National University of La Plata

About: National University of La Plata is a education organization based out in La Plata, Argentina. It is known for research contribution in the topics: Population & Stars. The organization has 12993 authors who have published 30013 publications receiving 495118 citations. The organization is also known as: UNLP & Universidad Nacional de La Plata.

Biozonación paleoflorística y cronoestratigrafía del Triásico argentino

Abstract: A paleobotanical biozonation and a chronostratigraphic chart for the continental Triassic of Argentina are proposed. The biostratigraphic study was based on the multivariate analysis of 218 taxa distributed in 15 lithostratigraphic units and 134 taxa from 28 paleocommunities. The biostratigraphic analysis was also supported on the Permian or Jurassic lineage of several species, their acme, the temporal turnover and the evolution of the paleofloras. This information was evaluated together with the stratigraphic location of the fossiliferous horizons, the geochronologic information and the relationship between paleocommunities and sedimentary facies and environments. Five biozones were defined: 1. Dictvoptiullum castellanosii, [ohnsionia stcizneriana and Saportaea dichotoma Biozone (CSD), Represented by a mixed forest and identified in the Barreal and lschichuca Forrnations. 2. Yabeiella marefesiaca, Scytophylllll11 bonettiae and Protoptvflloctadoxvion cormderitacnsis Biozone (MBC). Mixed forests recognized in the Potrerillos, Cortaderita (lower section) and El Alcazar Formations. 3. Ynbeiella brackebuschiana, Scytophylllll11 neuburgianum and Rhexoxvlon piatnitzkui Biozone (BNP). Mixed forests, identified in the Vera, Potrerillos and Ischigualasto Formations, and in the El Tranquilo Group. 4. Dicroidium odontopteroides and D. lancijolium Biozone (OL). Represented by a herbaceous and shrub-like paleocornmunity, defined in the Cacheuta Formation and in the upper section of the Cortaderita Formation. 5. Dictyop/iylllll11 tenuiserraium, Linguijoliuni arctum and Protocircoporoxylon nuirionoensis Biozone (DLM). Deciduous and mesoxerophytic forests, identified in the Los Colorados and Rio Blanco redbeds, the Paso Flores Formation and the Tronquimalal Group. The following local stages are defined on the bases of biozone chronology, analysis of the main stratigraphic unconformities and evolution of the basin infill: Barrealian (Early to Middle Triassic), Cortaritian (late Middle to early Late Triassic) and Flarian (upper Late Triassic).

Fish assemblage and environmental patterns in the Rı́o de la Plata estuary

Abstract: The presence of persistent fish assemblage areas in estuaries can result from spatially structured environmental gradients, which determine a pattern of biological zonation. In the Rio de la Plata estuary (36 °S, 56 °W), those assemblage areas were defined for summer, autumn, and spring of 1996. Cluster analysis identified groups of sampling stations with a similar species composition for each season. Our results identified three fish assemblage areas along the main axis of the estuary. These assemblages are persistent in specific composition and correspond to particular oceanographic environments throughout the year. The boundaries of the assemblage areas are associated with the highest horizontal gradients of salinity. Geographic variations of the boundaries, indicating contraction or expansion of fish assemblage areas, were associated with the spatial estuarine dynamics. The fish assemblage areas reflect the local pattern of habitat heterogeneity. This suggests that for large estuaries, the fish assemblage areas are indicators of this spatial scale of habitat heterogeneity, as defined by salinity and stratification of water column.