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The article focuses on the first documentation of Late Paleozoic conodonts from Argentina, which provides new biostratigraphic and paleoclimatic insights into the Late Paleozoic Ice Age in southwestern Gondwana. It details systematic paleontology, including the genus Neognathodus and its species, such as Neognathodus colombiensis and Neognathodus "pre-colombiensis," with emphasis on their evolutionary patterns and morphological variations.

The article provides new information on the osteology and development of Avitabatrachus uliana, a pipimorph frog species found in northwestern Patagonia, Argentina. It re-examines the type specimen and identifies remains of a metamorphosing individual of the same species. The findings suggest a reinterpretation of the pattern of contact between the sacrum and urostyle in young post-metamorphs of this species and provide evidence for the plesiomorphic configuration of the parasphenoid and the separate first two presacral vertebrae. The document describes the skeletal anatomy of Avitabatrachus uliana, focusing on the morphology of the parasphenoid, axial skeleton, pelvic girdle, and appendicular skeleton. It also provides insights into the ontogenetic development of presacrals I and II in pipimorph frogs. The references cited in the document offer additional sources for further research on the topic. [Extracted from the article]

Ordovician strata exposed across the Cordillera Oriental and the Sierras Subandinas in northwestern Argentina were part of a large retroarc foreland basin developed along the Proto-Andean margin within the Central Andes in South America. A revised chitinozoan biostratigraphy along and across-strike for the Tremadocian, Floian, Dapingian, Katian and Hirnantian stages, calibrated with other fossil groups in the basin, allow pinpointing the most characteristic events that affected the basin fill testing global versus local controls in accommodation, and suggesting comparisons with other peri-Gondwanan records. According to the chitinozoan data, the glacially-related Ordovician deposits in northwestern Argentina are restricted to the Hirnantian, and unconformably overlie late Katian deposits. In the Caspalá area (Cordillera Oriental), an interval with synsedimentary deformation and reworked chitinozoans correlate with glacially-related deposits in other sites of the eastern part of the basin (Río Capillas and Mecoyita areas). A glacial waning stage is determined by a thin interval of organic‐rich black shales with sparse dropstones at the top of the Zapla Formation, containing Spinachitina oulebsiri associated with Desmochitina gr. minor , which together are typical latest Hirnantian components in other regions of Gondwana. Our study strengthens the foreland systems tract for the Ordovician Central Andean Basin with a volcanically fed interarc and foredeep depozone to the west (Puna region); a lower-accommodation forebulge depozone in the central area (mostly the Cordillera Oriental region); and a backbulge depozone (Sierras Subandinas and Sierras de Santa Bárbara) extending as far as the eastern Paraná Basin (reaching Paraguay and Brazil). Contemporaneous unconformities driven by global sea-level fluctuations were amplified or reduced due to deepening-narrowing or widening-shallowing, allowing contrasted accommodation, respectively associated to loading and relaxation. Ordovician chitinozoans from the Central Andean Basin indicate Northern, Western and peri-Gondwanan affinities, although locally some more cosmopolitan species described in Baltica, Avalonia and South China, are also recorded. [ABSTRACT FROM AUTHOR]

This article discusses the discovery of cryptospores, which are dispersed spores from the oldest terrestrial flora, in Colombia during the Late Ordovician to early Silurian period. The presence of these cryptospores suggests the existence of a land flora in northern South America during this time. The article also provides information on the paleoenvironment and age constraints of the samples based on palynological data. This research contributes to our understanding of the early terrestrialization of land plants in eastern Gondwana. Additionally, the article discusses the sedimentary sequence of the Llanos Basin in Colombia and the limited exploration of the Paleozoic unit in the region. The document is a compilation of scientific articles and studies related to palynology, covering topics such as the identification and classification of microfossils, biostratigraphy, and the paleogeographic significance of certain plant species. The studies primarily focus on regions such as Colombia, Argentina, Brazil, and Iran, providing insights into the evolution and distribution of early land plants during the Ordovician and Silurian periods. Lastly, the given text is a list of references and an annotated list of palynomorphs from a study on the Ordovician-Silurian cryptospores of Colombia. The list provides detailed descriptions and illustrations of the different palynomorphs identified in the study, which can be useful for researchers studying the paleogeography, paleoclimatology, and evolution of plant life during this time period [Extracted from the article]

The present work documents the stratigraphic distribution of dinoflagellate cysts from the upper part (60–585 m) of the YPF.Ch. PV. es-1 borehole, Península Valdés, Argentina. The assemblages exhibit a relatively moderate to low diversity. Most samples are characterized by frequent to abundant taxa of the order Gonyaulacales, such as Spiniferites/Achomosphaera spp., Reticulatosphaera actinocoronata, Operculodinium centrocarpum, and Melitasphaeridium choanophorum. Furthermore, a continuous succession of Early Miocene–Late Miocene diagnostic dinoflagellate cyst events was recorded for the first time from the Península Valdés region. Eight diagnostic events of highest occurrences (HOs) of dinoflagellate cyst taxa are identified. These bioevents allowed a subdivision of the sedimentary succession into two well-defined stratigraphic sections: Early to Middle Miocene (Burdigalian–Langhian/probably Serravalian, 430/425–330/325 m) based on the HOs of Emmetrocysta urnaformis, Cannosphaeropsis quattrocchiae, Cousteaudinium auybriae, and Cleistosphaeridium ancyreum, and Late Miocene (Tortonian–Messinian, between 175–170 and 80/85 m) based on the HOs of Labyrinthodinium truncatum subsp. truncatum, Operculodinium piaseckii, and Reticulatosphaera actinocoronata. The ranges of these taxa are compared with well-documented information on Neogene dinoflagellate cysts recorded from different sites across the North and South Atlantic Ocean and adjacent seas. In general, the dinoflagellate cyst assemblages, as well as the selected diagnostic taxa, exhibit a clear similarity to those of the Northern Hemisphere. The only exception is Hystrichokolpoma rigaudiae, which is asynchronous, possibly indicating local paleoenvironmental conditions. [ABSTRACT FROM AUTHOR]

The Arroyo Malo Formation represents the first marine ingression during the Late Triassic in the Neuquén Basin, west-central Argentina. The presence of calcareous nannofossils in this unit provides an independent age constraint of a late Norian to Rhaetian age for its lower and middle parts, in agreement with known fossil invertebrates. Furthermore, this represents one of the only three records of this group known so far outside the Tethyan Realm. The presence of monospecific assemblages of Prinsiosphaera triassica in the late Norian and assemblages characterized by P. triassica and Eoconusphaera zlambachensis in the Rhaetian, together with a review of other known records worldwide, allows the formal proposal of a global biozonation for the Late Triassic. Prinsiosphaera triassica Biozone, from middle Norian to late Norian, and Crucirhabdus primulus Biozone, spanning the Rhaetian (comprising two sub-biozones in the Tethys), are defined. Based on the new record from the Upper Triassic of the Neuquén Basin, we interpret that calcareous nannofossils originated during the middle Norian in the Western Tethys, and we suggest that they then rapidly dispersed to the Southeastern Tethys and from there to the Eastern Pacific across Panthalassa by southern mid-latitude easterly oceanic currents. [ABSTRACT FROM AUTHOR]

Background: Unenlagiine paravians are among the most relevant Gondwanan theropod dinosaur clades for understanding the origin of birds, yet their fossil record remains incomplete, with most taxa being represented by fragmentary material and/or separated by lengthy temporal gaps, frustrating attempts to characterize unenlagiine evolution., Results and Conclusions: Here we describe Diuqin lechiguanae gen. et sp. nov., a new unenlagiine taxon from the Upper Cretaceous (Santonian) Bajo de la Carpa Formation of the Neuquén Basin of Neuquén Province in northern Patagonia, Argentina that fills a substantial stratigraphic gap in the fossil record of these theropods. Although known only from a very incomplete postcranial skeleton, the preserved bones of Diuqin differ from corresponding elements in other unenlagiines, justifying the erection of the new taxon. Moreover, in several morphological aspects, the humerus of Diuqin appears intermediate between those of geologically older unenlagiines from the Neuquén Basin (e.g., Unenlagia spp. from the Turonian-Coniacian Portezuelo Formation) and that of the stratigraphically younger, larger-bodied Austroraptor cabazai from the Campanian-Maastrichtian Allen Formation. Consequently, the morphology of the new taxon appears to indicate a transitional stage in unenlagiine evolution. Phylogenetic analysis recovers Diuqin as a paravian with multiple plausible systematic positions, but the strongest affinity is with Unenlagiinae. The humerus of the new form exhibits subcircular punctures near its distal end that are interpreted as feeding traces most likely left by a conical-toothed crocodyliform, mammal, or theropod, the latter potentially corresponding to a megaraptorid or another unenlagiine individual. Thus, in addition to filling important morphological and temporal gaps in unenlagiine evolutionary history, the new taxon also offers information relating to the paleoecology of these theropods., (© 2024. The Author(s).)

We analyse the taxonomic status and diversity of the late Miocene Octodontoidea (Hystricognathi) Cercomys primitiva and related samples, a taxon previously known only from the holotype specimen. New findings associated with an extensive review of late Miocene and early Pliocene rodents have allowed us to recognize the occurrence of this and other related species in several localities of central and western Argentina, and in south‐central Bolivia. We discuss the invalidity of Cercomys and propose the new genus Metacaremys, which includes the type species Metacaremys primitiva comb. nov. and two new species, Metacaremys calfucalel sp. nov. and Metacaremys dimi sp. nov. Osteological, brain and dental morphology show that the new genus is not related to Brazilian Echimyidae, as previously considered, but to the southern family Octodontidae. Although the molar morphology of this genus is quite conservative, comparison of the samples shows a variation in size. We discuss the plausible evolutionary pattern explaining this variation and the implied biochronological and biostratigraphical information. It is recognized as an anagenetic lineage in which an increase in size occurs from the oldest species, M. primitiva comb. nov. (early late Miocene, c. 9.23 Ma), to the youngest species, M. dimi sp. nov. (Miocene–Pliocene boundary, c. 5.28 Ma). Metacaremys calfucalel is intermediate in size and age between these two species. The polarity of this pattern of change is consistent with that shown by other partially synchronous independent lineages of octodontoids, thus providing new evidence for the biochronological and biostratigraphic scheme of the late Miocene and early Pliocene of southern South America. [ABSTRACT FROM AUTHOR]

This work documents the biostratigraphy of dinoflagellate cysts from the La Barca Formation at the Punta Ainol Locality, Tierra del Fuego Province, Argentina. The succession at Punta Ainol represents a new record for the Paleogene (late Paleocene–middle Eocene) from southern South America, based on current data on nannofossils and dinoflagellate cysts. Some significant events are in agreement with nannofossil data. In ascending stratigraphic order, they include the first occurrences (FOs) of Impagidinium crassimuratum, Apectodinium homomorphum, Pyxidiniopsis waipawaensis, Samlandia septata, Cleistosphaeridium diversispinosum, and Enneadocysta dictyostila, and the latest occurrence (LO) of Palaeocystodinium golzowense. Three Paleocene/Eocene dinoflagellate cyst zones (Palaeocystodinium golzowense, NZDP7 and Apectodinium homomorphum) are recognized here. [ABSTRACT FROM AUTHOR]

[Display omitted] • We present the first high-resolution Cambrian/Ordovician transition δ13C carb chemostratigraphy in the Eastern North China Platform. • The carbon isotope chemostratigraphy of the Yaowangshan section refines the correlation between North China and other palaeocontinents. • The Cambrian/Ordovician boundary was constrained by the combination of Cordylodus lindstromi Zone and the rising limb of the COTICE in the Yaowangshan section. Revised conodont biostratigraphy and new carbon isotope data through the Cambrian/Ordovician transition are presented for the Yaowangshan section in the eastern North China Platform. Eight conodont zones are recognized, including the Proconodontus muelleri Zone, Eoconodontus Zone, Cordylodus proavus Zone, C. caboti Zone, C. intermedius Zone, C. lindstromi Zone, C. angulatus Zone, and Rossodus manitouensis Zone, in ascending order. The Eoconodontus Zone can be subdivided into the E. notchpeakensis Subzone and the overlying Cambrooistodus minutus Subzone. The new δ13C carb data from the Chaomidian Formation are well constrained by the conodont biozonation and indicate pronounced carbon excursions and spike, Top of Cambrian Excursion (TOCE), Cordylodus proavus spike (CPS), and Cambrian–Ordovician Transition Isotopic Carbon Excursion (COTICE). The isotopic excursions are generally consistent with those of other sections in North China, South China, Tarim, North America, Argentina, and Baltica. [ABSTRACT FROM AUTHOR]

Introduction: Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools. Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed. Methods: A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibliography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine rocks obtained recently allowed their placement in a chronological scheme: "Iheringiella" sp. A is restricted to the late Oligocene, the genera Camachoaster and "Eoscutella" and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster corresponds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its northernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previ- ously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed "Monophoraster and Venericor Beds". Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good correspondence among the numerical ages, molluscan biozones and scutelliform assemblages. [ABSTRACT FROM AUTHOR]

Lytohoplites Spath, 1925 is a late Tithonian–?early Berriasian ammonoid genus with a southern perigondwanean distribution. Two Lytohoplites species, L. burckhardti (Mayer-Eymar in Burckhardt, 1900) (type species) and L. vetustoides (Burckhardt, 1903), were originally described from carbonate successions of the Vaca Muerta Formation, Neuquén Basin, Argentina. Nevertheless, the holotype of L. burckhardti consisted of a single incomplete specimen that is currently missing. This situation compelled the search for new Lytohoplites specimens in Argentina and the selection of a neotype for L. burckardti. New Lytohoplites representatives were obtained through bed-by-bed collections performed at five localities in the Neuquén Basin. In addition to the taxonomic revision of the Lytohoplites species occurring in the basin, a paleobiological approach was preferred to conduct a paleontological analysis of L. burckhardti, including a description of its ontogeny, probable sexual dimorphism, and spectrum of intraspecific variability. Results of the qualitative and quantitative analyses supported the homogeneity of L. burckhardti as a taxonomic unit, thus implying that L. vetustoides should be considered its synonym. Lytohoplites in the Neuquén Basin is restricted to beds assigned to the Andean Substeueroceras koeneni Assemblage Zone (upper Tithonian–lower Berriasian), and not to the Andean Corongoceras alternans Assemblage Zone (upper Tithonian). Furthermore, the paleobiogeographic distribution of Lytohoplites around southern Gondwana and the herein reported occurrence of L. subcylindricus Collignon, 1962, otherwise only known from Madagascar, lend support to the existence of a functional trans-Gondawana seaway at least since the upper Tithonian. [ABSTRACT FROM AUTHOR]

We analyzed new occurrences of Azygograptus lapworthi from the Cordillera Oriental, Argentina. The bearer sandstones levels, corresponding to the Acoite Formation, are overlying the deposits, in which the Didymograptellus bifidus Biozone (Lower Ordovician, upper Floian, Fl3) was previously recognized, and are overlain by younger pelitic levels yielding Xiphograptus lofuensis (Middle Ordovician, early Dapingian, Dp2). Previous records from the Central Andean Basin are also reviewed in detail and accurately correlated, allowing us to conclude that the Azygograptus lapworthi Biozone corresponds to the Middle Ordovician (lower Dapingian, Dp1). This biostratigraphic framework documents that the transition between the Lower and Middle Ordovician deposits occurs in the uppermost levels of the Acoite Formation in the Argentine Cordillera Oriental. It is additionally integrated with up to date conodont records to establish a high-resolution regional correlation, with equivalent deposits from the Puna of northwestern Argentina and Cordillera Oriental of Bolivia, and to discuss new insights for global correlation. [ABSTRACT FROM AUTHOR]

The main objective of this study is to provide a review of the Tithonian succession of the Neuquén Basin and related Andean areas with an update from recent results on biostratigraphy and radio-isotopic geochronology. The studied successions include continental clastics and volcaniclastics of the Tordillo Formation and economically-important hydrocarbon source rocks such as the widespread black shales of the Vaca Muerta Formation, which has been ranked in recent studies as one of the most important recoverable shale oil and gas resources at global level. Significant recent data include the discovery of hyaline calpionellids associated with global nannofossil markers which are relevant to investigations of the definition of the Tithonian/Berriasian boundary. In addition, new high precision radio-isotopic data provide robust evidence to modify the absolute ages presently assigned to the base and top of the Tithonian Stage by the International Commission on Stratigraphy. • Updated review of the Tithonian of Andean Basins of Central Argentina and Chile. • Biostratigraphy combining ammonites, nannofossils, radiolarians and calpionellids. • High precision radio-isotopic CA-ID TIMS U-Pb zircon dating of ash fall tuffs. • Proposal for new absolute ages for the base and top of the Tithonian Stage. [ABSTRACT FROM AUTHOR]

Upper Jurassic and Lower Cretaceous deposits of the Vaca Muerta Formation (Neuquén Basin, central-west Argentina) have yielded abundant marine reptile remains. Most of them correspond to faunal assemblages recovered from outcrops in the Neuquén Province (Argentina). Herein we report two new marine reptile-bearing localities documenting the Tithonian–Berriasian transition at the High Andes (Mendoza Province, Argentina). Marine reptiles have been mapped and/or collected in connection with an accurate ammonoid-based biostratigraphic control. All the skeletons have been found preserved in, or associated with, calcareous nodules. At both localities they are frequent in beds assigned to the upper Tithonian Corongoceras alternans ammonite Zone (Microcanthum to "Durangites" Standard Zones), and are rare to common in beds assigned to the upper Tithonian–lower Berriasian Substeueroceras koeneni Zone ("Durangites" to Jacobi Standard Zones). Newly discovered assemblages depict a similar pattern characterized by the lack of plesiosaurs (plesiosauroids and pliosaurids), and by the abundance of mesoconsumers represented by ophthalmosaurids and metriorhynchine metriorhynchids. Macropredator geosaurines, apex metriorhynchids predators, and thalassochelydian turtles are rare components of these assemblages. • The new localities of southern Mendoza have yielded abundant marine reptile remains. • Marine reptile remains are more abundant in the Corongoceras alternans ammonite Zone. • At Arroyo Durazno ichthyosaur records are abundant and metriorhynchids are common. • At Arroyo Paulino the records of ichthyosaurs and metriorhynchids are common. • One turtle and non plesiosauroids or pliosaurids were recorded. [ABSTRACT FROM AUTHOR]

The fossil record of the Famatina System of NW Argentina has been extensively studied by several authors, but its conodont fauna is poorly known. This contribution analyses a significant conodont association recovered from the Suri Formation cropping out at Chaschuil region (Catamarca province). Conodonts comprise a low diversity association consisting of four genera and five species of significant regional and global biostratigraphic importance: Baltoniodus cooperi Carlorosi, Sarmiento and Heredia, Baltoniodus triangularis (Lindström), Condorodus gracielae Carlorosi, Mestre and Heredia, Erraticodon patu Cooper and Gothodus costulatus Lindström. This association supports a Dapingian age for the bearing strata (Baltoniodus triangularis Zone), and the correlation of strata with some from northern Argentina and those globally referenced sections. Furthermore, the biostratigraphic patterns, distribution and evolution of the recovered species along with the associated fossils allow us to suggest a paleobiogeographic migration pattern that involved the Andean Basin, the Famatina System and the Precordillera during the latest Early Ordovician and the early Middle Ordovician. [Display omitted] • First taxonomic description of a Dapingian conodont association from the Suri Formation, Famatina System. • Possible faunal connections of Gondwanan regions with the Precordillera and Famatina in the Middle Ordovician. • Suggest a common pattern of migration between different taxa using the Famatina System as a bridge that allowed their dispersal and evolution. [ABSTRACT FROM AUTHOR]

Abstract This investigation documents the first palynoassemblage spanning the Middle-Upper Devonian from four outcropping sections located in northwestern Argentina. The recovered material includes fairly well-preserved palynomorphs, both from marine and continental origin, including acritarchs, prasinophytes, cryptospores, spores and chlorophytes. In two of the four studied localities chitinozoans were encountered, whilst only one of them have yielded scolecodonts. Five new species are described including one acritarch specimen: Gorgonisphaeridium impexus sp. nov., two prasinophytes: Cymatiosphaera robusta sp. nov. and Pterospermella simplex sp. nov., one chitinozoan: Angochitina plicata sp. nov. and one miospore species: Apiculatasporites ruptus sp. nov. Hierarchical cluster analysis recognize two well-differentiated palynofloras in Argentina for the Early and Middle-Late Devonian. A poor correlation with known Devonian biostratigraphical schemes from Gondwanan and peri Gondwanan regions, support the theory of an endemic flora in northwestern and eastern Gondwana even during the Middle and Late Devonian. The palynoassemblage studied here provides an important source of reference to improve former strata correlation in the Tarija and neighbouring basins. Highlights • Middle-Upper Devonian palynofloras from northwestern Argentina are accounted. • Five new species, including phytoplankton and one miospore, are described. • Statistical analysis prove two different floras during the Devonian in Argentina. [ABSTRACT FROM AUTHOR]

A detailed palynological analysis of the Chacoparaná Basin is presented. Thirty-one samples were recovered from boreholes YCF.CO1, YCF.CO2 and YCF.CO3, corresponding to the lower part of the Ordóñez Formation, at the Santiago Temple locality (Córdoba Province, Argentina). Three new species are described: Calamospora fissurata sp. nov., Retusotriletes archangelskyi sp. nov. and Horriditriletes chacoparanensis sp. nov.; Leiotriletes malanzanensis nov. nom., Endosporites menendezi nov. nom., emend. are proposed to replace L. tenuis Azcuy and E. parvus Menéndez; and the following species are proposed as new combinations: Brevitriletes coalescens (Menéndez & Azcuy) nov. comb., Brevitriletes papillatus (Menéndez & Azcuy) nov. comb., B. sparsus (Menéndez & Azcuy) nov. comb., B. delicatus (Menéndez) nov. comb. and Indotriradites malanzanensis (Azcuy) nov. comb. Two different associations were identified and are compared with the known biozones from the same basin and other biostratigraphical schemes for basins from central western Argentina. The palynological assemblage can be referred, in part, to the Potonieisporites-Lundbladispora Biozone (Chacoparaná Basin) and the Raistrickia densa-Convolutispora muriornata Biozone (central western basins of Argentina, latest Serpukhovian-Bashkirian). [ABSTRACT FROM AUTHOR]

In this paper we describe for the first time the calcareous dinoflagellate cysts and calpionellid associations from upper Valanginian-Hauterivian orbital-driven rhythmic distal ramp deposits (Agrio Formation) in the Neuquén Basin, Argentina. Three stratigraphic sections from the northern Neuquén province (Loma La Torre and El Portón) and southern Mendoza province (Arroyo Loncoche) were studied. The Agrio Formation contains a low diverse association of these microfossils, among which ten calcareous dinoflagellate cyst species and five calpionellid species were recognized, all of them known from the Lower Cretaceous pelagic sediments of the Tethyan region. Two calcareous dinoflagellate cyst zones (Carpistomiosphaera valanginiana , and Stomiosphaera echinata), as well one calpionellid zone (Tintinnopsella), previously proposed for the Tethyan realm, are confirmed for the Agrio Formation. These zones are consistent to late Valanginian - Hauterivian age assignments previously established based on ammonites, nannofossils, and organic-walled dinoflagellate cysts. • First record of Valanginian-Hauterivian calpionellids and calcareous dinocyts in the Southern Hemisphere. • New data that support the presence of family Calpionellidae up to the late Hauterivian. • Calpionellids and calcareous dinocyts zones in the Andes show a similar distribution to those defined for the Tethyan realm. [ABSTRACT FROM AUTHOR]

We study the conodont fauna and its biostratigraphy recorded in the lower 3 m of the Gualcamayo Formation at the Potrerillos Creek section, northern Central Precordillera of Argentina. The analysis of two conodonts samples from levels of biostratigraphic interest, allowed us to identify 828 conodonts, assigned to 31 genera and 42 species. The recognition of Baltoniodus cf. triangularis (Lindström), Tripodus laevis s.l. Bradshaw, Baltoniodus navis (Lindström), and abundant elements of Paroistodus originalis (Sergeeva) allowed us to determine the lower part of the Baltoniodus navis Zone in the basal section of the Gualcamayo Formation. This allows us to reconsider previous biostratigraphic interpretations that assigned the lower 10 m of the Gualcamayo Formation to the Baltoniodus triangularis-Tripodus laevis Zone, to be reassigned to the Baltoniodus navis Zone. The lower part of the Baltoniodus navis Zone recognized in the present work correlates elsewhere in Argentina (Puna, Famatina, and Precordillera), as well as in China and Sweden with the lower Baltoniodus navis Zone, whereas it correlates with the upper part of the Microzarkodina flabellum-Tripodus laevis Zone in North America. Also correlates to the Isograptus maximus Zone. The occurrence of abundant conodonts representative of the Baltoniodus navis Zone in the Potrerillos Creek section, makes it suitable for further studies of a biostratigraphic interval that is underrepresented in most published sections of the Precordillera. In addition, we analyzed the preservation and CAI of the conodont elements recovered, these have a CAI of 2.5–3, indicating burial paleotemperatures of 85°−200 °C. Most gracile elements show a lower CAI (2.5) than the robust ones (CAI 3). Most elements present silica crystals attached to surfaces and the basal cavity, while few elements have recrystallized surface lamella. These fossilization features could be attributed to diagenetic effects related to intense tectonic deformation. • The Baltoniodus navis Zone in the Gualcamayo Formation, Argentina. • Conodont biostratigraphy of the Gualcamayo Formation, Argentina. • Conodont from the Gualcamayo Formation, Precordillera, Argentina. [ABSTRACT FROM AUTHOR]

The palynological assemblages of the Talacasto and Punta Negra formations, from the Argentinean Precordillera, were analysed. Marine phytoplankton is dominant in both stratigraphic units. ?Cymatiosphaera florida,Evittia sommeri,Palacanthus ledanoisii,Riculasphaera fissa,Schizocystia pilosa,Tysanoprobolus polykionandWinwaloeusia distractaare among the most age-significant phytoplankton species of the Talacasto Formation, whileAmicosporitessp. cf.A. streelii,Dictyotriletes emsiensisMorphon,Dictyotriletes favosusand ?Knoxisporites riondaeprove the most biostratigraphically significant miospore species. A Lochkovian to probably late Pragian age is interpreted based on the marine and terrestrial palynomorphs. The lower part of the Punta Negra Formation contains phytoplankton species such asCordobesia oriental,Cordobesia uruguayensis,Duvernaysphaera stellata,Navifusa bacilla,Polyedryxium fragosulumandPterospermellasp. cf.P. pernambucensisas well as the miosporesAcinosporitessp. cf.A. lindlarensisandApiculatasporites microconus, which suggests an early Emsian age. Taxa such asCordobesia,SchizocystiaandWinwaloeusiasupport affinities of the Argentinean assemblages with Gondwana. [ABSTRACT FROM PUBLISHER]

The Bajo de Veliz Formation (Paganzo Basin, Argentina) is one of the key upper Paleozoic successions characterizing the Carboniferous-Permian transition in westernmost Gondwana. A rich paleoflora with the first records of glossopterid leaves suggests an earliest Cisuralian age for the Pallero Member of the unit, although associated insects have been assigned to late Pennsylvanian groups. In this paper we present a new palynological analysis of the fossiliferous section with the goal of to correlate with coeval palynofloras from the region. The palynological assemblages, referred to the Pakhapites fusus–Vittatina subsaccata (FS) Biozone are characterized by Vittatina, Protophaloxypinus, Hamiapollenites, Pakhapites and Weylandites pollen (in proportions less than ten percent) together with the presence of the Converrucosisporites confluens Morphon. They have similar composition to those described for the Carboniferous-Permian stratotype and correlate with several associations from western Argentina and the Protohaploxypinus goraiensis Subzone of Brazil and Cristatisporites inconstans-Vittatina saccata Biozone of Uruguay. Available radiometric ages allow us to consider the probable beginning of the FS Biozone in the Gzhelian as well as the appearance of the glossopterids. [ABSTRACT FROM AUTHOR]

A palynological study of the Yacimiento Los Reyunos Formation (San Rafael Block) Argentina was carried out in order to correlate the palynological data with other Permian assemblages and biozones from South America. The unit is included in the Cochicó Group deposited under the volcanic influence of the Choiyoi event. The palynological assemblages recovered from subsurface samples show a dominance of taeniate bisaccates like Corisaccites, Lueckisporites, Lunatisporites, Protohaploxypinus , Vittatina and Weylandites . A Lueckisporites complex, which would have biostratigraphical value, is established to include species of Lueckisporites, Corisaccites and Staurosaccites showing a wide morphological variation. The composition of the assemblages allows their inclusion in the Lueckisporites/Weylandites Biozone of Argentina, which is closely related to other biozones from southern South America. Analysis of the distribution of the species using cluster analysis confirms its similarity with the biozones from Bolivia and Brazil. Radiometric datings suggest an age not older than Kungurian for the occurrence of these assemblages in the Southern Hemisphere. [ABSTRACT FROM AUTHOR]

In Argentina, Quaternary paleontological and biostratigraphic studies were mainly conducted in the Pampas plains of the provinces of Buenos Aires, Córdoba, Formosa and Santa Fe. The aim of the present study is to analyse the Pleistocene-Holocene record of the high plains of mountain in Córdoba in order to make interpretations on their biostratigraphical, geochronological, and paleobiogeographical significance. Representatives of 20 extinct and four living mammal species are listed, documenting the existence of two successive Assemblage Zones: Scelidotherium leptocephalum-Glyptodon reticulatus (between 37,095 ± 2020 and 14,040 ± 785 years BP) and Panochthus-Equus ( Amerhippus ) (between 14,040 ± 785 and 9181 years BP). The presence of supposed Ensenadan or Bonaerian taxa (e.g., Mesotherium sp., Catonyx tarijensis, Megatherium americanum , and Glossotherium sp.) in late Pleistocene sediments suggests that the mountainous area of Córdoba has acted as a refuge area or reservoir. The Quaternary faunas recorded in the Pampean highlands, Pampean flats, and western and northern regions of Argentina do not show differences in the morphological characteristics and numbers of taxa. [ABSTRACT FROM AUTHOR]

A large collection of conodonts (over 4200 elements) from the Santa Gertrudis Formation of the Cordillera Oriental, NW Argentina, is analyzed. The mostly endemic fauna of this unit and the lack of index species require complex taxonomic and biostratigraphic interpretations. We determined new species apparatuses by reviewing previous literature with a different taxonomic approach: Erismodus saltaensis n. sp., Erraticodon aldridgei n. sp., Gallinatodus elegantissimus n. gen. et sp., Pyramidens cactus n. gen. et sp., P. spinatus n. gen. et sp., Zentagnathus gertrudisae n. sp. Although the lack of key conodont species for intercontinental correlation precludes biostratigraphic assignment to a particular biozone, the overlapping ranges of recorded species restrict the age range to the upper Lenodus variabilis , Yangtzeplacognathus crassus and the lower Eoplacognathus pseudoplanus zones, of middle Darriwilian age (Dw2, Middle Ordovician). The depositional environment of the Santa Gertrudis Formation is primarily a shallow inner platform influenced by waves but not by storms; its paleogeographic location in mid-high latitudes exerts important control over the conodont biofacies, similar to the Arabian Darriwilian faunas of the Gondwanan margin. A narrow marine seaway along the suture zone connecting East and West Gondwana is proposed to explain the evolution of lineages of shallow cold-water conodont faunas from the Middle Ordovician onwards. • Conodont biostratigraphy confirms that the Santa Gertrudis Formation is of Darriwilian age. • A shallow-water conodont fauna evolved in mid-high latitude Gondwanan seaways. • A shallow-water seaway allowed conodont migrations across Gondwana in the Middle Ordovician. [ABSTRACT FROM AUTHOR]

The Devonian System in northern Argentina has been broadly analysed, but details of its lithologies, biostratigraphy and fossil content have not been presented in a comprehensive study. We performed the first integrative analysis of the palynological and macrofossil content from the Pescado Formation at the Zenta Range, Argentina. We define a new species of cryptospore and extend the stratigraphic record of the ichnogenusPsammichnitesisp. for South America. The stratigraphic ranges of the palynomorphs suggest a time span from the ?late Lochkovian to Pragian–earliest Emsian, but the co-occurrences of key invertebrates narrow the age of the beds to the late Pragian and early Emsian. Moreover, sedimentary analysis indicates a proximal shoreface–foreshore depocenter during this time range for the Zenta region. The contraction phase of the basin during the middle Pragian and Emsian is evidenced by the presence of sand bodies at the top of the column and the higher supply of terrigenous components. During this regression event, a low diversity Malvinokaffric Realm brachiopod assemblage occurs, with dominance ofAustralospirifer hawkinsi. The predominance of the latter species during this event is coeval with the first decline of the Malvinokaffric Realm in the neighbouring Paraná basin. [ABSTRACT FROM PUBLISHER]

The article discusses the findings of several studies on the Ordovician Period. Topics covered include the movement of the Argentine Precordillera from tropical to higher latitudes, recurring taphofacies in the Upper Ordovician of the Cincinnati Arch, chitinozoan biostratigraphy and sanidine geochemistry of the Upper Ordovician K-bentonites in the East Baltic region and chemistratigraphy and conodont biostratigraphy in the Ordovician of Sweden.

Five new species of ostracods, Paralimnocythere musacchioi n. sp., Paralimnocythere aucamahuevoensis n. sp., Wolburgiopsis ballentae n. sp., Looneyellopsismultiornata n. sp. and Vecticypris punctata n. sp. are described. The significant number of Limnocytheridae taxa shows the importance of the family in brackish to freshwaterCampanian-Maastrichtian sediments of theAllen and Loncoche Formations (Neuquén Basin, Argentina) and provide new paleogeographic and biostratigraphic data of each genera. Our results extend the paleogeographic and biostratigraphic range of the genera. Looneyellopsis has a widespread geographic range through Late Cretaceous, and documents affinities with associations from Southern Europe of the same age. Vecticypris is the only genus of Timiriaseviinae which is represented, so far, in the uppermostCretaceous deposits of theNeuquénBasin. A new species ofWolburgiopsis confirms the great significance of this genus in the Upper Cretaceous. [ABSTRACT FROM AUTHOR]

South America late Paleozoic brachiopod biostratigraphy is herein revised considering the recent taxonomic updates, time-sensitive fossils associated and the radiometric data available in order to provide a tentative biostratigraphic scheme. Six zones are recognized in West and East-central Argentina, namely Azurduya chavelensis (Tournaisian-early Viséan), that contains the brachiopod fauna of Michiganites scalabrinii-Azurduya chavelensis Zone, restricted to the Río Blanco Basin and also identified in northern Chile; Levipustula levis (late Serpukhovian-Bashkirian), in the Calingasta-Uspallata Basin, typically associated with the postglacial transgression of the most widespread episode in the region, and also recorded from the Bolivian Tarija Basin; Marginovatia peregrina-Maemia tenuiscostata (late Bashkirian-early Moscovian), a zone of local value defined in the Barreal Hill of the Calingasta-Uspallata basin; Tivertonia jachalensis-Streptorhynchus inaequiornatus (Moscovian-early Kasimovian?), the most widely distributed and diversified in the Precordillera, developed in relatively warm temperate conditions; and the youngest Costatumlulus amosi (late Sakmarian-early Artinskian), a low-diversity brachiopod assemblage only recorded in the southernmost part the Calingasta-Uspallata Basin; to east, in the Sauce Grande Basin, Tomiopsis harringtoni Zone (Sakmarian-Artinskian) that includes the brachiopod assemblages of the Eurydesma Fauna also identified in the Paraná Basin, Brazil (Eurydesma - Lyonia Fauna herein referred to the informal Tomiopsis-Lyonia assemblage). A posglacial brachiopod assemblage, the Aseptella-Tuberculatella/Rhipidomella-Micraphelia Fauna (late Serpukhovian-Bashkirian), relatively coeval with the Levipustula levis Zone and compositional different, is also recognized in the Calingasta-Uspallata Basin. Late Paleozoic brachiopod faunas from Patagonia associated with a late Tournaisian-Artinskian glacial sequence would not have a biostratigraphic relationship with those of west-central Argentina. A few informal brachiopod assemblages, mainly dated by fusulinids and conodonts, are herein proposed for the other South American basins. These assemblages are Tapajotia tapajotensis-Rhipidomella penniana (late Serpukhovian) in the Amazon Basin (Brazil), and also recongnized in the Moscovian of the Madre de Dios Basin (Perú); Amazonoproductus amazonensis-Anthracospirifer oliveirai (Bashkirian) in the Amazon Basin; Gypospirifer condor-Linoproductus cora (Moscovian-Sakmarian), in the Madre de Dios (Bolivia and Perú) and Navidad-Arizaro basins (Chile-Argentina), within which the species Waagenoconcha humboldti - Kochiproductus peruvianus are dominant to the Cisuralian; Alispirifer assemblage (late Bashkirian-Moscovian), in the Central Cordillera of Colombia); and the "Tethyan brachiopod assemblages" (late Pennsylvanian-Cisuralian), in the De Los Llanos Basin (Colombia and Venezuela). • South America Late Paleozoic brachiopod biostratigraphy is revised. • Six brachiopod zones are recognized for West and East-Central Argentina, some of them associated with paleoclimatic events. • Age is mainly based on the palynological-paleofloristic information but radiometric data have been also provided. • Azurduya chavelensis , Levipustula levis and Tomiopsis harringtoni zones are important in terms of regional correlation. • Informal brachiopod assemblages are also proposed for the Late Paleozoic South American basins. [ABSTRACT FROM AUTHOR]

Fossil capybaras are morphologically extremely varied, but previous studies have disagreed on whether this diversity reflects intraspecific variation or the existence of multiple species. Here, we review the capybaras from the classic Argen-tinian Late Miocene localities of Paraná River cliffs ("conglomerado osífero" of the Ituzaingó Formation, Entre Ríos), and Chillhué and Guatraché shallow lakes (Cerro Azul Formation, La Pampa), and perform a morphometric analysis of their upper cheek teeth and the posterior portion of the rostrum. Our results confirm that all of the specimens from the "conglomerado osífero" belong to the single species Cardiatherium paranense. In addition, we refer a specimen from Tupungato (Río de los Pozos Formation, Mendoza) to C. paranense, thus expanding its geographical range. The material from La Pampa represents a different taxon, and is here preliminary referred to Cardiatherium aff. orientalis. Our sys-tematic interpretation of Late Miocene capybaras suggests that the early radiation of this group was not as explosive as previously thought, and was likely constrained by the early acquisition of large size, increasing complexity of the cheek teeth, and probably semi-aquatic habits. [ABSTRACT FROM AUTHOR]

Cicatricose spores have been described from Cretaceous basins worldwide. A complete revision of previous records from Argentina and other parts of South America is presented here, as well as the results of a detailed taxonomic study of the species found in the La Yesera and Lagarcito formations (north and central western Argentina, respectively). Four genera and 11 species are described:Cicatricosisporites cuneiformis,C. pramparoana,C.sp. 1,Fisciniasporitessp. cf.F. brevilaesuratus,F. sp.,Nodosisporitessp.,Ruffordiaspora australiensis,R.cardielensis,R.ludbrookiae,R.cf.R. ticoensisandR. sp. 1. The genusFisciniasporitesis recorded for the first time in Argentina (La Yesera Formation), andNodosisporitesin the San Luis Basin. The abundance of the cicatricose spores is higher in the La Yesera Formation (8–54.2% of the total assemblage) than in the Lagarcito Formation (2–16%). An acme of cicatricose spores diversity in Argentina was recognized during the Aptian–Albian interval. Taxonomic studies of these types of spores are very important as they constitute a useful contribution of accurate descriptions and illustrations within a morphologic group that has many misidentifications, and also considering the biostratigraphic significance of some species, e.g.Cicatricosisporites cuneiformisin Australia. [ABSTRACT FROM PUBLISHER]

Abstract: Ordovician deposits from the Central Andean Basin cover a vast region with thick exposed sequences in several areas, including the Sierras Subandinas, Cordillera Oriental and Puna geological provinces of northwestern Argentina. This basin was situated along the active margin of a Paleozoic foreland basin in western Gondwana. Continuous sedimentation occurred in different paleoenvironments from east to west: marginal marine settings with estuarine and deltaic deposits (Sierras Subandinas), shallow marine shelf environments with large clastic deposits in the central part (Cordillera Oriental–eastern Puna), and deep marine deposits with volcaniclastic supplies (western Puna). Limited biostratigraphic and chronostratigraphic data from these sequences are known from graptolites, conodonts and trilobites, and more recently also from palynomorphs. An analysis of Ordovician sections from the different sedimentological settings of northwestern Argentina produced 60 chitinozoan-bearing samples from which 19 genera and 45 species have been recorded. Four chitinozoan assemblages were observed in the Lower Ordovician from northwestern Argentina. Correlations with other fossil groups provide independent biostratigraphic control. A stratigraphic range chart of selected acritarch taxa throughout the Ordovician of the Central Andean Basin is developed and biostratigrapic or potential biostratigraphic markers for the basin are proposed. In northwestern Argentina, Late Ordovician chitinozoan assemblages display affinities with Polar to Subpolar faunas. [Copyright &y& Elsevier]

Abstract: Although documented from Estonia, Latvia, Sweden, eastern North America, and China, the Middle Ordovician (Darriwilian) positive δ13C excursion known as the MDICE has previously not been recognized with certainty in South America. The most promising region in South America for detailed Middle Ordovician carbon isotope research is the Precordillera of western Argentina, where there are many excellent exposures of biostratigraphically well-dated carbonate successions spaning the Tremadocian through Sandbian stratigraphic interval. For this project, we collected numerous isotope and conodont samples from the middle Darriwilian Las Chacritas and Aguaditas formations at their type localities, which yielded important biostratigraphic data as well as informative δ13Ccarb values. In the E. pseudoplanus Zone in the upper half of the Las Chacritas Formation, there is a relatively modest but distinct δ13Ccarb excursion. Because its stratigraphic position and magnitude closely agree with the MDICE in other parts of the world, we recognize it as the first firm record of this excursion in South America. The fact that the δ13Ccarb curve from the Las Aguaditas Formation shows no such excursion is due to the existence of a stratigraphic gap between the Lower and Middle Members of this formation that cuts out the excursion interval. The Precordilleran MDICE is used for detailed long-range correlations with successions in Baltoscandia, Newfoundland, and China illustrating the usefulness of also this δ13Ccarb excursion as a global stratigraphic tool. A recent proposal of a greatly extended chronostratigraphic range of the Table Head Group on Newfoundland is rejected based on well-established biostratigraphic evidence. [Copyright &y& Elsevier]

Abstract: Results of the systematic review and regional palaeobiogeographical context of Tegula atra, including morphometric, multivariate and cladistic analyses, show that it is a keystone species in the marine Quaternary of Argentina that can be used as Pleistocene biostratigraphical tool and paleoclimate-palaeoceanographical signal. While it was absent in warmer than present high sea-level episodes during the Miocene (“Entrerriense” transgression, ca. 10 Ma) and Pleistocene (MIS11), it exhibits an excellent and abundant fossil record within dominantly cool coastal settings exclusively during the Late Pleistocene (MIS9, 7 and 5) between Río Negro and southern Santa Cruz provinces (Patagonia). It first appeared in the SEP during the late Pliocene (cooling trend), dispersed during the Late Pleistocene into the SWA presumably by rafting on macroalgae along the Cabo de Hornos and Malvinas (Falkland) currents, but became extinct in the Mar Argentino (Magellan Malacological province) during the Holocene (amelioration trend). Its absence at present represents a climate change-driven range shift and independent evidence of palaeoceanographical changes after the LGM and at the Pleistocene/Holocene transition: changes in SST (ca. 2 °C higher), wind velocities (less), light (less), nutrient availability (less), extension and intensity of cold (less) and warm (increased) shallow water currents altering water masses and biogeographical boundaries. Altogether, these changes and the Holocene scenario were disadvantageous, causing direct effects on its physiology and survival, in turn preventing the occurrence of the associated macroalgae (Durvillaea antarctica) and its successful dispersal in the SWA or retraction to the cold Humboldt System waters. This study reinforces the importance of dispersalist models to explain the origin of key taxa, adding for a better understanding of molluscan taxonomic differences along the SWA and SEP margins of South America, with implications for future coastal scenarios. The distribution of T. atra across time is a new example of the strong linkage between earth history-climatic cycles-atmospheric and oceanic circulation and the late Quaternary biotic responses, showing a possible consequence of future climate change on nearshore communities. [Copyright &y& Elsevier]

Three different species of the Ordovician genus Erraticodon Dzik are described and illustrated. Erraticodon patu Cooper is reported from the Lower–Midde Ordovician strata of the Acoite and Alto del Cóndor formations. E. cf. Erraticodon balticus and Erraticodon hexianensis from Middle Ordovician carbonate deposits of the San Juan Formation are analyzed and compared to specimens of these species from Australia, China, Newfoundland, and Baltica. E. patu and E. hexianensis are recorded for first time in the San Juan Formation of Precordillera. The elements of E. cf. E. balticus resemble closely E. balticus Dzik but lack the important denticle on the posterior process of the S elements. An evaluation of the stratigraphic occurrences of these species relative to those of key Lower and Middle Ordovician conodont species such as Trapezognathus diprion Lindström, Oepikodus intermedius Serpagli, Baltoniodus triangularis (Lindström), Baltoniodus navis Lindström, Yangtzeplacognathus crassus (Chen and Zhang) and Eoplacognathus pseudoplanus (Viira) indicates they value for biostratigraphic correlation. [ABSTRACT FROM AUTHOR]

The Eoplacognathus pseudoplanus Zone is defined by a conodont fauna composed by E. pseudoplanus (Viira) and Dzikodus tablepointensis (Stouge) among others in the Central Precordillera, Sierra de La Trampra region. We revised the biostratigraphical distribution and control biofacies of the conodonts D. tablepointensis and E. pseudoplanus in the Middle Ordovician of the Precordillera. This study confirms that these species has a similar biostratigraphical distribution to those of equivalent age in south-central China, Baltica and Midcontinent region. We also corroborate that the presence of D. tablepointensis is accurately positioned in the E. pseudoplanus Zone. In this paper we discuss for the first time the morphological affinities of D. tablepointensis and E. pseudoplanus elements from the Precordillera with those same species from southcentral China and Baltica. On the other hand, we review the genus 'Polonodus' galerus Albanesi and propose it as Kallidontus? galerus (Albanesi), extending the biostratigraphical record of the genus Kallidontus from the late Tremadocian to middle Darriwilian. [ABSTRACT FROM AUTHOR]

Abstract: In the last twenty years, several geological and stratigraphical studies have been undertaken in Córdoba Province, and they have provided useful bases for biostratigraphic work in the late Cenozoic. However, paleontological contributions have been limited to preliminary analyses of mammal assemblages, or specific discoveries. The aim of this work is to contribute to biostratigraphic knowledge of Argentina through the study of late Cenozoic mammals from Córdoba Province. Five localities have been analyzed: San Francisco, Miramar, Río Cuarto, Isla Verde, and Valle de Traslasierra. Through biostratigraphic analysis the first records of several taxa were established, and mammal assemblages with the description and correlation of the sedimentary strata were confirmed. Finally, three Assemblage Zones (Biozonas de Asociación) were proposed: 1) Neosclerocalyptus paskoensis–Equus (Amerhippus) assemblage zone with type area and profile based on the San Francisco locality, referred to the Lujanian (late Pleistocene–early Holocene), and comparable to the Equus (Amerhippus) neogeus Biozone of Buenos Aires Province; 2) Neosclerocalyptus ornatus–Catonyx tarijensis assemblage zone with type area and profile based on the San Francisco locality, referred to the Ensenadan (early Pleistocene) and comparable to the Mesotherium cristatum Biozone of Buenos Aires Province, and 3) Nonotherium hennigi–Propanochthus bullifer assemblage zone with type area and profile based on the Los Sauces river, Valle de Traslasierra, referred to the Montehermosan–Chapadmalalan interval (Pliocene), and comparable to the Trigodon gaudryi, Neocavia depressidens and/or Paraglyptodon chapadmalensis Biozones of Buenos Aires Province. [Copyright &y& Elsevier]

Palynological analysis is reported here for the first time from glacial and postglacial deposits of the lower-middle section of the Guandacol Formation at the Huaco area, central Paganzo Basin, Argentina. Forty-nine spore species are assigned to twenty-seven genera and twenty-one pollen species are assigned to ten genera, however few acritarchs were identified. Biostratigraphic ranges of species suggest an age no older than late Serpukhovian for the section studied. This age is also supported by radiometric data that indicate an early Bashkirian age at the top of the Guandacol Formation. The palynofloras consistmostly of endemic spore species, and provide new evidence for delimiting the Subzone Aof the Raistrickia densa-Convolutispora muriornata Biozone in Argentina. Close correlation is suggested with palynological associations belonging to thewidespread glaciation occurred during the Serpukhovian-early Bashkirian in South America and Australia. [ABSTRACT FROM AUTHOR]

Early Mesozoic Argentinian darwinuloids, now re-assigned to the genus Penthesilenula ( incae group), are described and illustrated. These records seem to constitute the oldest known for the genus. The close similarities between the studied species and those described from eastern Asia enlarge the geographical distribution of Penthesilenula ( incae group), which, although restricted to the southern Hemisphere in Recent and Holocene times, may have had a wider distribution in the past. Additional information on the paleoecology, plus a preliminary account on the distribution of darwinulid species from Argentina are also offered. One new species is described: Penthesilenula loana sp. nov. [ABSTRACT FROM AUTHOR]

Abstract: Although the Agrio Formation (Valanginian–Early Barremian) yields rich ammonite faunas at many levels, the highest beds are very sparsely fossiliferous. However, intensive collecting over the years has yielded a sparse fauna of heteromorph ammonites that are completely new to Argentina. Three taxa are represented, Sabaudiella riverorum sp. nov., Curacoites rotundus gen. et sp. nov. and Hamulinites? sp. The fauna is placed in a new ammonite zone of Sabaudiella riverorum and dated as latest Hauterivian–Early Barremian. [Copyright &y& Elsevier]

Abstract: The Monte Hermoso Formation (Farola Monte Hermoso, Buenos Aires Province, early Pliocene) is very important because it is the type locality of biostratigraphic units of the South American mammal bearing Pliocene. These deposits were the base for the recognition of the Montehermosan and Lower Chapadmalalan stages/ages. The correlation of this unit, especially with the Chapadmalal Formation has been debated. Over the last twenty years, major improvements have been made in the knowledge of caviomorph rodents collected in the Monte Hermoso Formation. The results include information about systematics and morphological change within lineages of the families Echimyidae (incl. Myocastoridae), Ctenomyidae, Octodontidae, and Hydrochoeridae. This information allows refinement of biostratigraphic correlation with other localities of south-eastern Buenos Aires Province. First and last records, as well as evolutionary patterns of some lineages, suggest an important change between the faunas from the Monte Hermoso Formation (including Lithostratigraphic Units I and II) and the Chapadmalal Formation, rejecting the previously suggested similarity of the upper levels of the Monte Hermoso Formation (Unit II, Lower Chapadmalalan) with those of the Chapadmalal Formation (Upper Chapadmalalan). Studies of more lineages including new revisions are necessary to test this proposal. [Copyright &y& Elsevier]

The trilobite Reedops is documented from strata probably corresponding to the middle part of the Talacasto Formation in the Sierra de las Minitas, at the northernmost extent of the Precordillera in La Rioja Province, northwestern Argentina. The specimens resemble the type species of the genus, R. bronni, indicating a Pragian (Early Devonian) age for the strata, and suggesting the occurrence at this time of faunal exchange between the Old World Realm, particularly the Bohemian area, and the Malvinokaffric Realm. The taxon represents the flrst Early Devonian macrofaunal element in the Malvinokaffric Realm with global biostratigraphical significance. [ABSTRACT FROM AUTHOR]

Abstract: Spitidiscus is a widely-distributed Hauterivian genus that briefly invaded the Neuquén Basin, Argentina, in mid Hauterivian times, well after it first evolved in the west Tethyan area. Its appearance in Argentina is linked with a globally-significant mid Hauterivian sea-level rise. This is marked in the basin by a sharp facies change in the Agrio Formation, from non-marine sandstones of the Avilé Member to marine sediments, often laminated black shales, with Spitidiscus at the base of the overlying Agua de la Mula Member. Our extensive field work has shown that Spitidiscus occurs across the whole basin, where it is represented by two species, Spitidiscus riccardii Leanza and Wiedmann and Spitidiscus kilapiae sp. nov. For most of its vertical range Spitidiscus occurs alone, characterising the S. riccardii Zone. But at the top of its range it is joined by the first crioceratitid ammonites, their appearance marking the base of the Crioceratites schlagintweiti Zone. [Copyright &y& Elsevier]

From detailed fieldwork and biotite Ar/Ar dating correlated with paleomagnetic analyses of lithic clasts, we present a revision of the stratigraphy, areal extent and volume estimates of ignimbrites in the Cerro Galán volcanic complex. We find evidence for nine distinct outflow ignimbrites, including two newly identified ignimbrites in the Toconquis Group (the Pitas and Vega Ignimbrites). Toconquis Group Ignimbrites (~5.60-4.51 Ma biotite ages) have been discovered to the southwest and north of the caldera, increasing their spatial extents from previous estimates. Previously thought to be contemporaneous, we distinguish the Real Grande Ignimbrite (4.68 ± 0.07 Ma biotite age) from the Cueva Negra Ignimbrite (3.77 ± 0.08 Ma biotite age). The form and collapse processes of the Cerro Galán caldera are also reassessed. Based on re-interpretation of the margins of the caldera, we find evidence for a fault-bounded trapdoor collapse hinged along a regional N-S fault on the eastern side of the caldera and accommodated on a N-S fault on the western caldera margin. The collapsed area defines a roughly isosceles trapezoid shape elongated E-W and with maximum dimensions 27 × 16 km. The Cerro Galán Ignimbrite (CGI; 2.08 ± 0.02 Ma sanidine age) outflow sheet extends to 40 km in all directions from the inferred structural margins, with a maximum runout distance of ~80 km to the north of the caldera. New deposit volume estimates confirm an increase in eruptive volume through time, wherein the Toconquis Group Ignimbrites increase in volume from the ~10 km Lower Merihuaca Ignimbrite to a maximum of ~390 km (Dense Rock Equivalent; DRE) with the Real Grande Ignimbrite. The climactic CGI has a revised volume of ~630 km (DRE), approximately two thirds of the commonly quoted value. [ABSTRACT FROM AUTHOR]

Abstract: The presence of the calcareous nannofossil Sollasites falklandensis has been recorded in four exploration boreholes in the southeastern Austral Basin at levels assigned an Early to Middle Albian age. This study evaluates its biostratigraphic and paleoceanographic importance for the austral hemisphere and for the Austral Basin in particular. Illustrations and a description of S. falklandensis are provided, and all records are discussed to evaluate its origin and extinction bio-horizons. A Tethyan origin during the Late Aptian is proposed along with a subsequent migration to austral high-latitude regions during the Early Albian. It is believed that S. falklandensis has an affinity for cold surface waters in epicontinental shelf environments. Although it has a diachroneous geographic distribution, it serves as an important marker species in the Early Albian-Middle Albian austral high-latitudes. [Copyright &y& Elsevier]

Abstract: The Carboniferous and Permian fossiliferous sequences of the central-western Argentina contain abundant plant remains, palynomorphs and invertebrates. They include a continuous record of large distribution in the Paganzo, Rio Blanco, Calingasta-Uspallata and San Rafael Basins. The most recent biostratigraphic schemes recognize a floristic succession represented by the biozones: Archaeosigillaria–Frenguellia (AF Biozone), Frenguellia eximia–Nothorhacopteris kellaybelenensis–Cordaicarpus cesarii (FNC Biozone), Nothorhacopteris–Botrychiopsis–Ginkgophyllum (NBG Biozone), Interval Biozone and Gangamopteris Biozone. The associated palynological record is represented by the biozones: Reticulatisporites magnidictyus–Verrucosisporites quasigobbetti (MQ Biozone), Raistrickia densa–Convolutispora muriornata (DM Biozone), Pakhapites fusus–Vittatina subsaccata (FS Biozone), and Lueckisporites–Weylandites (LW Biozone). The precise age of the Upper Paleozoic western Gondwanan biozones has been under discussion and remains controversial to date in some regions. The main issue hampering an integrated comparison of the Gondwanan biozones was its imprecise chronostratigraphic framework. However, new studies in some Argentinian stratigraphic sections bearing floras and faunas have yielded several radiometric ages. From these 206Pb/238U zircon datings it is possible to determine the chronostratigraphic range of many fossiliferous assemblages in this sector of Gondwana. In this way, the AF and MQ Biozones are restricted to the Late Mississippian and they would be not younger than 335Ma according to radiometric ages. 206Pb/238U ages suggest that the NBG, DMa and DMb Biozones characterize the Late Serpukhovian glacial deposits and persisted up to the Late Bashkirian. Beds containing the Interval and DMc Biozones have yielded 206Pb/238U ages of 312.82±0.11Ma and 310.71±0.1Ma which would indicate that both zones characterize the Moscovian. The remains of Gangamopteris Biozone found in the Paganzo Basin overlie basalt levels ranging between 308±6 and 293±6Ma. Therefore, the incoming of the first glossopterids was closely associated to the Carboniferous–Permian boundary in this part of Gondwana. The data presented in this paper are used for establishing comparisons with other Gondwanan biozones, constrained by absolute ages. [Copyright &y& Elsevier]

Abstract: During his journey on the Beagle, Darwin observed the uniformity in the elevation of coastal Eastern Patagonia along more than 2000km. More than one century later, the sequences of Quaternary shorelines of eastern Patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics. Consequently, we i) mapped the repartition of the Quaternary coastal sequences in Argentinean Patagonia, ii) secured accurate altitudes of shoreline angles associated with erosional morphologies (i.e. marine terraces and notches), iii) took into account previous chrono-stratigraphical interpretations in order to calculate mean uplift rates since ~440ka (MIS 11) and proposed age ranges for the higher and older features (up to ~180m), and iv) focused on the Last Interglacial Maximum terrace (MIS 5e) as the best constrained marine terrace (in terms of age and altitude) in order to use it as a tectonic benchmark to quantify uplift rates along the entire passive margin of Eastern South America. Our results show that the eastern Patagonia uplift is constant through time and twice the uplift of the rest of the South American margin. We suggest that the enhanced uplift along the eastern Patagonian coast that interested Darwin during his journey around South America on the Beagle could originate from the subduction of the Chile ridge and the associated dynamic uplift. [Copyright &y& Elsevier]

Abstract: Middle Ordovician acritarchs, including enigmatic, spore-like microfossils, are recorded from the Labrado and Capillas formations, of the Sierras Subandinas (Capillas River Section, Sierra de Zapla), northwestern Argentina. The Sierras Subandinas represent the outermost exposures of the Central Andean Basin that display an alternation of shallow-marine deltaic systems and estuarine environments, where relative sea-level fluctuations are frequent. The scarcity of fossils in the section, due to the marginal marine settings and frequent subaerial exposures, hinders the biostratigraphic constraining of these sedimentary successions. Based on the palynological assemblages, a probably Dapingian age is interpreted for the upper Lagunilla Member of the Labrado Formation, whereas the lower part of the Capillas Formation is assigned to the Darriwilian. Acritarchs from the lower part of the Capillas Formation indicate clear affinities with the “peri-Gondwana province”. However the lack of Frankea, a marker taxa for the Middle Ordovician, could be related either to the intermediate paleolatitudinal position of the Central Andean Basin or to local paleoenvironmental conditions. The facies analysis and the distribution of palynomorph assemblages throughout the studied section, suggest that organic-walled microfossils are influenced by local paleoenvironmental conditions. A probable non-marine origin is proposed for the spore-like microfossils co-occurring within the acritarch assemblages. [ABSTRACT FROM AUTHOR]

Abstract: The Lotena Formation from two localities, Picún Leufú and Portada Covunco, in the Neuquén Basin of west-central Argentina was studied palynologically. The material examined produced moderately diverse Late Callovian dinoflagellate cyst assemblages. This age assignment is consistent with ammonite evidence. The dinoflagellate cyst floras are reminiscent of the Middle Jurassic associations of northwest Europe and surrounding areas. Marine palynomorphs typical of Australasia and the Arctic are absent. The similarity with Europe is strongly suggestive of an open marine connection between western Tethys and the Neuquén Basin during the Late Callovian. This is interpreted as being via the Hispanic Corridor, with the palynofloras being passively dispersed to the southwest by the circum-Tropical Marine Current. Earlier studies indicate that this trans-Pangean equatorial seaway first began to allow biotic interchange during the Mid Jurassic and this study proves that this open marine connection was established by the Late Callovian. The similarities between the dinoflagellate cyst assemblages of Europe and the Neuquén Basin are consistent with the distribution of other marine fossils and the existence of geographically continuous marine facies belts. [ABSTRACT FROM AUTHOR]