Glacial events in Carboniferous sequences from Paganzo and Río Blanco Basins (Northwest Argentina): Palynology and depositional setting

The age and depositional setting of two glacial events recognized in the western basins of Argentina are discussed in this paper. The older one corresponds to diamictites identified in the upper member of the Cortaderas Formation (Visean, Río Blanco Basin). The glacial sequence consists of shales, dropstone-bearing shales massive matrixrich diamictites, massive clast-rich diamictites, and stratified diamictites, all of them interpreted as deposited in distal glaciomarine settings. Palynological remains recovered from shales interstratified with diamictites were referred to the late Visean Reticulatisporites magnidictyus-Verrucosisporites quasigobbettii Biozone. Younger glacial deposits were studied at the base of the Guandacol Formation (Paganzo Basin) where are made up by clast-poor massive diamictites, clast-rich massive diamictites, stratified diamictites, thinly-bedded dropstonebearing diamictites, rhythmites, dropstone-bearing shales, and barren of dropstone shales. The whole sequence is interpreted as deposited in low-relief proximal glaciomarine environments (morainal banks). The abundant palynological assemblages found in the glacial interval were included in the subzone A of the Raistrickia densa-Convolutispora muriornata Biozone which is considered Serpukhovian-early Bashkirian in age. Palynological remains found in the Cortaderas Formation suggest that the beginning of the Glacial 2 event in Gondwana (according to Isbell's chronological proposal for glacial and interglacial stages) should be considered late Visean while the end, according to the assemblages recovered from the Guandacol Formation, was not younger than early Bashkirian. Moreover, sedimentological and stratigraphic data suggest the existence of a short interglacial period between the Cortaderas and Guandacol glacial events

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

Glacial events in Carboniferous sequences from Paganzo and Río Blanco Basins (Northwest Argentina): Palynology and depositional setting

The age and depositional setting of two glacial events recognized in the western basins of Argentina are discussed in this paper. The older one corresponds to diamictites identified in the upper member of the Cortaderas Formation (Visean, Río Blanco Basin). The glacial sequence consists of shales, dropstone-bearing shales massive matrixrich diamictites, massive clast-rich diamictites, and stratified diamictites, all of them interpreted as deposited in distal glaciomarine settings. Palynological remains recovered from shales interstratified with diamictites were referred to the late Visean Reticulatisporites magnidictyus-Verrucosisporites quasigobbettii Biozone. Younger glacial deposits were studied at the base of the Guandacol Formation (Paganzo Basin) where are made up by clast-poor massive diamictites, clast-rich massive diamictites, stratified diamictites, thinly-bedded dropstonebearing diamictites, rhythmites, dropstone-bearing shales, and barren of dropstone shales. The whole sequence is interpreted as deposited in low-relief proximal glaciomarine environments (morainal banks). The abundant palynological assemblages found in the glacial interval were included in the subzone A of the Raistrickia densa-Convolutispora muriornata Biozone which is considered Serpukhovian-early Bashkirian in age. Palynological remains found in the Cortaderas Formation suggest that the beginning of the Glacial 2 event in Gondwana (according to Isbell's chronological proposal for glacial and interglacial stages) should be considered late Visean while the end, according to the assemblages recovered from the Guandacol Formation, was not younger than early Bashkirian. Moreover, sedimentological and stratigraphic data suggest the existence of a short interglacial period between the Cortaderas and Guandacol glacial events