Los Menucos Group. Stratigraphic redefinition of the Upper Triassic f rom the Northpatagonian Massif

El Grupo Los Menucos incluye ignimbritas dacíticas y riolíticas ,lavas y tobas riolíticas, conglomerados yareniscas. El Grupo está compuesto por dos entidades: Formación Vera y Sierra Colorada; la primera de ellas (la más antigua) se integra con areniscas fosilíferas y flujos piroclásticos dacíticos; la segunda (la más moderna) comprende principalmente rocas riolíticas. En años recientes se avanzó en forma significativa en el conocimiento Iitoestratigráfico de estas unidades, lo cual permite su redefinición de acuerdo con el Código Argentino de Estratigrafía.Los Menucos Group includes Upper Tria ssic ignimbrites dacites, conglomerates, sandstones a nd pyroclastic acidic rocks (rhyolites). This group is composed by the Vera Formation (tbe lower unit) and the Sierra Colorada Formation (the upper unit); the form er includes fosi liferous sa nd stone and pyroclastic dacitic flux es, and the second one is mainly composed by rhyolitic rocks. In recent years, there has been a significant prog ress of knowledge of these lithoestratigraphical units, which favored their redefinitions according with the Argentine Stratigraphic Code.Fil: Labudia, Carlos Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Bjerg, Ernesto Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; Argentin

Paleontología y ambientes del Triásico Medio en el sector noroccidental de la cordillera ibérica (provs. de Soria y Guadalajara, España)

El Triásico Medio del sector noroccidental de la Cordillera Ibérica está compuesto por dos formaciones carbonáticas, que se corresponden con la unidad carbonática superior del Muschelkalk, y que hacia el NW pasan lateralmente a una formación terrígena. El registro fósil se encuentra en ambos tipos de formaciones. Tanto el estudio tafonómico como sedimentológico, permiten inferir la presencia de elementos acumulados que podrían corresponder a asociaciones autóctonas, compuestas en su mayoría por bivalvos infaunales de medios marinos someros y sometidos a fuerte influencia de terrígenos. Se caracterizan en la zona tres asociaciones faunísticas: 1. Asociación CostatoriaLyriomyophoria, que aparece tanto en la formación carbonática inferior como en la formación terrígena equivalente; 2. Asociación «Fauna de Terue!», que aparece en la formación carbonática superior, y 3. Asociación Lingula-Pseudocorbula, que aparece también en la formación carbonática superior, pero en niveles más altos. La «Fauna de Terue!» es característica de la Formación «Dolomías, Margas y Calizas de Royuela», y está bien representada en toda la Cordillera Ibérica. La presencia de la misma en nuestra zona constituye el registro más noroccidental de esta asociación en la misma. Por tanto, significa la penetración más occidental en la península de las faunas endémicas del «Dominio Sefardí» durante el Ladiniense.The Triassic of the NW Iberian Ranges consists of two carbonatic formations equivalent to the Upper Carbonatic Formation of the Muschelkalk Facies and pass laterally into siliciciastic deposits to the NW. Fossillocalities have been found in both formations. Taphonomic and sedimentologic studies allow for the interpretation as autochthonous associations of the infaunal Bivalves of shallow water marine environments with siliciciastic input. Three faunal associations have been distinguished: 1. Costatoria-Lyriomyophoria association, found in the lower carbonatic formation and the equivalent siliciciastic formation; 2. «Teruel Fauna» association, found in the upper carbonatic formation; 3. Lingula-Pseudocorbula association, found near the top of the upper carbonatic Formation. The «Teruel Fauna» is well represented in the Iberian Ranges, and always occur in the «Royuela Marls and Limestones» Formation, and our fossil localities are its most Northwestern record in the Iberian Ranges up to now, thus extending the presence of the endemic «Sephardic Faunas» during the [email protected]

Las unidades litoestratigráficas del Pérmico y Triásico Inferior y Medio en el sector de la Cordillera Ibérica

Se definen formalmente las unidades litoestratigráficas que constituyen el Pérmico y Triásico del SE de la Cordillera Ibérica representados en Facies Muschelkalk, Buntsandstein y Saxoniense. El rango definido para las unidades es de Formación, algunas de las cuales han sido a su vez subdivididas en Miembros. El conjunto total es de nueve Formaciones y catorce Miembros que constituyen dos Grupos subdivididos en dos Subgrupos cada uno. Los pasos seguidos para estas definiciones se han basado en las sugerencias de la Guía Estratigráfica Internacional redactadas por la Subcomisión Internacional de Clasificación Estratigráfica (ISSC, 1976). Se incluye en este trabajo una extensa revisión bibliográfica general para el Pérmico y Triásico del SE de la Cordillera Ibérica así como individualmente para cada formación, haciéndose un estudio de la evolución de cada unidad en su contexto sedimentario y tectónico. Finalmente, se realiza una discusión donde se exponen algunos de los principales problemas estratigráficos, sedimentológicos y tectónicos resueltos hasta el momento y otros que aún quedan por resolver. [ABSTRACT] The lithostratigraphic units of the Permian and Triassic SE Iberian Ranges represented in Muschelkalk, Buntsandstein and Saxonian Facies are formally described. The range of definition for the units is the Formation and sorne of these have been also subdivided into Members. The whole of these units constitute two Groups subdivided into two Subgroups each one. This work has followed for the definitions the suggestions of the International Stratigraphic Guide published by the International Subcommission on Stratigraphic Classification (ISSC, 1976). The evolutive study of each unit (formation or member) include their sedimentary and tectonic context and a general and extensive bibliographical review for the Permian and Triassic of the SE Iberian Ranges. Finally, it is included a discussion of sorne of the main stratigraphical, sedimentological and tectonical problems resolved until now as well as others not solved up to now

Propuesta de un sistema de informatización de la gestión de colecciones paleontológicas

This document was first presented to and distributed through the attendants to a Working Session of the V Jornadas de Paleontología (Valencia, november 1989) and has remained unpublished since then. By the end of 1991 a standard basic inventory card for the informatic management of palaeontological collections in Spain (Gallemí et al., 1993) was established. As this management system employs many of the codes originally stated in the former document, its publication becomes necessary and so we do in a thorough and –consequently– non updated way. Key words: Palaeontology, Collections, Management, Informatics, Spain.El presente documento fue presentado y distribuido a los participantes en una Sesión de Trabajo de las V Jornadas de Paleontología (Valencia, noviembre 1989), permaneciendo inédito desde entonces. A finales de 1991 se homologó en España una ficha básica de inventario para la gestión informática de colecciones paleontológicas (Gallemí et al., 1993). Al utilizar dicho sistema de gestión buena parte de los códigos postulados originalmente en aquel documento, se ha estimado conveniente la publicación del mismo que se hace de manera íntegra y –consecuentemente– no actualizada. Palabras clave: Paleontología, Colecciones, Gestión, Informática, España

The Triassic-Jurassic boundary in eastern North America

Rift basins of the Atlantic passive margin in eastern North America are filled with thousands of meters of continental rocks termed the Newark Supergroup which provide an unprecedented opportunity to examine the fine scale structure of the Triassic-Jurassic mass extinction in continental environments. Time control, vital to the understanding of the mechanisms behind mass extinctions, is provided by lake-level cycles apparently controlled by orbitally induced climate change allowing resolution at the less than 21,000 year level. Correlation with other provinces is provided by a developing high resolution magnetostratigraphy and palynologically-based biostratigraphy. A large number of at least local vertebrate and palynomorph extinctions are concentrated around the boundary with survivors constituting the earliest Jurassic assemblages, apparently without the introduction of new taxa. The palynofloral transition is marked by the dramatic elimination of a relatively high diversity Triassic pollen assemblage with the survivors making up a Jurassic assemblage of very low diversity overwhelmingly dominated by Corollina. Based principally on palynological correlations, the hypothesis that these continental taxonomic transitions were synchronous with the massive Triassic-Jurassic marine extinctions is strongly corroborated. An extremely rapid, perhaps catastrophic, taxonomic turnover at the Triassic-Jurassic boundary, synchronous in continental and marine realms is hypothesized and discussed

Los arenales costeros de la isla de Menorca

The grain size of Menorca coastal sediment varies from very Fine to granule grade. The mean oscillates between 200-300p in the sand of Migjorn region and between 250-450p in the Tramuntana beaches, except for two cases in which [he grain size is bigger. The amount of carbonates of the sand examiiied is in some beaches very liigh, over 80 %. and the samples are very poor in heavy minerals. The heavy fraction is characterized by the highest values of opaque minerals. Dolomite and piroxenes are dominant among the heavy transparent minerals and rircon, tourmaline and garnet are always present in the :amples examined: biotite. nitile, epidote-zoisite and andalucite may also appear but only in some beache

Cuencas triásicas del Oeste argentino: origen y evolución

The Triassic basins of western Argentina and northern Patagonia are located along fhe Pacific margin of Southwest Gondwana. They are narrow and elongated depressions oriented NW-SE, floored by a thick continental crust composed of Precarnbrian and Lower Palaeozoic magmatic rocks, and an Upper Palaeozoic plutonic-volcanic complex (Gondwana Magmatism). These basins are associated with the Choiyoi Magmatic Province, the Central Patagonian Batholith and the Comallo Volcanic Complex. For the Triassic of western Argentina the following stages are recognised: Barrealian (Early to Mid Triassic), Cortaderitian (Mid to early Late Triassic) and Florian (Late Triassic). During the Barrealian severa1 passive rfts are opened (Ischigualasto - Villa Unión, Marayes, Las Salinas - Beazley, Cuyo and the short-lived San Rafael basins). They are characterised by a synrift phase related to the activity of the main fracture systems along the active flank of the half-grabens, high accommodation space and frequent coarsegrained sediment supply (usually vocaniclastic) from the active margins. Intercalations of basic lava flows are common. In the Cortaderitian protracted extension, maximum regional development of the Triassic bgsins occurred. Most basins were controlled by thermal-tectonic subsidence. High accommodation space, limited coarse-grained cbntributions and high lacustrine base levels are the more characteristic conditions for basin sedimentary infill. In the Florian stagelthe Ischigualasto-Villa Unión, the Marayes and the Cuyo basins are characterised by fluvial-dominated red-bed successions, related to a transtensional stage of evolution. Several half-grabens (Malargüe, Paso Flores and Chacaico) are opened as precursors of the Neuquén Basin. In northwestern Patagonia, the combInation between regional strike-slip displacement along the Gastre Fault System and protopacific subduction, causes the development of the arc magmatism represented by the Central Patagonian Batholith and the thick volcano-sedimentary Comallo complex