Examinando por Autor "Gordillo, Sandra"

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  • Artículo
    Acceso Abierto
    Late Pleistocene–Recent marine malacological assemblages of the Colorado River delta (south of Buenos Aires Province): Paleoecology and paleoclimatology
    (2015) Charó, Melisa Paola; Fucks, Enrique; Gordillo, Sandra
    The most recent Quaternary marine transgressions are well represented along the South Atlantic coast. In the Colorado River delta (39°15′S–39°55′S), south of Buenos Aires Province these deposits are mostly littoral ridges and tidal plains with abundant fossil marine fauna. Seventeen localities were analyzed (five Pleistocene, seven Holocene and five modern ones) representing the Interglacials≥MIS 9, MIS 5e and MIS 1. A total of 51 species were recorded (29 bivalves and 22 gastropods), together with nine micromolluscs. MIS 1 and the modern coast (37 and 42 species respectively) are the richest ones in species, unlike MIS 5e and MIS 9 (18 and 2 species respectively). In ≥MIS 9, the most abundant species isPitar rostratus. MIS 5e and MIS 1 have in common the presence and abundance of the gastropodHeleobia australisand the bivalveTagelus plebeius, as typical fauna of low energy environments, being the bivalveGlycymeris longiorand the gastropodsBostrycapulus oditesandBuccinanops globulosuscommon species in both kinds of marine deposits. Approximately 90% of bivalves and 75-71% of gastropods of the marine fauna are recorded from MIS 5e to the present. According to the different descriptive analyses (Bray–Curtis Index and AC) the molluscan fauna was grouped in two and five assemblages respectively, defined by age, type of deposit, and presence and/or abundance of species. Marine species represented in the area of the Colorado River delta vary in abundance among the interglacials but not in faunal composition. One of the possible causes would be the global climatic changes (e.g., rise of sea surface temperature SST) and the heterogeneity of habitats that would have conditioned the development of the different faunal assemblages during the Quaternary.
  • Artículo
    Embargado
    Late Quaternary molluscs from the northern San Matías Gulf (Northern Patagonia, Argentina), southwestern Atlantic: Faunistic changes and paleoenvironmental interpretation
    (2014) Charó, M.P.; Gordillo, Sandra; Fucks, Enrique; Giaconi, Mario
    The Late Quaternary in the coastal area of South America is represented mostly by littoral ridges, cliffs and tidal plains, with associated remains of gastropods and bivalves currently used as paleoclimatic indicators. The aim of this study is to characterize the assemblages of molluscs (bivalves and gastropods) both Pleistocene (≥MIS 9, MIS 7, MIS 5e) and Holocene (MIS 1), from the northern San Matías Gulf (Northern Patagonia, Argentina) in the southwestern Atlantic Ocean, in order to assess whether faunal change occurred together with Late Quaternary climatic change. Twenty localities were studied, seven from different interglacial stages of the Pleistocene, six Holocene, and seven modern beaches, in which 42 species were recorded, 20 bivalves and 22 gastropods. Among bivalves, euryhaline, infaunal from sandy substrates, and filter feeders, prevail.Amiantis purpuratais the dominant species of the whole mollusc assemblage. Among gastropods, although also euryhaline, the epifaunal species of rocky and sandy substrates and carnivores prevail. On the basis of descriptive statistical analyses, Bray–Curtis and AC methods, the localities formed three groups according to ages (modern vs. Pleistocene and Holocene) and/or presence/abundance of species. 70% of the marine malacofauna of MIS 7 remains during MIS 5e, decreasing to 60% during MIS 1 and to 27% when compared to the modern beaches. The most notable changes in the distribution of the species were:Tegula atra, currently extinct in the Argentine Atlantic coast, but recorded in Pleistocene interglacials MIS 7 and MIS 5e;Anomalocardia brasiliana, which only appeared in MIS 5e, andMesodesma mactroidesin MIS 1. MIS 5e was likely the warmest stage within the period considered, followed by MIS 7, both with higher SST temperatures than the present ones, and since MIS 1, molluscs of temperate-cold lineages of the Magellan malacological province are recorded.
  • Artículo
    Embargado
    Late Quaternary molluscs from the northern San Matías Gulf (Northern Patagonia, Argentina), southwestern Atlantic: Faunistic changes and paleoenvironmental interpretation
    (2014) Charó, M.P.; Gordillo, Sandra; Fucks, Enrique; Giaconi, L.M.
    The Late Quaternary in the coastal area of South America is represented mostly by littoral ridges, cliffs and tidal plains, with associated remains of gastropods and bivalves currently used as paleoclimatic indicators. The aim of this study is to characterize the assemblages of molluscs (bivalves and gastropods) both Pleistocene (≥MIS 9, MIS 7, MIS 5e) and Holocene (MIS 1), from the northern San Matías Gulf (Northern Patagonia, Argentina) in the southwestern Atlantic Ocean, in order to assess whether faunal change occurred together with Late Quaternary climatic change. Twenty localities were studied, seven from different interglacial stages of the Pleistocene, six Holocene, and seven modern beaches, in which 42 species were recorded, 20 bivalves and 22 gastropods. Among bivalves, euryhaline, infaunal from sandy substrates, and filter feeders, prevail.Amiantis purpuratais the dominant species of the whole mollusc assemblage. Among gastropods, although also euryhaline, the epifaunal species of rocky and sandy substrates and carnivores prevail. On the basis of descriptive statistical analyses, Bray–Curtis and AC methods, the localities formed three groups according to ages (modern vs. Pleistocene and Holocene) and/or presence/abundance of species. 70% of the marine malacofauna of MIS 7 remains during MIS 5e, decreasing to 60% during MIS 1 and to 27% when compared to the modern beaches. The most notable changes in the distribution of the species were:Tegula atra, currently extinct in the Argentine Atlantic coast, but recorded in Pleistocene interglacials MIS 7 and MIS 5e;Anomalocardia brasiliana, which only appeared in MIS 5e, andMesodesma mactroidesin MIS 1. MIS 5e was likely the warmest stage within the period considered, followed by MIS 7, both with higher SST temperatures than the present ones, and since MIS 1, molluscs of temperate-cold lineages of the Magellan malacological province are recorded.
  • Artículo
    Acceso Abierto
    Moluscos marinos bentónicos del Cuaternario de Bahía Anegada (sur de Buenos Aires, Argentina): variaciones faunísticas en el Pleistoceno tardío y Holoceno
    (2013) Charó, Melisa P.; Fucks, Enrique; Gordillo, Sandra
    A lo largo del área costera del Atlántico sudoccidental se observan depósitos marinos que representan los dos últimos eventos transgresivos del Cuaternario (Pleistoceno tardío y Holoceno). La región de Bahía Anegada, sur de la provincia de Buenos Aires, se caracteriza por la buena preservación y abundancia de fauna marina fósil, en especial de gasterópodos y bivalvos en los cordones litorales. Estos registros no han sido investigados con anterioridad desde el punto de vista paleontológico, y son de utilidad como indicadores de cambios ambientales del Cuaternario. El objetivo de este trabajo ha sido describir y comparar la fauna de moluscos del Pleistoceno tardío y Holoceno en Bahía Anegada. Para ello se analizaron dos áreas de la región: Canal Villalonga y Los Pocitos. Los depósitos marinos pleistocenos (asociados al estadio isotópico marino MIS5e) analizados para Bahía Anegada mostraron mayor número de especies, tanto de gasterópodos (17 versus 9) como bivalvos (14 versus 12) respecto al Holoceno. En los depósitos pleistocenos de Canal Villalonga se destaca la presencia de Crassostrea rhizophorae (Guilding) y Abra aequalis (Say) que actualmente tienen un área de distribución en latitudes bajas. En cuanto a los micromoluscos, se menciona por primera vez Turbonilla argentina Doello -Jurado para el Pleistoceno. Con base en estos análisis se concluye para la región estudiada que el Pleistoceno tardío registró mayor número de especies, tanto de bivalvos como gasterópodos, respecto al Holoceno, y que la abundancia de las especies del Pleistoceno se ha mantenido durante el Holoceno. Dichas variaciones se interpretan en asociación con cambios de la temperatura e indicarían condiciones más cálidas para el Pleistoceno tardío (último interglacial).
  • Artículo
    Embargado
    Multi-proxy evidence of Late Quaternary environmental changes in the coastal area of Puerto Lobos (northern Patagonia, Argentina)
    (2013) Boretto, G.M.; Gordillo, Sandra; Cioccale, M.; Colombo, F.; Fucks, Enrique
    A multidisciplinary approach involving geomorphology, taxa composition of mollusks and taphonomy performed on bivalve shells, linked to mineralogical and microstructural analyses, provide evidence of Late Quaternary environmental changes in the coastal area of Puerto Lobos, in northern Patagonia. Digital elevation models (DEMs) showed a beach ridge system developed parallel to the coast, indicating sea level variations during MIS1, MIS5e, and earlier in the Pleistocene. These ridges can be correlated with other marine ridges along the Patagonian coast, showing a similar geomorphological pattern and similar temporal evolution. In relation to faunal composition, when comparing the Pleistocene with the Holocene, the most relevant differences are the presence ofTegula atraandMactra patagonicain the Pleistocene sediments and a diversification of taxa in the Holocene. During the late Holocene, the coastal area of Puerto Lobos also recorded a faunal shift in which species belonging to the Magellan Province displaced the fauna of the Argentinean Province to the north, probably in coincidence with the Little Ice Age (LIA). Taphonomic analysis onGlycymeris longiorandVenus antiquashells, two common taxa in these beach ridges, indicate greater energy in the depositional environment correlated with the youngest Holocene beach ridge. These shells exhibited taphonomic differences between them in relation to fracturing, explained on the basis of higher elasticity in theG.longiorshell than inV.antiquashell, because of its crossed lamellar microstructure.
  • Artículo
    Embargado
    Paleoecological significance of Late Quaternary molluscan faunas of the Bahia San Blas area, Argentina
    (2013) Charó, M.P.; Gordillo, Sandra; Fucks, Enrique
    Late Quaternary marine deposits in the area of Bahía San Blas (Buenos Aires, Argentina) form beach ridges and tidal plains bearing remains of organisms, mainly mollusc shells. These mollusc assemblages were characterized, and their changes assessed both over time, and related to local environmental factors. Twenty-six sites were analyzed, eleven Pleistocene, seven Holocene and eight modern sites. Fifty taxa (27 bivalves and 23 gastropods) were recorded for the area, with marine species predominant over estuarine. Within gastropods, epifaunal species and carnivores are predominant, with a lower proportion of herbivores and filter feeders, while bivalves are mostly infaunal and suspension feeders. Pleistocene associations are characterized by the high quantity of molluscs in rocky environments, and those of the Holocene by the presence of the warm waterCrassostrea rhizophorae, which is currently displaced to lower latitudes. Within the modern associations four taxa,Mesodesma mactroides,Solen tehuelchus,Barnea lamellosaandCrassostrea gigas(an introduced species), are not recorded as fossils, butMesodesma mactroidesis found in Holocene shell middens from the area. According to multivariate analysis, the sites were divided into two groups: high energy deposits (storm ridges) and low-energy deposits (tidal plains), regardless of their age. Based on these results, mollusc variations in the area are thought to be related in part to changes in temperature that took place since the Pleistocene (e.g.C. rhizophorae); but mostly associated with the presence of sub-environments of different energy levels. This would favor the presence of different taxa in accordance to their ecological requirements.