The Marine Isotopic Stage 3 (MIS 3) in Valleys of the Undulated Pampa, Buenos Aires Province, Argentina

A depositional unit called DU2 identified for the period MIS 3 (ca- 30,000-60,000 yr. B.P.) formed by only one sedimentary facies (F3) was found in the Luján and Salto-Arrecifes rivers basins. F3 is a fluvio?lacustrine unit that overlies in erosive unconformity over eolian sediments with ages of 56,400 ± 6,500 and 50,400 ± 10,200 years B.A. and is unconformably covered by another eolian vitroclastic sandy loess deposit, dated as 32,000 ±4,000 years (Infrared Stimulated Luminescence, IRSL) (Blasi, et al. 2010). It represents the recurrence of ephemeral fluvial streamlets and the development of temporary pools by subsequent damming of channels. It corresponds lithologically to sandy muddy gravel, gravelly muddy sand, gravelly mud, olive to pale olive feldspar and quartz sands, bearing extinct mollusks such as Heleobia ameghini and Diplodon lujanensis. Radiocarbon chronologies obtained on monospecific samples of Cyprideis salebrosa hartmanni and Heleobia ameghini yielded ages of 37,710 ± 840 years 14C B.P. and >40,000 years 14C B.P., respectively. Furthermore, the age obtained through the IRSL technique was of 44,000 ± 6,500 years. Based upon the analyzed bioproxies (malacological, phytoliths and diatomological content) F3 accumulated under variable climatic conditions, ranging from temperate to colder and from subhumid to drier. According to the exhaustive stratigraphic identification, it is proposed that in NE Buenos Aires Province, the so-called Undulated Pampa region, the sediments that were accumulated during MIS3 occur only in the central portion of the studied fluvial basins. This prompted two hypotheses related to the existence of a particular drainage pattern for the Late Pleistocene, different from the present one, and subsequent tectonic controls that allowed the identification of DU2 sediments only in some of the analyzed sections.Fil: Blasi, Adriana María. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Mineralogía y Petrología; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Castiñeira Latorre, Carola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Mineralogía y Petrología; ArgentinaFil: 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: Carignano, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentin

Meso-Cenozoic paleotopographies and paleolandscapes in the Deseado Massif (Santa Cruz province, Argentina)

International audienceThe Deseado Massif is the southernmost part of a continent, outside of Antarctica, where Gondwana Landscapes may be observed and investigated. This paper present preliminary observations and field data about the Gondwana Landscapes of this cratonic area of Southern Argentina, one of the most remote, isolated and less populated places on Earth. Under extreme cold-arid climate conditions, the region presents very scarce vegetation cover, which further enables the geomorphological observations. Remnants of planation surfaces of undisputable Late Mesozoic age, developed on Jurassic volcanic units and covered by Late Cretaceous and Paleogene sedimentary rocks, are exposed along tens of thousands square kilometres of this cratonic unit. In those remote times, the climate of this portion of Patagonia was very wet and warm, responsible for the development of extensive chemical weathering. Volcanic and sedimentary paleosurfaces of younger ages were also recognized in the regional landscape, allowing a reconstruction of uplift and denudation histories since the Late Mesozoic