Palynology of the Permian San Miguel Formation (Western Paraná Basin, Paraguay): Gondwanan biostratigraphic correlations

The palynological analysis of five samples from three levels in cores of the Mallorquín-1 well (Paraná Basin, eastern Paraguay) is presented here. The borehole penetrated the San Miguel Formation, the basal lithostratigraphic unit of the Independencia Group. This palynoflora represents the westernmost palynological record reported from Upper Paleozoic sequences along this basin margin at this latitude. This diverse spore-pollen flora includes several age marker taxa, viz. Verrucosisporites insuetus, Lueckisporites spp., Lunatisporites variesectus, Striatosporites heyleri, Weylandites lucifer, and Tornopollenites toreutos, as well as Reduviasporonites chalastus. The assemblages from the Mallorquín-1 well are assignable to the Lueckisporites virkkiae Zone from the Brazilian sector of the Paraná Basin, thus suggesting a Late Cisuralian-Guadalupian age for the section studied and its correlation with the Brazilian Palermo and Irati Formations. Moreover, palynostratigraphic regional correlation can be established with the Tornopollenites toreutos Biozone (northern Brazil), the Striatites and Lueckisporites-Weylandites Biozones (Argentina) and the Striatoabieites anaverrucosus-Staurosaccites cordubensis Biozone (Uruguay). The presence of abundant taeniate pollen also suggests similarities with palynofloras from South Africa and Australia

Inter- and intratill boulder pavements in the Carboniferous Hoyada Verde Formation of West Argentina: An insight on glacial advance/retreat fluctuations in Southwestern Gondwana

Two glacially abraded surfaces have been identified in the glaciomarine section of the Carboniferous Hoyada Verde Formation, Calingasta-Uspallata basin in west Argentina. The Glacial Erosion Surfaces (GES) found in the Hoyada Verde section are boulder pavements; one is an intertill boulder pavement developed as a single boulder layer resting on massive diamctites (Dmm) and overlain by thick- to thin-bedded diamictites with ice-rafted debris (IRD). The second surface, identified in recent field work, can be described as an intratill boulder pavement; it is also a single boulder layer but under- and overlain by massive diamcitites (Dmm). The intratill boulder pavement consists of a laterally discontinuous, planar concentration of large clasts with faceted and striated upper surfaces. It lies approximately 10mbelowthe intertill boulder pavement and is exposed on the southern closure of the Hoyada Verde anticline. In both pavements the upper surfaces of the clasts are polished and striated; thestriae are parallel and subparallel to the a-axes of the boulders and indicate similar paleoflow ice directions toward the S and S-SW. Both pavements were probably originally laid down as residual gravel lag surfaces, formed by the erosion of underlying diamict when wave and/or tidal reworking was strong during a low stand and were subsequently abraded by advancing glaciers. Although both boulder pavements can be considered to be equivalent to glacial erosional surfaces (GES) caused by abrasion during a glacial advance, and hence sequence boundaries form the sequence stratigraphic viewpoint, their hierarchies are different. The intertill boulder pavement demarks the demise of the mid Carboniferous glacial episode in west Argentinawhereas the underlying intratill boulder pavement can be interpreted as the product of a minor fluctuation during the same glacial episode.Fil: López Gamundí, O. P1C Consultants; Estados UnidosFil: Sterren, Andrea Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Cisterna, Gabriela Adriana. Universidad Nacional de La Rioja; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Palynology of the Permian San Miguel Formation (Western Paraná Basin, Paraguay): Gondwanan biostratigraphic correlations

The palynological analysis of five samples from three levels in cores of the Mallorquín-1 well (Paraná Basin, eastern Paraguay) is presented here. The borehole penetrated the San Miguel Formation, the basal lithostratigraphic unit of the Independencia Group. This palynoflora represents the westernmost palynological record reported from Upper Paleozoic sequences along this basin margin at this latitude. This diverse spore-pollen flora includes several age marker taxa, viz. Verrucosisporites insuetus, Lueckisporites spp., Lunatisporites variesectus, Striatosporites heyleri, Weylandites lucifer, and Tornopollenites toreutos, as well as Reduviasporonites chalastus. The assemblages from the Mallorquín-1 well are assignable to the Lueckisporites virkkiae Zone from the Brazilian sector of the Paraná Basin, thus suggesting a Late Cisuralian-Guadalupian age for the section studied and its correlation with the Brazilian Palermo and Irati Formations. Moreover, palynostratigraphic regional correlation can be established with the Tornopollenites toreutos Biozone (northern Brazil), the Striatites and Lueckisporites-Weylandites Biozones (Argentina) and the Striatoabieites anaverrucosus-Staurosaccites cordubensis Biozone (Uruguay). The presence of abundant taeniate pollen also suggests similarities with palynofloras from South Africa and Australia

A pure dipole analysis of the Gondwana apparent polar wander path: Paleogeographic implications in the evolution of Pangea

The paleogeography of prebreakup Pangea at the beginning of the Atlantic Spreading has been a subject of debate for the past 50 years. Reconciling this debate involves theoretical corrections that cast doubt on available data and paleomagnetism as an effective tool for performing paleoreconstructions. This 50 year old debate focuses specifically on magnetic remanence and its ability to correctly record the inclination of the paleomagnetic field. In this paper, a selection of paleopoles was made to find the great circles containing the paleomagnetic pole and the respective sampling site. The true dipole pole (TDP) was then calculated by intersecting these great circles, effectively avoiding nondipolar contributions and inclination shallowing, in an innovative method. The great circle distance between each of these TDPs and the paleomagnetic means show the accuracy of paleomagnetic determinations in the context of a dominantly geocentric, axial, and dipolar geomagnetic field. The TDPs calculated allowed a bootstrap analysis to be performed to further consider the flattening factor that should be applied to the sedimentary-derived paleopoles. It is argued that the application of a single theoretical correction factor for clastic sedimentary-derived records could lead to a bias in the paleolatitude calculation and therefore to incorrect paleogeographic reconstructions. The unbiased APWP makes it necessary to slide Laurentia to the west in relation to Gondwana in a B-type Pangea during the Upper Carboniferous, later evolving, during the Early Permian, to reach the final A-type Pangea configuration of the Upper Permian.Fil: Gallo, Leandro César. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Tomezzoli, Renata Nela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Cristallini, Ernesto Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin