Boletín del Instituto de Fisiografía y Geología

ISSN 1666-115X

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Lithofacies and age of the Quintuco Formation (Lower Cretaceous) in the Mallín Quemado area (Sierra de la Vaca Muerta, Neuquén Basin, Argentina). Stratigraphic and depositional implications.

Garrido A.C. & Parent H.

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A detailed lithostratigraphic study of the Quintuco Fm in the Cerro Mallín Quemado area (Sierra de la Vaca Muerta) has provided the opportunity to review the conflictive diversity of interpretations proposed in the last 40 years for this unit. In the study area the Quintuco Fm shows a heterolithic succession about 80 m-thick. This succession is composed of interbedded sandy mudstones, wacky sandstones and fine to medium-grained sandstones in a coarsening-upwards arrangement. Thin coquiniferous levels occur interestratified towards the medium and upper parts of the stratigraphic column. The underlying offshore Vaca Muerta Fm-facies, developed under euxinic to anoxic conditions change gradually towards the dysoxic, storm waves-influenced conditions of the offshore transition zone of the Quintuco Fm-facies. Upwards the Quintuco Fm passes gradationally to shoreface sandy deposits of the Mulichinco Fm. The transition between both units is defined in a short section of the sedimentary column.
  The Quintuco Fm can be clearly recognized, and differentiated from the contiguous units, following the lithologic characterization of the original definition. There are important discrepancies in its determination among the authors. The main source of these discrepancies has been the use of biostratigraphic, chronostratigraphic and/or sequence-stratigraphic criteria.
  Once recognized the lithostratigraphic unit from the observed lithology in the section, the ammonites collected from there were studied in order to date these rocks and to establish regional time-correlation. These ammonites indicate the Quintuco Fm in the study area is Berriasian in age. This age was obtained from the chronostratigraphic zones estimated from the ammonite biostratigraphy of the studied section. Towards northern positions in the basin, e.g. Pampa Tril area, the age of the Quintuco Fm is early Valanginian. This pattern of the units becoming younger towards north reflects the shoreline progradation towards the basin.

Alberto C. Garrido [albertocarlosgarrido@gmail.com]: Museo Provincial de Ciencias Naturales “Prof. Dr. Juan A.
Olsacher”, Dirección Provincial de Minería, Etcheluz y Ejército Argentino, 8340 Zapala, Neuquén, Argentina &
Departamento Geología y Petróleo, Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400,
8300 Neuquén, Argentina.

Horacio Parent [parent@fceia.unr.edu.ar]: Laboratorio de Paleontología, IFG, Facultad de Ingeniería, Universidad
Nacional de Rosario, Pellegrini 250, 2000 Rosario, Argentina.

Ornamentation and defense structures of the pelvic buckler of Eutatus pascuali (Xenarthra, Dasypodidae).

Brambilla L. & Ibarra D.A.

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Eutatus pascuali is a large armadillo characteristic of the Lower-Middle Pleistocene of Argentina. The number of published specimens is small and frequently they consist of isolated osteoderms and carapace fragments, in which the dorsal region is usually preserved. In this work we report the presence of modified thick spine-like osteoderms projected laterally on the lateral border of the pelvic buckler. This is a remarkable feature within the Euphractinae that contributes to the knowledge of the appearance of E. pascuali. The presence of spines projecting from the carapace, a convergent adaptation also observed in some Glyptodontinae, could have been developed as a defense against predators.

Luciano Brambilla [lbrambilla@fbioyf.unr.edu.ar]: Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina | Facultad de Ciencias Exactas, Ingeniería y Agrimensura, Universidad Nacional de Rosario, Av. Pellegrini 250, S2000BTP Rosario, Argentina.

Damián Alberto Ibarra [damianibarra341@hotmail.com]: Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina.

Ordenamiento territorial ambiental de la cuenca hidrográfica de aporte directo a la Laguna Melincué.

Peralta E.P.

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El ordenamiento territorial ambiental de la cuenca hidrográfica y de aporte directo a la laguna Melincue es una asignatura pendiente que se pone en evidencia ante cada inundación que sufre la localidad de Melincué. La adecuada planificación de las acciones en el corto, mediano y largo plazo, dentro de un plan estratégico ambiental, es sin duda la que permitirá ordenar, entre otras cosas, el uso sustentable de los recursos naturales y proyectar las obras necesarias y su ubicación en el terreno, en concordancia con la topografía, geomorfología y el medio ambiente.

Eduardo P. Peralta [peralta@fceia.unr.edu.ar]: Instituto de Fisiografía y Geología, Facultad de Ingeniería, Universidad
Nacional de Rosario, Pellegrini 250, 2000 Rosario, Argentina.

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