Claudio Carignano

Late Pleistocene to recent climate change in Córdoba Province, Argentina: Geomorphological evidence

Abstract Repeated episodes of climate change affected the Cordoba Plains during the Late Pleistocene and Holocene. Many of the geomorphologic features of Cordoba Province were developed in response to climatic oscillations, and their development can be correlated to changes in precipitation and hydrologic regimes. Alternating periods marked by dry climate and high evapotranspiration rates were interspersed with more humid intervals, and can be correlated using stratigraphic and geomorphic evidence at the regional level. The initial phase of the Late Pleistocene was characterized by significant loess deposition and the formation of large alluvial fans. These sediments and landforms are representative of a dry climate. The transition to the Late Pleistocene was marked by the initiation of a humid climate regime, giving rise to enhanced fluvial activity and sedimentation, expansion and integration of drainage networks, and development of paludal areas and successions. Pedogenesis occurred in the interbasin areas, involving precipitation of silica and sesquioxides. During Latest Pleistocene–Early Holocene time, coinciding in part with the ‘Last Glacial Maximum’, a dry and cool climate resulted in widespread aeolian sand and loess deposition. The Early to Mid-Holocene was characterized by humid subtropical conditions which became established throughout the region, accompanied by pedogenic development of profiles with prominent Bt horizons, and further modification of drainage networks. During the Mid to Late Holocene, these warm and humid conditions were replaced by a semiarid climate, resulting in widespread aeolian deposition. Wind action formed deflation hollows and dune fields in several areas. The climate reverted to subhumid and temperate conditions during the latter part of the Late Holocene, and small areas of wetlands developed. The Little Ice Age was marked by climatic deterioration, and the deposition of a thin layer of aeolian sediment. The current climate of Cordoba is subhumid and temperate.

A thermochronometric view into an ancient landscape: Tectonic setting, development, and inversion of the Paleozoic eastern Paganzo basin, Argentina

In this study, we utilize multiple thermochronometric methods, including apatite and zircon fission track, (U-Th)/He, and zircon U-Pb, to evaluate the cooling history and provenance of sedimentary strata of the late Carboniferous to Late Permian eastern Paganzo basin and adjacent basement rocks (Argentina). The strata in the study area represent a long-lived, composite basin system that is interpreted to have experienced multiple periods of deformation, and to have received sediment from a number of different source terranes. These strata are well exposed in the Sierra de Chepes of west-central Argentina. New thermochronometric data and field observations, together with published data from the surrounding mountains, allow us to reconstruct: (1) the cooling history of the underlying basement rocks and the highlands surrounding the basin, (2) the thermal history of the source areas that provided sediment to the basin, and (3) the timing of structural inversion of the basin. Our data suggest that parts of the Sierra de Chepes were rapidly exhumed in Late Devonian–Carboniferous times; these exhuming areas supplied sediment to the adjacent basin. In contrast, the overlying red-bed strata originated from a slowly exhuming region located farther east or north of the basin within the Pampean orogenic belt or the Famatinian belt, respectively. Burial by latest Carboniferous and younger strata and an elevated geothermal gradient resulted in heating of the underlying Upper Carboniferous strata and underlying granitoid basement to temperatures between 80 °C and 140 °C. During Triassic time, the eastern Paganzo basin was structurally inverted; this event was marked by rapid cooling and may be related to regional extension and the development of rift basins to the west. The basement and the Upper Paleozoic strata of the eastern Paganzo basin in the study area have remained below 50 °C since latest Jurassic–Early Cretaceous times and are characterized by very slow cooling. Results of this study provide a thermochronometric view along an ∼330 m.y. path defining the geologic evolution of the eastern Paganzo basin and the upper crust of west-central Argentina.

A General Overview of Gondwana Landscapes in Argentina

Gondwana Landscapes in Argentina were already identified by Juan Keidel and Walther Penck at the beginnings of the twentieth century, as well as by other geologists and naturalists of the different European schools that worked in this country. These studies were continued at a very good level in Brazil, thanks to the work of Lester C. King, later on intensively followed by Joao Jose Bigarella. However, these concepts gradually disappeared from the Argentine geological scene, dominated by the influence of American geomorphologists, and particularly William Thornbury, who doubted the existence of such ancient landforms, when one of the paradigms of the time was that “practically there is no landscape older than the Pleistocene.” These landforms are the result of the process of both deep chemical weathering, developed in very stable tectonic and climatic environments, under hyper-tropical climates, and pediment processes in semiarid to humid environments.

ASOCIACIONES FAUNÍSTICAS DEL CUATERNARIO DE SAN FRANCISCO, PROVINCIA DE CÓRDOBA, ARGENTINA. IMPLICANCIAS BIOESTRATIGRÁFICAS Y TAXONÓMICAS

Abstract. FAUNAL ASSEMBLAGES FROM THE QUATERNARY OF SAN FRANCISCO, CÓRDOBA PROVINCE, ARGENTINA. BIOSTRATIGRAPHIC AND TAXONOMIC IMPLICATIONS. The chronological scale and continental biostratigraphy of South America was established on the base of fossil mammals from the Pampean Region. This scheme consists of Stages/Ages based on Biozones, with the late Miocene—early Holocene type localities in the Buenos Aires province. In the Córdoba province, several geological and stratigraphical studies have been undertaken since the 1990s and have provided a regionally useful scheme for biostratigraphic studies of the Quaternary. The aim of this work is to perform a biostratigraphic study of the San Francisco locality, in the east central region of the Cordoba province through the analysis of its mammal assemblages and to analyze the correlation with the scale proposed for the Pampean Region. We describe two faunal assemblages from two stratigraphical levels: (1) the faunal assemblage from the stratigraphic level 2 consisting of Lomaphorus sp., Neosclerocalyptus ornatus Owen, Catonyx tarijensis (Gervais and Ameghino), Scelidotheriinae indet., Macrauchenia patachonica Owen, Hemiauchenia paradoxa Gervais and Ameghino, Smilodon populator Lund and Panthera onca (Linnaeus) and assigned to the Ensenadan (early—middle Pleistocene) of the Pampean region; and (2) the faunal assemblage from the stratigraphic level 3 consisting of Neosclerocalyptus paskoensis (Zurita), Equus (Amerhippus) sp., Toxodon sp., Arctotherium sp., and cf. Lagostomus Brokes and assigned to the Lujanian (late Pleistocene—early Holocene) of the Pampean region. New records for Córdoba Province include Neosclerocalyptus ornatus, Panthera onca, and Arctotherium sp.; in addition, the latter represents the first record of the Ursidae family.

Gondwana Glacial Paleolandscape, Diamictite Record of Carboniferous Valley Glaciation, and Preglacial Remnants of an Ancient Weathering Front in Northwestern Argentina

A record of glacier advance and retreat is preserved in Carboniferous strata exposed in an exhumed glacial paleovalley on the eastern side of the Paganzo basin. Previous investigations have focused on the sandstones in the paleovalley and inferred a glacial lacustrine history. New observations have demonstrated that remnants of a preglacial, ancient weathering front, developed under wet tropical conditions and composed of corestones, are found underneath the glaciogenic deposits. Delta and alluvial fan deposits were also recognized, but no inferences were made from the diamictites in the paleovalley regarding glacial events (Andreis et al., Bol Acad Nac Cienc Cordoba 57:3–119, 1986; Buatois and Mangano, J Paleolimnol 14:1–22, 1995; Sterren and Martinez, El Paleovalle de Olta (Carbonifero): Paleoambiente y Paleogeografia. 13o Congreso Geologico Argentino and 3o Congreso de Exploracion de Hidrocarburos, Actas, 2, 89–103, 1996). This chapter focuses on the diamictites and provides a link between the sediment infill and the glacial origin of the paleovalley. We describe diamictites and associated sediments at three main locations: at La Chimenea, near the mouth of the paleovalley; at Mid-Valley, near the middle of the paleovalley; and at the Campsite, near the head of the valley. We interpret some of the diamictites exposed at La Chimenea and at Mid-Valley to be subglacial tillite. Deformation in the sandstone underlying the tillite indicates warm-based conditions as the glacier advanced over soft deformable sediment. At the Campsite location, a diamictite bed, which is about 1.5 m thick, lies within a sequence of alternating sandstone and siltstone beds. The diamictite bed is interpreted to represent an ice-front readvance during a period of ice retreat. The diamictite may be a debrite originating off the ice front, or a subglacial deposit, i.e., a tillite, or a combination of both. Two additional diamictite beds, exposed higher in this sequence of alternating sandstone and siltstone beds, may also record minor ice-front advances into the flooded valley.

New Vertebrates of the Brochero Formation (Córdoba, Argentina): A Review of the Pliocene of Central Argentina

The “Horizonte Brocherense” sensu Castellanos was created on the basis of a mammal assemblage recovered from the San Alberto Valley and Los Reartes Valley (Córdoba, Argentina). This mammal association was placed in the “Uquian Stage” (early Pliocene) according to the stratigraphic scheme proposed by Castellanos in 1944. Later, different authors considered this association to belong either to the Montehermosan Stage/Age (early Pliocene) or Huayquerian Stage/Age (late Miocene), based on more updated stratigraphic schemes. Here, we present new vertebrates recovered from the type locality (San Alberto or Traslasierra Valley) of the Brochero Formation; we provide the first paleoenvironmental interpretation for this unit, and discuss the age of the fauna and its bearing sediments. As the main result, this work contributes to the knowledge of the Pliocene faunas, providing the first records of some anurans, snakes, and mammals for the Brochero Formation, and the biostratigraphic and chronological implications of such findings when comparing the fossil assemblage with its counterparts from South America.

Bioinorganic Chemistry of Trace Elements: Possible Role in the Epigenetic Modulation of Homoeostatic Processes in Complex Organisms

Fil: Ratti, Silvia Gabriela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Mendoza. Instituto de Medicina y Biologia Experimental de Cuyo; Argentina; Universidad Nacional de Cuyo. Facultad de Ciencias Medicas. Laboratorio de Neuropsicofarmacologia Experimental; Argentina;