Quistes de dinoflagelados de sedimentos holocenos y dinoflagelados modernos del estuario de Bahía Blanca, Argentina

En este trabajo se comparan los dinoquistes de sedimentos intermareales holocenos (perfil Canal del Medio) con los resultados de un estudio cualitativo de dinoflagelados en el área de Puerto Cuatreros. Tanto las asociaciones subfósiles como las modernas fueron analizadas en el sector interno del estuario de Bahía Blanca. Todas las especies de dinoquistes holocenas registradas en los sedimentos de las planicies de marea pertenecen a la Familia Gonyaulacaceae: Operculodinium centrocarpum (Deflandre y Cookson) Wall, Operculodinium centrocarpum de procesos cortos, Spiniferitesbulloideus (Deflandre y Cookson) Sarjeant, Spiniferites sp. cf. S. pachydermus (Rossignol) Reid, Spiniferites bentorii (Rossignol) Wall y Dale y Spiniferitesramosus (Ehrenberg) Loeblich y Loeblich. Por otro lado, el estudio de dinoflagelados modernos en la columna de agua mostró una asociación que incluye formas desnudas o atecadas, como Gymnodinium sp. y formas tecadas como Prorocentrum compressum (Bailey) Abé, Dinophysis sp., Protoperidinium conicum (Gran) Balech, Alexandrium tamarense (Lebour) Balech y Qeratiumspp. De estas especies actuales solamente Protoperidinium conicum, Alexandrium tamarense y Gymnodinium sp. producen quistes que pueden preservarse en el registro fósil. La forma móvil Protoceratiumreticulatum (Claparéde y Lachmann) Butschli que produce el dinoquiste Operculodinium centrocarpum no fue registrada hasta ahora en el fitoplancton del sector interno del estuario. Asimismo, las especies de Gonyaulax, tecas parentales de los dinoquistes del género Spiniferites, no fueron mencionadas para el plancton actual. Estas diferencias entre las asociaciones holocenas y las modernas sugieren cambios para el área de estudio, especialmente en la influencia oceánica y en otras condiciones del agua, como el contenido de nutrientes y la turbidez.The aim of this work is to compare the dinocysts of holocene intertidal sediments (Canal del Medio profile) with the results of a qualitative study of dinoflagellates in the Puerto Cuatreros area. The subfossil and modem associations were analyzed in the inner sector of the Bahia Blanca estuary. All the holocene dinocyst species registered in the sediments of the tidal flats belong to Familia Gonyaulacaceae: Operculodinium centrocarpum (Deflandre and Cookson) Wall, Operculodinium centrocarpum of short processes, Spiniferitesbulloideus (Deflandre and Cookson) Sarjeant, Spiniferitescf. S. pachydermus (Rossignol) Reid, Spiniferitesbentorii (Rossignol)Wall and Dale and Spiniferitesramosus (Ehrenberg) Loeblich and Loeblich. Otherwise, the study of modem dinoflagellates in the water column showed an association that includes unarmored or a the cate forms, such as Gymnodinium sp and armored or the cate forms like Prorocentrum compressum (Bailey) Abé, Dinophysis sp., Protoperidinium conicum (Gran) Balech, Alexandrium tamarense (Lebour) Balech and Ceratium spp. From these living species only Protoperidinium conicum, Alexandrium tamarense and Gymnodinium sp. produce cysts that may be preserved in the fossil record. The motile form Protoceratium reticulatum (Claparede and Lachmann) Butschli that produces the dinocyst Operculodinium centrocarpum was not registered hitherto in the phytoplankton studies carried out in the inner part ofthe estuary. Likewise, the species of Gonyaulax, parental thecae of the dinocyst of the genus Spiniferites, were not mentioned for the modem plankton. These differences between holocene and modem associations suggest changes for the study area, especially in the oceanic influence and in other water conditions such as nutrient contents and cloudiness.Material digitalizado en SEDICI gracias a la colaboración de la Facultad de Ciencias Astronómicas y Geofísicas (UNLP).Asociación Argentina de Geofísicos y Geodesta

Palinotaxonomia da seção cretácea a neogena da Bacia de Pelotas, Brasil: cistos de dinoflagelados das ordens Ptychodiscales e Gonyaulacales

Dinoflagellate cysts are commonly used to obtain the relative ages, correlations and paleoenvironmental interpretations of the Cretaceous and Paleogenic sections of the Brazilian continental margin. However, the micropaleontological data of the Pelotas Basin is mainly concerning to calcareous microfossils, which is not true for the sedimentary deposits of the Pelotas Basin, whose micropaleontological informations is mostly referring by calcareous microfossils. In this second contribution, we present the systematic and descriptive detailing of the dinoflagellates cysts of the Ptychodiscales and Gonyaulacales orders, from the analysis of 535 samples collected from two wells (BP-01 and BP-02) drilled by Petrobras S.A. in the offshore portion of the Pelotas Basin. The levels analyzed are rich and diverse, enabling the recognition of 137 species. In greater numbers, cysts belonging to the Order Gonyaulacales include 76 genera, 133 species, besides three sub-species. Two genera and four species were assigned to the Order Ptychodiscales. Among the described taxa, 72 are cited for the first time for the Brazilian basins. The recognized associations indicated ages between the Cretaceous and the Neogene, based on the occurrences of E. dettmanniae, D. acuminatum and O. indigena for the Cretaceous; D. californica, D. carposphaeropsis and E. reticulata for the Paleocene; B. longissimum, M. fimbriatum and M. perforatum for the Eocene; C. galea, C. aubryae and H. obscura for the Miocene. R. actinocoronata and A. andalousiensis recorded at the post-Miocene levels of the basin are indicative of younger ages, possibly positioned between the Pliocene and the PleistoceneCistos de dinoflagelados são comumente utilizados para a obtenção das idades relativas, correlações e interpretações paleoambientais das seções cretáceas e paleógenas da margem continental brasileira. Contudo, as informações micropaleontológicas da Bacia de Pelotas são referentes, na sua maioria, a microfósseis calcários. Nesta segunda contribuição, o detalhamento sistemático e descritivo das associações de cistos de dinoflagelados das ordens Ptychodiscales e Gonyaulacales é apresentado, a partir da análise 535 amostras de dois poços (BP-01 e BP-02) perfurados pela Petrobras S.A. na porção offshore da Bacia de Pelotas. Os níveis analisados mostraram-se ricos e diversificados, possibilitando o reconhecimento 137 espécies de cistos de dinoflagelados. Em maior número, cistos pertencentes à Ordem Gonyaulacales totalizaram 76 gêneros, 133 espécies, além de três subespécies. Dois gêneros e quatro espécies foram conferidos à Ordem Ptychodiscales. Do total de táxons descritos, 72 são citados pela primeira vez para as bacias brasileiras. As associações reconhecidas indicaram idades entre o Crétaceo e o Neogeno, tendo como base as ocorrências de E. dettmanniae, D. acuminatum e O. indigena para o Cretáceo; D. californica, D. carposphaeropsis e E. reticulata para o Paleoceno; B. longissimum, M. fimbriatum e M. perforatum para o Eoceno; C. galea, C. aubryae e H. obscura para o Mioceno. R. actinocoronata e A. andalousiensis, registradas em níveis pós miocênicos da bacia, são indicativas de idades mais jovens, possivelmente posicionadas entre o Plioceno e o Pleistoceno

Palinotaxonomia da seção cretácea a neogena da Bacia de Pelotas, Brasil: cistos de dinoflagelados da Ordem Peridiniales

Major part of micropaleontological knowledge of the Pelotas Basin is related to calcareous microfossils, justifying a systematic survey on the palynological data. This paper presents the taxonomic results from the study of 535 stratigraphic samples of two wells drilled in the offshore portion of the Pelotas Basin, enclosing Cretaceous to Neogene deposits. Palynological assemblages analized are diverse and abundant, consisting of spores (mosses and ferns), pollen grains (gymnosperms and angiosperms), dinoflagellate cysts, palynoforaminifers, scolecodonts and fungal spores. As a result of the large volume of generated data, it was necessary, for effect of publication, the compartimentation of the information. In this first part, dinoflagellate cysts Peridiniales Order are presented, with descriptions and photomicrographs. Among the 220 taxa identified of dinoflagellate cyst, 76 belong to the Peridiniales Order, attributable to 31 genera, 72 species, a subspecie, beyond two taxa described without specific determination. A considerable number of 24 species reported for the first time for Brazilian basins is highlighted. Biostratigraphic and paleobiogeographic considerations are synthetically discussed, based on the associations recognized for Late Cretaceous and Neogene in American Atlantic margin and regions close to the Antartic Polar Circle.Grande parte do conhecimento micropaleontológico da Bacia de Pelotas é referente a microfósseis de parede calcária, o que justifica a necessidade de levantamento sistemático de dados palinológicos. Este trabalho apresenta os resultados palinológicos obtidos a partir da análise de 535 amostras de dois poços perfurados na porção offshore da Bacia de Pelotas, incluindo depósitos do Cretáceo ao Neogeno. Os conjuntos palinológicos reconhecidos são ricos e diversificados, constituídos por esporos (briófitas e pteridófitas), grãos de pólen (gimnospermas e angiospermas), cistos de dinoflagelados, palinoforaminíferos, escolecodontes e esporos de fungos. Como consequência do grande volume de dados gerados, se fez necessário, para efeito de publicação, a compartimentação das informações. Nesta primeira contribuição, cistos de dinoflagelados da Ordem Peridiniales são apresentados, com descrições e fotomicrografias. Dentre os 220 táxons de cistos de dinoflagelados identificados, 76 são referentes à Ordem Peridiniales, compreendendo 31 gêneros, 72 espécies, uma subespécie, além de dois táxons sem determinação específica. Ressaltam-se ainda 24 espécies documentadas pela primeira vez para o Brasil. Considerações bioestratigráficas e paleobiogeográficas são discutidas sinteticamente, tendo como base as associações reconhecidas para o Cretáceo Superior e o Neogeno na margem atlântica americana e regiões próximas ao Círculo Polar Antártico

New insights on the Paleogene dinoflagellate cyst genera Enneadocysta and Licracysta gen. nov. based on material from offshore eastern Canada and southern Argentina

Enneadocysta is a biostratigraphically important Paleogene dinoflagellate cyst genus. Its original interpretation as a partiform gonyaulacoid (thus belonging to the gonyaulacalean suborder Cladopyxiineae) was based on the presence of two antapical processes. Another Paleogene genus, Areosphaeridium, is similar, at least superficially, to Enneadocysta, but has a single antapical process, placing it in the sexiform gonyaulacalean suborder Gonyaulacineae. The morphology of a new species of Enneadocysta from offshore eastern Canada, Enneadocysta magna, shows that the two antapical processes of the genus (unlike processes reflecting other plate series) are penitabular, not mesotabular, and indicates that the genus is gonyaulacinean, not cladopyxiinean. This new interpretation, as well as new material from southern Argentina, confirms the generic assignment of the Southern Hemisphere species Enneadocysta dictyostila (emended) and a new species, Enneadocysta brevistila. A new genus and species, Licracysta corymbus, from offshore eastern Canada is intermediate in morphology between Enneadocysta and Cleistosphaeridium and strongly suggests an assignment for all three genera to the gonyaulacinean family Areoligeraceae. The new combination Licracysta? semicirculata is questionably proposed, and the descriptive terms licrate, dolabrate, entire clypeate, ragged clypeate, intratabular, mesotabular, obtabular, contabular and nontabular are either proposed as new or reviewed.Fil: Fensome, R. A.. Natural Resources Canada, Geological Survey; CanadáFil: 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: Williams, G. L.. Natural Resources Canada, Geological Survey; Canad

A new areoligeracean dinoflagellate from the Miocene of offshore eastern Canada and its evolutionary implications

Volume: 41Start Page: 23End Page: 3

Eocene southern Atlantic Ocean dinoflagellate cysts: regional correlation and paleoenvironments

The Eocene was a time of regional tectonic events and climatological changes, related to the opening of the Drake Passage that separated South America from Antarctica. Knowledge of the timing of the Drake rifting can help us understand the new oceanographic regime and its consequences. In this sense, dinoflagellate cysts (dinocysts) are useful tools for biostratigraphy and palaeoceanographic reconstructions. For this purpose, we analyzed dinocyst assemblages from lithostratigraphic units adjacent to the Drake Passage, including the Man Aike (MA), the Upper Member of the Río Turbio (umRT) and Leticia (Le) formations, outcropping in the Austral-Magallanes Basin, southern Patagonia, and the La Meseta Formation (LM), from the James Ross Basin, Antarctica. Our quantitative information of the dinocyst assemblages of the aforementioned units together with the recently published radiometric data were taken into account to update the biostratigraphic scheme for the Austral-Magallanes Basin, adjusting the ages of the dinocyst biozones and bioevents proposed for the umRT. The statistical compositional analysis of the quantitative dinocyst assemblages performed in this work allowed us to confirm the correlation of the formations, showing a high equivalence between the middle Eocene (Bartonian, 41 ˗ 37 Ma) assemblages (lower part of the umRT, MA, Le and LM) separating from the late Eocene (< 36 Ma) ones (upper part of the umRT). In addition, the statistical results revealed different palaeoenvironments. While the Bartonian assemblages represent relatively warm waters in inland shelf environments, those of the Priabonian indicated coastal areas with cold, nutrient-rich surface waters.Fil: Daners, G.. Universidad de la Republica Montevideo; 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. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Cátedra de Paleontología; ArgentinaFil: Alperin, Marta Ines. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; 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; Argentina3rd Palaeontological Virtual CongressArgentinaPalaeontological Societ

Palinotaxonomia da seção cretácea a neogena da Bacia de Pelotas, Brasil: cistos de dinoflagelados da Ordem Peridiniales

Major part of micropaleontological knowledge of the Pelotas Basin is related to calcareous microfossils, justifying a systematic survey on the palynological data. This paper presents the taxonomic results from the study of 535 stratigraphic samples of two wells drilled in the offshore portion of the Pelotas Basin, enclosing Cretaceous to Neogene deposits. Palynological assemblages analized are diverse and abundant, consisting of spores (mosses and ferns), pollen grains (gymnosperms and angiosperms), dinoflagellate cysts, palynoforaminifers, scolecodonts and fungal spores. As a result of the large volume of generated data, it was necessary, for effect of publication, the compartimentation of the information. In this first part, dinoflagellate cysts Peridiniales Order are presented, with descriptions and photomicrographs. Among the 220 taxa identified of dinoflagellate cyst, 76 belong to the Peridiniales Order, attributable to 31 genera, 72 species, a subspecie, beyond two taxa described without specific determination. A considerable number of 24 species reported for the first time for Brazilian basins is highlighted. Biostratigraphic and paleobiogeographic considerations are synthetically discussed, based on the associations recognized for Late Cretaceous and Neogene in American Atlantic margin and regions close to the Antartic Polar Circle.Grande parte do conhecimento micropaleontológico da Bacia de Pelotas é referente a microfósseis de parede calcária, o que justifica a necessidade de levantamento sistemático de dados palinológicos. Este trabalho apresenta os resultados palinológicos obtidos a partir da análise de 535 amostras de dois poços perfurados na porção offshore da Bacia de Pelotas, incluindo depósitos do Cretáceo ao Neogeno. Os conjuntos palinológicos reconhecidos são ricos e diversificados, constituídos por esporos (briófitas e pteridófitas), grãos de pólen (gimnospermas e angiospermas), cistos de dinoflagelados, palinoforaminíferos, escolecodontes e esporos de fungos. Como consequência do grande volume de dados gerados, se fez necessário, para efeito de publicação, a compartimentação das informações. Nesta primeira contribuição, cistos de dinoflagelados da Ordem Peridiniales são apresentados, com descrições e fotomicrografias. Dentre os 220 táxons de cistos de dinoflagelados identificados, 76 são referentes à Ordem Peridiniales, compreendendo 31 gêneros, 72 espécies, uma subespécie, além de dois táxons sem determinação específica. Ressaltam-se ainda 24 espécies documentadas pela primeira vez para o Brasil. Considerações bioestratigráficas e paleobiogeográficas são discutidas sinteticamente, tendo como base as associações reconhecidas para o Cretáceo Superior e o Neogeno na margem atlântica americana e regiões próximas ao Círculo Polar Antártico

Campanian-Eocene dinoflagellate cyst biostratigraphy in the Southern Andean foreland basin: Implications for Drake Passage throughflow

The tectonic opening of the Tasmanian Gateway and Drake Passage represented crucial geographic requirements for the Cenozoic development of the Antarctic Circumpolar Current (ACC). Particularly the tectonic complexity of Drake Passage has hampered the exact dating of the opening and deepening phases, and the consequential onset of throughflow of the ACC. One of the obstacles is putting key regional tectonic events, recorded in southern Patagonian sediments, in absolute time. For that purpose, we have collected Campanian-Eocene sediment samples from the Chilean sector of Southern Patagonia. Using U-Pb radiometric dating on zircons and dinoflagellate cyst biostratigraphy, we updated age constraints for the sedimentary formations, and the hiatuses in between. Thick sedimentary packages of shallow-marine and continental sediments were deposited in the foreland basin during the early Campanian, mid-Paleocene, the Paleocene-Eocene boundary interval and the middle Eocene, which represent phases of increased foreland subsidence. We interpret regional sedimentary hiatuses spanning the late Campanian, early-to mid-Paleocene, mid-Eocene and latest Eocene-early Oligocene to indicate times of reduced foreland subsidence, relative to sediment supply. We relate these changes to varying subduction rates and Andean orogeny. Dinoflagellate cyst assemblages suggest that the region was under the influence of the Antarctic-derived waters through the western boundary current of the Subpolar Gyre, developed in the southwest Atlantic Ocean and thus argues for limited throughflow through the Drake Passage until at least the latest Eocene. However, the proliferation of dinoflagellate endemism we record in the southwest Atlantic is coeval with that in the southwest Pacific, and on a species level, dinoflagellate cyst assemblages are the same in these two regions. This suggests that both regions were oceanographically connected throughout the early Paleogene, likely through a shallow opening of a restricted Drake Passage. This implies a continuous surface-water connection between the south Pacific and the South Atlantic throughout the late Cretaceous-early Paleogene