Pisolitos ferruginosos en el Mioceno inferior-medio de Mallorca

El registro sedimentario Burdigaliense-Langhiense de Mallorca refleja el relleno de pequeños surcos de antepaís que se generaron por subsidencia flexural frente al orógeno bético. Este registro sinorogénico incluye una unidad inferior que caracteriza la sedimentación en una plataforma marina somera (Fm. Sant Elm) y otra superior turbidítica (Fm. Banyalbufar). En el límite entre ambas unidades se ha reconocido, en la zona central de la isla, la existencia de un nivel de pisolitos ferruginosos de menos de 20 cm de potencia. Los pisolitos llegan a superar los 6 mm de diámetro, son esféricos y están constituidos casi exclusivamente por delgadas envueltas concéntricas de goethita, aunque en los pisolitos de mayor tamaño alguna envuelta es de calcita. La posición estratigráfica del nivel de pinolitos coincide, aproximadamente, con el límite entre las dos unidades anteriormente citadas, localizándose inmediatamente antes del inicio de la sedimentación turbidítica, y se correspondería con el máximo transgresivo en la cuenca marina. Tanto el vulcanismo Burdigaliense que ha sido reconocido en la zona como la removilización de suelos lateríticos en relación con la transgresión marina pudieron haber actuado como fuentes suministradoras del hierro.The syn-orogenic Early-Middle Miocene of Mallorca constitutes a sequence which records the deepening and infill of small fore-deeps related to flexural subsidence caused by the Betic orogene thrusting. In the syn-orogenic Miocene of the central part of the island, a pisolitic iron bed less than 20 cm thick is first described in order to their stratigraphic, environmental and palaeogeographic significance. The pisolites are highly sphaerical and range from less than 0.25 to more than 6 mm in size. They are formed by concentric thin laminae (< 100 m) of goethite. The largest-sized pisolites also contain calcite laminae. The pisolitic bed is approximately located in the boundary between the shallow marine platform and the deeper turbidite deposits, recording the basin deepening and the maximum marine transgression. Both, the Burdigalian volcanism described in the zone as well as the removilization of continental lateritic soils by marine transgression are invoked as the probable iron sources

Palaeogene Charophytes of the Balearic Islands (Spain)

Fossil charophytes were recorded in two different stratigraphic units from the non- marine Palaeogene of the Balearic Islands. In the Peguera Limestone Fm. of Mallorca the charophyte flora is characterised by two assemblages. The first contains Raskyella peckii subsp. meridionale, Harrisichara caeciliana and Maedleriella mangenoti, from the Bartonian and Lutetian; whilst the second is characterised by Harrisichara vasiformistuberculata and Nitellopsis (Tectochara) aemula, Middle Priabonian in age. The Cala Blanca Detrital Fm. has yielded Lychnothamnus stockmansii and Sphaerochara inconspicua in Menorca whilst in Mallorca it contains Lychnothamnus praelangeri, L. langeri and Sphaerochara hirmeri. This flora is Late Priabonian and Oligocene in age. These results suggest that the beginning of Paleogene non-marine deposition was diachronic in Mallorca. In terms of biogeography, the Eocene charophytes of Mallorca show affinity with North-African floras. The presence of the Eocene African subspecies Raskyella peckii meridionale in Mallorca enables the biogeographic boundary between this form and the European subspecies R. peckii peckii to be drawn at about 32º N latitude in the Iberian Plate

Unlocking the correlation in fluvial outcrops by using a DOM-derived virtual datum: Method description and field tests in the Huesca fluvial fan, Ebro Basin (Spain)

Adequate characterization of depositional architecture is of great importance when studying fluvial outcrops as reservoir analogs. The complex three-dimensional (3D) distribution and lateral and vertical relationships of sandstone bodies require a high degree of stratigraphic control in order to make a proper assessment of the distribution and connectivity of the reservoir facies. This assessment demands the use of reliable correlation datums. Unfortunately, clear marker beds (e.g., ash layers, coal beds, and paleosols) are not always available in fluvial outcrops, and when present, they are often covered by vegetation or debris that prevents their tracking over long distances. A new method to achieve highly accurate and semiautomatic correlations within fluvial digital outcrop models (DOMs) is presented in response to the need for further correlation procedures, especially in the absence of suitable datums. The method is based on the hypothesis that the average depositional paleosurface of a sedimentary system can be represented by a plane at outcrop scale. If this assumption is valid, this plane can be used as a virtual datum to identify along the DOM the sediments that were deposited simultaneously. The method was tested and applied successfully within two kilometer-scale outcrops of the Huesca fluvial fan (Early Miocene, northern Spain), where the virtual datum provided accurate correlations regardless of stratigraphic or topographical complexities. Moreover, all the sedimentary successions of the outcrops could be automatically subdivided into the desired stratigraphic intervals by only moving the virtual datum vertically. These intervals can be subsequently isolated to facilitate the detection of subtle variations and trends of their fluvial properties. Consequently, a virtual datum is the equivalent of having a marker bed crossing the stratigraphic succession of an outcrop at any desired position. The advantages provided by a virtual datum prove to be especially useful in large and topographically complex outcrops that previously could not have been studied with such a high degree of 3D stratigraphic control

Estratigrafía y sedimentología del Paleógeno de la Sierra de Tramuntana (Mallorca)

El Paleógeno aflorante en la Sierra de Tramuntana muestra la existencia de dos unidades litoestratigráficas principales: la inferior (Fm. Calizas de Peguera) está constituida predominantemente por materiales carbonatados lacustres, con depósitos carbonosos en su base, un nivel intermedio de sedimentos detríticos fluviales y una intercalación marina a techo, mientras que la unidad superior (Fm. Detritica de Cala Blanca) registra la evolución lateral de un sistema detrítico fluvio-aluvial con paleocorrientes hacia el SE, progradante sobre una unidad basal de calcarenitas marinas

Sistemas lacustres paleógenos de Mallorca (Mediterráneo Occidental)

Dos importantes sistemas lacustres-palustres se desarrollaron durante el Paleógeno en las Baleares. En el primero de ellos, de edad Bartoniense (Eoceno medio), se formó una importante acumulación de sedimentos carbonatados biogénicos y organógenos (lignitos). La organización megasecuencial de las sucesiones lacustres registra la siguiente evolución del sistema: 1) implantación de los medios lacustres, 2) expansión y relativa profundización, 3) colmatación por progradación de los depósitos de las zonas marginales del sistema sobre las internas y 4) etapa final, dominantemente agradante, con un pronunciado equilibrio entre las tasas de sedimentación y subsidencia. El segundo sistema, de edad oligocena (Estampiense superior- Chatiense), esta constituido por una asociación de depósitos lacustres y palustres relacionados con facies distales de un sistema aluvial. Por ello, el aporte de materiales detriticos finos al sistema lacustre jugó un papel primordial; aunque en las zonas mis protegidas de las cubetas lacustres, la acumulación de carbonatos biogénicos y la de maicriaorginica fue también importante. Su evolución megasecuencial sugiere las siguientes fases: 1) implantación en zonas terminalesdistales del sistema aluvial, 2) expansión e implantación de depocentros carbonatados, y 3) colmatación final relacionada con la progradación de las zonas terminales del sistema aluvial. Ambos  sistemas lacustres indican el desarrollo de etapas de estratificación permanente u ocasional de la columna de agua. Ello permitió  lapreservación de materia orgánica derivada de macrófitos superiores y de organismos algales y bacterias

Estratigrafía y sedimentología del Paleógeno de la Sierra de Tramuntana (Mallorca)

El Palegeóno aflorante en la Sierra de Tramuntana muestra la existencia de dos unidades litoestratigráficas principales: la inferior (Fm. Calizas de Peguera) está constituida predominantemente por materiales carbonatados lacustres, con depósitos carbonosos en su base, un nivel intermedio de sedimentos detríticos fluviales y una intercalación marina a techo, mientras que la unidad superior (Fm. Detritica de Cala Blanca) registra la evolución lateral de un sistema detrítico fluvio-aluvial con paleocorrientes hacia el SE, progradante sobre una unidad basal de calcarenitas marinas

Estructura y relleno sedimentario de la semifosa neógena de Vilanova (Garraf, Barcelona)

A joint study involving geological mapping, well subsurface data and gravity modelling has been carried out in the Vilanova half graben in order to define the substralum structure and the character of the sedimentary in fill.The half graben is oriented following a regional ENE-WSW fault direction. Its structure is controlled by normal faults along the NW boundary and by an unconformity in the SE basin boundary. A perpendicular to the main direction fault system, configurate a block shaped hasement. From the residual gravity map a 3D density model, constrained with the depths infered kom bore oles, has been obtained. The sedimentary infill has been divided in four litostratigraphic units. One of them constitutes a marginal complex associated and genetically related with the main faults that bound the basin. The otber three units show a vertical evolution from continental alluvial environrnent at the bottom to marine (littoral and restricted shelf-bay) at tbe top.The paleomastological data allow ps to attribute to the autcropping sedimentary infill a Serravallian age. Nevertheless, an Aquitanian-Early Burdigalian age to the basal conglomeratic unit can't be definitively rejected

Icnología de vertebrados de la facies Buntsandstein de Mallorca

Se describen, por primera vez en Mallorca, hasta cinco tipos diferentes de icnitas y pistas de vertebrados continentales dentro de las facies  cuarzoareniticas y limosas rojas de la facies Buntsandstein del Triásico inferio

Detailed Studies of IPHAS sources. II. Sab 19, a true planetary nebula and its mimic crossing the Perseus Arm

The INT Photometric H$\alpha$ Survey (IPHAS) has provided us with a number of new-emission line sources, among which planetary nebulae (PNe) constitute an important fraction. Here we present a detailed analysis of the IPHAS nebula Sab\,19 (IPHASX\,J055242.8+262116) based on radio, infrared, and optical images and intermediate- and high-dispersion longslit spectra. Sab\,19 consists of a roundish 0.10 pc in radius double-shell nebula surrounded by a much larger 2.8 pc in radius external shell with a prominent H-shaped filament. We confirm the nature of the main nebula as a PN whose sub-solar N/O ratio abundances, low ionized mass, peculiar radial velocity, and low-mass central star allow us to catalog it as a type III PN. Apparently, the progenitor star of Sab\,19 became a PN when crossing the Perseus Arm during a brief visit of a few Myr. The higher N/O ratio and velocity shift $\simeq$40 \kms\ of the external shell with respect to the main nebula and its large ionized mass suggest that it is not truly associated with Sab\,19, but it is rather dominated by a Str\"omgren zone in the interstellar medium ionized by the PN central star.Comment: 12 pages, 8 figures, accepted for publication in MNRA

Sedimentology of a 'non-actualistic' Middle Ordovician tidal-influenced reservoir in the Murzuq basin (Libya)

The subsurface of the highly productive Murzuq Basin in southwest Libya remains poorly understood. As a consequence, a need exists for detailed sedimentological studies of both the oil-prone Mamuniyat Formation and Hawaz Formation reservoirs in this area. Of particular interest in this case is the Middle Ordovician Hawaz Formation, interpreted as an excellent example of a 'nonactualistic,' tidally influenced clastic reservoir that appears to extend hundreds of kilometers across much of the North African or Saharan craton. The Hawaz Formation comprises 15 characteristic lithofacies grouped into 7 correlatable facies associations distributed in broad and laterally extensive facies belts deposited in a shallow marine, intertidal to subtidal environment. Three main depositional sequences and their respective systems tracts have also been identified. On this basis, a genetic-based stratigraphic zonation scheme has been proposed as a tool to improve subsurface management of this reservoir unit. A nonactualistic sedimentary model is proposed in this work with new ideas presented for marginal to shallow marine depositional environments during the Middle Ordovician in the northern margin of Gondwana