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Reconstructing thermal histories in thrust belts is commonly used to infer the age and rates of thrusting and hence the driving mechanisms of orogenesis. In areas where ancient basins have been incorporated into the orogenic wedge, a quantitative reconstruction of the thermal history helps distinguish among potential mechanisms responsible for heating events. We present such a reconstruction for the Ischigualasto-Villa Unión basin in the western Pampean Ranges of Argentina, where Triassic rifting and late Cretaceous-Cenozoic retroarc foreland basin development has been widely documented, including Miocene flat-slab subduction. We report results of organic and inorganic thermal indicators acquired along three stratigraphic sections, including vitrinite reflectance and X-ray diffractometry in claystones and new thermochronological [(apatite fission-track and apatite and zircon [U-Th]/He)] analyses. Despite up to 5 km-thick Cenozoic overburden and unlike previously thought, the thermal peak in the basin is not due to Cenozoic burial but occurred in the Triassic, associated with a high heat flow of up to 90 mWm−2 and, We are grateful to the International Cooperation CONICET-FAPESP Project (2016, 23220160100035CO), the Agencia Nacional de Promoción Científica y Tecnológica (PICT 2015-3146, PICT 2015-1092 and PICT 2017-3177), the Proyecto de Investigación Secyt-UNLaR 2015/10736 and 2015/00422, for supporting our research work. Themochronometric analyses were funded by the FAPESP-CONICET SPRINT (Project 2016/50441-1).

Kinematic restorations in fold and thrust belts, which are a valuable tool for studying the deformational history of fold and thrust belts, have been poorly used to understand erosion rates. In this contribution, we estimated the amount of eroded material in thrust-belts via kinematic reconstructions. We combined kinematic restitutions with the classic critically-tapered Coulomb wedge model, following the assumption that at times when thrusting is triggered, the surface slope was less than the angle required to reach self-similar growth, i.e. critical. Following conservative geometrical considerations, we were able to compute a time-varying Coulomb wedge. Such unsteady wedge is used to calculate first-order, time dependent erosion rates, which are compared to denudation and provenance results derived from other techniques. We applied our model to the Argentine Precordillera at the Jáchal river section, whose extensively studied outcrop data have let establish a well-constrained episodic deformation of the thrust-belt; even though no kinematic model of the area had been presented so far. Our results show two contrasting erosion rates, one prior to the movement along the last-in-sequence fault (Niquivil) and one after, 0.1 and 1.34 Km/Myr, respectively. Our findings indicate that the amount of eroded material might not always be directly proportional to cumulative slip in the thrust system, as slip along Niquivil thrust is only 22% of the total horizontal displacement, though it produced most of the uplift and erosion. Our results are in striking accordance to long-term erosion estimation proxies, like U-Th/He, 10 Be and sedimentological studies, which highlights the validity of the economical methodology herein proposed. Furthermore, our kinematic model of the evolution of the Argentine Precordillera allows us to perform 2D flexural numerical modeling, which suggests that tectonic loading seems to not be enough to reproduce basin geometry and that additional mechanisms, such as dynamic subsidence or lithospheric mantle thickening (among others), would be required. Fil: Sánchez Nassif, Francisco Gabriel Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Canelo, Horacio Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Davila, Federico Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Ezpeleta, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

New apatite fission track (AFT) and (U–Th)/He (AHe) data from two sections recording Cretaceous-Cenozoic clastic successions (La Flecha - La Troya Sur creeks) in the northern sector of the Central Precordillera of Argentina are presented. The results show that the Ciénaga del Río Huaco, Puesto la Flecha and Vallecito Fms. would have crossed the 60 °C isotherm during burial, while the middle sector of the Vinchina Fm. would not have reached temperatures higher than 55 °C. Multimethod inverse thermal modeling suggests that the AFT ages of all the studied levels would not have been completely reset and allow inferring that the partial retention zone for the AHe system (AHe-PRZ) would have been reached during the Miocene in levels between the Vallecito and Vinchina Fms. Our 1D-modeling results for the Ciénaga del Río Huaco, Puesto la Flecha and Vallecito Fms. show that the maximum temperature would have been reached at ~15 Ma, with a sedimentary thickness of ~2750 m and a heat flow of 65 mW/m2. From these data, a geothermal gradient of ~27 °C/km at this time could be inferred. In turn, the Vinchina and Zapallar Fms. would have reached their maximum temperature at ~2 Ma, under a cooler thermal regime (20 mW/m2) and with an estimated geothermal gradient of

The Late Paleozoic Ice Age (LPIA) has been well recorded in the uppermost Mississippian?Pennsylvanian of Gondwana. Nevertheless, little is known about the temporal and geographic dynamics, particularly during the early Mississippian. We report on exceptional Tournaisian glaciomarine stratigraphic sections from central Argentina (Río Blanco Basin). Encompassing c. 1400 m, these successions contain conspicuous glacigenic strata with age constraints provided bypalaeontological data and U/Pb detrital zircon age spectra. A variety of marine, glaciomarine and fan-deltaic environments indicate relative sea-level variations mainly associated with tectonism and repetitive cycles of glacial activity. Provenance analysis indicates a source from the Sierras Pampeanas basement located to the east. Fifteen sequences were grouped into threedepositional models: (1) Transgressive Systems Tracts (TST) to Highstand Systems Tracts (HST) sequences unaffected by glacial ice; (2) Lowstand Systems Tracts (LST) to TST and then to HST with glacial influence; and (3) non-glacial Falling-Stage Systems Tracts (FSST) to TST and HST. The glacial evidence indicates that the oldest Mississippian glacial stage of the LPIA in southwestern Gondwana is constrained to the middle Tournaisian. In contrast with previous descriptions of Gondwanan coeval glacial records, our sequence analysis confirms complex hierarchical climate variability, rather than a single episode of ice advance and retreat. Fil: Ezpeleta, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; Argentina Fil: Rustán, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; Argentina Fil: Balseiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Davila, Federico Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Dahlquist, Juan Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Vaccari, Norberto Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; Argentina Fil: Sterren, Andrea Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina Fil: Prestianni, Cyrille. Royal Belgian Institute of Natural Sciences; Bélgica Fil: Cisterna, Gabriela Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; Argentina Fil: Basei, Miguel. Universidade de Sao Paulo; Brasil

Present knowledge of Late Triassic tetrapod evolution, including the rise of dinosaurs, relies heavily on the fossil-rich continental deposits of South America, their precise depositional histories and correlations. We report on an extended succession of the Ischigualasto Formation exposed in the Hoyada del Cerro Las Lajas (La Rioja, Argentina), where more than 100 tetrapod fossils were newly collected, augmented by historical finds such as the ornithosuchid Venaticosuchus rusconii and the putative ornithischian Pisanosaurus mertii. Detailed lithostratigraphy combined with high-precision U–Pb geochronology from three intercalated tuffs are used to construct a robust Bayesian age model for the formation, constraining its deposition between 230.2 ± 1.9 Ma and 221.4 ± 1.2 Ma, and its fossil-bearing interval to 229.20 + 0.11/− 0.15–226.85 + 1.45/− 2.01 Ma. The latter is divided into a lower Hyperodapedon and an upper Teyumbaita biozones, based on the ranges of the eponymous rhynchosaurs, allowing biostratigraphic correlations to elsewhere in the Ischigualasto-Villa Unión Basin, as well as to the Paraná Basin in Brazil. The temporally calibrated Ischigualasto biostratigraphy suggests the persistence of rhynchosaur-dominated faunas into the earliest Norian. Our ca. 229 Ma age assignment to Pi. mertii partially fills the ghost lineage between younger ornithischian records and the oldest known saurischians at ca. 233 Ma., Facultad de Ciencias Naturales y Museo

The understanding of modern topography, and basin and landscape evolution, requires clear comprehension of isostatic and dynamic forces (in addition to paleoclimate changes) over different temporal and spatial scales. Here we review different topographic features of South America using the residual topography concept at regional and local scales. Residual topography, the difference between modeled isostatic elevations and measured elevations, is considered the best measure of dynamic topography. We incorporate geological observations to test the dynamic topography for modern and ancient examples using local subsidence analyses, paleoelevation calculations from previous studies, and paleolithospheric thickness estimates based on geochemical studies of basalts. Three transects across the northern-central, southern-central, and southern Andes (Peruvian Andes-Solimoes-Amazonas, Precordillera-Pampas, and Patagonian areas, respectively) were inspected, particularly in areas affected by subduction of oceanic ridges, where subsidence and/or uplift may be influenced by dynamic forces. Our results show contradictory results among models and with respect to previous studies. The pericratonic and cratonic areas of Peru and Brazil, farther east from the leading edge of the Nazca ridge, show positive residual topographies (dynamic uplift) and local subsidence studies support residual subsidence driven by sublithospheric forces. The opposite occurs in Patagonia. Most geological interpretations and our subsidence models suggest the need for dynamic subsidence, which does not account for negative residual topography. In turn, estimates for the southern Central Andes show a relatively good match between subsidence models and residual topography in pericratonic areas (Pampas), which support dynamic subsidence and topography. But strong disagreements arise along the flat-slab segment, where dynamic uplift is expected from models of dynamic topography. We suggest that regional elevation is mainly ruled by lithospheric and crustal structure, along with bulk composition, as supported by dynamic forces that can change laterally and generate local morphological features such as isolated basins or promontories. Ongoing and future studies will help resolve these apparent contradictions.

A new fossil record of early Mississippian marine faunas is described from the Agua de Lucho Formation in the Sierra de las Minitas (La Rioja province, Rio Blanco Basin, western Argentina). Considered Tournaisian in age based on local palynological data and biostratigraphic correlations, this faunal record is notably diverse associated with glacially influenced deposits, in contrast with other early Mississippian assemblages from Argentina, traditionally described as developed in warm to temperate climates. The vertical distribution of bivalves and brachiopods, in particular, indicates significant faunal changes through the thick section studied, and their occurrences are compared with those described from the Zorritas Formation in northern Chile. The new records include some typical components of the regional Michiganites scalabrinii-Azurduya chavelensis assemblage Zone, but important vertical and lateral compositional variations of this biozone are discussed. It also highlights the importance of the species Azurduya chavelensis as a conspicuous component of the Early Mississippian deposits from South America, which would become a proper macrofaunal tool to intra and inter-basinal correlations.

We describe tetrapod burrows from the uppermost Middle–lower Upper Triassic (latest Ladinian–early Carnian) Chañares Formation (Ischigualasto-Villa Unión Basin), La Rioja Province, northwestern Argentina. The burrows were found in different localities of the unit, but restricted to the lowermost 17 m of the formation. They occur at the same interval as a tetrapod assemblage composed of erpetosuchid and basal paracrocodylomorph pseudosuchians, basal traversodontid and chiniquodontid eucynodontians, and stenaulorhynchine rhynchosaurids. This assemblage differs from the typical Chañares fauna that occurs in stratigraphically higher levels. The burrows were found within the deposits of moderately developed palaeosols formed in volcanically-influenced braided fluvial facies under semi-arid climate conditions. The burrow systems are cylindrical to sub-cylindrical in cross-section, up to 25 cm in diameter, and characterized by long, multiple branching tunnels, several metres long, that meander horizontally or are slightly inclined (

Flat-slab segments are considered refrigerated areas given that the asthenospheric wedge is forced to shift hundreds of kilometres away from the trench, and the flat and coupled subducting plate acts as a thermal insulator. Although lithospheric-scale thermal analysis based on numerical modelling and geophysical observations abound, studies on the thermal history of sedimentary basins are scarce. In this contribution, we present a temperature data compilation from more than 60 oil wells within the Chilean-Pampean flat-slab segment and the transitional zones to normal subduction to the north and south in the south-central Andes. The geothermal gradient data are correlated with basin-basal heat flow estimated from 1D modelling, Curie point depths derived from aeromagnetic surveys, and previous crustal and lithospheric thicknesses estimations. Their distribution evidences a quite good consistency and correlation from region-to-region. Our modelling demonstrates that sedimentation changes are not sufficient to explain the variations illustrated in the geothermal gradient map, and that basal heat flux variations are required to reproduce the reported values. According to our results, the coldest basins develop over the flat slab or cratonward regions, whereas the highest temperatures on areas where the slab plunges. This suggests that the flat-slab geometry as well as the lithospheric structure affects the thermal state within the upper crust and particularly the sedimentary basins. Further studies will allow improving our database as well as the knowledge about the radiogenic contribution of the lithosphere and the asthenospheric heat input to the basins basal heat flow.

Mantle convection can drive long-wavelength and low-amplitude topography, which can occur synchronously and superimposed to tectonics. The discrimination between these two topographic components, however, is difficult to assert. This is because there are still several uncertainties and debates in the geodynamic community, for example, the scales and rates of dynamic topography. Geological, geomorphological, geophysical measurements, and/or landscape analyses might assist to validate models. In this contribution, we provide new geological evidences along the Central and Patagonian Andes, which demonstrate that dynamic topography has been an important component on the South American landscape formation as well as in the ancient western Gondwana. Our examples in the Argentine Pampas show that dynamic topography is required to explain not only the basin subsidence but also the whole observed topography. We also suggest that the dynamic components in this region are much lower than numerical models (average dynamic subsidence rates of ~0.04 mm/yr—this work— which contrast with the ~0.1 mm/yr estimated in the US). We also propose two strategies to analyze ancient cases. The first requires of comparing a total elevation proxy, like the equilibrium lines (or ELA) in glaciated areas, with model topography derived from geochemical studies of mantle rocks. A second strategy was the analysis of the Triassic rifting evolution of western Argentina (post-rift sag deposits). Sag deposit thicknesses exceed 2 km, which do not correlate with the 100 m thick thermal calculated by rift subsidence modeling.

This work forms the concluding part of a series of systematic studies of typical Gondwanan Permian palynofloras from the type section of the La Veteada Formation in the Paganzo Basin, central-western Argentina. It deals with the description and/or illustration of the non-taeniate monosaccate, bisaccate and polysaccate gymnosperm pollen species that are richly represented in the La Veteada Formation and are attributed to 25 genera. These taxa are allied to, or derived from, a diverse range pteridosperms (corystosperms, peltasperms), conifers (including Voltziales) and cordaites; Ginkgoales, Cycadales and Gnetales also have some representation. The new species, Jugasporites vellicoites, is instituted and the new combination, Alisporites angustus (Ouyang & Norris) comb. nov. et emend., is proposed. New evidence to support a Lopingian age for the palynoflora, considered to be the youngest Permian palynoflora recorded hitherto in South America, is based on a summary of the published information about its composition, together with an assessment of previous records of the diversity of gymnosperm taxa analysed in this contribution. The co-occurrence of several species of taeniate pollen (described in a previously published part of our work) and the gymnosperm taxa documented here, which have not been reported before from South America, differentiates the palynoflora of the upper La Veteada Formation from all others so far described from this continent. The high ratio of pollen versus spores, plus the botanical and palaeoecological inferences of the gymnospermous component of the formation’s palynoflora, reflects a parent vegetation adapted to relatively dry conditions. Such a low-humidity environment is consistent with the sedimentological evidence, which suggests that, through the Lopingian, semi-arid to arid climates dominated the southern South American basins. Fil: Zavattieri, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla; Argentina Fil: Gutierrez, Pedro Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Ezpeleta, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

A diverse microphytoplankton assemblage recovered from terrestrial deposits of the La Veteada Formation, north of the La Rioja Province, Paganzo Basin, Argentina, is described and illustrated. The ~ 180 m thick sedimentary type section of the unit in the Los Colorados anticline is composed of a basal gray silcrete covered by gypsum beds and a thick succession of purple mudstones inter-layered with varicolored fine sandstone sheets and laminated yellowish dolomites. The aquatic assemblage is mainly characterized by a great variety of Syndesmorion stellatum (Fijałkowska) Foster et Afonin coenobia, recorded for the first time in the late Permian Gondwanic realm. All the previous morphotypes described for this chlorophycean alga are recognized in this assemblage, and new polymorph-coenobia are described and illustrated. The diversity of coenobia morphotypes of this alga is likely to reflect response to stress conditions. The genera Maculatasporites and Mehlisphaeridium are commonly present, and their algal origin is discussed. Maculatasporites gondwanensis, Maculatasporites amplus, Mehlisphaeridium parvum, and Mehlisphaeridium regulare and Mehlisphaeridium sp. are also described and illustrated. Representatives of the zygnematacean algae, Brazilea scissa, Brazilea plurigenus, Brazilea sp. A, Tetraporina tetragona, ?Lecaniella sp., as well as large clusters of sphaeromorphs incertae sedis chlorophyta algae, are described. In addition, planar colonial chlorococcalean Pediastrum-like forms suggesting hydrodictyaceaen algae are recorded for the first time in late Paleozoic strata of Argentina, and the zygnematalean affinity of Reduviasporonites chalastus as green algae is discussed. The highly diverse La Veteada microphytoplanktonic assemblage is composed by algae that grew in hypersaline lacustrine environment together with species commonly associated with either fresh or brackish water conditions; presumably these taxa were washed in after heavy rainfall and/or flooding events. In general terms, the land-derived palynological composition of the La Veteada assemblage at Central Famatina Range reflects parent vegetation adapted to arid or semi-arid climate as reported from late Guadalupian to late Lopingian in the Paganzo Basin. The whole palynological composition suggests a Lopingian age for the La Veteada Formation at its stratotype, based on the stratigraphic range of all the land-derived miospore species recognized, resulting younger than assemblages assigned to the Lueckisporites–Weylandites Biozone (LW: Wordian–Capitanian). Therefore, it is the youngest Permian palynofloral assemblage recorded up to now in Argentina and South America. Fil: Zavattieri, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Gutierrez, Pedro Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales ; Argentina Fil: Ezpeleta, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

This is a systematic study of the palynological assemblages 25 recorded in the upper part of the La Veteada Formation (La Veteada ssemblage). In this contribution, 38 species of trilete and monolete spores are described and/or illustrated. Two new species are described: Lundbladispora verrucosa sp. nov., and Secarisporites triangularis sp. nov., and also a new combination of Secarisporites imperialis (Jansonius) nov. comb. is proposed. The trilete spores are one of the dominant groups of the analized microflora reducing its frequency from the base to the top of the section (from 32.2 to 14.5%). Cingulate-cavate spores (derived from herbaceous lycophytes) represented by species of the genera Densoisporites-Lundbladispora, and Secarisporites are dominant. Smooth and apiculate trilete spores (derived from ferns and sphenopsids) are represented by the genera Calamospora, Punctatisporites, Granulatisporites, Brevitriletes, Cyclogranisporites, Osmundacidites, among others. The upper section of the La Veteada Formation at its type locality was deposited in fluvial-lacustrine environments under arid to semiarid climatic conditions. Semiperennial hypersaline/brackish lakes dominate the sedimentation with periodic expansion and retraction episodes suggesting a low-relief setting. In the surrounding areas of these water-bodies, dominated by evaporites, grew the vegetation mainly composed of the herbaceous lycopsids Isoetales, Selaginellales, Lycopodiales, and ferns. In the flood plain, vegetation of pteridophytes (Filicales, Zygopteridales), bryophytes and herbaceous sphenophytes developed along the river courses and in the surrounding areas of freshwater bodies (ponds and small lakes). The presence of Densoisporites complicatus, D. nejburgii, D. playfordii, D. solidus, Leptolepidites jonkerii, Lundbladispora brevicula, L. obsoleta, L. springsurensis, L. wilmotii, Ringosporites fossulatus, Secarisporites bullatus, S. imperialis, and S. lacunatus allow confirming a Lopingian age for the upper section of the La Veteada Formation. Microfloras containing high proportions of lycopsid-tetrads are commonly recorded mainly in extra-Gondwanic realm constrained to a Lopingian-early Triassic age Se presenta el estudio sistemático de las asociaciones palinológicas registradas en la sección superior de la Formación La Veteada (Asociación La Veteada). En esta contribución se describen y/o ilustran 38 especies de esporas triletes y monoletes. Se describen dos nuevas especies: Lundbladispora verrucosa y Secarisporites triangularis, también se propone una nueva combinación para Secarisporites imperialis (Jansonius). Las esporas triletes son uno de los grupos dominantes de la microflora analizada reduciendo su frecuencia de base a techo de la sección (de 32,2 a 14,5%). Dominan las esporas cíngulo-cavadas (derivadas de lycofitas/licópsidas herbáceas) representadas por especies de los géneros Densoisporites, Lundbladispora y Secarisporites. Esporas triletes lisas y apiculadas (derivadas de helechos y esfenópsidas) están representadas por los géneros Calamospora, Punctatisporites, Granulatisporites, Brevitriletes, Cyclogranisporites, Osmundacidites, entre otros. La sección superior de la Formación La Veteada representa ambientes fluvio-lacustres depositados en condiciones climáticas áridas o semiáridas. Las áreas que rodeaban estos cuerpos de agua dominados por evaporitas fueron vegetadas principalmente por licópsidas herbáceas (Isoetales, Selaginellales, Lycopodiales) y helechos. Pteridophytas (Filicales, Zygopteridales), briofitas y esfenofitas herbáceas se desarrollaron a lo largo de los cursos de ríos y en las áreas circundantes de los cuerpos de agua dulce (pantanos y pequeños lagos) en la llanura de inundación. La presencia de Densoisporites complicatus, D. nejburgii, D. playfordii, D. solidus, Leptolepidites jonkeri, Lundbladispora brevicula, L. obsoleta, L. springsurensis, L. wilmotti, Ringosporites fossulatus, Secarisporites bullatus, S. imperialis y S. lacunatus permite confirmar una edad lopingiana para la sección superior de la Formación La Veteada. Microfloras que contienen altas proporciones de lycopsidas en tétrades han sido registradas principalmente en áreas extra-gondwánicas para el período Lopingiano/Triásico Temprano Fil: Zavattieri, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Ezpeleta, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Gutierrez, Pedro Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina

Eighty-one species of spores and pollen grains together with algae and fungi remains were recovered from the shallow lacustrine successions of the La Veteada Formation at the Chaschuil river section (27°43′50.5″S-68°01′17.0″W), Sierra de Narvaez, Catamarca Province, Famatina Range, which are herein described and/or illustrated. This palynoflora is composed dominantly by a diverse association of taeniate pollen groups (68%), bisaccate (non-taeniate) pollen grains (24%), with less significant proportions of spores. The studied palynoflora is referred to the upper part of the LW (Lueckisporites-Weylandites) Biozone, thus a Middle Permian (Guadalupian) age is established, mainly based on the presence of Corisaccites alutas Venkatachala and Kar, Lueckisporites angoulensis Jardine, L. nyakapandensis Hart, L. stenotaensis Menendez, L. virkkiae (Potonie and Klaus) Clarke, Lunatisporites variesectus Archangelsky and Gamerro, Staurosaccites cordubensis Archangelsky and Gamerro, Striatoabieites anaverrucosu...

An uppermost Mississippian (Serpukhovian) fossil flora from western Argentina is described for the first time. Its particular composition includes both, warm climate plants typical from the Pennsylvanian of Gondwana, namely pteridosperms, sphenophytes as well as arboreous lycopsids; and small lycopsids characteristic of cooler climates of pre-Serpukhovian times. A warm–temperate climate is inferred for this association, which fills a time gap between those Pennsylvanian and Mississippian classic floras previously known. The presence of Tomiodendron, Nothorhacopteris kellaybelenensis and Paracalamites allow the recognition of the Paraca Floral Realm in Argentina, supporting the existence of a nonglacial paleoclimate period, developed just before of the Bashkirian–Moscovian Gondwanan glaciation and after a latest Visean glaciation. It likewise would indicate the paleogeographic position of south west Gondwana, which would have acceded to a warm temperature latitudinal belt during Serpukhovian times. The recognition of this floral assemblage has relevant biostratigraphic and lithostratigraphic implications for the western margin of Gondwana. It defines a new zone for western Argentina, herein named Frenguellia eximia–Nothorhacopteris kellaybelenensis–Cordaicarpus cesarii (FNC) zone, which is recorded in the oldest known lithostratigraphic unit from the Paganzo Basin, the Loma de los Piojos Formation nom. nov.

Se presenta el estudio sistemático de las asociaciones palinológicas registradas en la sección superior de la Formación La Veteada (Asociación La Veteada superior) la cual integra el perfil de la localidad tipo, provincia de La Rioja, Argentina. La microflora se compone de una alta diversidad de esporas, granos de polen, algas y hongos (más de 90 géneros). En esta parte se presentan 72 especies de granos de polen monosacados y bisacados estriados, plicados y colpados. Se describen 4 nuevas especies: Meristocorpus veteadensis sp. nov., Lueckisporites biformis sp. nov., Lunatisporites lenticularis sp. nov. y Marsupipollenites costatus sp. nov. y, se propone la combinación Striatopodocarpites gopadensis (Bharadwaj y Srivastava) comb. nov. Esta palinoflora presenta un marcado dominio de los granos estriados, los que se caracterizan por una alta diversidad específica del complejo Striatopodocarpites (con 11 especies)-Protohaploxypinus (9 especies)-Lueckisporites (9 especies)- Lunatisporites (8 especies), además tiene escasa participación de Vittatina, Weylandites, Marsupipollenites, Corisaccites, Staurosaccites y Pakhapites y de granos de polen referidos a las Cordaitales (Potonieisporites, Cannanoropollis, Caheniasaccites, Plicatipollenites, Barakarites). Comparte taxones de las biozonas LW (Argentina), Vc-Lv (Brasil) y IS-AC (Uruguay). Se presentan cuadros con la composición taxonómica total de la microflora aquí caracterizada, de correlación palinoestratigráfica del Neopaleozoico del centro de Argentina, sur de Brasil y Uruguay y con los registros estratigráficos previos mundiales y los correspondientes a América del Sur, de las especies aquí tratadas. La palinoflora de La Veteada superior se refiere al Lopingiano sobre la base del rango estratigráfico del total de especies reconocidas. Consecuentemente, constituye la palinoflora pérmica más jóven registrada hasta ahora en Sudamérica. This is a systematic study of the palynological assemblages recorded in the upper part of the La Veteada Formation (upper La Veteada Association), which constitutes the section of the type locality, La Rioja Province, Argentina. In this contribution, 72 species of striate (monosaccate and bisaccate), plicates and colpate pollen grains are presented. Four new species are described: Meristocorpus veteadensis sp. nov., Lueckisporites biformis sp. nov., Lunatisporites lenticularis sp. nov., and Marsupipollenites costatus sp. nov. and, a new combination, i.e., Striatopodocarpites gopadensis (Bharadwaj and Srivastava) comb. nov is proposed. This palynoflora has a marked dominance of striate pollen grains which have great species diversity of Striatopodocarpites (with 11 species)-Protohaploxypinus (9 species)-Lueckisporites (9 species)-Lunatisporites (8 species) complex, showing scarse participation of the genera Vittatina, Weylandites, Marsupipollenites, Corisaccites, Staurosaccites and Pakhapites, as well as pollen grains referred to Cordaitales (Potonieisporites, Cannanoropollis, Caheniasaccites, Plicatipollenites, Barakarites). It shares taxa recorded in the LW (Argentina), Vc-Lv (Brazil) and IS-AC (Uruguay) biozones. Tables include full taxonomic composition of the microflora of the La Veteada Formation at its type locality, the palynostratigraphic correlation of the Neopaleozoic strata of central Argentina, southern Brazil and Uruguay, and the global previous stratigraphic records of the species recorded and discussed herein. The palynoflora of the upper La Veteada Formation is referred to the Late Permian (Lopingian) based on the stratigraphic range of all the recognized species. Consequently, it is considered the youngest Permian palynoflora recorded hitherto in Argentina and South America. Fil: Gutierrez, Pedro Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Zavattieri, Ana Maria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Reg. de Invest. Cientif. y Tecnologicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Científico Tecnológico Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina Fil: Ezpeleta, Miguel. Universidad Nacional de Cordoba. Facultad de Cs.exactas Fisicas y Naturales. Centro de Invest.paleobiologicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

[1] In the distal region of the modern flat-slab segment in the southern Central Andes, an unusual stack of middle Miocene paleosols together with regional upwarping and normal faulting indicate episodic aggradation and condensed sedimentation contemporaneous with the principal stage of foreland basin development associated with foreland flexure farther to the west. These features are consistent with development of a forebulge zone during the early stages of a proposed asymmetric foreland basin system. Sedimentary thickness farther east and far from the Cordilleran tectonic loads suggests accommodation and preservation driven by “nonisostatic” dynamic subsidence. Regional overlapping relationships and basin modeling suggest that the Modern broken foreland (present Sierras Pampeanas) can be interpreted as a reactivation of a formerly partitioned broad forebulge.