Lacustrine black shales near to the Paleogene - Neogene boundary in north-western Neuquén Province: palynological evidence

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Héctor A. Leanza
Wolfgang Volkheimer
Carlos A. Hugo
Daniel L. Melendi
Elizabeth I. Rovere

Abstract

 Lacustrine sedimentary rocks referred to the Lileo Formation nov. cropping out near Los Miches locality, northwestern Neuquén Province, Argentine Republic, were sampled for palynological study. On the basis of the microfloristic analysis, the palynomorph-bearing beds can be ascribed a Late Oligocene to Early Miocene age. The sampled rocks are black, grey-green, dark grey and light brown shales alternating with thin,locally oolithic, light grey limestones, with yellowish white weathering. Among these rocks are interbedded andesites, tuffs, and volcanic agglomerates of mesosilicic composition. In the outcrops of the Guañacos river area, some irregular beds of fibrous carbonate have been observed as well as fibroradial nodular barite, together with some indeterminate fresh-water. The microfloristic assemblages have a relatively low diversity. In most of them the genus Nothofagidites dominates the association. The components present in the microflora are pollen grains corresponding to several angiosperm taxa, such as Baumannipollis sp. cf. B. variaperturatusCorsinipollenites atlantica, Milfordia sp.Nothofagidites saraensisSmilacipites sp. cf. S. echinatus and Tricolpites asperamarginis together with gymnosperm pollen grains of Araucariacites australis, Equisetosporites notensis and Podocarpidites spp. The Pteridophyta/Bryophyta elements are represented by Cyatheacidites annulatus, Cicatricosisporites sp.Deltoidospora sp.Lycopodiumsporites austroclavatiditesRicciaesporites spand Laevigatosporites ovatus, whereas among the lacustrine taxa Azolla sp. and Botryococcus sp. (Chlorophyta) were recognized.

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Leanza, H. A., Volkheimer, W., Hugo, C. A., Melendi, D. L., & Rovere, E. I. (2002). Lacustrine black shales near to the Paleogene - Neogene boundary in north-western Neuquén Province: palynological evidence. Revista De La Asociación Geológica Argentina, 57(3), 280-288. Retrieved from https://revista.geologica.org.ar/raga/article/view/736
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