Mediterranean Outflow Water and eastern Atlantic circulation during the Messinian

Messinian foraminiferal stable oxygen and carbon isotopes of the Montemayor-1 core (Guadalquivir Basin, SW Spain) have been investigated. This record is exceptional to study the Mediterranean Outflow Water (MOW) impact on the Atlantic meridional overturning circulation (AMOC) and global climate during the Messinian because the core is near the Guadalhorce Corridor, the last Betic gateway to be closed during the early Messinian. Our results allow dating accurately its closure at 6.18 Ma. Constant benthic d18O values, high difference between benthic and planktonic d18O, and low sedimentation rates before 6.18 Ma indicate the presence of a two-layer water column, with bottom winnowing due to an enhanced Mediterranean outflow current. The enhanced contribution of dense MOW to the North Atlantic Ocean likely fostered the formation of North Atlantic Deep Water (NADW). After 6.18 Ma, benthic d18O values parallel that of the global glacioeustatic curve, the difference between benthic and planktonic d18O is low, and sedimentation rates considerably increased. This indicates a good vertical mixing of the water column, interruption of the MOW, and a dominant glacioeustatic control on the isotopic signatures. According to the role of MOW in the modern Atlantic thermohaline circulation, the reduction of the MOW after the closure of the Guadalhorce Corridor might have resulted in a decreased NADW formation rate between 6.0 and 5.5 Ma weakening the AMOC and promoting northern hemisphere cooling. After the Gibraltar Strait opening, the restoration of the MOW and related salt export from the Mediterranean could have promoted an enhanced NADW formation

Messinian paleoenvironmental evolution in the lower Guadalquivir Basin (SW Spain) based on benthic foraminifera.

Benthic foraminiferal assemblages of a drill core from the lower Guadalquivir Basin (northern Gulf of Cádiz, SW Spain) have been analyzed in order to reconstruct the paleoenvironmental evolution in the vicinity of the Betic seaways during the Messinian. The core consists of marine sediments ranging from the latest Tortonian to the early Pliocene. Changes in the abundance of certain marker species, planktonic/benthic ratio (P/B ratio), paleodepth estimated with a transfer function, content of sand grains and presence of glauconitic layers indicate a complete transgressive-regressive sea-level cycle from the bottom to the top of the section. An abrupt sea-level rise, from inner-middle shelf to middle slope, is recorded at the lowermost part of the core (latest Tortonian-earliest Messinian), followed by a relatively rapid shallowing from middle slope to outer shelf. Magnetobiostratigraphic data show that this sea-level fall postdates the onset of the Messinian salinity crisis (MSC) in the Mediterranean. Finally, the early Pliocene deposits are interpreted as inner-middle shelf. Changes in the benthic foraminiferal assemblages through the core are mainly controlled by the trophic conditions, specifically by the quantity and quality of the organic matter reaching the sea floor. The upper slope and part of the outer shelf assemblages are highly diverse and dominated by shallow infaunal species, indicating a generallymesotrophic environment with moderate oxygenation. These environments have likely been affected by repeated upwelling events, documented by increased abundance of Uvigerina peregrina s.l., an opportunistic species thriving in environmentswith enhanced labile organic matter supply. The assemblages of the transitional interval between upper slope to outer shelf, and of the outer shelf are generally characterized by a relatively low diversity and epifaunal-shallow infaunal taxa, indicating oligotrophic and well-oxygenated conditions. The innermiddle shelf assemblages are characterized by very lowdiversity and dominance of intermediate to deep infaunal taxa, suggesting an eutrophic environmentwith lowoxygen content. These assemblages are dominated by Nonion fabum and Bulimina elongata, two taxa that are able to feed from continental low-quality organicmatter,most likely derived from river run-off. The paleoenviromental evolution on the Atlantic side of Betic and Rifian seaways is similar during the Messinian, with a Messinian continuous sea-level lowering driven by regional tectonic uplift and upwelling-related waters reaching the upper slope. This study will further contribute to understand the role of tectonics on the sea-level changes as well as on the closure of the Atlantic-Mediterranean gateways that led to the MSC, and on the paleoceanography on the Atlantic sides of these corridors

Messinian productivity changes in the northeastern Atlantic and their relationship to the closure of the Atlantic-Mediterranean gateway: implications for Neogene palaeoclimate and palaeoceanography.

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, wellventilated 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 wellventilated 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