Late Quaternary lacustrine ostracods (Ostracoda, Crustacea) and charophytes (Charophyta, Charales) from the Puna Plateau, Argentina

Relatively little is known about the recent palaeontological records of the high-altitude closed basin lakes of the Central Andes, but a great need exists to remedy this knowledge gap if microfossils are to be used to infer climatic and ecological transitions from lake sediment cores. Here, eight species of non-marine ostracods and two calcareous algae are recorded from modern sediments and late Quaternary strata from Laguna de los Pozuelos, Jujuy Province, northwestern Argentina. Four species, Limnocythere alexanderi, Limnocythere foresteri, Limnocythere lysandrosi and Limnocythere ruipunctifinalis, are described as new species. Limnocythere titicaca Lerner-Seggev, 1973 has only been recorded in Lake Titicaca prior to this study and this is the first time the species is recognized outside of Bolivia. The cypridoideans Ilyocypris ramirezi Cusminsky & Whatley, 1996, Eucypris virgata Cusminsky & Whatley, 1996 and Chlamydotheca pseudobrasiliensis Martens & Behen 1994 are known species that are rare in the stratigraphic sequence in core LP06-6A. Also, the gyrogonites of two well-known species of Charophyta, Chara filiformis Hertzsch and Chara vulgaris Linnaeus, are occasionally present in the sediment from Laguna de los Pozuelos. The results provide a new vehicle for clarifying the Quaternary palaeohydrological history of the Pozuelos Basin, which is a RAMSAR wetland that is likely to be sensitive to global environmental change.Fil: Palacios Fest, Manuel R.. Terra Nostra Earth Sciences Research,; Estados UnidosFil: Cusminsky, Gabriela Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: McGlue, Michael M.. University of Kentucky; Estados Unido

Ostracode biofacies and shell chemistry reveal quaternary aquatic transitions in the Pozuelos basin (Argentina)

Here we present the first use of calcareous microfossils to examine the late Quaternary paleoecology of the endorheic Pozuelos Basin (Argentina). Modern deposition in the basin centers on Laguna de los Pozuelos (LP),a shallow playa-lake that is fed by axial rivers and groundwater and dominantly accumulates siliciclastic sediments.Today, the distribution of limnocytherid and cypridoidean ostracodes across southern LP is strongly influenced bydistance to the Rıo Cincel delta, whereas the northern end of the playa-lake is characterized by a paucity of ostracodes due to frequent sub-aerial exposure. Ten ostracode biofacies define a sediment core retrieved from LP,which reveal progressive changes in aquatic environments that varied in salinity, depth, and proximity to deltas over the late Pleistocene. Closed lakes occupied the basin from ~ 37.6?30.7 ka, ~ 28.0?25.0 ka, and ~ 23.0?16.6 ka,whereas saline wetlands occurred when these lakes contracted. Extant LP has no analog in the late Pleistocene record; it formed after ~ 7.2 ka, following a hiatus that removed the Pleistocene?Holocene transition.Paleoecological evidence indicates that the core site was influenced by deltaic inflows from the eastern basin margin until ~ 24.3 ka, an area where today dry alluvial fans are found. Reorganization of the watershed by normalfaulting, most likely at ~ 18.0 ka, appears to have reduced the influence of these deltaic inflows. Extensional neotectonics, perhaps induced by incorporation of the Pozuelos Basin into the Andean hinterland, is a mechanism that along with tropical climate change is potentially important to water balance and ecology in high-altitude convergent orogenic basins.Fil: McGlue, Michael M.. University of Kentucky; Estados UnidosFil: Palacios Fest, Manuel R.. Terra Nostra Earth Sciences Research; Estados UnidosFil: Cusminsky, Gabriela Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Camacho, Maria. Universidad Nacional de Jujuy; ArgentinaFil: Ivory, Sarah J.. University of Kentucky; Estados Unidos. University Brown; Estados UnidosFil: Kowler, Andrew L.. University of California; Estados UnidosFil: Chakraborty, Suvankar. University of Utah; Estados Unido

Changes in ostracod assemblages and morphologies during lake-level variations of Lago Cardiel (49°S), Patagonia, Argentina, over the last 15.6 ka

Changes in the ostracod assemblages from two sediment cores collected from Lago Cardiel in southeastern Patagonia (49°S) reflect the main regional abrupt climatic changes over the last 15.6 cal. ka BP. Shifts in species abundance and switches in dominances suggest that these were mainly driven by variable salinity. During the Late Pleistocene, Limnocythere rionegroensis was abundant and dominant, indicating waters with high salinity and prevalence of evaporative processes. Between 12.6 and 10.8 cal. ka BP, Lago Cardiel expanded markedly and reached an Early Holocene highstand of +55 m above present lake level. A major change in ostracod assemblage in which Limnocythere patagonica appears as the dominant species in parallel with the disappearance of L. rionegroensis and Eucypris aff. cecryphalium mirrored this transitional period between the cold and dry Late Pleistocene and the humid and warm Early Holocene. Over the last 4 cal. ka BP, L. rionegroensis returned to the species assemblage and Riocypris whatleyi increased its abundance pointing towards increasing salinities. The variations in size, shape and ornamentation of L. rionegroensis and R. whatleyi fossil valves were examined using geometric morphometric techniques and further compared to those of modern Patagonian sites. Limnocythere rionegroensis specimens displayed high morphological variability during the evolution of Lago Cardiel. More specifically, the switch in reproductive mode – from sexual to parthenogenetic– and the increase in valve ornamentation around 12.7 cal. ka BP suggest that these changes were promoted by the hydrological alteration that occurred in the Late Pleistocene. This exercise provides a robust range of morphological variation for these proxies, which will be useful in further taxonomic and palaeoenvironmental studies adding more information about different factors influencing the observed morphological trends.Fil: Ramos, Lorena Yésica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Alperin, Marta Ines. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; ArgentinaFil: Schwalb, A.. Technische Universität Braunschweig. Institut für Geosysteme und Bioindikation; AlemaniaFil: Markgraf, Vera. University of Colorado; Estados UnidosFil: Ariztegui, Daniel. Universidad de Ginebra; SuizaFil: Cusminsky, Gabriela Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentin