DSpace Colección :

Caracterización de las interfaces mecánicas en la Formación Agrio inferior y evaluación de su impacto en su desarrollo como reservorio no convencional.

Mon, 19 May 2025 00:00:00 GMT

Título: Caracterización de las interfaces mecánicas en la Formación Agrio inferior y evaluación de su impacto en su desarrollo como reservorio no convencional. Autor(es): Zalazar, Manuela Abstract: In recent decades, unconventional reservoirs have received special attention due to their high potential to meet energy supply demands. The production of these low-permeability reservoirs requires specialized techniques such as hydraulic fracturing. This process enhances reservoir conductivity and maximizes hydrocarbon production. In the Neuquén Basin, the Vaca Muerta Formation is considered the primary source rock of the basin and the most significant shale unconventional reservoir in South America. However, in recent years, the Agrio Formation (Late Valanginian–Late Hauterivian) has emerged as an unconventional play due to the potential of the organic-rich intervals of the lower Pilmatué Member. Despite extensive geochemical and sedimentological knowledge of this unit, its geomechanical aspects remain poorly understood, particularly regarding mechanical properties, rock heterogeneity,anisotropy, and local stress conditions. The successful development of this unconventional reservoir requires a detailed understanding of rock mechanical properties and stress states to optimize hydraulic fracture design. However, characterizing the reservoir, understanding its heterogeneity, and assessing its impact on productivity pose significant challenges, as they require integrated multi-scale studies, both in the field and laboratory. This study provides a comprehensive analysis of the vertical and lateral variability of the Pilmatué Member, offering an in-depth evaluation of discontinuities and lithologies across three locations in the Neuquén Basin. A multiproxy approach was applied to analyze rock heterogeneity, focusing on mineralogical, textural, and mechanical properties such as strength and hardness. Additionally, field observations were integrated with microscopic and mechanical assessments to identify weak and strong interfaces, their distribution within the unit, and to characterize the organic-rich intervals (OL1, OL2, OL3, and OL4) of current interest. The findings of this research establish a close relationship between lithological discontinuities, mechanical properties, and facies variations. Quantitative and qualitative descriptions of discontinuities reveal lateral variability between the southernmost sector, Pichaihue, and the northern sectors, El Portón and Arroyo Cieneguita. The Pichaihue sector, characterized by a more siliciclastic composition, exhibits lower rhythmicity, more abrupt contacts, and higher roughness indices. Northward, the sequences become more carbonate-rich, with more transitional contacts and smoother roughness in net contacts. Vertical variability was found to be similar in mixed carbonate-dominated environments, with the middle interval of the surveyed sections exhibiting the highest rhythmicity, as well as the greatest lithological and geomechanical heterogeneity. Mechanical property contrasts were attributed to textural and compositional changes detected from macroscopic to microscopic scales. Moreover, the evidence from this study suggests that the organic-rich intervals meet optimal conditions to be considered as future targets based on their geomechanical properties. They exhibit thicknesses greater than 20 m, low clay content, and are predominantly composed of non-expandable minerals such as illite. The presence of quartz and carbonates makes these rocks strong and hard, which is advantageous in terms of brittleness. The organic-rich intervals OL2 and OL3, located in the middle/upper interval, exhibited a higher number of discontinuities and weak interfaces compared to OL1 in the lower interval and OL4 in the upper interval. The rhythmic limestone-mudstone cycles, along with the presence of calcareous concretions, thin tuffaceous levels, and sandy layers, increase the complexity of OL2 and OL3 intervals, imparting significant vertical variability and heterogeneity to the Pilmatué Member that must be considered in the geological and geomechanical model. The results of this study are important as they can contribute to a more efficient exploitation of the Pilmatué Member. A thorough understanding of the vertical distribution of facies and microfacies will enable better estimations of rock mechanical properties and the selection of target levels for drilling navigation and hydraulic fracturing. Identifying rock fabric and mapping the distribution of interfaces and lithological boundaries is crucial, as they can significantly impact drilling and completion stages and affect the production potential of this reservoir unconventional reservoirs have received special attention due to their high potential to meet energy supply demands. The production of these low-permeability reservoirs requires specialized techniques such as hydraulic fracturing. This process enhances reservoir conductivity and maximizes hydrocarbon production. In the Neuquén Basin, the Vaca Muerta Formation is considered the main source rock of the basin and the most significant shale unconventional reservoir in South America. However, in recent years, the Agrio Formation (Late Valanginian–Late Hauterivian) has emerged as an unconventional play due to the potential of the organic-rich intervals within the lower Pilmatué Member. Despite the unit’s extensive geochemical and sedimentological knowledge, its geomechanical aspects are limited, particularly regarding the mechanical properties, rock heterogeneity, anisotropy, and local stress states. A successful development of this unconventional reservoir requires a detailed understanding of the mechanical properties of the rocks and stress conditions to optimize hydraulic fracture design. However, reservoir characterization, understanding its heterogeneity, and evaluating its impact on productivity pose significant challenges, as they require integrated studies at multiple scales, both in the field and in laboratory. This study provides a comprehensive analysis of the vertical and lateral variability of the Pilmatué Member, delivering an exhaustive assessment of the discontinuities and lithologies present at three locations within the Neuquén Basin. A multiproxy approach was applied for the heterogeneous rock analysis, focusing on mineralogical, textural, and mechanical properties, such as strength and hardness. Additionally, field visual observations were integrated with detailed microscopic and mechanical evaluations to identify weak and strong interfaces and their distribution within the unit. The findings of this research are significant as they can be utilized to develop the Pilmatué Member more efficiently. A thorough understanding of the vertical distribution of facies and microfacies will allow for better estimating the rock’s mechanical properties and selecting target intervals for landing and hydraulic fracturing. The identification of rock fabric and the mapping of interface and lithology boundary distribution are crucial, as they can significantly impact the drilling and completion stages and affect the production potential of this reservoir.

Caracterización geoquímica y mineralógica de la Formación Agrio y su potencial como roca generadora de hidrocarburos en el centro-oeste de la Cuenca Neuquina.

Tue, 13 May 2025 00:00:00 GMT

Título: Caracterización geoquímica y mineralógica de la Formación Agrio y su potencial como roca generadora de hidrocarburos en el centro-oeste de la Cuenca Neuquina. Autor(es): Omarini Fernández, Julieta Abstract: This doctoral thesis constitutes a multi-proxy study that includes sedimentological, stratigraphic, mineralogical, and geochemical information from the deposits of the Pilmatué and Agua de la Mula members of the Agrio Formation (late Valanginian to early Barremian) spanning from the Arroyo Cieneguitas (in the south of Mendoza province) to the Pichaihue locality (in the north of Neuquén province). Four localities and seven boreholes were selected along two correlation transects oriented NW-SW and NW-SE to carry out the research. These transects include distal (i.e, Arroyo Cieneguitas), intermediate (i.e., YPF.Nq.FM.x-40) and proximal sections (i.e. Pichaihue) of a low-gradient mixed siliciclastic-carbonate depositional system. Detailed sedimentological profiles were elaborated and systematic sampling was conducted for mineralogical, petrographic, and geochemical analyses in all sections. Based on the analysis of the sedimentary records of outcrop and subsurface, total of eleven lithofacies were defined and grouped into silicoclastic, mixed, carbonate and pyroclastic facies, which allowed determining nine facies associations that characterize four main depositional systems: deltaic systems, offshore systems, mixed (siliciclastic and carbonate) and carbonate-dominated basin systems. The compositional characterization required of energy dispersive X-Ray Fluorescence (EDXRF), X-Ray Diffraction (XRD) and petrographic studies. All the analyses revealed that the succession is characterized by fine-grained material and compositionally homogeneous with the same association of mineral phases, though in differents proportions depending on the studied. The most abundant components identified were detrital quartz and calcite with subordinately clays, feldspars, plagioclases, algal and terrigenous organic matter and bioclastic fragments. Overall, the succession is characterized by a vertical and lateral decrease in carbonate content and a vertical and lateral increase in terrigenous components. For the geochemical characterization, the results obtained from Rock Eval pyrolysis analysis, organic petrography and C isotope and the estimations made with the Passey’s method and Gamma-Ray measurements were integrated. Correlation panels were designed to establish internal variations where the fluctuations of the different geochemical parameters were identified. A statistical analysis was also conducted to estimate the average values of total organic carbon (COT) and pyrolysis per member, sedimentary facies, and organic levels in each section. Finally, the organic matter type and quality, the hydrocarbon generation potential and thermal maturity were defined using distribution of samples interpreted from geochemical diagrams (S2 versus COT, modified Van Krevelen, IH versus Tmax). Based on all the data it was established that, in general, the Pilmatué Member presents higher organic content compared to the Agua de la Mula Member, and that together they present a total of eight organic levels (NO1-NO8) that disappears towards the southern sector. This decrease in organic content was linked to higher dilution rates due to the input of detrital material and/or degradation of organic matter in an environment with higher energy and oxygenation in more proximal areas. The NO1-NO2 organic levels in the Pilmatué Member and NO5-NO6 in the Agua de la Mula Member exhibit the highest organic content and lateral continuity, with NO1 and NO5 being prevalent along the entire transect. Regarding the facies, all those with generating potential were analyzed regardless of their relative abundance in the diferents sedimentary profiles. This allowed the identification of laminated mudstone-wackestone facies as the most organic-rich, followed by laminated siliciclastic shales (Psl) and massive mudstone-wackestone facies. The geochemical diagrams evidenced a mixture of kerogens ranging from Type I to Type IV, with a predominance of Types II/II-III. Based on the organic petrography, macerals did not show significant changes in their composition, therefore the cyclic variations in pyrolysis data reflect variations in organic matter preservation and/or the effects of thermal maturity. The thermal maturity range for the Agrio Formation was established between 401°C and 532°C of Tmax (%Ro measured and equivalent: ≤0.6-1.84 %Ro). The Pilmatué Member ranged between early maturity and the peak of oil generation in the north and even overmature in the south, associated with greater burial in more internal positions of the basin. The Agua de la Mula Member generally reached the stage of early maturity. Finally, the hidrocarbon generating potential was classified as fair to very good and in specific areas even excellent, to continue generating mainly oil in the north and gas in the south. As for its reservoir potential, two new intervals were identified in the Pilmatué Member associated with the NO2 and NO3 organic levels and one in the Agua de la Mula Member linked to the NO5 organic level. These levels, particularly NO2, coincide with the most enriched deposits in carbonate facies (MWm) and present better quality organic matter (Type I/II-II/III), which makes it possible to define them as those with the best potential and possible targets in the evaluation as unconventional reservoirs.

Evaluación e interacción de las influencias naturales y antrópicas sobre la cuenca del río Negro, Argentina.

Tue, 04 Feb 2025 00:00:00 GMT

Título: Evaluación e interacción de las influencias naturales y antrópicas sobre la cuenca del río Negro, Argentina. Autor(es): Longo, Ana Clara Abstract: The Patagonian region is an area of great extension and importance for the population and economic development of the country, whose productivity is closely linked to the source of water resources. It has numerous river basins of snowy source in the Argentinean Andes, which provide ecosystem services to the region, making their conservation and good management necessary. One of these large basins is the Negro river, which has its headwaters at the junction of two other basins, the Limay and the Neuquén rivers, which together make up the Negro River Fluvial System (SFRN). Despite its importance, represented by a drainage area of more than 26,000 km2, very little is known about the morphometric and geochemical characteristics of the Negro river basin and the three segments into which the main collector is divided: Upper Valley, Middle Valley, and Lower Valley of the Negro river. The general hypothesis of the present thesis states that the evolution of the Negro river along the territory has been significantly influenced by anthropic factors referred to the construction of dams and the contribution of chemical elements due to urban development and different industries. Based on this, a spatio- temporal study of the morphometry and dynamics of the Negro River was carried out, analyzing both anthropic and natural processes occurring along the Negro River system. More specifically, the regimes of the most significant climatic and hydrological parameters on the Negro River were analyzed, together with the analysis of the relationship of the most significant climatic and hydrological parameters on the Negro river with the climatic forcing influencing the region. In addition, the Negro river was described from the morphometric point of view through the analysis of remote sensors to provide a basis for the interpretation of the natural dynamic processes. Finally, a physicochemical and elemental classification of the sediments is added for the observation of possible direct human influences on the river systems. The project started by studying data from twenty meteorological stations distributed along the Negro river basin. We sought to identify the relationship between the parameter’s precipitation and temperature with ENSO, and the values found were statistically analyzed. An analysis of the morphometric parameters that define the SFRN and the Negro river was carried out employing remote sensors and geographic information systems (SAGA GIS). A relationship of parameters, interdependence, and consequence was generated between the two. Parameters of shape, the hierarchy of the SFRN, and the Negro river were studied as part of it and as an isolated system as well. A hypsometric and relief analysis of the SFRN and the Negro river was obtained. External parameters or factors such as the topographic factor (LS) about the erosion of the system, topographic index of humidity, and exposure to prevailing winds were added. An analysis of elemental chemical structure, texture, and parameters such as pH and conductivity of the sediments was carried out. Statistically, annual accumulated rainfall data were obtained, and the statistical analysis of the climate database showed that the summer months are those with the highest proportion of rainfall in the Alto Valle. ENSO has a significant influence as a climatic force in Northern Patagonia. In the winter months, mostly June, the correlation between rainfall and ENSO is significantly positive, while there is a negative correlation for the spring months. There is a clear interdependence between the parameters of flow, runoff, and spill, which in turn show a large decrease in value after the dams were put in place in the 1970s onwards, with the dams and anthropogenic control proving to be the main source of the current flow of the Río Negro. This generates the effect of clear water, increased conveyance, and erosion of the Upper Valley. The SFRN and the Negro river were defined as "very large" basins of more than 5,000 km2, and lengths of 1,317 and 719 km, respectively. The Gravelius Compactness Index (Kc), Caquot Mean Elongation Index (Ca), Horton Shape Index (Kf), and Elongation Ratio (Re) define the catchments as elongated, low concentration with low risk of high-impact floods. As for the order of the Negro River, when isolated from the system of tributaries that give rise to it, it is defined as order 1 since, along its 719 km, from its source in Confluence to its outflow into the Atlantic Sea, it has no contributions; but when integrated into the SFRN it takes value of 5, and is defined as a transition from a system of high torrential flow to a plain, with a low drainage network. Using the hypsometric curve, the SFRN was defined as a mature basin, with a peniplanized relief, and a significant development of the ritral and potamal sections. The Hypsometric Integral (HI) shows an initial senile system, and the kurtosis and asymmetries show erosion in the headwaters and areas of steeper slopes on the channel bottom and slopes. Relief (R) showed for the SFRN predominance of maximum heights and reliefs, large runoff and high velocity flows. For the Negro river, R reaches values of 500 m at the confluence and decreases in value towards the estuary giving moderate to low flows, with the formation of meandering systems, higher infiltration, and lower runoff. All of this is then demonstrated by the Relief Ratio Index (Rr) and the Roughness Value (Rn). Through the Melton Roughness Number (MNR) a higher percentage of debris input in the SFRN is exposed over the percentage of debris input in the Negro river. Then with the Terrain Roughness Index (TRI), we highlight the great flatness that characterizes the Negro River, with level or almost level heights and the high correlation of this index with the slope. Turning to the aspect and slope analysis, it is shown that the plain represents 33% of the SFRN, and 25% is observed as moderate north- facing slopes and 39% as steep north-facing slopes. The physicochemical studies of the sediments of the Río Negro show the highest proportions or dominance of loamy textures, with conductivities ranging from mean values of 4,857 μS/cm to maximum values of 44,600 μS/cm in old, abandoned meanders without anthropic influence on the north coast of the Middle Valley to minimum values of 263 μS/cm in an old, abandoned meander, but with the presence of current anthropic activity on the north coast of the Middle Valley. In terms of pH values, mean values of 7.9 and maximum values of 10 are found in an abandoned meander on the south coast of the Middle Valley, and a minimum of 4.5 on the north coast of the estuary. The basic chemical elements of the sediments along the Río Negro show a main composition of elements such as C, O, and Si, together with minor percentages of Na, Mg, Cl, Fe, S, K, and Ca. Then, variations in low concentrations, but the presence of elements such as Ti, Ag, P, Mn, As, Ba, Mo, Ta, Ga, Zn, Cu, and Ge were detected in sediments from several points. Some of these elements are of natural origin, from sediments of formations or geological units. Others are from anthropogenic activity in the valleys, such as agronomy and mining and oil extraction operations. It is proposed to continue this analysis from the point of view of the point origin of the elements, due to their importance in understanding the origin, polluting characteristics, consequences of their availability in the valley, and their impact on the environment. The present thesis provides an approach that contributes both basic and applied knowledge for similar studies of sediment dynamics, which allows an integrated approach to fluvial management of rivers such as the Negro River as an independent river and as part of a river system. The aim was to generate a contribution that allows the use of the soil and water resources of the Negro River, for management, land use planning, and a knowledge base for risk studies and different disciplines

Estudio infrasónico de volcanes activos de los Andes del Sur aplicado al monitoreo remoto

Wed, 14 Feb 2024 00:00:00 GMT

Título: Estudio infrasónico de volcanes activos de los Andes del Sur aplicado al monitoreo remoto Autor(es): Hantusch, Marcia Micaela Abstract: Volcanic activity produces a wide variety of acoustic signals. Infrasound is sound below 20 Hz, capable of propagating hundreds of kilometers in the atmosphere while preserving information about the source. For this reason, recording these signals is a widely used monitoring tool of surface activity, both local (<20 km) and regional (>100 km). The path of propagation is controlled by the atmospheric structure, mainly by temperature gradients and the horizontal components of the wind. The circulation conditions that prevail over Patagonia enhance the propagation of infrasound of eruptive sources located in the volcanic arc towards the east. For this reason, in this Thesis we deployed two small-aperture infrasound arrays (<300 m) in the Andean region of Neuquén, to test their performance as a monitoring tool for volcanic processes. The first infrasound array installed in Argentina was deployed in Caviahue in 2014, 13 km from the Copahue volcano (CPH, aperture 280 m). Applying the multichannel semblance analysis algorithm, we detected strombolian eruptions of the Villarrica volcano 192 km away (2015 and 2016), the subplinian eruption of the Calbuco volcano 410 km away (2015), and signals associated with the sustained emission of ash in the Copahue volcano (2016). During the summer of 2017 – 2018, the second array (GND 120 m) was installed 3 km away from the Lanín volcano. Using the same algorithm, the continuous tremor emitted by the crateric lava lake of the Villarrica volcano 47 km from the array was detected on several occasions. In addition, we detected 88 events associated with surficial mass movements (∼1 event/day) that occurred on the slopes of the Lanín volcano and on the flanks of the hills that border the Malleo river. Eruptive source parameters were derived from the acoustic analysis of the infrasound signals. Therefore, it was necessary to quantify signal amplitude losses during propagation due to interaction with topography and absorption in the atmosphere. For local propagation, we estimated amplitude losses caused by diffraction around topographic barriers between Copahue and CPH. In the Calbuco – CPH regional case, we used the software InfraGa to model the ray tracing through an atmospheric structure reconstructed with numerical weather models (analysis and re–analysis) and empirical models with the software AVOG2S. From this modeling we could simulate the main waveguides at a regional level. The comparison with the infrasound data showed discrepancies that were interpreted as the result of processes not considered by the method used. These effects could be due to the interaction of the wave with the topography and with small-scale atmospheric structures. The activity of Copahue was characterized by the continuous emission of low – altitude plumes that dispersed large amounts of ash to the southeast, tens of kilometers away. The analysis of the acoustic data suggests a process of rigid fragmentation of low magma overpressure, which is almost completely dissipated during the passage of the eruptive mixture through the ash – filled crater, which would explain the low amplitude that characterizes these signals. The estimated material exit velocity (10 – 20 m/s) is consistent with the emission of low-altitude plumes. On the other hand, the subplinian eruption of the Calbuco volcano generated two plumes over 13 km high above the volcano, with ashes dispersed over northern Patagonia. The analysis of these eruptive tremors, allowed us to estimate the first infrasound derived source parameters, such as the height of the plume (18 – 25 km), the exit velocity of the material (35 – 150 m/s) and the radius of the conduit (25 – 35 m). The heights obtained and the temporal variations of the acoustic parameters are consistent with observations from other studies. This work proves that the application of infrasound arrays in the Andes of Neuquén is useful to monitor and investigate both regional and local volcanic processes, as well as surficial mass movements. The latter is of great relevance in a context of climate change that promotes the destabilization of slopes due to the alteration of the natural cycles of freezing – thawing and precipitations.

Estructuras sedimentarias inducidas por la actividad microbiana (ESIAM) en sistemas petroleros no convencionales (Los Molles-Lajas), cuenca Neuquina: implicancias para el análisis paleoambental.

Wed, 27 Sep 2023 00:00:00 GMT

Título: Estructuras sedimentarias inducidas por la actividad microbiana (ESIAM) en sistemas petroleros no convencionales (Los Molles-Lajas), cuenca Neuquina: implicancias para el análisis paleoambental. Autor(es): Rodriguez, Maximiliano Nicolás Abstract: This doctoral thesis was carried out in deposits of the Los Molles Formation (Toarcian - Lower Callovian) located in the Chacay Melehue, Arroyo Lapa and Picún Leufú Anticline localities within the Neuquén Basin. The Los Molles Formation is one of the oldest source rocks in the Neuquén Basin and constitutes an unconventional shale gas reservoir of great economic importance. In recent years, the presence of levels with microbial mats has been recognized in this unit, although their characteristics and implications have not yet been evaluated. For this reason, the main objective of this study was to analyze, characterize and document the presence of microbial mats in the Los Molles Formation, as well as to discuss their sedimentological and ichnological implications. Finally, the initial results obtained from the comparison between the microbial levels of the Los Molles Formation and those recognized in the Vaca Muerta Formation, are presented. Field work consisted of detailed sedimentary sections and lithological profiling at the three localities, as well as level sampling with MISS. In the laboratory, the samples were analyzed by stereo microscope, petrographic microscope and scanning electron microscope. Five facies associations were recognized and described for the Los Molles Formation: offshore, platform, deltaic front, prodelta, turbidite. Most of the levels assigned to microbial mats were found on deposits belonging to the offshore and platform facies associations and, to a lesser extent, on the turbidite facies associations. The microbially induced sedimentary structures found in the Los Molles Formation comprised Kinneyia-type wrinkle structures, biolaminations, micro mat fabrics, possible dome constructions, reticulate patterns, small pinnacles and elephant skin. In the thin sections, textures and structures characteristics of microbial mats were recognized, such as anastomosing laminations, oriented grains, filaments and heavy minerals bound to the mat layers. Kinneyia-like wrinkled structures, biolaminations, mat microfabrics and pinnacles were also petrographically characterized. Scanning electron microscope images revealed the presence of structures resembling filaments and filament sheaths, spheroidal structures similar to coccoids, extracellular polymeric substances (EPS) and framboidal pyrite in isolation, in addition to EPS linked to filament-like structures and pyrite. Trace fossils assigned to Trichichnus isp., Chondrites intricatus, Chondrites patulus, and Phycosiphon incertum were recognized at the Chacay Melehue and Arroyo Lapa localities. These results reveal that the levels found and analyzed in the Los Molles Formation may have had a biological origin. The structures and textures identified may have originated from microbial mats located on the seafloor of the Neuquén Basin during the Toarcian – Lower Callovian. These communities were established in offshore and platform environments at depths between 200 and 400 m, in paleoecological and paleoenvironmental conditions that allowed their development, such as low oxygenation, low sedimentation rate, and low light. From the integration of ichnological and geobiological analyses, it was inferred that both Trichichnus isp. and the microbial mats could have a common origin from the biological activity of some genera of the Beggiaotoaceaea family. On the other hand, the microbial mats could have been a food source for benthic organisms, which would be reflected in trace fossils of undermat miners found in the organic levels. Comparison with microbial mats from the Vaca Muerta Formation indicates that the similarities in the thin section and the scanning electron microscope are unquestionable despite having formed in different environments. A very interesting aspect, which will be evaluated in the future, is to analyze the possibility that the biolaminated levels have been an important source of organic matter to the system, and thus may have contributed to the generation of hydrocarbons.

Evidencia y análisis de cambios temporales en la zona del cerro Domuyo. Caracterización geofísica de su campo geotermal, y su microsismicidad asociada.

Wed, 17 May 2023 00:00:00 GMT

Título: Evidencia y análisis de cambios temporales en la zona del cerro Domuyo. Caracterización geofísica de su campo geotermal, y su microsismicidad asociada. Autor(es): Godoy, Laura Beatriz Abstract: No posee.

Análisis estructural y litológico del distrito la paloma. Metalogénesis de la veta sulfuro, macizo del deseado, Patagonia

Wed, 17 May 2023 00:00:00 GMT

Título: Análisis estructural y litológico del distrito la paloma. Metalogénesis de la veta sulfuro, macizo del deseado, Patagonia Autor(es): Fernández, María Lis Abstract: La Paloma, a vein-hosted Au-Ag and base metal epithermal district of the Don Nicolás Mine, is located in the northeast of the Deseado Massif, Patagonia, Argentina. The mineralization is hosted in the Middle Jurassic volcanic rocks of the Bajo Pobre Formation which comprises three main lithological groups: (1) lavas and intrusive rocks, (2) pyroclastic rocks, and (3) reworked volcaniclastic rocks. The first group, composed of andesite to basaltic-andesite coherent and autobrecciated flows as well as shallow subvolcanic (stocks and lacoliths) intrusions, is the most representative in the district. The second group, either intercalated between andesitic lava flows or intruded by basaltic-andesite stocks and lacoliths, is represented by pyroclastic surge, fall and flow deposits. Reworked volcaniclastic sequences comprise debris and hyperconcentrated flow deposits and reworked pyroclastic deposits scarcely preserved and restricted to topographic highs that overlie primary volcanic units or are intercalate between them. The La Paloma district displays a complex vein network dominated by NNW to NW (with local N-S and NNE deflections) striking major veins (Sulfuro, Esperanza, Rocio, Princesa, Reyna and Verde), ENE to E-W (Duquesa) and NE (Arco Iris) striking structures. The NE-SW striking El Molino fault separates the Sulfuro Vein System (Sulfuro, Esperanza and Rocío veins) from the remaining veins located towards the north-northwest of the district. The normal to oblique- to strike-slip reactivation of pre-existing joints led to the hybrid extension-shear fractures hosting the mineralization of economic interest. Paleostress analysis unravels how all the resulting four sets of hybrid extension-shear fractures form two groups of structures that are kinematically compatible with a sub-vertical σ1 and either NNW (Group A) or ENE (Group B) trending σ3, within the framework of an extensional stress field characterized by multiple permutations between the σ3 and the σ2 axes. Such permutations are interpreted to have resulted from the reactivation of some of the NNW striking joints as normal faults in response to regional ENE stretching, and by orthogonal (i.e. NNW) extension in the hanging wall of such laterally-terminating normal faults associated with along-strike stretching produced by the differential downthrow of the hanging-wall block. Within this framework, further (i.e. NE and NW striking) joint sets were variably reactivated as oblique-slip dilational faults. The NNW trending hybrid extension-shear fractures (i.e. Sulfuro Vein System, Princesa–Reyna and Verde; Group B) were the most effective for hydrothermal fluid circulation and are characterized by the development of multi–episodic veins with exceptional width, strike continuity and ore grades whereas ENE to E-W striking structures (i.e. Duquesa; Group A) exhibit minor opening and filling events mainly represented by late stages. NE and NW striking oblique-slip dilational faults (i.e. Arco Iris Vein and El Molino fault; Group A and B, respectively) record no major vein opening history, and characterized by brecciated vein textures with minor silica cement and/or vein clasts within a fault gouge matrix. Later fault reactivation appears to be associated with far a field propagation of Andean stresses, probably related with the late Early Cretaceous shortening event known to have affected the studied sector of the Deseado Massif. This event is marked by superposed strike-slip and reverse fault slip components recording roughly E-W subhorizontal compression (σ1). The subsequent tectonic evolution of the study area, recorded by apatite fission track cooling ages, was characterized by steady-state exhumation at a rate of c. 1 °C/Ma during the last 90 Ma. The Au-Ag (Zn, Pb, Mo and Cu) Sulfuro Vein, the main ore body in the district (174.251 Oz of gold and 525.985 Oz of silver and an average grade of 6.6 g/t Au and 20 g/t Ag), exhibits a sub-horizontal ore-shoot geometry, as are the areas of greater vein thickness, consistent with dominant extensional faulting during mineralization except in the northern sector where Au, Ag and Cu shoots and the thickest areas reflect a larger strike-slip component of motion and depletion of the fluid in these metals. This strikeslip component seems not to have exerted an important control in the distribution of Zn and Pb in this sector, where these metals continued to precipitate at lower temperatures favoured by the permeability of the volcaniclastic units. The highest values of Au, Ag, Cu, Mo, Pb, Zn and Sb are concentrated at depths between 50 and 100 m a.s.l. High Mo values occur also at greater depths in the southern sector of the vein and its distribution in shallower sectors is controlled by remobilization processes. The geochemical distribution of metals shows a slight vertical zonation and a distinct lateral zonation, which suggests upward hydrothermal fluid flow from deep zones in the southern termination of the vein where ore shoots exhibit steeper plunges, to the north through the NNW-NW striking fractures. Three mineralizing stages contributed to the final metal endowment of the Sulfuro Vein. The first, which corresponds to stage 3, introduced Mo ± Au (Ag) ± Cu (molybdenite ± Au (electrum) ± chalcopyrite ± tennantite-tetraedrite) as millimetric dark sulfide-rich band at the beginning of the vein infill during the episode E1. The second and the third mineralizing stages, which correspond to stages 7 and 8, respectively, introduced Fe ± Au (Ag) and Fe ± Au (Ag) ± Cu ± Zn ± Pb ± As ± Sb, respectively, during the episode E2 and generated limited brecciation in the vein sealed by minerals of the E1 episode. Pyrite ± chalcopyrite ± tennantite-tetrahedrite ± sphalerite ± galena containing Au and/or electrum micro-inclusions, formed during this episode (E2) as breccia cement and filling veinlets. Based on the metal content and accompanying minerals, the Sulfuro Vein can be classified as a Au-Ag low sulfidation epithermal deposit enriched in Zn + Pb and unusually rich in Mo (up to 1.5 %). Quartz textures (colloform-crustriform banded, cockade, mosaic and brecciated) suggest several opening and subsequent vein filling events and the deposition of a silica gel from a boiling hydrothermal fluid which must have been responsible for the metal deposition. Chlorite ± albite ± epidote formed distal (>20 - 30 m) to the Sulfuro Vein could represent a regional propylitic alteration related to the magmatic heat source in the district prior to the onset of the Sulfuro Vein hydrothermal system. Host-rock interaction with boiling, neutral to slightly alkaline fluids formed chlorite ± albite ± adularia ± carbonates (dolomite, siderite and calcite) ± pyrite during the vein-related pre-ore stage. Syn-ore stage potassic dioctahedral phyllosilicates ± quartz ± pyrite overprint early formed minerals. Different grain size of dioctahedral potassic phyllosilicates were identified: – coarse-grained dioctahedral potassic phyllosilicates (>2 μm) or mica-like and – fine grained (<2 μm) potassic dioctahedral phyllosilicates represented by illite (or illite-richillite-smectite mixed layers) and by subordinated mixed-layers with variable amounts of illite. The composition and distribution of phyllosilicates near the vein (≤5 m) reflect paleotemperature gradients of the fluid with time, from >220°C (mica-like and illite-richillite-smectite mixed-layer) to <220°- 150° C (mixed-layer illite-smectite superimposed). In the post-ore stage, Al-bearing silicates were partially dissolved and replaced by widespread kaolinite. At shallow depths, above the central upflow zone, kaolinite ± aluminum phosphate-sulfate ± dickite dominate and represent an advanced argillic environment caused by steam-heated acid-sulfate waters. Smectite was the last mineral to form during the collapse of the hydrothermal activity. The chemical compositions of some hydrothermal minerals are potential indicators of paleo depths and proximity to the vein: - dolomite (Mg) was identified only at depth, while calcite (Ca) and siderite (Fe) formed at intermediate and shallow zones, respectively; - chlorites in the lower andesite shows more Fe than Mg near the vein and at greater depths; - secondary feldspars are scarce and relictic proximal to the vein compared to potassic dioctahedral phyllosilicates but are prominent alteration minerals with increasing distance from the vein. Relict adularia dominates in strongly altered rocks proximal to the vein whereas albite dominates in distal moderate to weakly altered rocks; and - the abundance and pervasiveness of potassic dioctahedral phyllosilicates + quartz + pyrite near the vein (≤5 m) constitute an excellent indicator of the mineralized structure as well as coarse-grained potassic dioctahedral phyllosilicate (>2 μm) confined to the contact with the vein and in deeper zones. The isotopic composition of fluids in equilibrium with quartz (δ18Ofluid –5.8 to –1.5‰) and phyllosilicates (δ18Ofluid 0.1 to -2.4‰; δ2Hfluid –48 to –69.5) deposited in the vein during episodes E1 and E2, and fluids in equilibrium with phyllosilicates (δ18Ofluid –1‰; –2.3‰; δ2Hfluid –62 to –65) in the host rock, suggest their formation by mixture of meteoric Jurassic water with magmatic water and/or meteoric water that have isotopically exchanged with basement rocks. The carbon isotopic signatures (δ13C in solution as H2CO3: –7.5 and –7.1‰) and the sulfur isotopic composition of sulfides (δ34S ‰ –0.1 to 3.3‰) indicate a magmatic source. Cooling and the increase in the fO2 of the hydrothermal fluid through mixing with meteoric water in the northern sector and in shallow parts of the central sector, could have resulted in lower δ34S values of sphalerite, galena and chalcopyrite (δ34S ‰ –3.1, –5.3 and –11.1‰). The Pb isotopic compositions of the galenas: 206Pb/204Pb (18.37 and 18.39), 207Pb/204Pb (15.61 and 15.62), 208Pb/204Pb (38.32 and 38.39) are similar to the isotopic composition of the volcanic rocks of the Bajo Pobre Formation and suggest a mixed sources of Pb, with contributions from the mantle and crust. Ar–Ar ages (168.48 ± 1.21 Ma) obtained for illite-rich illite-smectite mixed layer and Re–Os molybdenite age (169.7 ± 0.9 Ma), indicate that the formation of the potassic dioctahedral phyllosilicates in the alteration halos of the Sulfuro Vein was coeval with Au-Mo mineralization in the vein. These radiometric ages are among the oldest ages known for Middle-Upper Jurassic epithermal deposits of the Deseado Massif.

Evolución tectono-estratigráfica durante el triásico superior de la región de Los Menucos, macizo norpatagónico nor-occidental, provincia de Río Negro

Thu, 25 Aug 2022 00:00:00 GMT

Título: Evolución tectono-estratigráfica durante el triásico superior de la región de Los Menucos, macizo norpatagónico nor-occidental, provincia de Río Negro Autor(es): Vera, Dario Ruben Abstract: Two sets of volcano-sedimentary rocks of different ages, one of the Permian-Early Triassic age corresponding to the Los Menucos Complex and another of probable Late Triassic age, were identified in the Los Menucos region, in the northern sector of the North Patagonian Massif. The lithological, stratigraphical and sedimentological characteristics of the provisionally assigned to the Upper Triassic rocks that crop out in the vicinity of Llancaqueo farm, 6 km towards the NE of Los Menucos, will be first presented. There is a volcanic and volcaniclastic succession with at least 368 m thick, which overlies an angular and erosive unconformity developed on the Los Menucos Complex. The lower section of the succession is characterized by deposits corresponding to alluvial fan systems, high-energy braided rivers and sinuous rivers with floodplains, while the upper section is represented by a syn-sedimentary magmatism composed of mesosilicic to basic lava flows associated with subvolcanic bodies, and riodacitic ignimbrites. The informal denomination of sucesión volcanosedimentaria Llancaqueo was proposed to separate the volcano-sedimentary sequence of the Llancaqueo-type area from the rocks belonging to the Los Menucos Complex. In a regional context, the possible Upper Triassic age and the lithological characteristics of the sucesión volcano-sedimentaria Llancaqueo, suggest the search for correlations with the pyroclastic, volcanic and epiclastic sequences belonging to the Precuyano Cycle, or lateral equivalent within the Neuquén Basin. Second, the main structures that affect the Llancaqueo volcano-sedimentary succession in the area surrounding the Llancaqueo farm and in the areas of La Laja and La Mina hills, in the vicinity of Los Menucos, were characterized. Three first and second-order fault domains were recognized, with strikes: 1) E-W with WNW-ESE and ENE-WSW variations, sub-vertical and mostly dextral or, to a lesser extent, leftlateral kinematics; 2) NE-SW to N-S and dextral or dextral-normal or occasionally sinestral kinematics and 3) NW-SE to WNW-ESE, high angle and sinestral or sinestral-normal kinematics, or low angle and reverse motion. In addition, meso and megascopic folds trending NW-SE to WNW-ESE and NE-SW are developed both in the rocks of the Los Menucos Complex and in the Llancaqueo volcano-sedimentary succession. The integration of the geometry of the faults and folds at their different scales and the kinematic analysis of the major faults from the study of minor faults, allowed establishing two successive deformation phases (D1 and D2). D1, of late triassic - early jurassic age, would be linked to a transtensive regime with NNE-SSO to NE-SW extension directions and WNW-ESE to NW-SE shortening. Within the framework of this phase and actively controlled by the structure, the basin containing the Llancaqueo deposits would have been developed. On the other hand, D2, of possible Late Jurassic - Early Cretaceous age, would have a transpressive character related to a general NE-SW shortening and would have generated reactivations of the previously generated faults. In the regional context, the stratigraphic and structural characteristics of the study area and the northwestern sector of the Northpatagonian Massif, in general, are very similar to the tectonics described in the Neuquén basin for Triassic-Cretaceous times. In this sense, both in the Neuquén basin and in the area of the north-western Northpatagonian Massif, a generalized crustal extension regime in a NE-SW direction would have dominated, in the first instance, during the Late Triassic – Early Jurassic, equivalent to what is shown here is proposed as deformation phase D1. Then, during the Upper Jurassic – Lower Cretaceous, a transpressive deformation event would have occurred, comparable to the D2 deformation phase (proposed in this thesis) that generated the reactivation of the previously formed structures.

Tafonomía de los depósitos con vertebrados y leños fósiles en los niveles continentales de la Formación Mulichinco (Valanginiano) Cuenca Neuquina, Argentina

Mon, 29 Aug 2022 00:00:00 GMT

Título: Tafonomía de los depósitos con vertebrados y leños fósiles en los niveles continentales de la Formación Mulichinco (Valanginiano) Cuenca Neuquina, Argentina Autor(es): Pino, Diego Alejandro Abstract: no posee

SEDIMENTOLOGÍA E ICNOLOGÍA DE LA FORMACIÓN LOS MOLLES EN LAS LOCALIDADES DE PICÚN LEUFÚ, SIERRA DE CHACAICÓ Y CORDILLERA DEL VIENTO, CUENCA NEUQUINA, ARGENTINA

Fri, 29 Jul 2022 00:00:00 GMT

Título: SEDIMENTOLOGÍA E ICNOLOGÍA DE LA FORMACIÓN LOS MOLLES EN LAS LOCALIDADES DE PICÚN LEUFÚ, SIERRA DE CHACAICÓ Y CORDILLERA DEL VIENTO, CUENCA NEUQUINA, ARGENTINA Autor(es): Campetella, Débora Mical Abstract: Sedimentological and ichnological studies in the Los Molles Formation (Toarcian- Aalenian), in Picún Leufú, Sierra de Chacaicó and Cordillera del Viento localities allowed to recognize six facies associations and six ichnoassemblages. These facies associations comprise shoreface, offshore, shelf, prodelta and delta front affected by turbidites and storms deposits. The six ichnoassemblages are characterized, in general, by low ichnodiversity and abundance. The most common ichnoassemblage is the one recognized in offshore-shelf environments, consisting of Chondrites intricatus, Trichichichnus appendicus, Trichichnus isp., Phycosiphon incertum. Subordinately, Phymatoderma isp, Cylindrichnus concentricus, Teichichnus rectus and Thalassinoides isp. also occur The ichnoassemblage developed in levee deposits of turbidite systems consist of Chondrites intricatus, Phycosiphon incertum, Trichichichnus isp, Chondrites patulus, and Nereites missouriensis, whereas the ichnoassemblage recognized in storm dominated – shelf deposits includes specimens of Chondrites intricatus, Phycosiphon incertum, Nereites isp., Skolithos linearis, Planolites isp., Arenicolites isp., Ophiomorpha isp., and Gyrochorte comosa. The shoreface, delta front and prodelta deposits were only recognized at Picún Leufú locality, where the transition between Los Molles and Lajas formations is well exposed. In this context, the ichnoassemblage recognized in the distal shoreface deposits consist of Skolithos linearis, Ophiomorpha isp. and Arenicolites isp., the ichnoassemblage developed in the prodelta deposits is composed of specimens assigned to Chondrites intricatus, Phycosiphon incertum and Planolites isp, while the ichnoassemblage recognized in the delta front deposits is characterized by the presence of Chondrites intricatus, Phycosiphon incertum, Nereites isp., Skolithos linearis and Ophiomorpha isp. Integration of the sedimentological and ichnological data, indicates that variations in salinity, turbidity and sedimentation rate were limiting factors that affected the development of benthic communities. However, oxygenation would have been the most important parameter controlling not only the diversity but also the abundance of biogenic structures in these substrates. Moreover, in this analysis it is important to take into account the regional context, since during most of the Jurassic and Cretaceous, the Neuquén basin behaved as a back-arc basin associated with a magmatic arc, which was connected to the proto-Pacific Ocean through narrow passages between the volcanic island chain. This palaeogeographic situation produced an important regulation on the internal circulation of the basin, affecting the stratification of the water column, and its physical-chemical properties, and thus significantly affecting the development and establishment of benthic communities.

Los Alvarezsauridae (Dinosauria, Theropoda, Coelurosauria) de América del Sur: anatomía y relaciones filogenética.

Thu, 07 Jul 2022 00:00:00 GMT

Título: Los Alvarezsauridae (Dinosauria, Theropoda, Coelurosauria) de América del Sur: anatomía y relaciones filogenética. Autor(es): Meso, Jorge Gustavo Abstract: This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects. Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype. The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level. The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae. The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.

El registro fósil de equinodermos en el Eoceno-Mioceno de Patagonia Argentina y Antártida

Wed, 15 Jun 2022 00:00:00 GMT

Título: El registro fósil de equinodermos en el Eoceno-Mioceno de Patagonia Argentina y Antártida Autor(es): Palópolo, Evangelina Elizabeth Abstract: This thesis includes a review and a compendium of the record of the phylum Echinodermata in Argentina, including Antarctica and the South Atlantic Islands, from Eocene to late Miocene. Echinoderms are bilaterial organisms, with secondary radial symmetry, mutable connective tissue, aquiferous vascular system and multielemental calcareous endoskeleton, composed by calcite with high magnesium content. They constitute an important part of the benthic marine ecosystems, as part of the trophic chain. They have low tolerance to changes in water temperature and salinity, and to the sediment and organic matter input, being good environmental indicators. The environmental conditions that improve the echinoderm preservation are: little to null transport, rapid burial or in life entombment, absence of subsequent reworking, anoxia or dysoxia, and deposit of fine to very fine sediments. The first studies on echinoderms in Latin America date back to the 19th century and laid the foundations for the rest of the studies on the subject. In Argentina, rocks from the Eocene-Miocene interval yielding echinoderm remains are assigned to the Man Aike (Middle-Late Eocene), San Julián (Late Oligocene), El Chacay (Early Miocene), Río Foyel (Early Miocene), Monte León (Early Miocene), Estancia 25 de Mayo (early Miocene), Chenque (early Miocene), Gran Bajo del Gualicho (early-middle Miocene) and Puerto Madryn (late Miocene) formations. These formations represent several transgressive-regressive pulses within the Patagonian territory in the Golfo San Jorge, Peninsula Valdés and Austral-Magallanes basins. In the Antarctic Peninsula, the echinoderm records come from the La Meseta (Middle Eocene), Submeseta (Late Eocene-Early Oligocene), Polonez Cove (Middle-Late Oligocene) and Cape Melville (Early Miocene) formations. Using high resolution imaging (SEM and microtomography), the species Zoroaster marambioensis was described from La Meseta Formation. Its preservation allowed identifying death and burial positions, inferring their possible life habits. It was interpreted that starfishes colonized the distal part of an estuary during a period when salinity was normal, died from a freshwater discharge through a hyperpychnic flow, and were immediately buried in fine sand, without further rework. In the La Meseta and Submeseta formations (Seymour Island, Antarctica), the genera Abatus, Schizaster and Stigmatopygus were identified, using high contrast images and digital diagrams. These genera were previously recorded in Antarctica (Seymour and King George islands) and Patagonia (Santa Cruz and Chubut provinces, Argentina). These findings enabled making inferences about ancient marine connections between New Zealand, Australia, Antarctica, and Patagonia. In the Monte León Formation, a layer yelding spatangoid echinoids of the genus Brisaster preserved in situ, associated with their own traces and other ichnofossils that suggest a shallow marine environment. The depositional framework was interpreted as subtidal, affected by migration of large-scale bedforms, with important pyroclastic participation. The compendium of the Eocene-Miocene record of echinoderms from Patagonia Argentina and Antarctica gathered more than 1,200 specimens, housed in 26 institutions, 9 of them located in Argentina. It includes 37 genera grouped into 13 orders, from all current classes, except the Class Holothuroidea. The Class Echinoidea is the best represented, with 19 genera (9 of them endemic from Patagonia). Irregular echinoids are recorded in the Eocene of Antarctica, the Oligocene of southern Santa Cruz, the early Miocene of northern Santa Cruz and southern Chubut, and the middle and late Miocene of northern Chubut, Río Negro, and Entre Ríos. A possible distribution pattern was proposed, running from south to north over time. The Cenozoic echinoderm global diversity is marked by a peak in the Eocene and another in the Miocene. In Antarctica, generic greatest diversity occurs in the middle Eocene, in La Meseta Formation, with 17 genera (5 of crinoids, 6 of asteroids, 5 of echinoids and 1 of ophiuroids). The observed communities are similar to those of the Mesozoic, indicating a shallower and warmer environment than the current one in Antarctica, with a scarcity of durophagous predators and abundant organic matter content. In Patagonia, the echinoderm diversity peak was documented during the early Miocene as in the rest of the world, in coincidence with the maximum flood of the second cycle from the Patagonian transgression (~ 20 Ma). Descripción: Artículos publicados en el marco de esta tesis: Palópolo, E.E., Brezina, S., Casadío, S., y Santillana, S. (2017). A little window to Eocene: exceptional preservaition of sea stars from La Meseta Fromation, Seymour Island, Antarctic Penninsula. In Guaiquil, I., Leppe, M., Rojas, P., y Canales, R., (eds.). Visiones de Ciencia Antártica, Libro de Resúmenes, IX Congreso Latinoamericano de Ciencias Antártica, Punta Arenas-Chile, 654- 657. Publicación del Instituo Antártico Chileno. Palópolo, E.E., Brezina, S., Casadío, S., Santillana, S. y Griffin, M. (2018). A Thousand ways to die: exceptional preservation of sea stars on a paleosurface from La MEseta Formation (Eocene, Antarctic Peninsula). In Libro de resúmenes de la Reunión de comunicaciones de la Asociación Paleontológica Argentina (RCAPA 2018). Publicación Electrónica de la Asociación Paleontológica Argentina, 19:R21. Palópolo, E.E., Casadío, S, Kroh, A., Harzhauser, M, y Griffin, M. (2019). Life and death in a submarine volcanic ash dune: the case of a group of patagonian miocene echinoids. In Libro de resúmenes de la Reunión de comunicaciones de la Asociación Paleontológica Argentina (RCAPA 2019): 137. Palópolo, E.E., Kroh, A., Harzhauser, M., Griffin, M., Casadío, S., y Carmona, N. (2021a). An early Miocene spatangoid assemblage on a submarine volcanic ash dune from Patagonia (Argentina). Journal of South American Earth Sciences, 103214. Palópolo, E.E., Brezina, S.S., Casadío, S., Griffin, M., y Santillana, S. (2021b). A new zoroasterid asteroid from the Eocene of Seymour Island, Antarctica. Acta Palaeontologica Polonica 66. https://doi.org/10.4202/app.00714.2019