Basin Argentina Research Articles

Redescription of Corydoras undulatus Regan, 1912 (Siluriformes: Callichthyidae), with comments on the identity of Corydoras latus Pearson, 1924.

A redescription of Corydoras undulatus Regan, 1912 is presented. The original description of C. undulatus is very succinct, as is its diagnosis, which is based only on external morphology. Additional information in the scientific literature on this species is scarce. Specimens from the distribution area of this species were analyzed; Paraná and Paraguay river basins in Argentina, Uruguay river basin in Argentina, Brazil and Uruguay, and the Laguna dos Patos system in Brazil. Morphological analysis, principal component analysis (PCA), meristic comparison and osteological description were performed. Corydoras undulatus can be distinguished from its congeners mainly by having the following combination of characters: mesethmoid short, with anterior tip short, smaller than 50% of the entire bone length; posterior margin of the pectoral-fin spine with nearly all serrations directed towards origin of spine; pectoral-fin spine with conical serrations; and its peculiar color pattern. The analysis of the material from the different basins did not indicate relevant morphological differences, suggesting that the species presents a wide distribution in La Plata and Laguna dos Patos drainages. The shared geographic distribution between these two systems is also present in other fish species. The current work presents data about the type locality, taxonomy, osteology, distribution and ontogenetic variation of color pattern in C. undulatus. Comments on the identity of a very similar congener, Corydoras latus, will also be provided.

Origin of bitumen fractions in the Jurassic-early Cretaceous Vaca Muerta Formation in Argentina: insights from organic petrography and geochemical techniques

This paper investigates chemical functional groups of the two extracted bitumen fractions in shales of the Jurassic to early Cretaceous Vaca Muerta Formation of the Neuquén Basin in Argentina, South America. The results indicate that Bitumen I is strongly aliphatic and appears to be genetically related to fluorescent amorphous organic matter. In contrast, Bitumen II consists of highly condensed, aromatic hydrocarbons, and has some correspondence to nonfluorescent amorphous organic material. Comparison of Rock-Eval VI pyrolysis data (S1 and S2) with the bitumen yields suggests that Bitumen I relates to S1 but also to S2. In addition, Bitumen I has a positive correlation with light liquid hydrocarbons (C5–C29), but also partially with heavier hydrocarbons (above C30). This suggests that Bitumen I corresponds to the majority of lighter hydrocarbons up to C29 and some portion to heavier hydrocarbons. These results have implications for the assessment of the mobility of generated hydrocarbons and their availability for production.

Heat flow and lithospheric thickness analysis in the Patagonian asthenospheric windows, southern South America

The lithosphere–asthenosphere boundary (LAB) is a first-order discontinuity, essential to understand the Earth composition and evolution. However, its detection has been critical and several regions still lack of coverage. Southern Patagonia, in southern most South America, is one such area, which has been affected by the subduction of a seismic oceanic ridge (South Chile Ridge) and formation of an extensive slab window since ~12 Ma. We calculate the LAB position by defining the thermal lithospheric thickness of the southernmost Patagonia using the thermal conductivity equation to estimate the surface heat flow. We used data from seventy-five hydrocarbon wells of two from the most productive petroleum basins in Argentina: the Golfo de San Jorge and Magallanes-Austral basins. Our results show the highest heat flow values in the southernmost region, over the Austral basin and core of the slab window (~70–90 mW/m2). These values are twice as hot as global average. To the north, over de Golfo de San Jorge basin and northern margin of the slab window, heat flows are “normal” (~50–60 mW/m2). These thermal contrasts, from south to north, agree with the kinematic reconstructions of the Chile ridge and northward widening of the slab window. These heat flows values evidence an attenuated lithospheres, which thickens eastward from between 25 km (to the west, trench region) to 50 km (to the east, foreland region).

Distribution of the Unionida (Bivalvia, Paleoheterodonta) from Argentina and its conservation in the Southern Neotropical Region.

Bivalves are one of the most representative groups in the Phylum Mollusca, with over 1,100 freshwater species around the world except Antarctica. About 900 of these species belong to the Order Unionida Gray, 1854. In South America, the distributional range of the Unionida includes all countries in the region and extends as far south as the lakes and rivers of Argentinean-Chilean Patagonia. With the aim of generating distribution maps for the different genera of Unionida in Argentina, we consulted the databases of the nation’s main official malacological collections. The data were analyzed and georeferenced using the point-radius method. Spatial analyses were performed with the software Q-GIS 2.16.3 Nødebo using vector layers under the 2007 Argentinean Geodesic Positions reference system. A total 1,833 lots were analyzed, of which it was possible to georeference 1,503. The distribution of Unionida in Argentinean territory was analyzed according to political provinces, Surface Drainage Basins and the Argentinean Protected Areas. Species richness was analyzed using the surface drainage basins of Argentina. We generate distribution maps for each genus and discuss the species threat status and conservation degree in the region. Only six (18%) of the Unionida present in Argentina have been classified by the IUCN, four are Least Concern and two are Data Deficient. This pattern is also valid for all of South America. More than 95% of the distributional range of the Unionida has no protected area. Conservation management is necessary for the preservation of Unionida diversity in southern South America.

Regional flood frequency analysis in the central‐western river basins of Argentina

AbstractKnowing the probability of occurrence of a flood event is an important issue for water resources planning. At‐site probability models require a long extension of hydrological data for robust estimation of low‐frequency events. As the mean record length of 25 gauge stations in western river basins of Argentina is 49 years (until 2010), regional models are an interesting tool to determine mountain rivers system dynamics. This study aims to estimate low‐frequency quantiles of annual maximum flow in Argentinean western river basins (28°S–37°S) applying regional frequency analysis based on the L‐moments method. Besides, mean annual maximum flow of 75 gauge stations (22°S–52°S) was analysed. First, an exploratory data analysis was performed; normality, independence, and randomness were accepted in the 27%, 87%, and 91% of cases, respectively. Increasing trends in annual maximum flows in the north‐western and central‐western rivers of Argentina were detected, whereas decreasing trends in annual maximum flow in the Patagonian Andes were identified. Base on at‐site characteristics and at‐site statistics, a homogeneous region of 12 stations with a record period of 568 years was formed. General extreme value was the most appropriate distribution for this homogeneous study region. Estimation accuracy using Monte Carlo simulations was performed. The error bounds were set at 90%, the mean square error was 9.23%, and the relative bias was 1.6%. The regional method performed better than the at‐site estimation.

The palynology of the Ordóñez Formation (Pennsylvanian) in the Chacoparaná Basin, northern Argentina

AbstractA 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).

Facies and architecture of river-dominated to tide-influenced mouth bars in the lower Lajas Formation (Jurassic), Argentina

The Middle Jurassic Lajas Formation in the Neuquen Basin of Argentina has been considered an ideal analog for tide-dominated deposits because of the widespread presence of tidal sedimentary structures and its heterolithic nature. Outcrops of the Lajas in the Los Molles area provide excellent exposures allowing both sedimentary structures and large-scale architectural information to be documented in detail. The extensive event bed stratification that characterizes the delta front and interdistributary bay deposits is interpreted to be the result of river floods because of the sharp base, fining-upward grain size trend, and seaward-directed paleocurrent indicators within each bed. The absence of wave-generated structures precludes a storm wave origin for these beds. Interflood deposits have two forms. The first is fine-grained sandstone and siltstone that is highly bioturbated with no tidal structures and is indicative of an overall river-dominated system. The second is also finer grained than the river flood beds but shows distinctive tidal features, indicative of a tide-influenced system during times when river influence was least. Mouth bars can be classified as purely river-dominated or river-dominated with tidal influence, depending on the type of interflood beds present. Tide-influenced mouth bars tend to be muddier, with more internal flow baffles or barriers and a lower-angle dip than their river-dominated counterparts. This study suggests that heterolithic successions containing pervasive tidal structures need not be tide-dominated because not all tidal structures are of equal importance in environmental interpretations. Their location (in river flood layers versus interflood layers) can be used as a methodology for determining the dominant and subordinate processes responsible for shaping the delta.

Oil Types of the Norwest Basin of Argentina

Oil Types of the Norwest Basin of Argentina

Multicomponent 3D-3C data acquisition and processing for characterization of Vaca Muerta Formation in Neuquén Basin, Argentina

The Neuquén Basin in Argentina has been producing for more than 100 years. Currently, the unconventional resources of the Vaca Muerta Formation are the ones that are most actively explored and studied. The reservoir is thick and heterogeneous in geomechanical properties and organic content. Therefore, to put a successful drilling program in place, one should study the reservoir using existing vertical wells and remote sensing methods like surface seismic, vertical seismic profiling, microseismic, etc. Properties derived from laterally dense seismic methods can be coupled with rock property measurements from the vertically dense well logs via developed rock physics relationships. An integrated reservoir model populated with rock properties will high-grade areas of the reservoir suitable for horizontal drilling and hydraulic fracturing. To better understand the Vaca Muerta Formation, the first multicomponent survey was shot in the Neuquén Basin at the beginning of 2017.

Geology of the Río de la Plata and the surrounding areas of Argentina and Uruguay related to the evolution of the Atlantic margin

An integrated study of geological and geophysical data of the Río de la Plata region and its relation to the evolution of the Atlantic passive margin is herein described. This characterization is based on the available geological and geophysical information and on the correlation of the southern end of the best-known Santa Lucía Basin in Uruguay to the Salado Basin in Argentina, and their connection through the Quilmes Trough. Furthermore, a new Meso-Cenozoic depocenter is characterized and identified as Recalada Trough, subparallely aligned to the Quilmes Trough and separated from it by the Magdalena-Montevideo High. Both sedimentary fillings present ENE-WSW trending main axes and reach an average thickness of almost 2000 m. This suggests an evolution from a triple junction where interconnected extensional arms developed, which have had common Mesozoic tectosedimentary histories related to the early opening of the Atlantic Ocean. Based on the geophysical and geological evidence, the previously accepted existence in the Río de la Plata of a first-order structural feature along the international border between Argentina and Uruguay, associated to an ENE-WSW trending tectonic high, identified as Martín García, is unjustified. The tectonic evolution of the Atlantic margin in front of the Río de la Plata estuary is the consequence of a long deformation history starting in the Precambrian up to recent times. Each Precambrian, Paleozoic, Mesozoic and Cenozoic tectonic scenario adds different weak trends on the continental crust, which control the evolution of the sedimentary depocenters. The presence of these tectosedimentary records influence the bathymetric control of the Río de la Plata and the dynamics of the recent estuarine deposits. The Meso-Cenozoic sedimentary infill is estimated to comprise considerable ranges of sandstones and conglomerates associated with faulted blocks of the crystalline basement, with expected petrophysical conditions oscillating in the order of 12%–15% of effective porosity and with expected traps of the stratigraphic and combined (closing against faulting) type, and overlapped by fine sediments with excellent quality as seals. The economic significance of these sedimentary volumes lies in their yet unexplored potential as natural fluid reservoirs (hydrocarbons and groundwater), of great importance due to their strategic position near the large urban areas of Buenos Aires and Montevideo.

Analyzing a suitable elastic geomechanical model for Vaca Muerta Formation

Accurate geomechanical evaluation of oil and gas reservoir rocks is important to provide design parameters for drilling, completion and predict production rates. In particular, shale reservoir rocks are geologically complex and heterogeneous. Wells need to be hydraulically fractured for stimulation and, in complex tectonic environments, it is to consider that rock fabric and in situ stress, strongly influence fracture propagation geometry.This article presents a combined wellbore-laboratory characterization of the geomechanical properties of a well in El Trapial/Curamched Field, over the Vaca Muerta Formation, located in the Neuquén Basin in Argentina. The study shows the results of triaxial tests with acoustic measurements in rock plugs from outcrops and field cores, and corresponding dynamic to static correlations considering various elastic models. The models, with increasing complexity, include the Isotropic Elastic Model (IEM), the Anisotropic Elastic Model (AEM) and the Detailed Anisotropic Elastic Model (DAEM).Each model shows advantages over the others. An IEM offers a quick overview, being easy to run without much detailed data for heterogeneous and anisotropic rocks. The DAEM requires significant amounts of data, time and a multidisciplinary team to arrive to a detailed model. Finally, an AEM suits well to an anisotropic and realistic rock without the need of massive amounts of data.

Suspended sediment concentration controlling factors: an analysis for the Argentine Pampas region

ABSTRACTIn the Argentine Pampas region, there is little information about sediment concentration in agricultural catchments. The aims of this work are: (1) to analyse fluctuations in sediment concentration and discharge, as a first attempt to characterize hysteresis patterns; and (2) to study sediment concentration controlling factors and to assess the importance of these factors using principal component analysis and a multiple regression model. Twenty-five events registered during 4 years in a 560 ha gauged basin of Argentina were studied. Analysis of data suggested a positive clockwise pattern. The multiple regression model was performed with three factors obtained by principal component analysis: runoff, precipitation and antecedent conditions. The model explained 83% of the variability of sediment concentration. The runoff factor contributed to modelled sediment concentration with the highest magnitude, followed by precipitation and antecedent condition factors. Although the watershed is under conservation tillage, rill erosion seems to be the main source of sediment concentration.Editor M.C. Acreman; Associate editor X. Fang

Colloidal-Dispersion Gel in a Heterogeneous Reservoir in Argentina

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 174704, “CDG in a Heterogeneous Fluvial Reservoir in Argentina: Pilot and Field-Expansion Evaluation,” by D. Diaz and N. Saez, YPF; M. Cabrera, InLab; E. Manrique, Consultant; and J. Romero, M. Kazempour, and N. Aye, Tiorco, prepared for the 2015 SPE Enhanced Oil Recovery Conference, Kuala Lumpur, 11–13 August. The paper has not been peer reviewed. The Loma Alta Sur (LAS) field is a multilayer fluvial sandstone reservoir in the Neuquén basin of Argentina. Reservoir heterogeneities and an adverse mobility ratio (30-cp oil) led to an early water breakthrough soon after water injection started. Colloidal-dispersion- gel (CDG) injection was considered a viable strategy to improve oil recovery in the field. LAS-58 CDG Pilot Summary The CDG pilot was implemented in the LAS-58 injector located on the northeastern side of the field. LAS-58 is an irregular pattern that began water injection in 2002, showing an early water breakthrough. The operator estimates that after 3 years of water injection in the LAS-58 pattern, cumulative secondary oil recovery is only 5.48% of original oil in place (OOIP). The LAS-58 pattern includes 10 producers: six first-line producers with well spacing ranging from 138 to 164 m and four second-line producers. The first tracer-injection program was implemented in March of 2003, 3 months after initial water injection in the LAS-58 injector. The fastest tracer breakthrough was observed in offset producer LAS-18 (50 days). However, the amount of tracer recovered in LAS-18 and LAS-26 was below 1.5% of the total injected. Producer LAS-49 showed the second-fastest breakthrough but with a cumulative tracer recovery of 4%. Each of the CDG-injection phases was followed by water injection at similar injection rates. The total volume of CDG injected (62 179 m3) represented 3.06% of the pore volume of the LAS-58 pilot area. Phase I consisted of a small injection volume intended to test CDG injectivity and did not affect pilot oil-production response but definitively contributed to adjusting the polymer concentration used in the pilot through Phases II and III of CDG injection. The main observation after Phase II of CDG injection was a very distinctive change in the injection profile of the LAS-58 injector. The water-injection flow paths were diverted into the middle (Mandrel 2) and bottom (Mandrel 1) zones of the pay zone because of the reduction in injectivity in the thief zones located at the top (Mandrel 3) of the reservoir. In October 2007, the incremental oil production for the 10 offset producers was reported as 133,292 bbl, with a reduction in water production of 406,949 bbl.

The ‘Helmut’ geophysical anomaly: A regional left-lateral transtensional shear zone system connecting Santos and Campos basins, southeastern Brazil

In the ultradeep water of Santos and Campos basins, eastwards from the area of present day pre-salt exploration in southeastern Brazil, there is a nearly 1000 km long, curved magnetic anomaly here named ‘Helmut’. On a magnetic map, the anomaly orientation switches from NE–SW in Santos basin to nearly N–S in Campos, mimicking the curved Neoproterozoic shear zone pattern of the basement exposed onshore. From the comparison between the position of such anomaly and gravity-derived modeling and residual maps, it is suggested that the magnetic anomaly also corresponds to a major gravimetric boundary, separating different crustal domains. This boundary is slightly oblique to the rift-related normal fault trend in Santos basin. Based on interpreted 3D seismic data, the NNE trending normal faults are dragged to the NE direction close to the magnetic anomaly in southern Santos basin, where an en echelon array of oblique magnetic anomalies occurs, which resulted mainly from the left lateral component of an overall transtensional displacement field.In regional 2D deep reflection seismic profiles, the ‘Helmut’ anomaly is correlated to major eastward dipping, down-to-the basin stepped faults sometimes arranged in a fan-like fashion in Santos basin, and as a landward dipping normal fault zone in Campos basin, north of the E–W Araruama transfer zone. In some areas, the fault zone displaces the base salt reflector and cross-cuts the entire stretched continental crust. The analysis of potential field and seismic data suggests that the ‘Helmut’ anomaly may be interpreted as a crustal-scale shear zone system, active after salt deposition during the Late Aptian. Regionally, the ‘Helmut’ anomaly connects two approximately N–S trending branches of the South Atlantic Rift System: the northern branch that runs from Espírito Santo basin northwards up to the Camamu (south of the Recôncavo-Tucano-Jatobá aborted trough), and the southern branch running southwards from Santos basin through Pelotas basin in Brazil as far as the basins offshore Uruguay and Argentina basins southwards. Extensional faulting of the salt reflector along early NNE rift-related normal faults and dextral transtension on the NW trending fault zones are all consistent with a sinistral transtensive motion on the NE-trending ‘Helmut’ anomaly during the Late Aptian.

The role of tidal, wave and river currents in the evolution of mixed‐energy deltas: Example from the Lajas Formation (Argentina)

AbstractMany modern deltas show complex morphologies and architectures related to the interplay of river, wave and tidal currents. However, methods for extracting the signature of the individual processes from the stratigraphic architecture are poorly developed. Through an analysis of facies, palaeocurrents and stratigraphic stacking patterns in the Jurassic Lajas Formation, this paper: (i) separates the signals of wave, tide and river currents; (ii) illustrates the result of strong tidal reworking in the distal reaches of deltaic systems; and (iii) discusses the implications of this reworking for the evolution of mixed‐energy systems and their reservoir heterogeneities. The Lajas Formation, a sand‐rich, shallow‐marine, mixed‐energy deltaic system in the Neuquén Basin of Argentina, previously defined as a tide‐dominated system, presents an exceptional example of process variability at different scales. Tidal signals are predominantly located in the delta front, the subaqueous platform and the distributary channel deposits. Tidal currents vigorously reworked the delta front during transgressions, producing intensely cross‐stratified, sheet‐like, sandstone units. In the subaqueous platform, described for the first time in an ancient outcrop example, the tidal reworking was confined within subtidal channels. The intensive tidal reworking in the distal reaches of the regressive delta front could not have been predicted from knowledge of the coeval proximal reaches of the regressive delta front. The wave signals occur mainly in the shelf or shoreface deposits. The fluvial signals increase in abundance proximally but are always mixed with the other processes. The Lajas system is an unusual clean‐water (i.e. very little mud is present in the system), sand‐rich deltaic system, very different from the majority of mud‐rich, modern tide‐influenced examples. The sand‐rich character is a combination of source proximity, syndepositional tectonic activity and strong tidal‐current reworking, which produced amalgamated sandstone bodies in the delta‐front area, and a final stratigraphic record very different from the simple coarsening‐upward trends of river‐dominated and wave‐dominated delta fronts.

Quality and Conservation of Riparian Forest in a Mountain Subtropical Basin of Argentina

The aims of this work were to describe the conservation status of riparian forests located in a mountain subtropical basin of Tucumán province, Argentina, and assess how the quality of riparian forests is related with altitude, plant species richness, proportion of exotic species, and Total Suspended Solids (TSS) in adjacent rivers. Composition and species richness of riparian forests were studied at 16 sites located along an altitudinal gradient and TSS was determined from water samples collected in each site. In order to evaluate conservation status of riparian forests, we calculated an index of Quality of Yungas Riparian Forests (QBRy). We recorded 90 plant species at all sites, from which 77% were native. QBRy index was mainly associated with altitude and varied from riparian forests with good preservation or slightly disturbed to those with extreme degradation. At lower altitude, forests were more disturbed, more invaded by exotic plant species, and closer to urban and cropped areas. QBRy was not correlated with species richness or TSS. Like other riparian forests of Argentina, plant species invasion increased their degradation; therefore, future studies should focus on native riparian forests conservation and on the management of invasive plant species, which affect their quality.

BIENESTAR EN TERNEROS LECHALES EN DOS SISTEMAS DE CRIANZA. ESTUDIO DE CASO EN LA CUENCA LECHERA SANTAFESINA

SUMMARY Well-being of suckling calves under two different rearing systems. Case study in the central milk basin of Argentina. In this paper we conducted a case study with quantitative approach. The aim of this study was to assess welfare in suckling calves during the winter season under two different rearing systems, which are used in the area. Calves were housed in two systems: a stake in males and females cage. All animals received 4 L milk per day, in two servings. Water and a commercial starter were offered ad libitum. Initial and final weights were recorded, weight gain was analyzed using descriptive statistical techniques. Saliva samples were taken at four times over the day, to analyze saliva cortisol

Geological evidence for fluid overpressure, hydraulic fracturing and strong heating during maturation and migration of hydrocarbons in Mesozoic rocks of the northern Neuquén Basin, Mendoza Province, Argentina

In the northern Neuquén Basin of Argentina (especially in Mendoza Province), there is strong geological evidence for fluid overpressure in the past. The evidence takes the form of bitumen veins and bedding-parallel veins of fibrous calcite (‘beef’). Such veins are widespread in the fold-and-thrust belt of the Malargűe area, where bitumen mining has been active for a century or so. So as to collect information on the development of fluid overpressure in this part of the Neuquén Basin, several old mines were visited and studied in the Malargűe area. Here the bitumen veins have intruded mainly the Late Jurassic to Early Cretaceous Mendoza Group, but also the Late Cretaceous Neuquén Group. The veins have the forms of bedding-parallel sills or dykes and they are especially thick within anticlines, forming saddle-reefs in several places. Beef veins are also numerous in the Malargűe area. They contain bitumen and therefore seem to have formed at the same time as the bitumen veins. Near many outcrops of bitumen and beef, we have found fine-grained volcanic intrusive bodies. The best examples are from the La Valenciana syncline. According to 39Ar-40Ar dating, these bodies are mainly of Mid-Miocene age. More generally, volcanism, deformation and maturation of source rocks seem to have reached a climax in Miocene times, when the subducting Pacific slab became relatively flat.

The Early Cretaceous megaflora of the Springhill Formation, Patagonia. Paleofloristic and Paleonvironmental inferences

The Springhill Formation (Lower Cretaceous) is considered as one of the most important oil producer units within the Austral Basin in Argentina. However, knowledge regarding this formation's plant community composition is still very scarce. In this work a thorough survey of the outcrops of the Springhill Formation was conducted regarding both geological and palaeobotanical aspects. Abundant fossil plant material was collected at the Estancia El Salitral and Río Correntoso localities in Santa Cruz Province, Argentina, consisting primarily of compressions of leafy shoots with several branching orders, completely to partially preserved fronds, simple to pinnate leaves and fertile scales. Analysis of these materials made it possible to describe 20 new taxa which add to the already known flora of the Springhill Formation; nine of these taxa were found in Estancia El Salitral, and the remaining 11 were found in Río Correntoso. The floristic diversity of the unit has increased through the discovery of the first megafossils of ginkgophytes (Baiera sp. 1 and Baiera? sp. 2), whereas new taxa have been described within the divisions of Pteridophyta, Pteridospermophyta, Cycadophyta and Pinophyta. Analysis of the vegetative and reproductive epidermal structures of the various groups included within this megaflora has been demonstrated to be a valuable tool for the recognition and differentiation of species. Analysis has also made it possible to suggest paleoenvironmental inferences. Finally, the megaflora from the Springhill Formation was compared to other relevant plant assemblages from the Lower Cretaceous of Western Gondwana. The megaflora was determined to be most similar to that of the well-known Patagonian Anfiteatro de Ticó Formation and most different from that of the Brazilian Crato Formation.

Vulnerability of water systems: a comprehensive framework for its assessment and identification of adaptation strategies

Most climate projections predict that average surface temperature and precipitation variability will increase at the global scale, triggering hydrological variations and alterations in river flows and groundwater table levels. Climate change impacts on freshwater resources are likely to affect freshwater availability and quality and by extension, the ability of water systems to support natural processes and ensure population needs. As a result, the vulnerability of water systems to adverse conditions (e.g. water shortages, overexploitation, and quality deterioration) is intensified; hence, methods and tools for vulnerability assessment and identification of adaptation measures are necessary. This paper proposes a comprehensive framework for the assessment of water systems’ vulnerability to adverse water related conditions and the identification of potential adaptation strategies. The proposed methodology is applied in the four study site areas of the FP7 COROADO project (selected river basins in Argentina, Brazil, Chile, and Mexico), and an indicator-based framework is adopted, expressing natural, physical, socio-economic, and institutional attributes of the examined areas. The vulnerability assessment was conducted following a disaggregated analysis (use of proxy indicators). The vulnerability profiles of the four study sites were formulated, describing the factors shaping vulnerability and the aspects that need improvement. Additionally, the anticipated contribution of alternative strategies to vulnerability mitigation was assessed. The systems’ response to alternative strategies (what-if scenarios) was analyzed following an aggregated analysis (estimation of an overall vulnerability index).