Argentine Pampas Research Articles

Counting Cattle in Argentina with AI and Satellite Images

Abstract. From a specific need of the national institution responsible for plant and animal health in Argentina, SENASA, this collaborative work between the public sectors together with academia arises. The objective was the development of a Deep Learning algorithm for the detection of livestock, cows in particular, in very high-resolution satellite images (provided by the Argentine Space Agency (CONAE)) and its subsequent counting. The basic elements involved in the development of artificial intelligence are detailed, such as the selection and acquisition of satellite images, their very thorough preprocessing and labelling, details of the training stage and some forms of error quantification. The image database is made up of about 320 scenes (based on very high resolution (VHR) satellite data from the Pleiades and Pleiades NEO sensors, ©Airbus 2022, distributed by CONAE) of the Pampas and Patagonian regions in Argentina. Around 8,000 labels of different types of animals were generated, the most common were cows and sheep. Also labels that did not represent animals to contribute to training. Finally, some very promising preliminary results are presented, such as the average error in the count that was achieved was ± four cows. The usefulness of these tools is reflected in better management of renewable natural resources linked to animal health issues, fiscal issues and within the framework of the 2030 Agenda and Sustainable Development Goals #12, #15 and #17.

Agroecological farmer perceptions and opinions towards pest management and biodiversity in the Argentine Pampa region

ABSTRACT Agroecology has recently become an alternative production model that tries to face the negative environmental and socioeconomic consequences of the agricultural model based on excessive agrochemical use and no-tillage practices. It searches for alternatives to pest management so as to increase yields while promoting biodiversity conservation. Our goal was to know the perception and opinion of agroecological farmers of the Pampa region on crop pests, the techniques they use for pest management and their perceptions on biodiversity. A survey was conducted which provided 103 responses. The main pest mentioned was ants. Of farmers surveyed, 64.71% claim that their main pest significantly reduces their yields, 79.42% claim that they monitor their crops for pests, although those with over 25 years of experience tend not to. Farmers have a mostly positive perception of biodiversity, particularly birds even though many identify pigeons and parrots as damaging. These results make it possible to describe the agroecological Pampa farmers and to show some common pest issues that need to be observed to benefit production in the area. The study highlights the importance of biodiversity for these farmers and their willingness to use tools that attract birds that could potentially manage pests.

Agricultural pesticides in feathers of the burrowing owl (Athene cunicularia) and its relationship to land-use in the argentinean pampas

The pampas of South America represent one of the most productive lands for agriculture in the world, and consequently this activity has expanded throughout the region, especially in Argentina. In this context, native fauna faces various risks associated with agriculture, with exposure to pesticides being one of the most dangerous and deadly. Assessing the impact of pesticides on wildlife becomes fundamental and the use of sentinel species emerges as an important tool to monitor environmental health. In this study, we determined pesticide levels in the burrowing owl Athene cunicularia nesting in both rural and urban areas of the argentinean pampas. We used a multiple scale approach to evaluate the influence of land-uses (urban, crops, and grazing fields) at the nesting site on the contaminant load of A. cunicularia individuals, and assessed the potential use of this owl as a sentinel species. From March 2018 to January 2020, A. cunicularia feathers were collected at their nest sites in one urban and two rural areas. These samples were analyzed for the presence of contaminants, including chlorpyrifos and 18 organochlorine pesticides. All the compounds analyzed were detected in A. cunicularia samples. The chlorpyrifos showed the highest frequency of occurrence and concentration, thus denoting the exposure of owls to current-use pesticides. ∑DDTs showed the highest occurrence among organochlorines, followed by ∑HCHs > ∑Endosulfans > ∑Heptachlors > ∑Drins = ∑Chlordanes > methoxychlor. Principal Component Analysis showed that most of the compounds found in A. cunicularia samples showed a positive association with grazing fields, suggesting that exposure to contaminants does not depend on specific habitat use at the local scale, but probably the regional scale. Our results evidenced the exposure of A. cunicularia individuals to past and current-use pesticides in the pampas of Argentina, and indicate that this owl would be useful as a sentinel species.

N Stress Alleviation in Crops—A System Approach Analysing Residual N From Winter Crops in a Late‐Maize‐Wheat Sequence

ABSTRACTNitrogen (N) is crucial for crop production. Crop sequences with different legume participation affect N availability and therefore N fertiliser management. The study aimed to assess the inclusion of winter crops (WC) with different amounts of residues and different C:N ratios on the following: (i) the response to N fertilisation in the following late‐maize (Zea mays L.), and to carry that comparison into a subsequent wheat crop (Triticum aestivum L.), and (ii) identify soil N indicators associated with these responses. Two field experiments (E1 and E2) were conducted in the Argentinean Pampas during two growing seasons to evaluate a WC/late‐maize‐wheat sequence under no‐tillage. In each experiment, late‐maize was sown after a bare‐fallow and three WC: wheat, vetch (Vicia villosa L.) and field pea (Pisum sativum L.), where five rates of N fertilisation were evaluated. An area of late‐maize that was not fertilised with N within each previous WC was used to evaluate the response to N fertilisation in the subsequent wheat crop. Indigenous N was estimated by using N uptake in the non‐N‐fertilised treatments. Soil N indicators and C:N ratio of WC residues were evaluated as indicators of response to N fertilisation in both crops. Significant responses to N fertilisation in grain yield and N uptake were observed in late‐maize when bare‐fallow and wheat were the previous treatments in both experiments. In contrast, vetch and field pea supplied 32 and 40 kg N ha−1 in E1 and E2, respectively, and showed no response to N fertilisation, satisfying the N required by late‐maize. However, this supply was not enough to sustain the N demand of the subsequent wheat, where the response to N addition ranged from 36% to 74% when vetch and wheat were the previous WC, respectively. Only soil inorganic N indicators were associated with indigenous N supply. Moreover, the apparent net WC effect was linked to late‐maize (r2 = 0.91) and subsequent wheat (r2 = 0.67) grain yield response, which was also related to the C:N ratio of the WC residues in late‐maize and the subsequent wheat (r2 = 0.78), suggesting that mineralisation occurs when C:N ratio is below 18. Consequently, in future studies the C:N ratio of the WC residues can be included in N fertilisation recommendation schemes when late‐maize is sown as a double crop in more intensified crop sequences.

Predicting land use and environmental dynamics in Argentina's Pampas region: An agent-based modeling approach across varied price and climatic scenarios.

This study, employing the AGRODEVS Agent-Based Model (ABM), systematically examined land use dynamics in Argentina's Pampas Region. Simulations under diverse scenarios highlighted the significant role of economic determinants, particularly crop price relationships, in influencing maize or wheat/soybean double cropping prevalence. Maize-dominated landscapes consistently achieved carbon sequestration goals, while wheat/soybean landscapes faced challenges, notably in ecotoxicity. Scenarios encompassed varying climatic conditions and soybean/maize price ratios, providing insights into the interplay shaping agricultural land use decisions among individual agents. The AGRODEVS model's robust performance underscored its effectiveness in integrating economic and environmental factors, contributing to a practical understanding of sustainable land use planning complexities.

Variability of Winter Frosts in Central South America: Quantifying Mechanisms with Decision Trees

Agricultural production in Central South America (CSA) is substantially influenced by frost events. This study characterises and quantifies the physical processes leading to frost conditions in CSA from 1979 to 2022, focusing on three innovative aspects: regional frost properties, a novel multi-parametric upper-level jet description, and the quantification of underlying mechanisms through decision trees (DTs). The regionalisation analysis identifies five homogeneous frost regions in CSA. In all regions, the events tend to occur more frequently during the La Niña phase. Moreover, a significant increase in the frequency of widespread frost events has been observed in the Argentinean Pampas during the study period, primarily due to negative trends in minimum temperatures. Furthermore, the synoptic mechanisms triggering frosts, such as cold fronts and post-frontal anticyclones enhanced by subsidence near the subtropical jet (STJ) entrance, have not shown major long-term changes. To describe the jets, we compute six parameters for the STJ and seven for the polar front jet, including latitude, intensity, height, tilting, longitudinal extent, and branch number. DTs are used to identify key jet parameters linked to frost events, such as the latitude, longitudinal extent, and tilt of the Atlantic STJ. Frost likelihood increases when the STJ is north of 31°S, and the extension of the Atlantic STJ is longer than 35° and has a negative tilt. Finally, DTs focused on the onset and end of events highlight geopotential height anomalies and STJ extension as critical variables. These DTs provide concise and accessible information for agricultural decision-makers in CSA.

Insecticides Cypermethrin and Chlorpyrifos Exposure: Effects on Sperm Motility and Fertility in Cyprinus carpio (Cypriniformes, Cyprinidae)

The agricultural production of the Argentine Pampa is based on intensive cultures, and the most widely used insecticides correspond to cypermethrin (pyrethroid) and chlorpyrifos (organophosphate), among others. Sperm motility and fertility assessments are essential topics for biology and population dynamics studies on fish species. In this study the alterations of these endpoints after exposure to commercial formulation of both insecticides were used to analyze the effects on common carp sperm. After the in vitro exposure at nominal concentrations of 0.25, 0.5, 1, and 2 μg/L of cypermethrin, a significant reduction in motility in 0.5 μg/L concentrations was observed respect control group. The same nominal concentrations were tested for chlorpyrifos, and the same significative effect was detected at 2.0 μg/L. Fertilization rate was significantly reduced at concentrations from 0.5 μg/L cypermethrin exposure, and from 1.0 μg/L in the case of chlorpyrifos. Eggs LC50 / 24 h (95% confidence limit) exposed to cypermethrin was 0.57 μg/L (0.36 - 0.88), and exposed to chlorpyrifos was 2.45 μg/L (1.13-5.29). However, is still debatable how these insecticides impact on fish reproduction, using this in vitro scenario we found a clear reduction in sperm motility and fertility.

Crop intensification influences water infiltration and microbial activity in agricultural soils from the southeast of the Argentinean Pampas

Crop intensification influences water infiltration and microbial activity in agricultural soils from the southeast of the Argentinean Pampas

Seasonal changes in habitat use and behavior of the threatened Pampas meadowlark Leistes defilippii

The Pampas grasslands’ biodiversity is severely threatened by habitat modification, as is the case for the Pampas meadowlark ( Leistes defilippii). Here we study the areas used by the species throughout the year in the Southern Pampas of Argentina, in association with seasonal changes in behavior, in an attempt to provide information for its effective conservation. We selected four grassland sites with livestock activities in which we studied vegetation characteristics and the abundance and behavior of the Pampas meadowlark, during breeding and non-breeding seasons. The species was absent in sites with higher bare ground cover and lower cover of >30 cm vegetation, and with high proportions of forb, shrub or exotic grass species. In those areas where the Pampas meadowlark was present during the breeding season, its abundance was higher where the grassland was entirely dominated by native grasses, and abandoned another site when the grassland became dominated by introduced plant species, after the breeding period. We are the first to report the behavior of a Pampas meadowlark population throughout an entire year with its seasonal changes. Our results and description of the behavior throughout the year highlight the importance of structural heterogeneity of the grasslands, determined by a low intensity of grazing, for the breeding of the Pampas meadowlark. Also, features associated with breeding habitat can’t predict the presence of flocks during the non-breeding season, as noted in our results for vegetation structure, but vegetation composition, food availability and landscape variables could play an important role in determining which areas serve as appropriate habitat during the non-breeding season, when large flocks search the grasslands for food. A better understanding of the habitat requirements and the use of space at different scales by the Pampas meadowlark will allow the identification of the most urgent and effective measures for its conservation.

CSI (Crime Scene Investigation) Beagle: Darwin's contribution to taphonomy

In the last decades, the impact of Darwin's legacy has been emphasized in many scientific fields. Nevertheless, there are still lesser-explored aspects of his life as researcher that deserve attention, such as his role as taphonomist. In this context, we highlight here this relevant facet of Darwin's investigations. During his voyage on the H.M.S. Beagle, Darwin collected numerous vertebrate fossils from South America. Particularly, in the Argentine Pampas he recorded information on the paleontology, stratigraphy, and sedimentology of different late Cenozoic fossiliferous sites. He also made observations on the preservation features of bone remains and the mechanisms that favored their fossilization, aspects currently included in the taphonomy field. In this frame, the information published in Geological Observations on South America regarding the fossils from Monte Hermoso and Punta Alta sites and his comments about the “imperfection of the geological record” on the Origin of the Species, are particularly noteworthy as an indicator of his interest in the relationship between the environmental context of preservation and the taphonomic features of bone remains. After 150 years, his scientific work continues to fascinate us. Darwin's keen eye for detail and his curiosity about the history of each fossil, about a century before taphonomy was born as a discipline, can indeed be likened to that of a Crime Scene Investigator (CSI) in some regards, reconstructing the taphonomic histories of both single remains and whole assemblages.

The golden butterfly: a new species of Pampasatyrus Hayward, extending northwards the range of the genus in the Andes (Lepidoptera: Nymphalidae, Satyrinae)

Abstract A remarkable new species, Pampasatyrus karri sp.n. is described from the upper valley of the river Pampas on the border of the departments of Apurímac and Ayacucho in the central Andes of Peru. It occurs in grassland puna on rocky slopes around 3500 m a.s.l. It is characterized by bright golden wing uppersides, a colour unique among the Satyrinae. It is only the third known Andean representatives of this, otherwise predominantly low to mid elevation genus associated with Brazilian and Argentinian pampa, and is most closely related, as indicated by COI data and male genitalia, to P. gorkyi found 200 km south-eastwards in Cuzco. Its discovery extends the northern range limit of the genus Pampasatyrus in the Andes.

Changes in productive, socio-economic, and environmental performance of field crop farming in the Argentine Pampas, 2007–2018

This study fills important gaps in research by analyzing the evolution over time of productive, environmental, and socio-economic aspects of agricultural production in the Argentine Pampas, utilizing farm-level data. A longitudinal study was conducted to examine the changes that occurred in farming systems during the period 2007–2018. The study evaluated the changes in 30 farms, examining modifications in the structure and management of each farm, as well as in productive, economic, and environmental performance. Canonical correlation analysis was used to relate the changes that occurred in performance to farms' characteristics at the beginning of the study period. The results indicated that, among the farms that stayed in business, there were no significant changes in land tenure and the amount of labor employed. There was a significant increase in the average age of farmers by 7 years, along with a decrease in the percentage of farmers expecting growth, dropping from 70% to 42% over the period. Canonical correlation analysis revealed that smaller farms, with a higher number of workers at the beginning of the period, were more likely to expand their farming area during the analysis period. The findings also indicate a substantial turnover of producers, with leaving farms being succeeded by larger-scale operations. The yields of the main crops and the direct production costs increased by 16% and 48% respectively, during the period. The environmental indicators for the main crops present a mixed picture: soil organic carbon input increased by 12%, while environmental impact quotient decreased on average, by 6% for cereals but increased by 40% for soybeans, and nutrient imbalances rose. The significance of this study resides in its application of a comprehensive approach to analyze the transformation of farming systems over time.

Socio-technical transitions towards sustainable development: A proposal for learning assessment in livestock SMEs in the semi-arid Pampas of Argentina

The urgency to achieve the Sustainable Development Goals in the face of climate change has increased interest in studies on innovation niches in food systems. Strategic Niche Management in the framework of the Multi-Level Perspective considers that deep learning must be achieved in experimenting with innovations and demands greater understanding of instrumental aspects to guide the evolution of a niche. This study proposes to assess the progress of innovative performance towards sustainability of small and medium livestock enterprises in the Southwest of Buenos Aires, a fragile region of the Pampas biome of Argentina, as a result of learning generated in rural extension activities of the National Institute of Agricultural Technology (INTA) in order to identify leverage points in the process of technological change towards more sustainable systems. An exploratory-descriptive study was carried out using qualitative-quantitative methods. Ten producers were interviewed and the MESMIS method was proposed for the construction of indicators and assessment of learning goals towards sustainability. A rapprochement of producers from modal practices to more innovative ones was observed, reflecting conditions for the progress and consolidation of the niche. However, they need for greater professionalization and institutional articulation. The study generated a measurement instrument for the self-assessment of the niche enterprises and the planning of INTA's intervention strategies. It sought to broaden empirical research in Latin America, which is still scarce in approaches to socio-technical transitions, and to advance in the evaluation of experiments in transformative innovations on the agenda for the literature.

Physical properties and organic carbon in no-tilled agricultural systems in silty Pampas soils of Argentina

Context Under continuous long-term no-till farming, many silty soils develop platey and massive compacted structures in topsoil, ascribed to low crop diversification and intense agricultural traffic. Aims We hypothesise that agricultural scenarios of greater diversification and cropping intensity should increase carbon (C) inputs and total and particulate organic C, resulting in the disappearance of these platey and massive compacted structures and soil compaction. Methods The hypothesis was tested in 55 selected production fields (lots or macro-plots of trials with a cultivated area greater than 15 ha) and five non-cultivated sites across the Rolling Pampas of Argentina. The whole area was covered by fine, illitic, thermal, silty loams (Typic Argiudolls, US Soil Taxonomy; Typic Phaeozems, FAO Soil Map). Based on estimations of the crop intensity index (CII; proportion of days in the year with active crop growth) and recent agricultural history of crop sequences, sampled fields were grouped into five categories: soybean (Glycine max) monoculture (CII < 0.45; mean CII = 0.39); low intensity cropping sequence (CII = 0.45–0.60; mean CII = 0.50); high intensity cropping sequence (CII = 0.60–0.80; mean CII = 0.66); pastures for hay bale production (CII = 1.0); and quasi-pristine situations (areas with non-implanted and non-grazed grass vegetation or with negligible stocking rate, CII = 1.0). Key results Total C inputs to soil varied within ~1400–7800 kg C ha−1 year−1 and were significantly and positively related to crop intensity index (P < 0.0001, r = 0.83). The highest (P < 0.05) soil organic C levels were observed in the first 0.05 m of soil and quasi-pristine conditions (even higher than under pasture), and the lowest (P < 0.05) under soybean monoculture. In the 0.05–0.20 m soil layer, quasi-pristine conditions had significantly (P < 0.05) higher soil organic C levels; the other situations did not differ. Soil organic C and particulate organic C levels (0–0.05 m layer) were related to both CII and annual C input. Platey structures and clods >0.1 m (0–0.2 m layer) were negatively related to CII (r = −0.59 and −0.45, respectively; P < 0.0001) and C inputs from crops (r = −0.60 and −0.29, respectively; P < 0.01). Nevertheless, this did not result in soil compaction alleviation, as shown by soil bulk density, maximum penetration resistance and water infiltration variations. About 92% of the samples with soil bulk density above the threshold (1.35 Mg m−3), and about 32% of the total records, presented levels of maximum penetration resistance, aeration porosity and/or water infiltration beyond the values suggested as critical. Conclusions Although soil organic C in topsoil varied as hypothesised, the studied soil physical properties did not. This partially rejects our hypothesis. Implications This study underscores the intricate interplay between crop intensity, SOC enhancement, soil structure improvement and the persistent challenge of subsoil compaction.

Nitrogen deficiency in maize fields of the Southern Pampas does not affect kernel number but reduces weight per kernel.

Nitrogen (N) requirement of maize has been increasing over the past decades, but there has been a lack of adjustment in fertilization management practices across different regions in Argentina. The higher N requirement in modern hybrids is associated with a higher post-flowering N accumulation. Additionally, soil fertility in the Argentina Pampas has consistently decreased in recent years. Whether the effects of N deficiency are expressed in the post-flowering period is still unclear at field level. The objective of this work was to quantify the yield reduction attributed to N deficiency and to identify the physiological basis of this effect at the field level for typical high-tech farms across the south-eastern Pampas of Argentina. Nineteen experiments were conducted during the 2020/2021 growing season in the south-eastern Pampas, evaluating two N managements i) Farmers' N level; ii) High N input. Results showed that the additional N input increased grain yield by an average of 6.4% (average grain yield difference of 712 kg ha−1). Weight per kernel was the only yield component that responded to N fertilization. Farmers' N management did not affect N accumulation or growth-related variables such as leaf area index, green leaves per plant, PAR interception, nitrogen sufficiency index until flowering, but the farmers' N level reduced these variables during the grain filling period leading to differences in aerial biomass and N accumulated at physiological maturity. Farmers' N level led to decreased post-flowering N uptake during grain filling period, which reduced the photosynthetic capacity of the canopy. These findings suggest that N management strategies and models need to be reviewed for high-tech maize systems.

From science to practice: The AGSUS protocol for monitoring and certification of sustainable soil management and carbon sequestration

Sustainable soil management is indispensable for achieving the UN Sustainable Development goals and soil carbon sequestration for climate change mitigation has gained importance in recent years, yet there are few examples of projects carried out to this purpose, and protocols that facilitate this task. Here we present a monitoring system that relies on sampling soils in the field, as opposed to a modeling approach. The high spatial variability of SOC was addressed by requiring that the participating farms divide their land according to management zones, based on soil type, slope position and land use history, and the sampling density was established as one sampling point per one hundred hectares, while for environments smaller than 500 ha minimum of five points must be used. These points are georeferenced and will be revisited for annual monitoring of sustainable soil management, and every five years for soil sampling for SOC, texture, bulk density, pH, electric conductivity (if indicated), and available phosphorus determinations. The monitoring of sustainable soil management will be carried out through a visual evaluation of 12 soil quality parameters, as described in the handbook published by the AGSUS group. The data obtained from the visual evaluation and the soil analyses (bulk density, particle size fractions, C content, and pH) in the baseline monitoring of Argentinean and Brazilian farms during 2022 were analyzed for the relation between visual evaluation score and the means of these soil parameters. The organic matter indicator (OMI)was calculated by the formula OMI = OM/clay plus silt*100. The data base contained visual soil evaluation scores at 80 georeferenced sampling points, representing 12 farms located in different agroecological zones of the Argentinean Pampas, and 47 sampling points on two farms in Mato Grosso, Brazil. Our results showed a relationship between the VE (Visual Evaluation) score and SOC contents of the soils, especially when these were expressed in relation to their fine mineral particles as with the OMI for the soils of the Argentinean Pampa and the Brazilian Mato Grosso. The OMI showed differences between the three VE scores ranging from 4.7 to 6.7 and from 3.1 to 5.1 in the 0–0.1 m and 0.1–0.2 m depths, respectively. Relationships between the VE score and SOC, OMI, Sand, Silt and Clay plus Silt were only found for the 39 cases of VE “moderate” score in Pampas soils, whereas for the 39 cases of “good” scores no significant relations were encountered. These soils had high SOC and OMI, indicating that they are healthy soils, near saturation level, with low C sequestration potential.

Water footprint in rainfed summer and winter crops: The role of soil moisture

Argentina is one of the main producers and exporters of grains and oilseeds, ranking third in soybean exports and fourth in barley ones. The 90% of this production occurs within the Argentine Pampas region (APR) under rainfed conditions, but its water consumption and pollution has not been studied in depth. Likewise, the link between soil moisture (SM) and Water Footprint (WF) generation is poorly studied at the global level. And yet, SM is a critical factor for the development of rainfed crops. This study aims to evaluate, at plot scale, the role of SM in the generation of the green (WFgreen) and grey (WFgrey) (WF). Additionally, it estimates the WF for rainfed barley and soybean crops in the Southeast of APR, where there are no reference values. Yields, water consumption and nitrogen (N) pollution load were estimated for different campaigns. Field data (weather, crop and production management) recorded in the study plots were used. Results indicated an average WFgreen of 1236 m3/t for soybeans and a WFgreen of 349 m3/t and WFgrey of 547 m3/t for barley. The study highlights the critical role of SM in both WF sub-indicators. Soil water availability, based on the evaporative fraction during critical growth stages, influenced yields and final WFgreen volumes. In addition, there was an effect on N uptake by crops. In the driest barley campaign, WFgrey increased by 234%. Insufficient SM restricted nutrient uptake, reducing yields and increasing N with the potential to leach or runoff. Consequently, it is suggested to adjust the WFgrey methodology incorporating SM fluctuations and unaccounted N losses. The study contributes to understand the WF drivers and highlights the need to assess them accurately. In particular, it aims to reduce the gaps surrounding the water consumption of rainfed crops, thereby supporting resource conservation and grain provisioning efforts.

Reply to the comment on Sanz-Pérez et al., “Paleoenvironment and paleoecology associated with the early phases of the Great American Biotic Interchange based on stable isotope analysis of fossil mammals and new U[sbnd]Pb ages from the Pampas of Argentina” [Palaeogeography, Palaeoclimatology, Palaeoecology 634 (2024), 111917

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.

Comment on “Paleoenvironment and paleoecology associated with the early phases of the Great American Biotic Interchange based on stable isotope analysis of fossil mammals and new U[sbnd]Pb ages from the Pampas of Argentina” by Sanz-Pérez et al. [Palaeogeography, Palaeoclimatology, Palaeoecology, 634 (2024), 111917

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.

The missing sedimentological section linking the Neogene and quaternary of the Tandilia system and the Salado basin, Buenos Aires province, Argentina

The Tandilia system and the Salado basin are two adjacent morphostructural units located within the Argentine Pampean plain, each exhibiting distinct and independent geological histories. The Tandilia system preserves outcrops of Argentina's oldest Proterozoic rocks, while the sedimentary record of the Salado basin began during the Jurassic period. However, starting in the Cenozoic era, both units began to display common continental sedimentary fill characteristics. Despite this connection between the Tandilia system and the Salado basin, there is no unified lithostratigraphic framework for the Cenozoic that varies according to the studied localities. This study aims to define the stratigraphy of a sedimentary section that demonstrates the link between these morphostructural units from the Neogene onwards and to correlate it with the formal lithostratigraphic frameworks proposed in the literature. The analysis of well records led to the description of lithofacies and the establishment of facies associations, which were integrated to generate three correlation transects between the wells. Four facies associations were identified, three of which were fluvial and one aeolian. The analysis of these facies associations revealed that the sedimentary fill could be divided into two sedimentary sequences, lower sedimentary sequence and upper sedimentary sequence, separated by a sequence boundary marked by conglomeratic deposits. The definition of a stratigraphic framework for the middle section of the Del Azul creek basin and its correlation with the formal lithostratigraphic frameworks of the region indicate that from the Neogene onwards, both morphostructural units, the Tandilia system and the Salado basin, share sedimentological and tectonic characteristics. This study highlights the significance of subsurface information in understanding the geology of plain areas and its influence on regional geological evolution.