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Benthonic marine species show a wide range of biological reactions to seawater chemical changes through time, from subtle adjustments to extinction. The Early Toarcian Oceanic Anoxic Event (T-OAE) was recently recognized in the Neuquén Basin, Argentina, confirming its global scope. The event was identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion (δ13C org) in bulk rock and fossil wood in the upper Pliensbachian–lower Toarcian interval in the Arroyo Lapa section (Neuquén). Simultaneously with collection of lithological samples, a high-resolution biostratigraphical survey was carried out, and the scarce benthonic fauna was collected in order to check the biotic response to changing marine geochemical conditions. We present here an analysis of size and abundance data from the T-OAE interval in the Neuquén Basin for the dominant bivalve species, the paper-clam Posidonotis cancellata (Leanza), and relate these data to geochemical proxies (%TOC and δ13C org) obtained at the same locality. The abundance of P. cancellata increased when the rest of the benthos diminished, reaching a maximum at the onset level of the T-OAE, and then decreasing. Size-frequency distributions show a noteworthy lack of juvenile shells. Shell size shows a positive correlation with %TOC in the whole section, though over the T-OAE interval proper, it decreases below the level where the maximum %TOC value is attained and increases above it. Posidonotis cancellata shows features of opportunistic species, such as high tolerance to hypoxia, strong dominance in impoverished environments and a strong dependence on primary productivity, but at the same time had a reproductive strategy more similar to equilibrium species, with relatively low juvenile mortality rates. Several anatomical features suggest adaptation to permanently dysaerobic environments. The species disappeared just before the minimum negative carbon-isotope value was reached; and by the same time the genus became extinct worldwide. Unlabelled Image • P. cancellata size and abundance data from Toarcian relate to OAE geochemical proxies. • Shell size correlates positively with %TOC, probably linked to primary productivity. • Maximum abundance at the onset of the T-OAE, and then decreasing until its extinction. • P. cancellata shows opportunistic species features, but with a low juvenile mortality. • P. cancellata anatomical features suggest adaptation to dysaerobic environments. [ABSTRACT FROM AUTHOR]

In the comment on our paper, Prevosti et al. (2024) make a series of criticisms regarding the alleged lack of information provided on the dated samples and their geographic and stratigraphic provenance. In this contribution, we will give a reply to their comments. Our new zircon dating achieves the objective of the original study and provides valuable insights into the paleoecological dynamics of the period. It was out of the scope for our work to undertake a high resolution stratigraphical/sedimentological and dating analysis of each of the selected outcrops/sites. • First zircon dates from Neogene classic sites in central Argentina are provided. • The new dating achieves the objective of the original study. • Dating sets a solid time frame for paleoecological interpretations. [ABSTRACT FROM AUTHOR]

Sanz-Pérez et al. (2024) recently, based on detrital zircon, presented new maximum depositional ages for several sites of the Neogene of central Argentina to constraint the age of the faunas studied with stable isotopes. Unfortunately, the precise provenance of the dated samples is not clear. In this comment, we discuss the absence of key basic information to replicate their (geochronological) study, or even to evaluate their inferences and conclusions. Without more information about the precise geographic provenance of the dated detrital zircons, and their stratigraphic position in the geological profile/schema of each locality the interpretation of the authors is not supported by the presented information. • Detrital Zircon Dates presented by Sanz-Pérez et al. (2024) lack of precise geographic location information. • These samples lack of any stratigraphic position in the profile of each location. • Based on a new work, the date of Salinas Grandes is from the top of the profile, and irrelevant for age constraint. • Geochronological inferences of Sanz-Pérez et al. (2024) are unsupported by the data presented in the paper. [ABSTRACT FROM AUTHOR]

Factors affecting cetacean preservation and distribution in ancient sedimentary successions are not well understood. Actualistic studies have focused on coastal and deep marine examples, and little is known about taphonomic processes occurring within shelf environments. In this paper, we integrate sedimentological, taphonomic and palaeontological data for the cetacean-bearing lower Miocene Gaiman Formation from Patagonia, Argentina, to analyse which factors affected the distribution and preservation of cetaceans in several localities of the Southwestern Atlantic. Facies analysis shows that the formation represents a transgressive-regressive stratigraphic cycle, with palaeoenvironments including coastal, storm-dominated shoreface, inner shelf embayment and open inner shelf. Cetacean remains show preservation styles varying from isolated elements to articulated specimens, with nearly all remains restricted to both embayment and open marine inner shelf settings. Two fossil cetacean assemblages are recognized: Assemblage A comprises small-sized odontocetes dominated by Platanistoidea, preserved mostly in inner shelf embayment deposits; and Assemblage B comprises large-sized odontocetes and mysticetes, dominated by Physeteroidea and Balaenopteroidea, preserved mostly in open inner shelf deposits. Cetacean preservation style is controlled by a combination of palaeoenvironmental conditions, such as energy and sedimentation rate, and by biological factors, such as cetacean body plan and its impact on carcass buoyancy. Ecological factors may also explain the stratigraphic distribution of cetaceans between coastal and oceanic assemblages. This novel integrative and multidisciplinary analyses improves our knowledge of cetacean taphonomy in shelf environments. • Four coastal and shelf marine facies are identified for the lower Miocene Gaiman Formation of Argentina. • Cetaceans are mostly recorded in inner shelf deposits. • Cetacean preservation style is controlled by environmental and biological factors. • Cetaceans distribution is mostly controlled by palaeoecological factors. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the paleoclimatic and paleoenvironmental evolution of Laguna Yema in semi-arid Chaco region of Argentina over the past six hundred years. High resolution multiproxy studies of lake sediments utilize analyses of lithology, mineralogy, geochemistry, palynology, and are constrained by radiocarbon and gamma spectrometry dating. Laguna Yema sediments were mainly composed of well stratified fine sediments (silts and clays), with variable proportions of quartz, clays (illite) and feldspar (microcline and albite). Twelve light and heavy geochemical elements were registered. Most elements (Al, Si, K, Ti, Fe, Rb, Ba, and Br) are associated with illite and albite. Different material transport processes related to the changes in aridity and humidity of the basin were identified using the main mineralogical origins of geochemical elements. Palynological records indicate cycles of contraction and expansion of the lake, with an increase in concentration of Alternanthera aquatica during wet periods (expansion of lake), and an increase in Ambrosia , Poaceae and fern spores during dry periods (contraction of lake). These changes are linked to fluctuations in moisture conditions in the Subandean Mountains and semi-arid Chaco regions, in response to interactions between the South American Monsoon System (SAMS) and the South American Low Level Jet (SALLJ), which send warm and humid air to northern Argentina. In a regional context, the Laguna Yema records are in accordance with the analyses of the temporal and spatial pattern of moisture distribution for the last six centuries. • High-resolution variations of moisture conditions were registered by multiproxy lake sediments studies for the last 553 years. • Dissimilar material transport processes, related to the precipitation, were identified through mineralogy and geochemistry. • The palynological analyses allowed us to complement the paleohydrologic reconstruction in the basin. • The climatic model responds to the interconnection between the South American Monsoon System and South American Low Level Jet. [ABSTRACT FROM AUTHOR]

Abstract: In a recent paper (Verzi, D.H., Montalvo, C.I., 2008. The oldest South American Cricetidae (Rodentia) and Mustelidae (Carnivora): late Miocene faunal turnover in central Argentina and the Great American Biotic Interchange. Palaeogeography, Palaeoclimatology, Palaeoecology 267, 284–291) the potentially oldest South American Cricetidae (Rodentia) and Mustelidae (Carnivora) have been reported from a Late Miocene (Huayquerian) assemblage located in central Argentina (Caleufú site, La Pampa province). These findings expand the biochron of these important families in South America 3–4Ma earlier than previous records. However, several observations prevent us from accepting the validity of these assumptions. In this paper we discuss the age of the Caleufú assemblage, and the assignment of the GHUNLPam 21722 to Mustelidae. The Caleufú assemblage contains a mixture of Pliocene and Late Miocene faunal elements, and has been assigned to the Huayquerian only due to the “stage of evolution” of some rodents. The lack of isotopic or paleomagnetic data coupled with the isolation of this locality and the absence of a local stratigraphic succession inhibit its correlation with other palaeontological comparable sites and a robust inference about its chronology. The “stage of evolution” of a taxon is not a biostratigraphic tool, thus we cannot rule out the possibility that the Caleufú assemblage has an Early Pliocene (Montehermosan) age. The GHUNLPam 21722, a poorly preserved specimen, shows several characters (e.g., 4 lower incisors, mental foramina below the incisors absent, third lower incisor smaller than the first and second ones) that do not match with Mustelidae (or Carnivora) but instead strongly resemble those observed in didelphimorphian marsupials. The discussed caveats regarding Caleufu assemblage chronology and taxonomy indicate that new and detailed studies are needed before the hypotheses advanced by Verzi and Montalvo can be accepted. [Copyright &y& Elsevier]

Abstract: This paper presents the first record of charophytes from the Triassic sedimentary rocks of Argentina and the entire southern hemisphere. Algal remains were found in the Cerro Puntudo Formation dated as Anisian (243.8±1.9Ma). The formation is part of the Cuyana Basin, which formed as consequence of the Triassic rifting of Pangaea. The paleoenvironments represented by this succession include from bottom to top: (1) a proximal to medial alluvial fan system; (2) a distal alluvial fan deposit; (3) a braided fluvial system with small channelized bodies; (4) a distal fluvial system containing rare carbonates; and (5) a carbonate-rich lacustrine system. The lacustrine facies association corresponds mainly to carbonate microbialites with three recognized facies, namely disrupted micritic limestones (Lmd), stromatolitic limestones (Ls), and oncolitic limestones (Lo). The Lo facies is rich in oncolites formed by filamentous algae in the cortex and charophyte remains (gyrogonites) in the nucleus and is interpreted as being deposited in a carbonate-rich pond environment, perhaps sourced from springs. Filamentous algae are thought to cause the precipitation of carbonates and trigger the development of micritic coatings in the ponds. Sedimentary and paleobiologic evidence suggest minor movement of the oncolites in a ponded environment where charophytes developed. The charophyte remains found in the Cerro Puntudo Formation are gyrogonites attributed to the Porocharaceae family. All the previous records for Triassic Charophyta correspond to Laurasia in the northern hemisphere, therefore, the paleolatitudinal location of this finding allows the expansion of the paleobiogeographic distribution of the group into Gondwana. [Copyright &y& Elsevier]

Abstract: Argentina is a special place to study Late Palaeozoic life and environmental change because of the excellent exposures of Late Palaeozoic sedimentary sequences. In particular, Patagonia has an almost continuous Late Palaeozoic succession containing well-preserved faunal assemblages characterized by both strong endemism and distinctive palaeobiogeographic links to Australia and northeast Asia. In this contribution an overview of the current knowledge of the invertebrate faunas of Patagonia and their biostratigraphic and palaeobiogeographic significance are presented, along with comments on the future prospects of research in the light of new findings. The Late Palaeozoic outcrops in central-western Patagonia belong to the Tepuel–Genoa Basin (Chubut province, Argentina), then located in southwestern Gondwana during the Late Palaezoic. In this basin the succession is >6000m thick, and constitutes a continuous and complete succession from the Lower Carboniferous to lower Permian. As such, it has the potential to serve as an important reference section for regional and intercontinental correlations. The marine Late Palaeozoic of Patagonia has yielded abundant and well-preserved representatives of most invertebrate groups: brachiopods, bivalves, gastropods, cephalopods, hyolithids, pelmatozoans, ostracods and cnidarians. Recently, studies of the Patagonian faunas have resulted in different opinions on the ages of the faunas. Biostratigraphic correlation is complex due to strong faunal provincialism. For this reason, there are several hypotheses concerning the biostratigraphic zonation in the basin. Since 1920, when studies of Late Palaeozoic strata in Patagonia were first carried out, numerous papers on stratigraphic, palaeogeographic and taxonomic subjects have been published, but our knowledge of Carboniferous–Permian fossils from the Tepuel–Genoa Basin is still incomplete. At present, we are attempting to integrate and calibrate the different faunal associations with a view to achieving a unified biostratigraphic biozonation scheme and hence a much improved understanding of the palaeobiogeographic relationship of Patagonian faunas with those from western Argentina and other continents. Currently, detailed stratigraphic and palaeontological research is being done in the type section of the Tepuel–Genoa Basin. The aim of our studies is to integrate all partial sequences exposed throughout the basin and to propose a biostratigraphic chart based on key invertebrate taxa. Once this goal is achieved, a global correlation can be conducted, especially with other sections in Gondwana and the Arctic. [Copyright &y& Elsevier]

Interactions between human societies and the environment that they inhabit have been a controversial topic in archaeology for at least the past fifty years. Currently, modern theoretical approaches take this subject as a key issue in their research agenda. This paper presents a review of the main outcomes of several archaeological and multidisciplinary South American projects related to this theme. The case-studies discussed here are all located within arid settings, and can be grouped into three broad geographic areas: Puna (or Altiplano) of northwestern Argentina, Cuyo (west-central Argentina), and southern Patagonia. These regions cover a wide latitudinal range extending from 22° to 52° S. They were selected for comparison due to environmental similarities, and a common record of past climate impacts mainly related to the Medieval Climatic Anomaly (MCA) and the Little Ice Age (LIA). Although the impacts of these climatic changes were locally heterogeneous in their intensity and the quality of the available information is regionally variable, they provide a base-line for comparison and supra-regional integration. The integration of archaeological and palaeoenvironmental data on this broad supra-regional spatial scale allows us to identify interesting historical trajectories associated with particular time periods. As an example, there are some spatial rearrangements of large populations during the MCA, in the three areas. Additionally, there are variable patterns in the changes associated with the different social contexts that impose specific demographic and economic constraints. Finally, this study sets the basis for new questions and provides a guide to the methodological and theoretical issues that we need to address in order to answer them. [Copyright &y& Elsevier]

Abstract: This paper documents the occurrence of the Little Ice Age (LIA) in the El Azufre and El Peñón glaciers at 35°S and in the Las Choicas and Las Damas glaciers at 34°55′S in the headwaters of the Rio Grande basin in the Central Andes of Argentina. Moraine morphology, stratigraphic relationships, radiocarbon ages obtained from peat on these glacial deposits and the proximity to the active glaciers enabled us to reconstruct the LIA advance in this area. The LIA maximum advance occurred between cal. yr 1550 and 1720 AD, and a readvance occurred around cal. yr 1830 AD. In addition, glacier fluctuations of the Las Vacas and Güssfeltd glaciers (33°S) and El Peñón and El Azufre glaciers were documented from the end of the 19th century to the present based on historical and aerial photographs, and satellite images. The glaciers showed a marked retreat during 1894–2007. Minor readvances occurred in the 1980s and 1990s, which could be related with strong warm ENSO events during these decades. Our results are consistent with observations made by other authors in the region. [Copyright &y& Elsevier]

Abstract: This paper presents an updated, extensive review of glacier fluctuations during the past 1000years in the extratropical Andes of South America between ca. 17° and 55°S. Given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range, regional accounts are given for the Desert Andes (∼17°–31°S), the Andes of central Chile and Argentina (31°–36°S), and the North (36°–45°S) and South (45°–55°S) Patagonian Andes. The techniques, dating limitations, and interpretations of the glacier records along this transect are also discussed. Information on glacier fluctuations in the Desert Andes is limited to the 20th century. Documentation on past glacier variations is more abundant in the Central Chilean-Argentinean Andes, but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited. Most records indicate that glaciers were generally more extensive prior to the 20th century, with dates of maximum expansion ranging from the 16th to the 19th centuries. The number and extent of glaciers increase significantly in the Patagonian region, where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area. For some Patagonian glaciers, maximum Little Ice Age (LIA) or post-LIA advances have been precisely dated by dendro-geomorphological determinations or in situ measurements. However, for most sites, the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum LIA expansion identified in most areas between the 16th and 19th centuries. Evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium. These events were generally less extensive than the LIA maximum pulses. Despite the occurrence of several post-LIA readvances over the past 100–110years, most areas in the Andes of extratropical South America have experienced a general pattern of glacier recession and significant ice mass losses. The differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and/or the dating techniques used in each case together with the varying dominance of precipitation, temperature and other climatic and non-climatic factors on glacier mass balance and glacier dynamics. These differences indicate that the late Holocene glacier history of southern South America is more complex than commonly assumed. The evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed, well-dated records of glacier fluctuations. [Copyright &y& Elsevier]

Marine sedimentary rocks of the lower Miocene Monte León Formation of southeastern Patagonia (Austral Basin), Argentina are important geological archives for better understanding regional tectonics, paleoenvironments, oceanography, and climate. In this paper, we describe assemblages of invertebrates, palynomorphs, foraminifera, ostracods and calcareous nannofossils in a stratigraphical and sedimentological framework, which suggest deposition during a transgressive-regressive cycle. From base to top, the lowermost outcropping deposits of the Punta Entrada Member represent an inner shelf environment, formed during a transgressive phase. The zone of maximum flooding is marked by a high diversity of protoperidiniaceans (heterotrophic) and offshore dinoflagellate cysts, an increase in the percentage and size of planktonic foraminifera, and a decrease in shallow water benthic foraminifera. Regressive deposits in the upper part of the Punta Entrada Member exhibit a progradational stratal stacking pattern and are characterized by an upward decrease in bioturbation and in the content of marine invertebrates; the dinoflagellate cyst assemblages point toward shallower and more restricted marine conditions than in underlying deposits. The cycle ends with the Monte Observación Member, which contains an impoverished and mostly reworked fauna of invertebrates. The presence of monospecific reefs of Crassostrea orbignyi , the decrease in dinoflagellate cysts and calcareous microfossils diversity, and the increase of continental palynomorphs suggest progressively shallower conditions and increasing influence of freshwater discharge. Although eustatic controls could have contributed to the sedimentary evolution of the Monte León Formation, the upward regressive trend is interpreted as the result of tectonism linked to the Andean orogeny, which led to the uplift, exhumation, and erosion of the highlands in the west. This is supported by the abundance of pyroclastic material, together with reworked specimens of Upper Cretaceous forams and Upper Cretaceous and middle Eocene dinoflagellate cysts in the upper part of the Punta Entrada Member and in the Monte Observación Member. • Multiproxy data indicate that study rocks represent a transgressive-regressive cycle. • A maximum flooding and/or higher organic flux zone was identified at the coastal cliffs. • The regressive trend was the result of tectonics, sediment supply dynamics, and volcanism. • Cretaceous/Eocene forams and dinocysts evidence exhumation and reworking from the Andes. [ABSTRACT FROM AUTHOR]

This paper analyzes the distribution patterns of pollen and spore assemblages in modern surface sediments recovered from the bottom of the San Jorge Gulf (SJG) and from offshore sites, in relation to the location of different phytogeographic provinces surrounding the SJG, including the distant forest from southwestern Patagonia. Results reveal that pollen spectra are dominated by Chenopodiaceae-Amaranthaceae, Poaceae, Asteraceae subf. Asteroideae, Colliguaja integerrima and Ephedra sp.; which represents the vegetation adjacent to the SJG. Overall, the pollen distribution in surface sediments reflects the location of the different phytogeographic provinces and will be used as modern-analogues to document vegetation history around the SJG. Pollen assemblages also reveal the latitudinal variation of vegetation taxa in the Patagonian steppe, which is characterized by a slight increase in herbaceous pollen and a decrease in high shrubs (e.g. Colliguaja integerrima) towards the southern-central part of the SJG. Furthermore, we identified two pollen taxa from the southwestern Patagonian forest, Nothofagus and Podocarpus that could be used as indicators of past dynamics and variations of the Southern Westerly Wind Belt (SWWB) in the SJG during the Late Pleistocene and Holocene. High pollen concentrations are recorded at the central part of the SJG (480–8080 grains/g), while low concentrations are measured in the northern and southern parts of the Gulf, as well as at offshore sites (26–1806 grains/g). The pollen distribution in the study area is most likely governed by the SWWB in combination with the marine sediment composition and surface currents flowing through the SJG. • Pollen and spore surface distribution patterns from the San Jorge Gulf. • Pollen assemblages echo different phytogeographic provinces surrounding the gulf. • Nothofagus and Podocarpus reflect long distance transport by westerly winds. • Pollen distribution results from transport by westerly winds and surface currents. [ABSTRACT FROM AUTHOR]

The lower Miocene Santa Cruz Formation (dated to ~18–16 Ma) of Southern Patagonia, Argentina, preserves rich vertebrate faunas, which are representative of communities that existed prior to the Great American Biotic Interchange (GABI). Some previous researchers have hypothesized that these pre-GABI faunas had a low richness of mammalian carnivores (an impoverished predator guild), while others argue for a predator/prey ratio similar to those of recent communities. In this paper, we analyze faunas from the lower part of the Santa Cruz Formation (FL 1–7) using a methodology that allows us to quantify (i) the meat resources that were available to the secondary consumers of the palaeocommunity; and (ii) the competition intensity for these resources. In our modeling, we considered different scenarios related to meat consumption, including the possibility that several taxa had a scavenging behavior, and also differences in mortality rates between young and adult prey. Our results provide estimates of the nutritional requirements from the predator/scavenger guild under maximum and minimum quantities of meat offered by the prey community, which indicate the presence of a well-balanced palaeocommunity. Moreover, the competition indices point to a relatively high level of competition for prey of small-to-medium size, although competition for resources from large mammal prey was rather low. This suggests that the predator/scavenger guild was not impoverished, although there were insufficient carnivore species to fully consume the megaherbivore biomass. • We analyze predator richness of mammalian communities that preceded the Great American Biotic Interchange in Patagonia. • The biomass supplied and required is quantified for palaeocommunites in the Miocene (Burdigalian) Santa Cruz Formation. • The biomass demanded by carnivores falls within the range of biomass available. • Competition intensity was high for small mammalian prey, but low for large ones. • Predator richness was well-balanced in this palaeocommunity, except for large prey. [ABSTRACT FROM AUTHOR]