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

First bird footprints from the lower Miocene Lerín Formation, Ebro Basin, Spain

A new tracksite with bird footprints, found in the Bardenas Reales de Navarra Natural Park (Navarre, Spain), is presented in this study. The footprints are preserved in four sandstone blocks of the Lerín Formation from the northwest sector of the Ebro Basin. According to the magnetostratigraphic data, the age of these blocks is 20.4 Ma (Agenian, lower Miocene). The footprints are more than 100 mm in length, mesaxonic, and tridactyl, and have a prominent central pad impression with the digit impressions not jointed proximally. These features allow classifying them as Uvaichnites riojana. Some of the studied footprints are better preserved than the type series of Uvaichnites, which were found also in the northwest sector of the Ebro Basin. Therefore, the original diagnosis has been emended. Available chronostratigraphic data for these localities as well as for other footprints from China indicate a latest Oligocene-earliest Miocene age (from about 23 to 20 Ma) for Uvaichnites-like footprints. Sedimentological data also indicate similar continental environments, namely perilacustrine deltaic systems and distal alluvial systems. The information about early Miocene avian remains (bones, eggs and footprints) in the Iberian Peninsula is scarce. The skeletal and oological record of this age has been included within the families Phoenicopteridae, Phaisanidae and Cathartidae (or incertae sedis), while the ichnological record was related with trackmakers belonging to Charadriiformes, Ardeidae and Gruidae taxa. For this scenario, in which there are few avian remains, the ichnological diversity shown in this paper complements and improves the knowledge about the Iberian avian diversity in the early Miocene

Icnitas de artiodactilos (Mammalia) del Paleogeno de Olcoz (Depresion del Ebro, Navarra)

A group of fossil mammal ichnites from the proximity of the town of Olcoz (Navarra, Ebro Basin) is described herein. The tracks occur on sandstone beds of the Mués Formation of Suevian (Early Oligocene) age. Owing to their morphology these ichnites have been assigned to artiodactyl mammals and can be compared to Entelodontipus forms. Moreover, this represents the second known finding of this ichnogenus. Among the tracks of this deposit there is a significant heterogeneity which is due to the variable penetration and displacement of the autopodes on the substrate. On Olcoz the presence of abundant ichnites that follow subparallel tracks allows the establishment of the gregarious behaviour of the producers of such tracks.Se describe un conjunto de icnitas fósiles de mamíferos ubicado en los alrededores de la localidad navarra de Olcoz (Depresión del Ebro). Las huellas se localizan en niveles areniscosos de la «Formación de Mués», de posible edad Sueviense (Oligoceno inferior). Por su morfología pueden asignarse a mamíferos artiodáctilos y resultan comparables a Entelodontipus, constituyendo este hallazgo una segunda cita para dicho icnogénero. En este yacimiento se constata una notable variabilidad morfológica de las huellas, resultado de la distinta penetración y desplazamiento de los autópodos en el sustrato. La presencia en Olcoz de numerosas icnitas formando rastros subparalelos permite inferir el comportamiento gregario de sus productores

Nuevos datos sobre Andegameryx (Mammalia, Ruminantia) del Mioceno Inferior de las Bardenas Reales (Navarra, España)

New fossil remains of ruminants from the Lower Miocene (Ramblian, MN3) of the Bardenas Reales (Navarre) are studied in this paper. The material, which comprises dentition, is assigned to Andegameryx aff. andegaviensis Ginsburg, 1971. Morphological and metrical similarities exist between these remains and the Spanish population of Andegameryx andegaviensis from Cetina de Aragón (Zaragoza), which is somewhat larger than the French material of this species. However, there are also some affinities with Andegameryx fossils from other Spanish localities as Loranca del Campo (Cuenca). The new material from the Bardenas Reales allows us to confirm certainly the presence of Andegameryx in the area and to provide the evidence that it was a widespread genus of ruminant in Spain during the early Miocene.En este trabajo se describen los nuevos hallazgos de rumiantes fósiles del Mioceno inferior (Rambliense, MN3) de las Bardenas Reales (Navarra). Este material está compuesto por dentición y ha sido clasificado como Andegameryx aff. andegaviensis Ginsburg, 1971. El estudio morfológico y métrico muestra que los restos de las Bardenas son muy semejantes a los de la población española de Andegameryx andegaviensis de Cetina de Aragón (Zaragoza), de talla algo mayor que las poblaciones francesas de esta especie. Sin embargo, también tiene afinidades con material de Andegameryx procedente de otras localidades españolas como Loranca del Campo (Cuenca). Los nuevos hallazgos permiten confirmar sin dudas la presencia de Andegameryx en las Bardenas Reales (Cuenca del Ebro), poniendo de manifiesto que este género de rumiante estuvo ampliamente extendido en las cuencas interiores de España durante el Mioceno inferior

Micromammalian faunas from the middle miocene (middle Aragonian) of the Tudela formation (Ebro Basin, Spain)

Two new fossil micromammal localities of Middle Miocene age (Pico del Fraile 2, PF2 and Sancho Abarca 5, SA5) from the Tudela Formation (northeastern Ebro Basin) are described. PF2 contains rodents and insectivores of Aragonian age (local zone Dc). The rodent assemblage from the locality SA5 is very scarce and probably of Middle Aragonian age, like PF2. The micromammal fauna from the locality PF2 is very similar to that from Valdemoros 3B (VA3B) (Calatayud-Daroca Basin), including Microdyromys cf. remmerti, a species until now only described from the Miocene of the Daroca-Villafeliche area. Among the fauna recorded in PF2, a form of Democricetodon is described. The sedimentary record of the Pico del Fraile and Sancho Abarca sections and the mammalian findings extend the stratigraphic and paleontological knowledge of this part of the Ebro Basin, and allow its study in a continuous stratigraphic context

Las asociaciones de ostrácodos en secuencias aluviales como indicadores de cambios ambientales holocenos (Bardenas Reales de Navarra, Cuenca del Ebro, NE Península Ibérica)

En este trabajo se estudian las asociaciones de ostrácodos identificadas en tres unidades aluviales preservadas en Bardenas Reales de Navarra (Cuenca del Ebro, NE Península Ibérica), para reconstruir la evolución paleoambiental de esta área durante el Holoceno final. Las especies de ostrácodos más comunes en las muestras estudiadas son Ilyocypris bradyi Sars y Paralimnocythere aff. psammophila (Flössner), acompañadas por Pseudocandona albicans (Brady). Las variaciones en su abundancia relativa a lo largo de dichas unidades aluviales permiten caracterizar cambios internos en el ambiente de depósito. Así, la unidad depositada entre 4763±87 y 2848±55 años cal. BP presenta como especie más abundante a I. bradyi, lo que indica la existencia de pequeños arroyos o riachuelos con agua corriente que se desarrollaron probablemente en llanuras de inundación fluviales. Sin embargo, de 2848±55 a 836±65 años cal. BP Paralimnocythere aff. psammophila es la especie dominante, representando el establecimiento de un medio acuático efímero y de aguas estancadas, posiblemente relacionado con condiciones climáticas más áridas (Anomalía Climática Medieval). Finalmente, la asociación de ostrácodos identificada en el Reciente (191±97 a 127±82 años cal. BP) está constituida principalmente por I. bradyi, que indicaría la presencia de nuevo de aguas corrientes. Esta última asociación parece estar vinculada a la influencia de condiciones climáticas húmedas y frías (Pequeña Edad del Hielo) durante el Reciente en esta área. Por lo tanto, la evolución paleoambiental para el Holoceno final de Bardenas Reales de Navarra, identificada a partir de las asociaciones de ostrácodos, muestra una buena correlación con los cambios climáticos rápidos holocenos deducidos en otros registros continentales del NE de la Península Ibérica. In this paper, the ostracod assemblages identified in three alluvial units preserved in Bardenas Reales de Navarra (Ebro Basin, NE Iberian Peninsula) have been studied, with the aim of reconstructing the palaeoenvironmental evolution of this area during the late Holocene. The most common ostracod species in the studied samples are Ilyocypris bradyi Sars and Paralimnocythere aff. psammophila (Flössner), accompanied by Pseudocandona albicans (Brady). Variations in their relative abundance along these alluvial units allow us to characterize internal changes in the depositional environment. Thus, the unit deposited between 4763±87 and 2848±55 years cal. BP is dominated by I. bradyi, indicating the presence of small streams with running water developed probably in fluvial flood plains. Nevertheless, from 2848±55 to 836±65 years cal. BP Paralimnocythere aff. psammophila is the dominant species, representing the establishment of an ephemeral and stagnant aquatic environment, mainly related with more arid climatic conditions (Medieval Warm Period). Finally, the ostracod assemblage identified in Recent times (191±97 to 127±82 years cal. BP) is mainly dominated by I. bradyi, which indicates the presence of running waters. This later assemblage probably defines the influence of cold and wet climatic phase (Little Ice Age) during Recent times in this area. The palaeoenvironmental evolution identified from the late Holocene according to ostracod assemblages in Bardenas Reales de Navarra shows good correlation with rapid climatic changes deduced from other continental records of the NE Iberian Peninsula

The turtles from the upper Eocene, Osona County (Ebro Basin, Catalonia, Spain): new material and its faunistic and environmental context

Eochelone voltregana n. sp. is a new marine cryptodiran cheloniid found at the Priabonian levels (latest Eocene) of the Vespella marls member of the Vic–Manlleu marls formation. It is the second cheloniid from Santa Cecília de Voltregà (Osona County, Spain), the first one being Osonachelus decorata from the same formation. Shell parameters indicate that the new species belongs to a branch of sea turtles including the Eocene Anglo–Franco–Belgian forms Argillochelys, Puppigerus and Eochelone (the shell of the latter was studied here for the first time) as well as Glarichelys from the Oligocene of Switzerland, all of them predating the worldwide living Miocene genera. The description of two other more littoral–continental Eocene species is given: Trionyx sp., from an older layer of the same formation; and the podocnemidid erymnochelyine, Cordichelys from a more basal layer of a middle Eocene (Lutetian) formation. The last one is identified as the only evidence of the Shweboemys subgroup in the European record, being distinct from the other known Osona County pleurodire Eocenochelus farresi, which is a member of the Erymnochelys group (same subfamily), from the younger Priabonian Sant Martí Xic layer. Thus, an update on the marine turtle fauna of the eastern Ebro Basin that variably opened in the east during Eocene times is provided. The turtles of Osona County belong to two suborders and five genera with three new species and extend the known distribution of their families (LSID urn:lsid:zoobank.org:act:48CE8676-7B82-4EF2-8165-27BEE90129F2).</p

Análisis paleoambiental de los depósitos aluviales de la sección de Cenicero a partir de las asociaciones de ostrácodos (Mioceno inferior, NO de la Cuenca del Ebro)

In this work we perform for the first time a palaeoenvironmental and biostratigraphic analysis of the lower Miocene alluvial deposits of the Cenicero section (NW sector of the Ebro Basin; N Iberian Peninsula), based on the ostracod and micromammal assemblages. One of the main characteristics of this section is the unusual abundance on non-reworked ostracods present in the studied samples compared to other European sequences of similar age and sedimentary environment. This fact has allowed us to develop precise palaeoenvironmental reconstructions. The variations of the identified ostracod assemblages, defined by species such as Cyclocypris laevis, Ilyocypris bradyi, Ilyocypris gibba, Limnocythere sp. or Pseudocandona parallela, record the development of small, ephem-eral and shallow ponds in a distal alluvial and/or floodplain environment. Towards the upper part of the section the ponds appear to be less ephemeral, being the aquatic systems more stable for ostracods development. Variations in the water temperature and salinity have been observed along the section, which are related to changes in the local pluviometric regime. On the other hand, the presence of micromammals in one of the studied samples has allowed the precise dating of this section. Thus, the presence of Armantomys daamsi dates the Cenicero section as Agenian (lower Miocene), local zone Y2 (MN2).En este trabajo se realiza, por vez primera, un análisis paleoambiental y bioestratigráfico de los depósitos aluviales del Mioceno inferior de la sección de Cenicero (sector NO de la Cuenca del Ebro; N de la Península Ibérica), a partir de las asociaciones de ostrácodos y micromamíferos preservadas en estos materiales. Una de las principales características de esta sección es la inusual abundancia de ejemplares de ostrácodos no transportados, en comparación con otras secciones europeas de edad y ambiente sedimentario similares, lo que permite hacer inferencias paleoambientales precisas. La variación en las asociaciones de ostrácodos identificadas, defini-das por especies como Cyclocypris laevis, Ilyocypris bradyi, Ilyocypris gibba, Limnocythere sp. o Pseudocandona parallela, parece sugerir el desarrollo de pequeños cuerpos de agua dulce, someros y efímeros, enmarcados en un ambiente general aluvial distal y/o de llanura de inundación. Hacia techo de la sección, se registra una mayor permanencia temporal de estas acumulaciones y condiciones más estables y favorables del medio para el desarrollo de los ostrácodos. Así mismo, se observan variaciones en la temperatura y salinidad del agua a lo largo de la sección, que podrían estar relacionadas con cambios en el régimen pluviométrico local. La presencia de micromamíferos en uno de los niveles estudiados ha permitido obtener una datación precisa de la sección. Así, la aparición de Armantomys daamsi sitúa la sección de Cenicero dentro de la zona local Y2 (MN2) de edad Ageniense (Mioceno inferior)

Aproximación al registro paleoambiental de la cueva de Goikoetxe (Busturia): Evidencias sedimentarias y paleontológicas

Aproximación al registro paleoambiental de la cueva de Goikoetxe (Busturia): Evidencias sedimentarias y paleontológica