Middle to upper eocene dinoflagellate cysts from Punta del Este and colorado basins, mid latitude southwest Atlantic Ocean

The analysis of middle Eocene dinoflagellate cyst assemblages from sites at Punta del Este (~36°S, Uruguay) and Colorado (~38°S, Argentina) basins allows to interpret ocean circulation patterns on the South American Shelf prior to the opening of the Drake Passage. The assemblages contain endemic-Antarctic taxa such as Enneadocysta, Deflandrea, Vozzhennikovia and Spinidinium, which are also dominant in several circum-Antarctic sites, located southern 45°S. Enneadocysta dictyostila is the most abundant species recorded from the studied sites and the unique member of the endemic assemblage apparently tolerant to warm surface waters. The presence of endemic taxa at mid latitudes has been related to a strong clockwise subpolar gyre favoured by the partial continental blockage of the Tasmanian Gateways and the Drake Passage. The distribution of the dinoflagellate cyst assemblages along the South Atlantic Ocean Shelf can be explained by a similar dynamical mechanism induced by a cyclonic subpolar gyre on the South Atlantic Ocean. The western boundary current of this gyre, starting on the west Antarctic continental slope, would follow a similar path to the present Malvinas Current on the Patagonian slope, which introduce cold oceanic waters to the shelf and intensifies the northward shelf transport. In the same way, during the middle Eocene the western boundary current of a proto-Weddell Gyre transported the circum-Antarctic waters and the endemic taxa northward along the Southwestern Atlantic Shelf. The opening and deepening of the Tasmanian Gateway and Drake Passage and the development of an incipient Antarctic Circumpolar Current during the latest Eocene-Oligocene disrupted the subpolar gyres and promoted the extinction of the endemic species

Paleogene distribution of Enneadocysta (Dinoflagellata) in the southwestern Atlantic Ocean: paleoceanographic implications

En las asociaciones de quistes de dinoflagelados del Eoceno medio a tardío de cuencas subtropicales del Atlántico Sudoccidental se registra la presencia de especies de Enneadocysta, entre ellas: E. dictyostila (Menéndez) Stover y Williams emend Fensome et al., E. brevistila Fensome et al. y E. multicornuta (Eaton) Stover y Williams. La especie Enneadocysta dictyostila fue registrada en secciones del Paleógeno medio de altas latitudes del Hemisferio Sur. Se hallaron numerosos ejemplares de Enneadocysta spp. junto con otros componentes de la flora de dinoflagelados endémica del Océano Austral en las cuencas del Colorado (~38°S), Argentina y Punta del Este (~36°S), Uruguay. Previamente, en un trabajo realizado en el área de Tasmania, otros autores relacionaron la presencia de componentes de dicha flora en latitudes medias con el desarrollo de giros oceánicos supbolares (“cold traps”) favorecidos por la obstrucción continental del conducto de Tasmania. El presente trabajo propone que la distribución de quistes de dinoflagelados en las cuencas del Atlántico Sudoccidental puede ser explicada por una dinámica similar que habría funcionando como un proto-Giro de Wedell. Tanto el conducto de Tasmania cerrado como un Pasaje de Drake parcialmente abierto habrían contribuido a la formación de giros en sentido horario con intensos flujos en los bordes occidentales. Estos flujos serían los responsables de transportar parte de la flora endémica, principalmente representada por Enneadocysta spp., desde las costas del continente Antártico hacia el norte a lo largo de la plataforma sudamericana durante el Eoceno medio-tardío.The study of Middle to Late Eocene dinoflagellate cyst assemblages from subtropical Southwest Atlantic basins shows the presence of species of Enneadocysta, including E. dictyostila (Menéndez) Stover and Williams emend. Fensome et al., E. brevistila Fensome et al. and E. multicornuta (Eaton) Stover and Williams. The species Enneadocysta dictyostila has been widely recorded in middle Paleogene sections from Southern Hemisphere high latitudes. High representativity of Enneadocysta spp., along with other components of the Southern Ocean endemic dinoflagellate flora, have been observed in samples from Colorado Basin (~38°S), Argentina and Punta del Este Basin (~36°S), Uruguay. Previous research in the Tasman area has related the presence of these endemic taxa at mid-latitudes to the formation of a strong clockwise subpolar gyre (“cold trap”) favoured by the continental blockage of the Tasman Gateway. In this paper we propose that the observed dinoflagellate cyst distribution in the Southwest Atlantic basins can be explained by a similar dynamical mechanism operating close to the present Weddell Gyre. The blockage of the Tasman Gateway and a partially open Drake Passage both contributed to the formation of a strong western-intensified clockwise gyre that may have transported the endemic flora components, mainly represented by Enneadocysta spp., from the Antarctic continent northward along the Southwest Atlantic Shelf during the Middle - Late EoceneFil: Guerstein, Gladys Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Daners, Gloria. Facultad de Ciencias. Departamento de Evolución de Cuencas; Urugua

Diconodinium lurense sp. nov., a late Maastrichtian to Danian dinoflagellate cyst from Southwest Atlantic basins

Los depósitos del Cretácico Superior y Cenozoico de las cuencas del Colorado y Austral, Argentina y Cuenca Punta del Este, Uruguay son portadores de asociaciones de quistes de dinoflagelados diversas. Diconodinium lurense sp. nov. es un elemento común en las asociaciones provenientes del Maastrichtiano tardío-Daniano en las distintas cuencas. Esta nueva especie se caracteriza por presentar un autofragma densamente cubierto por espinas cortas, cuernos apical y antapical relativamente largos y por un arqueopilo variable Ia-IPa. Nuestras evidencias indican que el rango estratigráfico de Diconodinium lurense sp. nov. se extiende desde al Maastrichtiano tardío hasta el Daniano, constituyendo un importante marcador bioestratigráfico para la transición Cretácico-Paleógeno en las cuencas del Atlántico Sudoccidental.Upper Cretaceous and Cenozoic deposits from the Colorado and Austral basins, Argentina and the Punta del Este Basin, Uruguay contain diverse organic-walled dinoflagellate cysts, including Diconodinium lurense sp. nov. which occurs in the late Maastrichtian and Danian throughout the basins. The new species is characterized by an autophragm that is densely covered by short spines and by relatively long apical and antapical horns, and by a variable Ia to IPa archeopyle. On our evidence, the stratigraphical range of Diconodinium lurense sp. nov. is latest Maastrichtian to Danian, and is thus a useful biostratigraphical marker for the Cretaceous-Palaeogene transition in the southwest Atlantic basins.Fil: Guerstein, Gladys Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Junciel, Gabriela. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Guler, Maria Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Daners, Gloria. Universidad de la República. Facultad de Ciencias; Urugua

Pragian–Emsian palynomorphs from the Cordobés Formation, Norte Basin, Uruguay: stratigraphically restricted and regionally correlative palynological events in the cool-water Malvinokaffric Realm

International audienc

Middle to Upper Eocene dinoflagellate cysts from Punta del Este and Colorado basins, mid latitude southwest Atlantic Ocean

The analysis of middle Eocene dinoflagellate cyst assemblages from sites at Punta del Este (~36°S, Uruguay) and Colorado (~38°S, Argentina) basins allows to interpret ocean circulation patterns on the South American Shelf prior to the opening of the Drake Passage. The assemblages contain endemic-Antarctic taxa such as Enneadocysta, Deflandrea, Vozzhennikovia and Spinidinium, which are also dominant in several circum-Antarctic sites, located southern 45°S. Enneadocysta dictyostila is the most abundant species recorded from the studied sites and the unique member of the endemic assemblage apparently tolerant to warm surface waters. The presence of endemic taxa at mid latitudes has been related to a strong clockwise subpolar gyre favoured by the partial continental blockage of the Tasmanian Gateways and the Drake Passage. The distribution of the dinoflagellate cyst assemblages along the South Atlantic Ocean Shelf can be explained by a similar dynamical mechanism induced by a cyclonic subpolar gyre on the South Atlantic Ocean. The western boundary current of this gyre, starting on the west Antarctic continental slope, would follow a similar path to the present Malvinas Current on the Patagonian slope, which introduce cold oceanic waters to the shelf and intensifies the northward shelf transport. In the same way, during the middle Eocene the western boundary current of a proto-Weddell Gyre transported the circum-Antarctic waters and the endemic taxa northward along the Southwestern Atlantic Shelf. The opening and deepening of the Tasmanian Gateway and Drake Passage and the development of an incipient Antarctic Circumpolar Current during the latest Eocene-Oligocene disrupted the subpolar gyres and promoted the extinction of the endemic species.O estudo de associações de cistos de dinoflagelados do Eoceno médio nas bacias de Punta del Este (~36°S, Uruguai) e do Colorado (~38°S, Argentina) permite interpretar os padrões de circulação oceânica na plataforma sul-americana antes da abertura da Passagem de Drake. As associações são caracterizadas pela presença de táxons antárticos endémicos, como Enneadocysta , Deflandrea , Vozzhennikovia e Spinidinium , dominantes em vários locais da região Circumpolar Antárctica localizados ao sul do 45°S. A espécie mais abundante registrada nos locais estudados é Enneadocysta dictyostila , que é o único membro da associação endêmica aparentemente resistente às águas aquecidas na superfície. Pesquisas anteriores já haviam mencionado a presença de táxons endêmicos em latitudes médias a um forte giro subpolar no sentido horário favorecido pelo bloqueio parcial das passagens da Tasmânia e de Drake. Propõe-se aqui, que a distribuição das associações de cistos de dinoflagelados, ao longo das bacias da margem continental do Atlântico Sul, pode ser explicada por um mecanismo dinâmico semelhante induzido por um giro subpolar ciclônico no Oceano Atlântico Sul. O atual limite ocidental deste giro, começando no talude continental da Antártica ocidental, iria seguir um caminho semelhante ao presente atual Corrente das Malvinas na encosta da Patagônia, que introduz as águas oceânicas frias na plataforma e intensifica o transporte das águas na plataforma para o norte. De maneira similar, durante o Mesoeoceno, o limite ocidental da corrente Protogiro de Weddell transportou as águas circum-antárticas e os táxons endêmicos para o norte ao longo da margem Atlântico Sudoeste. A abertura e o aprofundamento das passagens de Tasmânia e Drake, assim como o desenvolvimento de uma incipiente corrente circumpolar Antártica no final do Eoceno e início do Oligoceno, interromperam os giros subpolares e promoveram a extinção das espécies endêmicas.Fil: Daners, Gloria. Universidad de la República; UruguayFil: Guerstein, Gladys Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Rodriguez Amenabar, Cecilia. 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"; ArgentinaFil: Morales, Ethel. Universidad de la República; Urugua

Early Devonian organic-walled microfossils from outcrop samples of the Cordob´es Formation, Durazno Group, Norte Basin, Uruguay

The Durazno Group documented an Early Devonian transgressive-regressive cycle of sedimentation in the southernmost portion of the intracratonic Paran´a Basin, in Uruguay known as the Norte Basin. The group comprises from base to top the Cerrezuelo, Cordobes and La Paloma Formations. The Cordobes Formation was deposited during the maximum flooding of the transgressive event, and contains Malvinokaffric marine invertebrates that inhabited Gondwanan cold marine waters, acanthodian fishes and trace fossils. The first palynological studies of the Cordobes Formation date from the 60?s and 70?s, from one outcrop, which reports the presence of phytoplankton and miospores but they only described a few acritarchs. In recent years, works referred to this unit have notably increased due to hydrocarbons exploration, but the results come from samples obtained mainly from boreholes. In order to expand the knowledge regarding Devonian palynofloras of Uruguay, in this contribution, we document the palynological assemblages collected from outcrop samples of the Cordobès Formation, near Blanquillo town in the Durazno Department. Some identified species allowed constraining the age of the unit and its correlation with other Early Devonian assemblages from South America. The studied samples contain acritarchs, prasinophytes, chlorophytes, chitinozoans, scolecodonts and miospores. The most representative phytoplankton species are Cordobesia urguayensis, Dictyotidium dictyotum, Estiastra uruguaia, Exochoderma arca, E. triangularis, Palacanthus ledanoisii, Polyedrixium fragosulum, Triangulina alargada, Quadrisporites horridus, Veryhachium trispinosum and V. woodii. The miospores include the following species: Apiculiretusispora brandtii, Cymbohilates sp., Emphanisporites rotatus, Dibolisporites echinaceus, Dictyotriletes emsiensis and Knoxisporites riondae. The presence of the acritarch Veryachium woodii, recently described from borehole samples of the Cordobes Formation, allows to constrain the age at the proximity of the Pragian-Emsian boundary, where also Knoxisporites riondae becomes a common taxa. Cordobesia species and Dictyotriletes emsiensis are forms restricted to Gondwana. Besides this, Dictyotriletes emsiensis allows the correlation with Furnas and Ponta Grossa Formations (Brazil) and Talacasto Formation (Argentina). The Early Devonian age is also supported by fossil invertebrates as well as U-Pb ages of detrital zircons obtained from the Duranzo Group.Fil: Daners, Gloria. Universidad de la República; UruguayFil: Rodriguez Amenabar, Cecilia. 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"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Cátedra de Paleontología; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Uriz, Norberto Javier. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; ArgentinaFil: Rojas, Alejandra. Universidad de la República; Uruguay5th International Palaeontological CongressParisFranciaInternational Palaeontological Associatio

Exploring the diversity of Uruguayan native flora honeys

This work proposes the revaluation of honeys from the native flora of Uruguay. The results obtained in the pollen and physicochemical analysis allow us to conclude that it is possible to characterize and distinguish monofloral honeys produced from Uruguayan native flora, and that they also present interesting properties that make them stand out from the rest of the honeys. This could be a starting point for the exploitation of this market of little-known honeys with great nutritional potential

Correlation of Middle to Upper Eocene Units from High Latitude Southwestern Atlantic Sites

To understand the important significant climatic and paleoceanographic changes occurred in the Southern Hemisphere during the Paleogene, and especially those related to the opening of the Drake Passage, is essential to correlate the Eocene lithostratigraphic units in areas adjacent to this passage, such as those from the Austral-Magallanes and James Ross basins, to the north and to the south, respectively. For many years, there was no correlation between these units due to the absence of reliable chronostratigraphic and biostratigraphic information. Recently, other authors published U/Pb data for the Austral-Magallanes Basin and introduced important modifications to the previous stratigraphic scheme. Subsequently, due to reinterpretating the available isotope data together with U/Pb ages, the chronostratigraphic model has modified again, also including the James Ross Basin. In light of an updated quantitative dinoflagellate cyst dataset from the units adjacent to the Drake Passage, we performed a Principal Component Analysis (PCA) to discuss the correlation between the studied sections. The PCA groups assemblages with a high contribution of Antarctic taxa (e.g., Enneadocysta dictyostila, Deflandrea antarctica) containing in the Upper Member of the Río Turbio Formation (lower part), Man Aike, Leticia, and La Meseta formations, being Bartonian in age. The other group joined assemblages with younger ages, Priabonian, dominated by Antarctic species (Vozzhennikovia-Spinidinium) and cosmopolitan taxa, corresponding to the Upper Member of the Río Turbio Formation (upper part). This study reinforces the most recent chronostratigraphic proposal and proves the biostratigraphic useful of some taxa for sites near the Drake Passage.Fil: Rodriguez Amenabar, Cecilia. 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"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Cátedra de Paleontología; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Guerstein, Gladys Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Alperin, Marta Ines. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; ArgentinaFil: Daners, Gloria. Universidad de la República; UruguayFil: Casadio, Silvio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Rodriguez Raising, Martin Eduardo. Universidad Nacional de La Pampa; Argentin