Cambrian sponge spicules and Chancelloriid sclerites from the Argentine Precordillera : a Review

Spicules of sponges and sclerites of chancelloriids have been collected from in situ Cambrian sections of the La Laja Formation (San Juan Precordillera). They have also been collected from carbonate olistoliths, which were emplaced from the Cambrian units in the Early Ordovician Los Sombreros Formation (San Juan Precordillera) and Empozada Formation (Mendoza Precordillera). The Cambrian La Laja Formation sequences were deposited in a shallow carbonate platform in the eastern part of the Precordillera. The Cambrian carbonate rocks, which make up the olistoliths in the Los Sombreros and Empozada Formations, record deposition in the slope environments which developed in the western Precordillera. Cambrian Porifera and sponge-like chancelloriid assemblages are known mainly from fragments of skeletal nets, dissociated spicules and sclerites, which enable us to define two assemblages. The first assemblage of spicules was defined from the upper Lower to Middle Cambrian sequences of the La Laja Formation. This assemblage consists of a variety of stauractines and sclerites of Chancelloria WALCOTT. The family Protospongiidae is represented by triradiate prodianes, pentactines and hexactines, all belonging to Kiwetinokia WALCOTT. The second assemblage, which consists of isolated hexactines, pentactines, monaxons and skeletal nets, was defined in the Cambrian derived olistholiths of the Los Sombreros and Empozada Formations. Early hexactinellid Protospongiidae with body preservation (Diagoniella ? and Kiwetinokia) also occur. Demosponges have a very limited record in the Cambrian of the Precordillera. Anthaspidellid sponges had been reported from the La Laja Formation and now from the San Martín olistolith (Empozada Formation). The occurrences of these two assemblages of spicules and sclerites in both the Cambrian platform and slope facies of the Precordillera contribute additional data for a better understanding of the relationships between the eastern and the western facies assemblages, which developed in the Precordillera during the Cambrian. Therefore, they are useful for paleoenvironmental and paleogeographical interpretations of the Cambrian depositional framework

Oxfordian sponge association from the Neuquén basin, Mendoza,west central Argentina

This paper describes an Upper Jurassic association of siliceous sponges from the Neuquén basin, southern Mendoza province, at Ŕo Potimalal. Wackestones crop out in this stratigraphic section, and massive sponge-bearing micritic limestones of the La Manga formation (Plicatilis zone) have been deposited in outer shelf to slope settings. Sponges are regularly preserved as whole bodies. Their skeletons are mostly calcified, but the skeletal siliceous structure is sometime preserved. The siliceous sponges belong to the Order Hexactinosa (Class Hexactinellida, Subclass Hexasterophora) (Laocoetis sp., L. parallela, L. procumbens, Cribrospongia sp., C. clathrata, C. cucullata, Ordinatus sp., Linonema calyx ) and Lyssakinosa (Poligonatyum sphaeroides). The majority of the sponge specimens correspond to the Families Cribrospongiidae (genus Cribrospongia) and Laocoetidae (genus Laocoetis). The Upper Jurassic carbonates are interpreted as deposits of a highstand systems tract, similar to other Oxfordian sequences found around the world. © 2003 Elsevier Ltd. All rights reserved.El presente trabajo describe una asociación de esponjas silíceas de la cuenca Neuquina, en el sur de la provincia de Mendoza, en la sección del Río Potimalal. En esta sección afloran wackestones y calizas micríticas masivas con esponjas de la Formación La Manga (Zona de Plicatilis) depositadas en ambiente de plataforma externa y talud. Las esponjas están regularmente preservadas como cuerpos enteros. La estructura espicular silícica se ha preservado en algunos especímenes aunque generalmente está calcificada. Las esponjas silíceas pertenecen a la Clase Hexactinellida, Subclase Hexasterophora, Order Hexactinosa (Laocoetis sp., L. parallela, L. procumbens, Cribrospongia sp., C. clathrata, C. cucullata, Ordinatus sp., Linonema calyx) and Order Lyssacinosa (Poligonatyum sphaeroides). La mayorı´a de los especímenes corresponden a la Familia Cribospongiidae, género Cribospongia y a la Familia Craticularidae, género Laocoetis. Se interpreta que los carbonatos del Jurásico superior se depositaron durante un estadio de mar alto, similar a otras secuencias oxfordianas del mundo.Fil: Beresi, Matilde Sylvia. Ministerio de Relaciones Exteriores, Comercio Internacional y Culto. Direccion Nacional del Antártico. Instituto Antártico Argentino. Instituto Antártico Argentino - Sede Cricyt (Mendoza); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin

Upper Ordovician cryptostomatid bryozoans and microfossils from the Don Braulio Formation, Eastern Precordillera, Argentina

En la clásica sección de la Quebrada de Don Braulio, en la Precordillera Oriental de la Provincia de San Juan, afora la Formación Don Braulio de edad hirnantiana. Fragmentos de colonias de Bryozoos,algunas espículas de esponjas mal conservadas y una placa de crinoideos, fueron recuperados de los sedimentos silicoclásticos de esta formación. Los restos de las colonias de briozoos se caracterizan por su hábito de crecimiento erecto, su diámetro pequeño y por la presencia de estriaciones longitudinales. Estos fragmentos tienen una pobre preservación, sin embrago los mismos han sido comparados con el género Nematopora perteneciente a la familia Arthrostylidae (suborden Rhobdomesina, orden Cryptostomata), que tuvo numerosos representantes durante el Ordovícico. Escasas y fragmentadas espículas de esponja hexactinéllidas y otros tipos de microfósiles también han sido recuperados de los depósitos post-glaciales de la Formación Don Braulio.In the classical section of the Don Braulio Creek at the Villicum Range, Eastern Precordillera of San Juan Province, crops out the siliciclastic Don Braulio Formation of Hirnantian age. Fragments of bryozoan colonies, few poorly preserved sponge spicules and a crinoidal plate, were recovered from these shelf sedi-ments. The bryozoan colonies remains are characterized by its erect growth habit, its small diameter, and for showing clear longitudinal striations. These fragments have a poor preservation, but they have been compared with the genus Nematopora belonging to the Arthrostylidae family (Rhobdomesina suborder, Cryptostomata order), that had numerous representatives during the Ordovician. Very scarce and highly fragmented sponge spicules are classifed as hexactins. These microfossils have been recovered in the post-glacial deposits from the Don Braulio section at the Villicum range.Fil: Jiménez Sánchez, Andrea. University of West Bohemia; República ChecaFil: Beresi, Matilde Sylvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Mestre García, Ana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Investigaciones Mineras; ArgentinaFil: Heredia, Susana Emma. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Investigaciones Mineras; Argentin

Middle Cambrian protospongiid sponges and chancelloriids from the Precordillera of Mendoza Province, western Argentina.

A Middle Cambrian faunule from different sections of the San Isidro region, Precordillera of Mendoza Province, western Argentina, include previously unrecorded and new material. Specimens in the collections are simple reticulosan hexactinelliid determined as Diagoniella cf. cyathiformis, Diagoniella sp., (?) Diagoniella sp., indeterminate protospongioid spicule assemblages and several root tuft types. In addition a possible scleritome of Chancelloria cruceana Rusconi, 1954 is redescribed and figured and scleritos assigned to Allonia and Archiasterella are here described for the first time.Fil: Beresi, Matilde Sylvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Rigby, J. Keith. Brigham Young University. Department of Geological Sciences; Estados Unido

Darriwilian Conodont Biostratigraphy of the Las Chacritas Formation, Central Precordillera (San Juan Province, Argentina)

The Las Chacritas Fm in the type section in the Sierra de La Trampa, Central Precordillera (San Juan Province) was deposited in an outer carbonate ramp setting that evolved from relatively deep to shallow water. Samples from this well-exposed Middle Ordovician section yielded collections of low-diversity conodont faunas stratigraphically significant. The top of the underlying San Juan Fm and the lower and middle parts of the Las Chacritas Fm contain conodonts representative of the Lenodus variabilis Zone, and the upper part of the Las Chacritas Fm yields conodonts that correlate with the Paroistodus horridus subzone of the upper part of the Lenodus variabilis Zone. The occurrence of Dzikodus tablepointensis and Eoplacognathus pseudoplanus in the upper part of the Paroistodus horridus subzone is especially significant. The occurrence of Histiodella kristinae in the highest levels indicates that the top of the Las Chacritas Fm correlates with the Eoplacognathus suecicus Zone. Conodont biofacies are analyzed trough the entire section, supporting an outer platform or open sea conditions. Baltic and Sino-Pacific affinities are stated

A Probabilistic Automaton for the Dynamic Relevance Judgement of Users

Conventional information retrieval (IR) evaluation relies on static relevance judgements in test collections. These, however, are insufficient for the evaluation of interactive IR (IIR) systems. When users browse search results, their decisions on whether to keep a document may be infuenced by several factors including previously seen documents. This makes user-centred relevance judgements not only dynamic but also dependent on previous judgements. In this paper, we propose to use a probabilistic automaton (PA) to model the dynamics of users' relevance judgements. Based on the initial judgement data that can be collected in a proposed user study, the estimated PA can further simulate more dynamic relevance judgements, which are of potential usefulness for the evaluation of IIR systems

Producción, significación y uso del espacio urbano de Valparaíso desde las acciones cotidianas de la cultura urbana

Las presentes líneas representan un esfuerzo de índole teóricometodológico que tiene por finalidad actualizar los códigos de interpretación y lectura de la compleja trama de significados urbanos que hoy constituye la ciudad de Valparaíso. De allí que se exponga, en un primer acápite, la mirada que, desde los estudios de las estéticas urbanas contemporáneas, se da a la fragmentación urbana. En particular, aquella visión que intenta reconocer en la diversidad de género un asunto central para la teoría y práctica urbanística actual. En este sentido, las temáticas abordadas en el presente texto buscan exponer las herramientas metodológicas y la generación de códigos de lectura, que permiten dar cuenta del acelerado proceso de cambios de la ciudad. La aproximación al tema de estudio ha sido caracterizada como cartografía, en tanto el proyecto implica un viaje por pasajes sinuosos que buscan haceros navegar en un imbricado, coqueto y a veces confuso camino, por territorios, discursivos, simbólicos y materiales, con el fin de establecer coordenadas que permitan caracterizar los “decires” y “haceres”, en nuestra ciudad. En fin, una cartografía, una brújula preliminar para movernos en la laberíntica forma de la ciudad de Valparaíso. Se pretende, siguiendo a Martín Barbero, desarrollar una lógica cartográfica que se vuelve fractal. En los nuevos mapas el mundo recupera la diversa singularidad de los objetos y se expresa de forma textual. Como se ha dicho los nuevos mapas cognitivos, pueden cartografiarse, por ejemplo, bajo la forma de archipiélago “lugar de diálogos y confrontación entre las múltiples tierras – islas que los entrelazan”. Pensar el archipiélago, es entonces indagar el nuevo tipo de logos que interconecta lo diverso. “Logos otro, en cuya raíz se hallan las profundas alteraciones perceptivas que atraviesa nuestra experiencia espacio / temporal”. En este sentido, la primera parte del proyecto, busca construir, mediante un breve recorrido por los territorios actuales de la investigación en urbanismo, una suerte de “cartografía cognitiva”4 sobre las principales problemáticas teóricas e investigativas del pensamiento urbanístico en los últimos años. El objetivo de la generación de un marco conceptual, es bosquejar un “orden del discurso”5, que permita establecer coordenadas al interior del difuso campo actual de los estudios sobre lo urbano. En América Latina la cartografía opera. Y lo hace en múltiples direcciones. Desde los planos turísticos de las ciudades – que nos aseguran ver lo que todos ven para que no haya desencuentros culturales- al mapeamiento de circuitos y trayectos que develan en las cibernéticas metrópolis actuales la existencia de ciudades invisibles: místicas esotéricas, vivenciales. Y desde las cartografías catastrales construidas desde arriba y, a las que nada escapa, como en el panóptico de Foucault. Mapas trazados no sólo sobre, sino también desde los márgenes. Porque también los márgenes urbanos se mueven siguiendo los derroteros de los marginales o los desplazados laborales, y también los trayectos nómades de las subculturas urbanas. En este sentido se hace referencia al orden y la fragmentación; y las múltiples entradas interpretativas para entender la realidad urbana de Valparaíso. Una cartografía, como la propuesta en el presente proyecto, implica un ejercicio de comprensión, de una parte de nuestra realidad (la ciudad), desde las múltiples perspectivas que han intentado aprehenderla. La ciudad, desde tiempos inmemoriales, ha sido considerada como objeto de observación por los hombres. Pero es en la modernidad donde el saber de la ciudad se transforma en un corpus de conocimiento sistemático, de la mano de las nacientes ciencias sociales y del urbanismo moderno

Related scientific information: a study on user-defined relevance.

This dissertation presents an investigation into the manifestations of relevance observed in the context of related scientific information. The main motivation is to observe if researchers, in the context of knowledge discovery, use different criteria to judge the relevance of the information presented. Additionally, the effects that discipline and research experience background may have on these manifestations are investigated. The scenario selected to carry out the observation is that of Literature Based Discovery (LBD). LBD is a trial-error interactive search strategy, developed by Swanson (1986a), which supports the finding and retrieving of complementary bodies of literature “ sets of articles that are bibliographically non-interactive yet logically connected. Research scientists from three different disciplines and research experience backgrounds are observed while they interact with an LBD system built for the purposes of this study. Their cognitive processes and interactions are recorded and analysed. To aid in the analysis of the data, the concept of relevance criteria profiles is developed. Relevance criteria profiles are a technique to count and group the expressions of relevance criteria as observed during the search sessions. These offer the possibility of aggregating the observations into group profiles as well as the ability to measure the (dis)similarities that may arise in between profiles. As relevance criteria profiles provide a global view of the criteria used to judge relevance, a complementary visualisation technique is also developed. This technique displays the relevance judgement processes, as well as the interactions, in a sequential fashion allowing the researcher to perform temporal analyses on the session data. The results show that researchers do use a variety of criteria when judging the relevance of information in the context of LBD. Moreover, individuals use these criteria in different frequencies; both discipline and research experience background seem to influence these frequencies however they may not be the only intervening factors. The observed interaction patterns suggest that researchers approach the problem in two stages: i) an initial more exploratory stage followed by ii) a more focused and engaged stage. The main contribution of this thesis is the observation of these manifestations of relevance together with the interaction patterns. The final recommendation offered is that the multi-dimensional nature of relevance in this context should be addressed when evaluating LBD systems. Additionally, it is acknowledged that certain interaction behaviours may also be used during the design and testing of such systems

The first occurrence of Silurian sponge spicules of the Precordillera, San Juan Province, Argentina

An association of silicified spicules of hexactinellid sponges was collected from Silurian sandstones at the top of the La Chilca Formation, outcropping at Cerro del Fuerte, near Jáchal, San Juan Province. These spicules are the first to be recorded from the Silurian of the Precordillera. The spicules were extracted by means of acetic acid treatment from yellowish coarse sandstones with carbonate cement and associated fragmented braquiopod shells. The age of the upper La Chilca Formation ranges from late Llandovery to early Wenlock, based on graptolites and brachiopods. The spicule association is only composed by hexactins (triaxons), the basic type of megasclere of the class Hexactinellida (Phylum Porifera). These sponges secrete siliceous elements that confer strength and protect them from physical perturbations. The spicules can subsequently fuse in rigid dictyonal frameworks. In the hexactins here studied, some rays are somewhat broken, but they clearly show the six rays with 90º angles between their rays. These spicules are the only microfauna found in the sandstones. No conodonts have been recovered in these levels. These spicules are common within the Class Hexactinellida, and they cannot be attributed to any specific hexactinellid taxon. These sponges are mostly confined to quiet, deep and silicon-rich environments which have no lithological record in this Silurian section. Consequently, these spicules restricted to outer platform and peri-platform were transported towards the shallow sandstone environments. Its occurrence reveals the existence of a hexactinellid fauna, which flourished in deep waters with low energy and mud substratum during the Early Silurian of the Precordillera. The greater abundance of sponge skeletons in the fossil record corresponds to periods of high sea level of the Phanerozoic oceans, whereas almost no sponge spicules have been found during the periods of low sea level as for example could have occurred during the Llandovery of the Precordillera.Simposio I: 2º Simposio de bioestratigrafía y eventos del Paleozoico inferiorSymposium I: 2nd Symposium of biostratigraphy and Lower Paleozoic eventsSimpósio I: 2 º Simpósio de bioestratigrafia e eventos do Paleozoico InferiorFacultad de Ciencias Naturales y Muse

Cambrian, Ordovician and Silurian non-stromatoporoid Porifera

The Cambrian, Ordovician and Silurian distributions of non-stromatoporoid sponges are reviewed. The earliest Cambrian faunas contain mostly hexactinellids, with protomonaxonids dominating middle Cambrian assemblages. There are no obvious palaeobiogeographical patterns, with many genera being found widely. Vauxiids, lithistids and heteractinids are apparently confined to low latitudes, but this may be due to a poor fossil record. Most known Ordovician faunas are from low latitudes, although some high-latitude faunas are known, which contain reticulosan hexactinellids and protomonaxonids. There is some division of faunas within Laurentia, into eastern and western provinces, with the western assemblage extending across low northern latitudes during the Late Ordovician. During the Silurian Period, sponge diversity was very low during the Llandovery Epoch, probably partly owing to lack of habitat for taxa restricted to carbonate facies, and also because of sampling bias. There was a dramatic increase in diversity through the Silurian Period, mostly owing to an apparent diversification in the demosponges; however, there are many ghost lineages, indicating that their fossil record is poorly known. Non-lithistid sponges are very poorly known, with few recorded outside Euramerica. The currently available data for Early Palaeozoic sponges are too incomplete to allow any reliable palaeobiogeographical inferences.Fil: Muir, Lucy A.. Chinese Academy of Sciences. Nanjing Institute of Geology and Palaeontology; ChinaFil: Botting, Joshep P.. Chinese Academy of Sciences. Nanjing Institute of Geology and Palaeontology; ChinaFil: Carrera, Marcelo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Beresi, Matilde Sylvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin