Salinas Grandes Research Articles

Vertebrates from the Late Miocene of Salinas Grandes de Hidalgo (central Argentina). New faunal data: biochronological and paleoenvironmental considerations

ABSTRACT Salinas Grandes de Hidalgo (La Pampa Province) is a relevant locality of the Cerro Azul Formation in central Argentina because of its abundant and diverse vertebrate remains, including representatives of Reptilia, Aves and mostly Mammalia. Concerning previous records, the present faunal list adds one Argyrolagidae marsupial, one Ctenomyidae and two Caviidae rodents, as well as the first detailed analysis and description of glyptodonts from the Cerro Azul Formation in La Pampa Province. New geological information is added about the two fossiliferous outcrops included in Salinas Grandes de Hidalgo area. The classically studied outcrop located in the saline lake and the nearby one in the so-called ex-Autódromo, both herein correlated based on lithostratigraphy, particularly by the presence of paleosols in the intermediate section of the sedimentary succession. These sandy silts deposits in the base of the outcrops indicate the development of poorly confined flows and intervals of surface stabilisation by paedogenesis. We offer a biochronological interpretation based on a recently published U-Pb detrital zircons dating (5.9 ± 0.4 Ma) and the presence of significant taxa such as octodontoid rodents recovered from the dated levels and below it. From a paleoenvironmental viewpoint, we infer variations from woodlands to open environments.

Hot, dry, and salty: The present and future of an Extremophile model lizard from Argentina

Global warming poses a threat to lizard populations by raising ambient temperatures above historical norms and reducing thermoregulation opportunities. Whereas the reptile fauna of desert systems is relatively well studied, the lizard fauna of saline environments has not received much attention and—to our knowledge—thermal ecology and the effects of global warming on lizards from saline environments have not been yet addressed. This pioneer study investigates the thermal ecology, locomotor performance and potential effects of climate warming on Liolaemus ditadai, a lizard endemic to one of the largest salt flats on Earth. We sampled L. ditadai using traps and active searches along its known distribution, as well as in other areas within Salinas Grandes and Salinas de Ambargasta, where the species had not been previously recorded. Using ensemble models (GAM, MARS, RandomForest), we modeled climatically suitable habitats for L. ditadai in the present and under a pessimistic future scenario (SSP585, 2070). L. ditadai emerges as an efficient thermoregulator, tolerating temperatures near its upper thermal limits. Our ecophysiological model suggests that available activity hours predict its distribution, and the projected temperature increase due to global climate change should minimally impact its persistence or may even have a positive effect on suitable thermal habitat. However, this theoretical increase in habitat could be linked to the distribution of halophilous scrub in the future. Our surveys reveal widespread distribution along the borders of Salinas Grandes and Salinas de Ambargasta, suggesting a potential presence along the entire border of both salt plains wherever halophytic vegetation exists. Optimistic model results, extended distribution, and no evidence of flood-related adverse effects offer insights into assessing the conservation status of L. ditadai, making it and the Salinas Grandes system suitable models for studying lizard ecophysiology in largely unknown saline environments.

New light on the late Middle Miocene–Early Pliocene representatives of Lagostomus (Chinchillidae, Rodentia) from Cerro Azul Formation, Argentina

Lagostominae (Rodentia, Caviomorpha, Chinchillidae) include a single living species, the plains vizcacha Lagostomus maximus, but representatives of this subfamily are registered since the Early Miocene. The oldest record of this genus was recently extended to the late Middle Miocene in one locality of center of La Pampa Province. Previously, from levels of the Late Miocene Cerro Azul Formation in Buenos Aires and La Pampa provinces, two species of Lagostomus were recognized based on specimens from two localities, L. telenkechanum from Arroyo Chasicó (Buenos Aires Province) and L. pretrichodactyla from Salinas Grandes de Hidalgo (La Pampa Province). In the present work, new materials from these two and other localities of the Cerro Azul Formation are analyzed. This study supports the presence of both species, which had coexisted in several of the analyzed assemblages. The studied sample includes several incomplete specimens and others interpreted as juvenile individuals, which can only be determined as Lagostomus sp. Also, a similar behavior to that of the extant L. maximus (i.e., gregarious populations with fossorial habits) is proposed to explain the different representation of Lagostomus in each assemblage. In Cerro Azul Formation the presence of representatives of Lagostomus is mainly linked with levels with paleosols and accumulations by predator activity. Finally, we conclude that this genus has less biostratigraphic value than previously thought, at least for central Argentina.

The origin of the depressions interrupting the eastern Sierra Pampeanas broken foreland, explained by localized crustal extension through the juan Fernández ridge path, using gravimetric data

The Salinas Grandes and Salina de Ambargasta salt pans are located in the Eastern Sierras Pampeanas in the Pampean broken foreland zone, a product of the Chilean-Pampean flat subduction zone. This region constitutes an anomalously flat morphology of 350 × 150 km and occupies an extensive area in a northeast-southwest direction.These flat depressions abruptly interrupt the eastern Sierras Pampeanas morphology, burying the structure beneath Late Cenozoic-Quaternary deposits of the Andean orogenic front. We obtained from a previous model in spherical harmonics, the geometry of the Moho observing a lower crustal attenuation below the salt pan areas, which is maximum towards the north of the Salina de Ambargasta. From the Bouguer anomaly, calculated by unifying data from different sources, and its residual anomaly, we calculated the analytical signal to adjust the gravimetric anomaly's wavelength, which shows that this flat morphology follows NE to NNE gravity minima. Werner deconvolution and localized Euler deconvolution calculated from the residual Bouguer anomaly indicate that the anomalous masses are located above 15 km depth, by the wavelengths of the anomalies, presumably indicating the differential uplift of high-density rocks placed in the lower and mid-crust, following the measured crustal attenuations. Additionally, these solutions show that this NE depression is segmented by NNW structures perpendicular to the main trough. Crustal thickness attenuation is interpreted as related to the track of the Juan Fernandez Ridge beneath the eastern Pampean broken foreland sector, based on plate kinematic reconstructions. As depicted in recently released tomographic data, its tearing and related asthenospheric upwelling could have promoted lithospheric localized extension, explaining the Salinas Grandes-Ambargasta depressions that are segmenting the eastern Sierras Pampeanas at the Andean orogenic front.

Taxonomic and ontogenetic diversity of Dinomyidae (Rodentia) from the late Miocene-early Pliocene of La Pampa province (Argentina) based on cranio-dental remains

Dinomyidae is a clade of caviomorph rodents that include medium to gigantic forms. They are represented by a single living species, Dinomys branickii, distributed from Venezuela to Bolivia in forested regions. However, in the past, they were very diverse. The oldest confident fossil records come from the early and middle Miocene, and during the late Miocene they reached their greatest diversity, reducing since then. In this contribution, the diversity of late Miocene-early Pliocene dinomyids from the Cerro Azul Formation in La Pampa Province (Argentina) is studied. New craniodental remains of at least three species are reported: Tetrastylus laevigatus, T. intermedius, and Diaphoromys gamayensis. Tetrastylus laevigatus is reported for this region based on abundant material, including a portion of the skull associated with the mandible. The presence of juvenile and adult individuals permitted us to analyze the ontogenetic variability of some traits. The specimens assigned to T. intermedius and D. gamayensis consist of mandibular and lower cheek teeth remains. Based on these new remains, we propose that D. gamayensis and D. fiegi are synonymous, with the priority being D. gamayensis. Considering the findings in each faunal association from the Cerro Azul Formation, representatives of T. laevigatus were registered in Salinas Grandes de Hidalgo, Algarrobo del Águila, Victorica, Bajo Giuliani, Laguna Chillhué, and Telén; T. intermedius was recorded in Caleufú. One new specimen of D. gamayensis from Guatraché (species originally described from Gamay) add information about its distribution. Finally these records are added to that of T. araucanus, previously described for Toay. This association suggests the existence of biogeographic connections with regions from northwestern Argentina during the late Miocene.

“¡Había ahí un Archivo!” Acts of Sovereignty between Burial and Exhibition

In 1879, in those territories that are currently part of the Argentinian Patagonia and few months after the genocide carried out against the natives, euphemistically called the “Conquest of the Desert”, the prolific writer, geographer, politician, and attorney Estanislao Zeballos organized a mission in order to “survey” and “explore” the recently conquered area. He thus gathered – though the correct word would be “sacked” – human skulls, bones that still haunted the battlefields, cult objects, clothing, and metal artifacts. During that journey Zeballos discovered, buried in the middle of a sand dune, a forgotten archive: boxes containing press clippings, XIX century correspondence between the national government and the Indigenous cacicazgos, account entries, governmental stamps pertaining to the cacicazgos, and a Castilian dictionary. This text works out the relationship between this buried “Indian archive” and the remains and objects looted from the defeated population, to be collected and then exhibited. The article attempts to demonstrate that if we read the buried Archive of Salinas Grandes along with that collection of items, gathered in order to be exhibited, like two distinct but nevertheless continuous operations pertaining to the construction of a sovereign discourse, we could better understand the power that the signifying matrix separating culture and history, chaos and state, ritual and politics, archive and trophy, tradition and sovereignty still acquires in the present.

Nuevos registros de Lagostomus Brookes, 1828 (Rodentia, Chinchillidae) en el Mioceno tardío de Argentina y su importancia bioestratigráfica

In this work, we present two new records of Lagostomus from the late Miocene of Argentina. A right mandible from the Huachipampa Formation (Loma del Camello, San Juan Province) is assigned to Lagostomus telenkechanum, previously recorded in the Arroyo Chasicó Formation (Chasicoan Stage/Age, late Miocene; Arroyo Chasicó, Buenos Aires Province). A skull fragment from the Cerro Azul Formation (Salinas Grandes de Hidalgo, La Pampa Province) is referred to L. pretrichodactyla, previously recorded in several units assigned to the Huayquerian Stage/Age (late Miocene) in Catamarca and Mendoza provinces, and sediments of uncertain age in Buenos Aires Province. The presence of L. telenkechanum in the Huachipampa Formation supports a Chasicoan age for this unit, which corroborates previous hypotheses, and extends the area of distribution of this species. The presence of L. pretrichodactyla in the Cerro Azul Formation suggests a late Miocene age (probably Messinian) for this unit, at least at Salinas Grandes de Hidalgo, supporting previous hypothesis. These new records allow recognizing the biostratigraphic value of Lagostomus to a higher geographic scale than previously considered.

Lithium Might Hold the Key to our Clean Energy Future, but Will this Star Metal Fully Deliver on its Green Potential?

Salinas Grandes is a vast salt flat in the high-altitude Puna region of Salta and Jujuy, two north-western provinces of Argentina. It is situated in one of the world’s driest regions, with an extremely fragile ecosystem. Salinas Grandes is so iconic and beautiful that Argentinians voted it amongst the country’s top seven natural wonders in May 2019.1 In addition to its beauty, this stunning desert of salt also holds one of the largest reserves of lithium in the world. Lithium is a light and versatile metal used to produce, among other things, the lithium-ion batteries that power electric vehicles (EV). As global efforts to phase out fossil fuels from our transport systems and adopt clean energy alternatives increase, lithium is becoming increasingly critical. It is no wonder, therefore, that industry has coined it the ‘white gold’.2 Salinas Grandes is only one of many salt lakes in North West Argentina which, together with Bolivia and Chile, form what is known as the ‘lithium triangle’. It is estimated that these three countries alone account for more than half of the world’s lithium.3 Global demand for lithium to produce EV is expected to grow rapidly over the coming decade. To meet this demand, the lithium industry will require significant investment to ramp up additional supply.4 As a result, all eyes have turned to the ‘lithium triangle’ and investment in the region has soared in recent years.5 For the three developing countries, this represents a unique opportunity to attract much-needed foreign investment and boost economic growth.6

Landscape and drainage evolution during the Cenozoic in the Salinas Grandes Basin, Andean Plateau of NW Argentina

Endorheic basins are distinctive features of the modern Andean plateau. These basins record thick Neogene-to-Modern evaporite successions that are considered as the onset of internal drainage and aridity. Some isolated older (Paleogene) evaporites and intermontane depocenters have been also described across the Argentine Puna, suggesting that some degree of hydrological isolation would have pre-dated the main Miocene-Pliocene plateau uplift. Evaporites beds, however, are not conclusive evidence for endorheism, given that their formation depends not only on the tectonically-driven paleo-drainage, but also on other sensitive variables as climate, and salinity of the sources. Here, we discuss the paleo-drainage evolution across the eastern Puna plateau at 23°-24° S, combining landscape numerical modeling with seismic stratigraphy. Seismic observations suggest an intermontane configuration as early as the late Paleogene, and relief formation to the east and west basin margins. Using different combinations of precipitation rates, our landscape models allowed us to reproduce the modern elevations observed in the study region as well as published thermochronological data. Our results suggest that endorheism would have started in the Paleogene, and would have dominated most (>70%) of the Cenozoic basin history. Models show the recurrence of endorheism, interrupted by intermittent phases of drainage connectivity (exorheism) to the east (foreland) in the upper half Eocene and the early Miocene. According to these results, the formation of closed basins in the Puna region would have pre-dated the main Miocene-Pliocene uplift stage of the Andean plateau.

Anatomía foliar de cuatro especies halófilas del noroeste argentino

Las hojas de las plantas halófilas desarrollan estrategias para afrontar las con- diciones adversas de los ambientes salinos. El objetivo de este trabajo fue caracte- rizar la anatomía foliar de Atriplex argentina, Alternanthera nodifera, Ehretia cortesia y Trianthema argentina, especies halófilas del noroeste argentino. Hojas de las especies mencionadas fueron colectadas en las Salinas Grandes (provincia de Catamarca) y Aimogasta (provincia de La Rioja). Se aplicaron técnicas histológicas convencionales. E. cortesía, A. argentina y T. argentina presentaron tricomas glandulares y A. nodifera eglandulares. Los estomas de E. cortesía y A. nodífera se encontraron hundidos. Se observó mesofilo isolateral en E. cortesía y mesofilo con estructura Kranz en A. argentina, A. nodífera y T. argentina. A. argentina, A. nodífera y E. cortesia presentaron parénquima acuífero. Todas las especies evidenciaron abundantes y diversos tipos de cristales de oxalato de calcio en mesofilo y en caso de E. cortesia presentó además cristales de carbonato de calcio en glándulas de sal. El trabajo describe por primera vez la anatomía foliar de estas especies y contribuye al conocimiento de las adapta- ciones anatómicas de la vegetación halófila del noroeste de Argentina.

Miocene to Quaternary basin evolution at the southeastern Andean Plateau (Puna) margin (ca. 24°S lat, Northwestern Argentina)

AbstractThe Andean Plateau of NW Argentina is a prominent example of a high‐elevation orogenic plateau characterized by internal drainage, arid to hyper‐arid climatic conditions and a compressional basin‐and‐range morphology comprising thick sedimentary basins. However, the development of the plateau as a geomorphic entity is not well understood. Enhanced orographic rainout along the eastern, windward plateau flank causes reduced fluvial run‐off and thus subdued surface‐process rates in the arid hinterland. Despite this, many Puna basins document a complex history of fluvial processes that have transformed the landscape from aggrading basins with coalescing alluvial fans to the formation of multiple fluvial terraces that are now abandoned. Here, we present data from the San Antonio de los Cobres (SAC) area, a sub‐catchment of the Salinas Grandes Basin located on the eastern Puna Plateau bordering the externally drained Eastern Cordillera. Our data include: (a) new radiometric U‐Pb zircon data from intercalated volcanic ash layers and detrital zircons from sedimentary key horizons; (b) sedimentary and geochemical provenance indicators; (c) river profile analysis; and (d) palaeo‐landscape reconstruction to assess aggradation, incision and basin connectivity. Our results suggest that the eastern Puna margin evolved from a structurally controlled intermontane basin during the Middle Miocene, similar to intermontane basins in the Mio‐Pliocene Eastern Cordillera and the broken Andean foreland. Our refined basin stratigraphy implies that sedimentation continued during the Late Mio‐Pliocene and the Quaternary, after which the SAC area was subjected to basin incision and excavation of the sedimentary fill. Because this incision is unrelated to baselevel changes and tectonic processes, and is similar in timing to the onset of basin fill and excavation cycles of intermontane basins in the adjacent Eastern Cordillera, we suspect a regional climatic driver, triggered by the Mid‐Pleistocene Climate Transition, caused the present‐day morphology. Our observations suggest that lateral orogenic growth, aridification of orogenic interiors, and protracted plateau sedimentation are all part of a complex process chain necessary to establish and maintain geomorphic characteristics of orogenic plateaus in tectonically active mountain belts.

Diferencias de conocimientos, valoración y uso de Cactáceas entre pobladores de Salinas Grandes y Sistema Serrano (Córdoba, Argentina)

Introducción y objetivos: La valoración, uso y manejo de los recursos naturales por parte de pequeños productores se sustenta en el conocimiento ecológico local (CEL). Con el objeto de comparar entre sí las comunidades de dos unidades fisiográficas: Salinas Grandes y Sistema Serrano, abordamos el estudio del CEL sobre las cactáceas. M&M: Realizamos 21 entrevistas a informantes claves sobre diversidad, usos y valoración. Resultados: En Salinas Grandes nos mencionaron por lo menos un uso para cada taxón y formas de manejo asociadas a tradiciones; en cambio, los informantes del Sistema Serrano mencionaron menos tipos de usos y cobraron relevancia otros tipos relacionados al turismo y la comercialización. Conclusiones: Por un lado, los pobladores de Salinas Grandes, que viven en condiciones de aridez extrema y con escasos recursos herbáceos, conservan conocimientos ligados a tradiciones que son necesarios para asegurar su reproducción social, donde las Cactáceas aparecen como recursos claves para su subsistencia. Por otra parte, los del Sistema Serrano, que cuentan con mayor diversidad de recursos forrajeros, pueden ofrecer otros servicios y reorientan sus conocimientos hacia nuevas actividades, donde se evidencia la flexibilidad de estos saberes (dentro del CEL) que permite ajustes a las situaciones de cambio contextual.

Effect of UV-B radiation on the content of UV-B absorbing compounds and photosynthetic parameters in Parmotrema austrosinense from two contrasting habitats.

We studied the resistance of Parmotrema austrosinense to UV-B stress. We focused on the effects of a high dose UV-B radiation on the content of chlorophylls, carotenoids and UV-B screening compounds. Photosynthetic parameters were measured by chlorophyll fluorescence (potential and effective quantum yields, photochemical and non-photochemical quenching) and evaluated in control and UV-B-treated lichens. Lichens from two different locations in Cordoba, Argentina, were selected: (i) high altitude and dry plots at (Los Gigantes) and (ii) lowland high salinity plots (Salinas Grandes). UV-B treatment led to a decrease in the content of photosynthetic pigments and UV-B screens (absorbance decrease in 220-350nm) in the samples from Salinas Grandes, while in Los Gigantes samples, an increase in UV-B screen content was observed. Chlorophyll fluorescence parameters showed a UV-B-induced decline in FV /FM , ΦPSII and qP indicating limitation of primary photosynthetic processes in photosystem II (PSII) of symbiotic alga, more pronounced in Salinas Grandes samples. Protective mechanism of PSII were activated by the UV-B treatment to a higher extent in samples from Salinas Grandes (NPQ 0.48) than in Los Gigantes samples (NPQ 0.26). We concluded that site-related characteristics, and in particular different UV-B radiation regimen, had a strong effect on resistance of the photosynthetic apparatus of P.austrosinense to UV-B radiation.

La dimensión territorial en la frontera sur del Virreinato del Río de la Plata:las expediciones hacia las Salinas Grandes en la época tardocolonial

En el transcurso del siglo XVIII, la ciudad de Buenos Aires se abasteció de sal mediante la organización de expediciones hacia las Salinas Grandes localizadas en el actual departamento de Atreucó de la provincia de La Pampa (actual República Argentina). Presentamos aquí las transcripciones de tres diarios acerca de las incursiones realizadas en los años 1786, 1787 y 1788 y un listado de los cautivos rescatados durante los tres viajes. Estas fuentes documentales elaboradas por Manuel Pinazo, el comandante, nos permiten conocer los acontecimientos cotidianos en el terreno, del estado de los caminos, de la disponibilidad de recursos para los expedicionarios, de las interacciones con caciques y grupos indígenas así como las diversas estrategias implementadas por los funcionarios, la tropa y los demás integrantes de la expedición para transitar por lugares lejanos de los puestos fronterizos y cercanos a las tolderías indígenas. En este trabajo analizamos la dimensión territorial de aquellos parajes en los que interactuaban los sujetos que concurrían a las expediciones coloniales y los grupos indígenas que se acercaban a ellas, haciendo énfasis en las estrategias de conocimiento y control efectuadas por los distintos actores que circulaban entre la guardia de Luján y las Salinas Grandes.

Taxonomic Implications of a Large Sample of Tremacyllus (Hegetotheriidae: Pachyrukhinae) from the Late Miocene Cerro Azul Formation of La Pampa, Argentina

More than 40 remains of Tremacyllus Ameghino (Notoungulata, Hegetotheriidae, Pachyrukhinae) from the Province of La Pampa (Argentina) are analyzed. They were recovered from different outcrops of the late Miocene Cerro Azul Formation at Laguna Chillhue, Quehue, Telen, Salinas Grandes de Hidalgo, Estancia Re, Bajo Giuliani, Barrancas Coloradas and Caleufu. During the late Miocene, pachyrukhines are represented by two genera, Tremacyllus and Paedotherium Burmeister. The present sample of Tremacyllus allows for the dental morphological variation to be evaluated, especially in lower and upper premolars. This study shows high variability in the diagnostic characters of two recognized species, T. impressus Ameghino (Pliocene–Pleistocene of the Pampean Region) and T. incipiens Rovereto (late Miocene of Catamarca). We interpret these differences to actually correspond to intraspecific variation and, consequently, propose their synonymy. T. impressus has priority over T. incipiens, and an emended diagnosis is provided. This nomenclatural action implies, in turn, the extension of the biochron of Tremacyllus impressus from the late Miocene to the Pleistocene. T. impressus differs from Paedotherium in its smaller size, post-incisive impressions extended beyond the level of P2 (even reaching the anterior margin of P3), M3 shorter or equal to M2, relatively shorter mandibular symphysis, and lower premolars not molariform and more imbricated. Within the studied sample, we identify several juvenile specimens that confirm the dental eruption pattern previously proposed for Tremacyllus based on fewer remains.

Origin and Evolution of the Salinas Grandes and Salina De Ambargasta, Argentina

The Salinas Grandes and Salina de Ambargasta, on the eastern side of the Sierras Pampeanas in Argentina, constitute an 18,000 km2 tectonic depression. The eastward advance of the tectonic deformation is evident in the topographic elevations that intercept the Llanura Chaqueña. The interpretation of the tectonic processes that create the Salinas Grandes and Salina de Ambargasta are primarily due to the observation of morphotectonic macro indicators and structural field data. These geoforms allow us to interpret the horizontal deformation that has produced the right side displacement of parallel shears within a dextral releasing bend and restraining bend setting. This process occurred within a transtensional-transpressional setting, which produced a depression closure where lakes formed, the formation of Alto de Mancilla, deviation of rivers, the rotation and displacement of ranges and the transformation of lakes into salt flats. These processes are active and are shown by the hydro transference area where the Dulce River discharges into the Salado River, resulting in a considerable decrease of water flow into the Laguna Mar Chiquita.

Fusarium equiseti LPSC 1166 and its in vitro role in the decay of Heterostachys ritteriana leaf litter.

The role of microorganisms in litter degradation in arid and semi-arid zones, where soil and water salinization is one of the main factors limiting carbon turnover and decay, remains obscure. Heterostachys ritteriana (Amaranthaceae), a halophyte shrub growing in arid environments such as "Salinas Grandes" (Córdoba, Argentina), appears to be the main source of organic matter in the area. Little is known regarding the microorganisms associated with H. ritteriana, although they are a potential source of enzymes such as cellulolytic ones, which might be important in biotechnological fields such as bioethanol production using ionic liquids. In the present study, by studying the microbiota growing on H. ritteriana leaf litter in "Salinas Grandes," we isolated the cellulolytic fungus Fusarium equiseti LPSC 1166, which grew and degraded leaf litter under salt stress. The growth of this fungus was a function of the C substrate and the presence of NaCl. Although in vitro the fungus used both soluble and polymeric compounds from H. ritteriana litter and synthesized extracellular β-1,4 endoglucanases, its activity was reduced by 10% NaCl. Based on these results, F. equiseti LPSC 1166 can be described as a halotolerant cellulolytic fungus most probably playing a key role in the decay of H. ritteriana leaf litter in "Salinas Grandes."

New record of Liolaemus ditadai Cei, 1983 (Squamata, Liolaemidae) from Santiago del Estero province, Argentina

Liolaemus ditadai is a rare liolaemid lizard originally described from Salinas Grandes salt-pans flat, in the border between Cordoba and Catamarca Province in central Argentina. Only a few specimens of this species are known. Here, we present a new record that result in a significant extension of the known distribution of the species, which is currently considered to be restricted to a small area in Salinas Grandes. In addition, we comment on previous records of the species in central Argentina.

Cambio hidrológico asociado al Último Maximo Glacial-Altitermal durante la transición Pleistoceno-Holoceno en el borde oriental de Puna Norte.

The environment of the Andean Puna Plateau is mostly characterized by the dominance of evaporative processes due to aridity. Since the intermittent runoff lacks the morphodynamic competence to generate the present day landscape, authors have usually considered that the Puna landscape is a remnant feature of the Miocene arid-climate persistence. Then, a Quaternary-sensu lato-age was assigned to salars, alluvial fans and other geomorphologies. We present evidences from the endorheic depression of Guayatayoc-Salinas Grandes (GSG) located at 3,400 m a.s.l. in the eastern border of northen Puna. The basin includes a saline playa domain in the north (Guayatayoc Playa Lake) and a salt pan in the southern part (Salinas Grandes). We have identified two dissimilar processes originating the subdivision of the GSG depression. The characterization of those processes included sedimentological and geomorphological observations, as well as chronologies using luminescence and radiocarbon. Evidences reveal the development of a saline-lacustrine water body that is associated with the Last Glacial Maximum. During the Late Pleistocene and until ~13.8 cal kyr BP, lake shores were modelled in the front of distal-alluvial fans, the sedimentary aggradation was widespread, and associated with kaolinitic-clay accumulation, inyoite, and the formation of peat-deposits. An environmental change towards aridity occurred after 13.8 cal kyr BP, and wetter conditions returned during the early to middle Holocene, around 9 cal kyr BP. Then, incisive river dynamics accompanied the establishment of a playa lake, with montmorillonitic-fine sediments and ulexite generation during later Holocene. The subdivision of the GSG depression onset by the two following processes: 1. the topographic decoupling, that is associated with Las Burras’s alluvial fan aggradation during Pleistocene; 2. the lacustrine regression phase at 13.8 cal kyr BP. Therefore, Guayatayoc and Salinas Grandes are saline systems functioning as a playa lake and a salt pan, respectively, since the Holocene, due to environmental constraints.

The flooding of the San Matías Gulf: The Northern Patagonia sea-level curve

Northern Patagonia is characterised by tectonic depressions below present sea level. Some of them are today flooded by the sea; others remain emerged although they are at altitudes of −50m (Bajo del Gualicho), −35m (Salinas Grandes) and −7m (Salina La Piedra). San Matías Gulf also was such an emerged depression below contemporary mean sea level during the Late Pleistocene. It flooded between 11,500 and 11,000years ago, when the sea level surpassed the sill of the gulf (today 50m below mean sea level) during postglacial sea-level rise. In those days, shrublands extended on the slopes of the tectonic depression. In-situ pieces of woods dredged from the bottom of the gulf at depths of 70m gave a conventional age of 11,310±150years BP. We used the wood, together with dated shells from the continental shelf, and shells and organic matter dated from the San Blas, Negro and Chubut coastal plains to construct a sea-level curve. Sea level rise surpassed the present level somewhat before 6000years BP, reaching a maximum stand of +6m. It has since gently diminished towards present sea level.