Contribución al conocimiento de los foraminíferos del Rocanense de la cuenca de Añelo (provincia de Neuquén)

A foramíníferal fauna From three profiles coIlected in cuenca de Añelo (Provincia de Neuquén ) has been studíed. A list of bentonic and planctonic specimens ís given. From planctonic foramínífera Globoconusa daubiergensis, Subbotina triloculidinoides and Turborotalia peudobulloides, a Lower Paleocene age js assigned to the studied samples.Facultad de Ciencias Naturales y Muse

Contribución al conocimiento de los foraminíferos del Rocanense de la cuenca de Añelo (provincia de Neuquén)

A foramíníferal fauna From three profiles coIlected in cuenca de Añelo (Provincia de Neuquén ) has been studíed. A list of bentonic and planctonic specimens ís given. From planctonic foramínífera Globoconusa daubiergensis, Subbotina triloculidinoides and Turborotalia peudobulloides, a Lower Paleocene age js assigned to the studied samples.Facultad de Ciencias Naturales y Muse

Spatial and temporal uplift history of South America from calibrated drainage analysis

A multidisciplinary approach is used to analyze the Cenozoic uplift history of South America. Residual depth anomalies of oceanic crust abutting this continent help to determine the pattern of present-day dynamic topography. Admittance analysis and crustal thickness measurements indicate that the elastic thickness of the Borborema and Altiplano regions is ≤₁₀ km with evidence for sub-plate support at longer wavelengths. A drainage inventory of 1827 river profiles is assembled and used to investigate landscape development. Linear inverse modeling enables river profiles to be fitted as a function of the spatial and temporal history of regional uplift. Erosional parameters are calibrated using observations from the Borborema Plateau and tested against continent-wide stratigraphic and thermochronologic constraints. Our results predict that two phases of regional uplift of the Altiplano plateau occurred in Neogene times. Regional uplift of the southern Patagonian Andes also appears to have occurred in Early Miocene times. The consistency between observed and predicted histories for the Borborema, Altiplano, and Patagonian plateaux implies that drainage networks record coherent signals that are amenable to simple modeling strategies. Finally, the predicted pattern of incision across the Amazon catchment constrains solid sedimentary flux at the Foz do Amazonas. Observed and calculated flux estimates match, suggesting that erosion and deposition were triggered by regional Andean uplift during Miocene times

Antarcticella: a Paleogene typical foraminiferal genus from southernmost South America

The Patagonian and Fuegian regions conform a wide latitudinal and chronostratigraphical study area, where the abundant calcareous benthic foraminifera endemic to the Austral high and high-mid latitudes, have a partially or totally tuberculate surface. Among them, is the extinct Antarcticella, a small globular genus initially regarded as planktonic. The oldest species, A. pauciloculata (Jenkins), is widespread in the Danian from Patagonia, Antarctica, and New Zealand; the subsequent A. cecionii (Cañón and Ernst) is constrained to the Fuegian early and early middle Eocene; there is no record of Antarcticella from the mid middle Eocene, partially due to a sedimentary gap. The youngest, and type species A. antarctica (Leckie and Webb), originally recorded from the latest Oligocene up to early Miocene of Antarctica, ranges from the late Eocene up to the middle Miocene, reaching the maximum latitudinal distribution of the genus in the latest Oligocene-early Miocene, from the Austral Basin up to Península Valdés Basin (43°S). Because extreme morphotypes of megalospherical forms of the three species exhibit some preferential paleogeographical distribution and have a very different morphological aspect from the typical microspheric ones, they are informally named as infrasubspecific entities: A. pauciloculata forma primitiva, from the Danian of the Colorado and Golfo de San Jorge basins; A. cecionii forma noguerense and A. cecionii forma buenoense, from the Austral Basin lower Eocene and lower mid Eocene, respectively, and A. antarctica forma incognita, from the Austral Basin upper Eocene. The marked dimorphism, unknown in planktonic foraminifera, confirms the benthic paleohabit of Antarcticella. Its distribution in different paleoenvironments points to an opportunistic behavior, and its abundance in organic-rich paleoenvironments is consistent with the preferences of modern infaunal spherical morphotypes. The distribution of this genus reveals the major penetration of Antarctic waters in Patagonia in the latest Oligocene-early Miocene.Simposio II: El Paleógeno de América del Sur y CentralFacultad de Ciencias Naturales y Muse

A case of pore mounds in Paleogene buliminids from the Austral Basin, Argentina

Pore mounded (mamelones centralmente perforados) wall texture is characterized by the accumulation of shell material around pores, creating mound structures described as a typical wall texture often present in serial planktonic foraminifera such as the Santonian-Paleocene triserial genus Guembelitria. A surface wall texture with well developed and distinctive pore mounds is also recorded in the Austral Basin in two phylogenetically related buliminid species, Bulimina fueguina Malumián and "Kolesnikovella" severini (Cañón and Ernst). Both species have no adequate generic assignment and both are frequent and apparently endemic to the Austral Basin. The former has three chambers per whorl and is mostly recorded in the late middle Eocene, and the latter one, exhibits a tendency to have two chambers per whorl and is recorded in the late Eocene. Although rare, pore mounds are also known from other buliminid species elsewhere, thus being apparently associated to buliminid taxa among benthic foraminifera. This association seems consistent with the buliminid ancestors proposed for the modern triserial planktonic foraminifera, based on genetic studies, as well as for Cretaceous serial planktonic foraminifera, based on morphological and stratigraphical grounds.Simposio II: El Paleógeno de América del Sur y CentralFacultad de Ciencias Naturales y Muse

The Upper Cretaceous-Paleogene from the Río Bueno area, Atlantic coast of the Isla Grande de Tierra del Fuego

A composite section, 1400 m thick, is established for the Upper Cretaceous-Paleogene strata in the fold and thrust belt of the Andes Fueguinos, south of 54° 30′S. The basal Policarpo Formation, > 350 m thick, consists of tuffaceous sandstones and bioturbated sandstones and siltstones. The ammonites Maorites densicostatus and Diplomoceras sp.; foraminifera common to the Gaudryina healyi Zone; and the dynocysts Manumiella seelandica and Operculodium cf. azcaratei indicate a Maastrichtian age. The Paleocene to lower Eocene include four new formations. The Cabo Leticia Formation, c.150 m, Paleocene, consists of gravity flows deposits: brecchias; conglomerates; and massive, tuffaceous sandstones. La Barca Formation, c. 220 m, includes two members: LB1, tuffaceous sandstones and intercalated carbonaceous siltstones; and LB2, black mudstones with Palaeocystodinium golzowense and Spiroplectammina spectabilis. P. golzowense and the Bulimina karpatica Assemblage in LB1 indicate a late Paleocene age. Punta Noguera Formation, 380 m, is dominated by glauconite rich, massive, tuffaceous sandstones with interbedded turbidite packages. The dynocyst group Apectodinium, Deflandrea robusta, Palaeocystodinium sp., and Odontodinium askinae; the foraminifera Alabamina creta, Charltonina acutimarginata, Valvulineria teurensis and the first ocurrence of Elphidium and Cribrorotalia suggest an age near the Paleocene/Eocene boundary. The Cerro Ruperto Formation, 200 m, is dominated by glauconite rich, silty very fine sandstones and siltstones; dominance of Deflandrea dartmooria indicate an early Eocene age. Resting on angular unconformity, the Río Bueno Formation, c. 60-80 m, consists of carbonate rocks; its member RB1, rhythmically bedded grainstones, with the planktic foraminifera Planorotalites australiformis and Subbotina linaperta is of early middle Eocene age; and its member RB2, regular alternation of grainstones and bioturbated marls and micrites, with Elphidium saginatum and Bulimina cf. bortonica, is assigned to the mid middle Eocene. The sedimentary and stratigraphic features of the Maastrichtian/Eocene have a strong tectonic control, suggesting that the foreland phase of evolution of the basin has been active at least since the Maastrichtian.Fil:Olivero, E.B. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Malumián, N. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Scasso, R.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Una nueva megaflora (maderas y hojas fósiles) del Mioceno del suroeste de la Patagonia

A new megaflora composed of fossil woods and leaves is described. The bearing sediments overlie the Santa Cruz Formation (early Miocene), making it one of the youngest fossil megafloras described from southern Patagonia. The fossil woods is carbonized and found as clasts within a conglomerate. It includes a few specimens representing Araucariaceae (Agathoxylon sp.), Podocarpaceae (Phyllocladoxylon sp.), Cupressaceae (Cupressinoxylon sp.) and two indeterminable angiosperms with anatomical features consistent with Nothofagaceae. Most leaves are assigned to Nothofagaceae while a few specimens are related to Lauraceae, Typhaceae, Leguminosae, and a conifer. The recovered assemblage suggests a temperate climate similar to that of northern Patagonia today, inhabited by extant relatives of the fossils described herein.Una nueva megaflora compuesta por maderas y hojas fósiles es presentada. Los sedimentos portadores sobreyacen a la Formación Santa Cruz (Mioceno inferior), por lo tanto es una de las megafloras más jóvenes del sur patagónico descripta. Las maderas fósiles están carbonizadas y se encuentran como clastos de un conglomerado. Están representadas por unos pocos especímenes de Araucariaceae (Agathoxylon sp.), Podocarpaceae (Phyllocladoxylon sp.), Cupressaceae (Cupressinoxylon sp.) y dos angiospermas no determinadas que poseen una anatomía consistente con la de las Nothofagaceae. Las hojas son en su mayoría asignadas a las Nothofagaceae, acompañadas por Lauraceae, Typhaceae, Leguminosae y una conifera. El conjunto de fósiles sugiere un clima templado similar al actual de la Patagonia norte, donde viven parientes vivos de los fósiles descriptos.Fil: Pujana, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; ArgentinaFil: Panti, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; ArgentinaFil: Cuitiño, José Ignacio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: García Massini, Juan Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Cientificas y Transferencia Tecnológica de Anillaco; ArgentinaFil: Mirabelli, Sebastian Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentin