Año 2008, Boletín IFG vol. 78, números 1 - 2

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https://rephip.unr.edu.ar/handle/2133/1266

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    ÍtemAcceso Abierto
    Recordatorio: Eliseo Popolizio (19/04/38 - 27/04/08).
    (Instituto de Fisiografía y Geología, 2008-12) Canoba, Carlos A.
  • Miniatura
    ÍtemAcceso Abierto
    Alternative gravimetric methodology for isostatic analyses. An example for Bolivian Andes
    (Instituto de Fisiografía y Geología, 2008-12) Crovetto, Carolina Beatríz; Introcaso, Antonio
    In this work we present a new, alternative methodology for performing isostatic studies by means of geoid undulations, excluding the use of measured gravity anomalies. An example on Bolivian Andes is presented as case study. Considering a digital elevation model as input data, a theoretical perfectly isostatically balanced Airy crustal model was constructed for Bolivia. The free-air and the Bouguer anomalies, and the geoid undulations produced by this theoretical model, were directly evaluated by means of three-dimensional integration. The “real” geoid undulations were computed from the EGM96 global geopotential model, and were filtered from long wavelengths by means of a sparse Fourier transform method. The residual “real” geoid undulations were compared with the theoretical geoid undulations for Bolivian Andes, showing a global tendency towards isostatic balance, agreeing with previous results obtained using traditional gravimetry. The free-air and the Bouguer anomalies from the EGM96 residual geoid undulations were also evaluated and then compared with the anomalies produced by the theoretical model. The Bouguer anomalies support definitely the results obtained using the geoid undulations while the free-air anomalies, although less consistently, showed the same global tendency.
  • Miniatura
    ÍtemAcceso Abierto
    Pasottia, a new genus of Tithonian oppeliid ammonites (Late Jurassic, Ammonoidea: Haploceratoidea)
    (Instituto de Fisiografía y Geología, 2008-12) Parent, Horacio; Schweigert, Günter; Scherzinger, Armin; Enay, Raymond
    Pasottia, un nuevo género de amonites tithonianos de la famlia Oppeliidae (Jurásico Tardío, Ammonoidea: Haploceratoidea). Extensos muestreos de la fauna de amonites tithonianos de la Cuenca Neuquén-Mendoza realizados en los últimos años han puesto en evidencia la ocurrencia de un nuevo género descripto como Pasottia n. gen., con Pasottia andina n. sp. como su especie tipo. El holotipo proviene de la Zona Zitteli del Tithoniano Medio de La Amarga, localidad del extremo sur de la cuenca. P. andina n. sp. ha sido registrada en su localidad tipo y en Cerro Lotena, confinada en un horizonte de la parte media de la Zona Zitteli. Pasottia n. gen. es incluído en la subfamilia Taramelliceratinae sobre la base de: (1) la característica microconcha que posee un marcado surco con una fila de estructuras linguiformes en la mitad del flanco de la última vuelta del fragmócono y la cámara habitacional, la cual es geniculada, y (2) ambos dimorfos sexuales poseen un vientre estrecho y redondeado, sin quilla. Sobre la base del conjunto de amonites asociados en el horizonte tipo se concluye que éste es de edad Zona Semiforme del estándar primario interenacional.
  • Miniatura
    ÍtemAcceso Abierto
    Geoid undulations chart of the San Luis range (Argentina). Geophysical application
    (Instituto de Fisiografía y Geología, 2008-12) Cornaglia, Laura L.; Introcaso, Antonio
    In this work we show that it is possible to define the isostatic state of a geological structure using a geoid undulations chart. We have built: (1) a detailed geoid undulations chart of the San Luis range area using (a) the global geopotential model EIGEN CG03C for long wavelength free-air gravity anomalies and geoid undulations, and (b) observed residual free-air gravity anomalies and the equivalent sources method for short wavelength geoid undulations, and (2) a theoretical undulations chart of San Luis range area, involving effects from an isostatically compensated model. By comparing charts (1) and (2) we have found agreement between them, thus indicating the San Luis range is rather well isostatically balanced.