Constructive micrite envelope developed in vadose continental environment in pleistocene eoliantes of Mallorca (Spain)

In this study we analyze and explain the formation of the constructive micrite envelope in the vadose continental environment. This constructive micrite envelope shows a wide variety of textural components. The principal textural components are: microorganisms, micritic and microspar LMC cement, whisker crystals, microfibres and aggregates of LMC acicular crystals. The main microorganisms are hyphae fungi, although actynomicetes and bacteries also occur. The constructive micrite envelope is due to the action of calcified filaments (hyphae fungi) which collapse and coalesce forming an intertwined mesh as well as due to the precipitation of micritic and microspar cement. The whisker crystals, microfibres and aggregates of LMC acicular crystals are secondary microtextures. Constructive micrite envelopes does not indicate a specific diagenetic environment. The constructive micrite envelopes present irregularities or bumps at the outer surface of the grains, and the destructive micrite envelopes present irregularities towards the grain interior. This morphologic criterion is useful to differenciate the micrite envelope origin, constructive or destructive, in the fossil record

Evolución diagenética en los sedimentos carbonatados marinos del Pleistoceno de Mallorca

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Nota previa sobre el analisis comparativo de elementos traza en las aguas de escorrentia superficial, como indicadores de la acción alterante de microorganismos

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La plataforma carbonatada epeírica (Formaciones Imón e Isábena) del Triásico superior del Noreste de la Península Ibérica

Las principales unidades litoestratigráficas localizadas en el límite Triásico/Jurásico del noreste de la Península Ibérica son las facies Keuper, los carbonatos de la Formación Imón/Formación Isábena y las dolomías, evaporitas y lutitas de la Formación Carniolas de Cortes de Tajuña/Zona de Anhidrita. Los carbonatos del Triásico superior son conocidos como Formación Imón en la Cordillera Ibérica, Cordilleras Costero Catalanas y Depresión del Ebro y como Formación Isábena en la vertiente surpirenaica. La asociación de foraminíferos (Gandinella falsofriedli, Aulotortus friedli, Trochammina jaunensis, Agathammina austroalpina, Trocholina cf. laevis y Trocholina crassa) localizada en la base de la Formación Imón y de la Formación Isábena determina una edad Alauniense terminal-Sevatiense medio (Noriense superior). La asociación de bivalvos (Neoschizodus reziae, Pseudocorbula alpina, Protocardia cf. Rhaetica y Laternula cf. amicii) localizada en la parte alta de la Formación Imón indica un “Retiense” (Noriense p.p.). La Formación Imón está constituida básicamente por dolomías bien estratificadas, mientras que la Formación Isábena está formada por calizas. La Formación Imón presenta dos tipos de dolomías: dolomías grises en la base y dolomías blancas a techo. A partir del estudio petrológico, mineralógico, de elementos traza e isótopos de oxígeno y de carbono de las dolomías, se ha establecido que las dolomías grises son de origen “seepage-reflux” y las dolomías blancas de origen hipersalino. Las curvas de isopacas de la Formación Imón son redondeadas a elongadas y presentan pendientes muy suaves, lo cual sugiere que la sedimentación de esta plataforma carbonatada estuvo controlada por la subsidencia termal. El modelo sedimentológico de los materiales carbonatados de la Formación Imón y de la Formación Isábena es el de una plataforma carbonatada epeírica.The lithostratigraphic units associated with the Triassic/Jurassic boundary in the northeast of the Iberian Peninsula are the Keuper evaporites and lutites, the Imón Formation/Isábena Formation carbonates and the Cortes de Tajuña Formation/Anhidrite zone evaporites, dolomitic breccias and lutites. The upper Triassic carbonates are known as the Imón Formation in the Iberian Ranges, the Catalan Coastal Ranges and the Ebro Depression, and as the Isábena Formation in the southern Pyrenees. The foraminifera associations (Gandinella falsofriedli, Aulotortus friedli, Trochammina jaunensis, Agathammina austroalpina, Trocholina cf. laevis and Trocholina crassa), which are located in the lower part of the Imón and Isábena sections, indicate a late Alaunian-mid Sevatian (late Norian) age. The bivalve associations (Neoschizodus reziae, Pseudocorbula alpina, Protocardia cf. rhaetica and Laternula cf. amicii), located in the uppermost part of the Imón Formation indicate a “Rhaetian” (Norian p.p.) age. The Imón Formation consists of stratified dolomites whereas the Isábena Formation is made up of limestones. The Imón dolomites present two dolomites types: grey dolsparites and white dolmicrites. These dolomites are interpreted as seepage-reflux (grey dolomites) and hypersaline dolomites (white dolomites) according to with their mineralogy, elemental geochemistry and stable isotope characteristics. The isopach curves are round to elongated with very gentle slopes, indicating that thermal subsidence played the main role in controlling the sedimentation of this upper Triassic carbonate platform. The sedimentary model of the Imón Formation and the Isábena Formation is an epeiric carbonate platform

Stratigraphy and petrology af the miocene Montjuïc delta (Barcelona, Spain)

The Neogene rift in the Catalan Coastal Ranges, which is located in the NE part of the Eastern Iberian Margin, corresponds to a system of grabens formed at the north-western edge of the Valencia Trough. In the central part of the Catalan Coastal Ranges are the Vallès - Penedès half-graben in the onshore and the Barcelona half-graben in the offshore, which are separated by the Garraf and the Collserola-Montnegre horsts. Montjuïc hill is a tilted block, which is located to the S of the Barcelona city, between the Collserola-Montnegre horst and the Barcelona half-graben . The Middle Miocene section of Montjuïc is constituted by an alternation of conglomerate, sandstone, mudstone and marlstone beds. The Montjuïc section was divided into four lithostratigraphic units from base to top: (1) The Morrot conglomerate and sandstone Unit, interpreted as delta plain deposits; (2) the Castell conglomerate, sandstone and mudstone Unit considered as proximal delta front deposits; (3) the Miramar marlstone Unit attributed to prodelta deposits; and (4) the Mirador conglomerate, sandstone and mudstone Unit interpreted as delta front deposits. As regards the foraminifera association, the Miocene of Montjuïc may be attributed to the N9-N10 zones of Blow, indicating a Serravallian age. The palaeobotanical record suggests that the climate during the deposition of the Miocene of Montjuïc was temperate-warm and humid. The sandstones and conglomerates are litharenites and lithorudites; they show variable amounts of matrix and are well cemented. The main framework components are quartz, rock fragments and K-feldspar. The Collserola mountain, where Palaeozoic materials crop out is the deduced source area. Montjuïc sandstones are characterized by an early silicic cementation consisting of K-feldspar overgrowths, quartz overgrowths, mesoquartz intergranular cement and a microquartz transformation of a former detrital matrix. A surface cementation is considered for these cements in the absence of compaction and the geological setting.Peer ReviewedPostprint (published version

Silicification superficielle et précose d'une formation deltaïque: les grès néogènes de Montjuïc, Barcelone, Espagne

Peer ReviewedPostprint (published version