Here we describe new microfossil assemblages for the Miocene Hobbs Glacier Formation and the first possibly indigenous assemblages for the Plio-Pleistocene Weddell Sea Formation on Seymour Island, West Antarctica. The assemblages are composed mainly of foraminifers, but radiolarians, calcitarchs and poriferan sclerites are also present. For the Hobbs Glacier Formation, we report the foraminifers Bolivina sp., Oolina globosa and Rosalina cf. globularis; and for the Weddell Sea Formation, we report Favulina hexagona, Globigerinita uvula, Globocassidulina cf. subglobosa and Psammosphaera fusca. The low abundance and diversity of microfossils, allied with the complex taphonomical processes that prevailed in Antarctic glacial–marine palaeoenvironments, make it impossible to define whether the assemblages are composed of a mixture of indigenous and re-elaborated specimens or exclusively of re-elaborated remains. Nevertheless, the indigenous nature of some specimens is suggested by their inherent fragility, excellent preservation and/or taxonomic association with indigenous assemblages from correlated strata. The taxonomic compositions are not directly comparable with other Antarctic assemblages, although most of the species were previously reported from pre-Quaternary or modern deposits of both West and East Antarctica. This lack of correspondence is probably due to preservation biases, but any further significance is hidden by the complex taphonomy of the deposits.

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Western Antarctic deposits, especially those from the Eocene-Oligocene transition, provide important geological data on Cenozoic global climate changes and their impact on the southern biota. Fossil assemblages, including foraminifers, are known from geological units from all Cenozoic epochs, in outcrops of the James Ross and South Shetlands archipelagos. However, the diamictites of Hobbs Glacier (Miocene) and Weddell Sea (Plio-Pleistocene) formations, exposed in James Ross and Seymour islands, were never subjects of micropaleontologic analysis targeting inorganic-walled microfossils. Twelve stratigraphic sections on Seymour Island were analyzed, including the top of the La Meseta Formation (Eocene) and several strata of Hobbs Glacier and Weddell Sea formations. Assemblages of inorganic-walled microfossils, composed mainly of foraminifers, were found for the first time in the La Meseta Formation and in strata from the Hobbs Glacier and Weddell Sea formations. Autochthonous or parautochthonous remains of the foraminifer Textularia sp. were found in the La Meseta Formation, being the first occurrence of the genus in this unit. The best preserved autochthonous or parautochthonous assemblage from Hobbs Glacier Formation is composed of the Lagenid foraminifer Oolina stellula and radiolarian Larcopyle polyacantha. The Rotaliid foraminifer Bolivina sp. is rare and represents an allochthonous elements in this formation. In the Weddell Sea Formation, the best preserved autochthonous or parautochthonous assemblage is composed of the Lagenid foraminifer Favulina hexagona and the planktonic Globigerinita uvula, as well as the Rotaliid foraminifer Globocassidulina subglobosa and the radiolarian L. polyacantha in the same and in other strata. In these Miocene and Plio-Pleistocene deposits also occur large agglutinated foraminifers typical of the deep sea, whose taphonomic features indicate their reelaboration from older deposits, possibly from the Paleocene, given their taphonomic and stratigraphic association with the foraminifer Reticulophragmium garcilassoi, a Paleocene index-fossil. Besides R. garcilassoi, other typical deep-sea taxa occur in the Hobbs Glacier Formation, such as Alveolophragmium orbiculatum, Ammodiscus sp. nov., Ammodiscus pennyi, Ammomarginulina cf. aubertae, Bathysiphon sp. 1, Bathysiphon sp. 2, Cyclammina placenta and Nothia robusta. In the Weddell Sea Formation the agglutinated specimens are represented by Ammodiscus sp. nov., Bathysiphon sp. 1, Budashevaella cf. laevigata, Cyclammina cancellata, Glomospira charoides, Saccammina grzybowski, Sculptobaculites barri and Verneulinoides cf. neocomiensis. Some taxa from Seymour Island also occur in the Paleocene deposits of New Zealand and New Guinea, suggesting some chronological correlation. Although the fossil record of the La Meseta, Hobbs Glacier and Weddell Sea formations is sparse, it was possible to identify autochthonous or parautochthonous remains that indicate the partial composition of the infaunal communities and plankton that thrived in the are...

Microbialites played a major role in the Precambrian ecosystems but became restricted to stressful marginal environments for most of the Phanerozoic, reaching comparable abundance and expansion only in the aftermath of some mass extinctions.Microbialite occurrences are known from Permian deposits of the Paraná Basin, but they are all geographically restricted and mostly associated with hypersaline settings.Here are reported silicified, microfossiliferous microbialite beds of the middle Permian Teresina Formation at two localities in the center of São Paulo State, Brazil, which are separated from each other by approximately 40 km. These microbialites occur in successions that are mainly devoid of animal body and trace fossils. Similarities in microbialite morphotype and microstructure, microfossil content and preservation, and diagenetic histories strongly suggest a stratigraphic correlation and, therefore, a major microbial development over an extensive area, contrasting with the previously known restricted occurrences. This development seems to be related to the establishment of more arid conditions in the Paraná Basin, ultimately linked to the formation of Pangea.

Our knowledge of the foraminiferal fossil record of Antarctica is notoriously patchy but still offers us an overview of its Cenozoic faunas. Few occurrences have been reported for the continent, with deep-sea assemblages described mainly for its eastern portion. Here we describe 21 taxa of large agglutinated foraminifers from the Miocene Hobbs Glacier Formation and the Plio-Pleistocene Weddell Sea Formation on Seymour Island, West Antarctica, including the gigantic Ammodiscus vastus new species. Most of them consist of genera or species typical of deep-sea agglutinated assemblages. All specimens are completely filled and partially covered by lithified micrite. This, along with the postfill fragmentation of some tests, indicates their re-elaboration from older deposits. Because all of these foraminifers share the same taphonomic features and most of them represent taxa associated with deep-sea settings, they probably represent a flysch-type assemblage from an unknown deposit that was eroded and had its microfossils scattered through post-Paleogene sediments. A Paleocene age for this putative assemblage is indicated by the presence of Reticulophragmiun garcilassoi (Frizzell, 1943), a Paleocene index fossil, and by its association with the Cretaceous–Paleocene Ammodiscus pennyi Cushman and Jarvis, 1928. If taken as a coherent foraminiferal assemblage, it represents one of the few deep-sea assemblages known for West Antarctica, and the first flysch-type assemblage recognized for the Antarctic Cenozoic. In addition, it would show that the Paleocene foraminiferal communities of the West Antarctica's deep-sea floor were more like their Pacific counterparts than their Atlantic equivalents. UUID: http://zoobank.org/0d281489-c0c6-47b4-9884-f820806485b7