Micropaleontology of the Agrio Formation (Lower Cretaceous) in different areas of the Neuquén Basin

The nanoflora and microfauna from the Agrio Formation are analyzed in three different areas of the Neuquén Basin to establish its age and paleonvironmental variations. In the northern area of the basin, the oldest Agrio Fomation sedimentites are recognized and assigned to the Lower Valanginian through ammonites. A monospecific Epistomina loncochensis Ballent microfauna is recovered from these levels, which indicates disoxic environments. Up to the top of the section, siltstones contain a diverse foraminifera microfauna of normal shelves, which are replaced by an impoverished fauna related to shallowing processes. The age defined by calcareous nannofossils is Late Valanginian-Late Hauterivian. In the central and southern position of the Neuquén Basin, the nannofossil assemblages indicate the Upper Valanginian-Upper Hauterivian for the Agrio Formation. The benthic microfauna suggests frequent eustatic variations ranging from shelves to shallow marine environments. In the austral sector of the basin, a poorly diversified foraminiferal assemblage is recorded and a high ostracods/foraminifera ratio indicates a restricted marine environment, and normal salinity. The presence of a level with abundant attached foraminifera indicates high energy episodes. The high diversified Platycopida ostracods suggest warm-temperate to subtropical waters.Fil:Concheyro, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Lescano, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Caramés, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Cretaceous deposits in the Precordillera of La Rioja (Ciénaga del Río Huaco Formation)

This paper reports the presence of Maastrichtian rocks in the north of the Precordillera (La Rioja province). The Cretaceous succesion (122 m thick) is a classical red bed sequence composed of sandstones, mudstones, marls and thin levels of evaporites. According to lithological features 6 facies associations have been recognized that mainly characterize a lacustrine system developed under arid to semiarid conditions. Probably as a result of an increase in aridity, eolian sediments were deposited at the top of the Cretaceous unit. At least two transgressive-regressive events have been recognized in the lacustrine sequence. The best developed is the first event formed by fossiliferous black shales corresponding to the maximum flooding stage. These rocks have yield remains of calcareous microfossils, palynomorphs and gastropods. The former comprise charophytes, with Platychara compressa (Knowlton) an Tectochara sp. A Musacchio, anda ostracods, with Ilyocypris wichmanni punctata Musacchio y Simeoni, Eucandona? sp., Cypridopsis and Ovo cytheridea? rionegrensis Musacchio.. Palinomorphs form a monospecific assemblage of algae colonies corresponding to Pediastrum. The lithological features, stratigraphic location and fossiliferous remains clearly suggest a regional correlation with the Ciénaga del Rio Huaco Formation. This correlation considerably enlarge the regional distribution of the Cretaceous sediments which were previously limited to the Precordillera of San Juan province. © 2005 Asociación Geológica Argentina.Fil:Ciccioli, P.L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Tedesco, A.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Barreda, V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Limarino, C.O. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Gated communities: Definitions, causes and consequences

Gated communities became an 'object of study' in the 1990s as social scientists observed their growth in several cities; they are now a feature of the urban landscape in most cities around the world. The expansion of gated communities has led to prolific research, examining different aspects of this type of residential development and providing evidence from case studies worldwide. This paper reviews how gated communities are conceptualised according to the literature and identifies the main factors influencing their development. It also considers spatial, economic, political and social consequences of the development of gated communities. These elements should be taken into account by planners and policymakers to minimise their negative impacts and maximise the positive consequences of a residential option that is likely to be part of the urban landscape for a long time

Latest Cretaceous climatic and environmental change in the South Atlantic region

Latest Maastrichtian climate change caused by Deccan volcanism has been invoked as a cause of mass extinction at the Cretaceous-Paleogene (K-Pg) boundary (~66.0 Ma). Yet late Maastrichtian climate and ecological changes are poorly documented, in particular on the Southern Hemisphere. Here we present upper Maastrichtian-lower Danian climate and biotic records from the Bajada del Jagüel (BJ) shelf site (Neuquén Basin, Argentina), employing the TEX86 paleothermometer, marine palynology (dinoflagellate cysts), and micropaleontology (foraminifera). These records are correlated to the astronomically tuned Ocean Drilling Program Site 1262 (Walvis Ridge). Collectively, we use these records to assess climatic and ecological effects of Deccan volcanism in the Southern Atlantic region. Both the TEX86-based sea surface temperature (SST) record at BJ and the bulk carbonate δ18O-based SST record of Site 1262 show a latest Maastrichtian warming of ~2.5-4°C, at 450 to 150 kyr before the K-Pg boundary, coinciding with the a large Deccan outpouring phase. Benthic foraminiferal and dinocyst assemblage changes indicate that this warming resulted in enhanced runoff and stratification of the water column, likely resulting from more humid climate conditions in the Neuquén Basin. These climate conditions could have been caused by an expanding and strengthening thermal low over the South American continent. Biotic changes in response to late Maastrichtian environmental changes are rather limited, when compared to the major turnovers observed at many K-Pg boundary sites worldwide. This suggests that environmental perturbations during the latest Maastrichtian warming event were less severe than those following the K-Pg boundary impact

A review of the Mesozoic ostracod genus Progonocythere and its close allies

Volume: 39Start Page: 919End Page: 93

Micropaleontology of the Agrio Formation (Lower Cretaceous) in different areas of the Neuquén Basin

The nanoflora and microfauna from the Agrio Formation are analyzed in three different areas of the Neuquén Basin to establish its age and paleonvironmental variations. In the northern area of the basin, the oldest Agrio Fomation sedimentites are recognized and assigned to the Lower Valanginian through ammonites. A monospecific Epistomina loncochensis Ballent microfauna is recovered from these levels, which indicates disoxic environments. Up to the top of the section, siltstones contain a diverse foraminifera microfauna of normal shelves, which are replaced by an impoverished fauna related to shallowing processes. The age defined by calcareous nannofossils is Late Valanginian-Late Hauterivian. In the central and southern position of the Neuquén Basin, the nannofossil assemblages indicate the Upper Valanginian-Upper Hauterivian for the Agrio Formation. The benthic microfauna suggests frequent eustatic variations ranging from shelves to shallow marine environments. In the austral sector of the basin, a poorly diversified foraminiferal assemblage is recorded and a high ostracods/foraminifera ratio indicates a restricted marine environment, and normal salinity. The presence of a level with abundant attached foraminifera indicates high energy episodes. The high diversified Platycopida ostracods suggest warm-temperate to subtropical waters.Fil:Concheyro, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Lescano, M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Caramés, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Cretaceous deposits in the Precordillera of La Rioja (Ciénaga del Río Huaco Formation)

This paper reports the presence of Maastrichtian rocks in the north of the Precordillera (La Rioja province). The Cretaceous succesion (122 m thick) is a classical red bed sequence composed of sandstones, mudstones, marls and thin levels of evaporites. According to lithological features 6 facies associations have been recognized that mainly characterize a lacustrine system developed under arid to semiarid conditions. Probably as a result of an increase in aridity, eolian sediments were deposited at the top of the Cretaceous unit. At least two transgressive-regressive events have been recognized in the lacustrine sequence. The best developed is the first event formed by fossiliferous black shales corresponding to the maximum flooding stage. These rocks have yield remains of calcareous microfossils, palynomorphs and gastropods. The former comprise charophytes, with Platychara compressa (Knowlton) an Tectochara sp. A Musacchio, anda ostracods, with Ilyocypris wichmanni punctata Musacchio y Simeoni, Eucandona? sp., Cypridopsis and Ovo cytheridea? rionegrensis Musacchio.. Palinomorphs form a monospecific assemblage of algae colonies corresponding to Pediastrum. The lithological features, stratigraphic location and fossiliferous remains clearly suggest a regional correlation with the Ciénaga del Rio Huaco Formation. This correlation considerably enlarge the regional distribution of the Cretaceous sediments which were previously limited to the Precordillera of San Juan province. © 2005 Asociación Geológica Argentina.Fil:Ciccioli, P.L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Tedesco, A.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Barreda, V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.Fil:Limarino, C.O. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Modelled transport of benthic marine microplastic pollution in the Nazaré Canyon

With knowledge of typical hydrodynamic behavior of waste plastic material, models predicting the dispersal of benthic plastics from land sources within the ocean are possible. Here we investigated the hydrodynamic behavior (density, settling velocity and resuspension characteristics) of non-buoyant preproduction plastic pellets in the laboratory. From these results we used the MOHID modelling system to predict what would be the likely transport and deposition pathways of such material in the Nazaré Canyon (Portugal) during the spring/summer months of 2009 and the autumn/winter months of 2011. <br><br> Model outputs indicated that non-buoyant plastic pellets would likely be transported up and down canyon as a function of tidal forces, with only a minor net down canyon movement resulting from tidal action. The model indicated that transport down canyon was likely greater during the autumn/winter, primarily as a result of occasional mass transport events related to storm activity and internal wave action. Transport rates within the canyon were not predicted to be regular throughout the canyon system, with stretches of the upper canyon acting more as locations of pellet deposition than conduits of pellet transport. Topography and the depths of internal wave action are hypothesized to contribute to this lack of homogeneity in predicted transport

Physical transport properties of marine microplastic pollution

Abstract. Given the complexity of quantitative collection, knowledge of the distribution of microplastic pollution in many regions of the world ocean is patchy, both spatially and temporally, especially for the subsurface environment. However, with knowledge of typical hydrodynamic behavior of waste plastic material, models predicting the dispersal of pelagic and benthic plastics from land sources into the ocean are possible. Here we investigate three aspects of plastic distribution and transport in European waters. Firstly, we assess patterns in the distribution of plastics found in fluvial strandlines of the North Sea and how distribution may be related to flow velocities and distance from source. Second, we model transport of non-buoyant preproduction pellets in the Nazaré Canyon of Portugal using the MOHID system after assessing the density, settling velocity, critical and depositional shear stress characteristics of such waste plastics. Thirdly, we investigate the effect of surface turbulences and high pressures on a range of marine plastic debris categories (various densities, degradation states and shapes tested) in an experimental water column simulator tank and pressure laboratory. Plastics deposited on North Sea strandlines varied greatly spatially, as a function of material composition and distance from source. Model outputs indicated that such dense production pellets are likely transported up and down canyon as a function of tidal forces, with only very minor net down canyon movement. Behaviour of plastic fragments under turbulence varied greatly, with the dimensions of the material, as well as density, playing major determining roles. Pressure was shown to affect hydrodynamic behaviours of only low density foam plastics at pressures ≥ 60 bar. </jats:p