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In central-western Argentina, an Early Paleozoic belt including mafic-ultramafic bodies and marine metasedimentary rocks occurs along the western margin of the Precordillera and in the eastern Frontal Cordillera. In this paper, we present the analysis of aeromagnetic data and its processing focused on mapping geological limits, structures and the relation at depth of the southern Precordillera. With this main objective were applied filtering algorithms, reduction to the pole, tilt derivative, analytic signal, and particularly, the use of Improved Logistic Function (IL) as a new method of edge detection, in combination with the inversion map obtained from the Magnetization Vector Inversion (MVI) method. The results allow us to describe at depth the main trend of the Southern Precordillera Mafic Ultramafic Belt as two separated bocks, one in Peñasco and another in Cerro (Co.) Cortaderas, passing through Cerro (Co.) Pozos with a possible NNE-SSW direction. The combination of this techniques also can be used as prospecting guide to Pb–Zn–Ag vein deposits and High sulfidation Au-Epitermal deposits. • Determination of the Precordillera Mafic-Ultramafic Belt. • Linkage of maximum susceptibility, IL filter, outcrops of Mafic Ultramafic rocks and structural lineaments. • Magnetic Susceptibility 3D Model. [ABSTRACT FROM AUTHOR]

The Magallanes-Austral Foreland Basin preserves an important record of orogenesis and landscape evolution in the Patagonian Andes of Chile and Argentina. This paper evaluates the comparison between the thick Paleogene sequences in the Chilean Peninsula Brunswick (Chorrillo Chico and Agua Fresca formations) and the reduced Paleogene sequence (La Barca Formation) in the Punta Ainol locality, Argentina, by taking account of palynological and geochemical analyses. Warm and humid subtropical conditions (Subtropical Gondwanic Paleoflora) are inferred for the late Paleocene-Eocene interval studied. A new record of Lactoridaceae in the La Barca Formation expanded the known fossil range of this family in Patagonia. During the late Paleocene the Chorrillo Chico and La Barca formations would have been deposited mainly from hyperpycnal flows and this accumulation process continued until the Lutenian in the La Barca Formation. A relative rise in the sea level in the early Eocene would be recognized in both sections. In the middle Eocene a relative fall in the sea level would have occurred with increased terrigenous influx. The rate of sedimentation was similar in both sections during the Thanetian and Ypresian intervals according to the ages assigned by biostratigraphy, suggesting that the sedimentation rate would have been controlled mainly by relative changes in sea level during the Paleocene-Eocene transition. Paleoenvironmental changes during the Paleocene-Eocene transition were characterized at the La Barca Formation of the Punta Ainol section, considering the new geochemical and palynological data provided in this contribution. • A new register of early Paleogene flora of Patagonia. • Paleogeographic changes based on palynological and geochemical data. • New geochemical inferences of the Paleocene-Eocene transition in South America. • A new Paleocene-Eocene record from Southern Hemisphere. [ABSTRACT FROM AUTHOR]

The Pehuen Co Paleoichnological site (Buenos Aires Province, Argentina) contains one of the more diverse and well-preserved mammal and bird fossil footprint assemblages from the Late Pleistocene. The purposes of this paper were a detailed paleoenvironmental assessment of the footprint-bearing unit (middle member of the Agua Blanca Sequence) and to date key stratigraphic surfaces to constraint the temporal development of the site. A total of twenty-two detailed sedimentological sections were measured and correlated and five sediment and fossil remain samples were dated by the Optically Stimulated Luminescence (OSL) and Electron Spin Resonance (ESR) methods, respectively. The lower part of the local sequence represents dense to dilute alluvial deposits that were pedogenized. The middle part contains an alternance of sandy sheet-flood and lacustrine mudflat deposits with sand patches of eolian origin. Most of the fossil footprints with better preservation quality were recorded in the mudflats of a shallow lake sourced by unconfined fluvial currents. The participation of eolian deposits increases up section. Locally, a sandy plain of fluvial origin is developed at the top of the section. The new OSL ages along with a previous radiocarbon date led us to propose that sedimentation of footprint-bearing levels would have extended approximately between 28.5 and 12.0 ka. Reworked marine shell remains from the lowermost levels of site with fossil footprints gave considerably older analytical ages in the range of 97.6–62.5 ka, which is probably the maximum age for the middle member of the Agua Blanca Sequence. The "marine levels of Pehuen Co", which are exposed at very low tides and contains in situ specimens of Ophiomorpha nodosa, are dated 7.0 ± 0.4 ka (OSL method). They reflect a Middle Holocene sea level rise in the area. • ESR and OSL dating methods allow to determine ages in the Pehuen Co Peloichnological site. • Sedimentological studies allow the reconstruction of late Pleistocene paleoenvironments. • The preservation of footprints is linked to grain size, the content of moisture and the presence of microbial mats. • Levels with Ophiomorpha nodosa , they reflect a Middle Holocene sea level rise in the area. [ABSTRACT FROM AUTHOR]

Ice age mass-transport deposits (MTD) occur in multiple stratigraphic intervals within the Permocarboniferous Itararé Group, in the Paraná Basin, and are exposed in several disconnected quarries and road cuts around the region of Mafra, southern Brazil. The most typical deposits are diamictites with muddy matrix, but silty-sandy diamictites and metric intercalations of deformed layers of sandstones and siltstones occur subordinately. Similar MTD facies have been described from better exposed and time equivalent successions in western Argentina. There, because of the km-scale exposures, MTDs can be mapped in their plenitude, giving better insights about their emplacement. In this paper, we describe the Brazilian MTDs and infer their modes of transport and deposition supported by comparisons with published Argentinean examples. Based on matrix constitution, presence of coherent blocks and rafts, and sedimentation phases, at least four types of MTDs can be identified: 1) Mud-rich MTD and isolated sandstone blocks; 2) Resedimented MTD represented by diamictites with folded blocks of diamictite, possibly corresponding to two phases of remobilization; 3) Sand/silt-rich MTD (evolved stage), and formed by deformed bands of sandstones and siltstones (mature stage); and 4) MTD with rafts of heteroliths and sandstone blocks. Usually MTDs rest on and scour into a fine-grained substrate such as thin-bedded turbidites and shale. The regional geological setting at Mafra points to an open embayment. The collapse of inclined depositional slopes related to high sediment supply associated with deglaciation was the major control on MTD development. However, the inferred proximity of the ice margin during slope failure was variable, suggesting MTD formation during different stages of a glacial cycle. • MTDs occur in different stratigraphic positions in Itararé Group during the LPIA. • The constitution of the MTD depends on the protolith and stage of evolution. • Comparing Paganzo with Mafra added knowledge about LPIA Mass Transport Deposits. [ABSTRACT FROM AUTHOR]

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

The volcano-hosted geothermal system of Copahue is one of the most promising resources of renewable energy in Argentina. The associated geothermal field is bounded by a set of N60° trending normal faults to the north and by WNW-ESE trending faults to the south. This paper aims to review this first-order distribution of the structures, using previously published b-value data, and to explore the relationship between the local stress field, the superficial structural setting, the magmatic source, and the geothermal fluid flow paths related to the volcanic complex. The 2D dilation tendencies of the geomorphic lineaments is calculated, defining a structural domain with dilatant lineaments that agrees well with high b-values observed at shallow depths(2 km below the surface), and with the known extension of the geothermal field. A rough spatial correspondence is also observed between domains of unfavorable oriented to dilate lineaments and shallow low b-value areas, suggesting that these discontinuities inhibit the horizontal motion of fluids at the same structural level, and constraining the reservoir both to the northwest and to the southeast. b-value data unravels the potential magmatic plumbing system at depth, highlighting a major NW-elongated high b-value body centered at 5 km below surface, from Chancho-có hill towards the south of Maquinas fumaroles. It is coincident at surface with a high density of lineament intersections domain, which creates in depth an intense structural damage zone that may facilitate the ascent of magmatic fluids. The NW anomaly can be extrapolated to the western margin of the Caviahue lake, agreeing with the occurrence of volcano-tectonic seismic events and elevated heat flows reported in this area, and therefore suggesting the presence of the geothermal reservoir at depth. Vertical appendices branching from the b-value anomaly reach up to 3 km below Termas and Maquinitas fumaroles, outlining the possible bottom of the geothermal reservoir. The shallower one is interpreted as a blob of magma injected below the Copahue Village fault system, providing the main heat source. These findings contribute to the current understanding of the geothermal reservoir, its depth coverage and upflow zones, providing insights for future geophysical exploration stages. [ABSTRACT FROM AUTHOR]

Patagonia features the most extensive glaciers of the Southern Hemisphere, excluding Antarctica, and a vast inventory of glacial landforms, so it is thought to have played a key role in (paleo)glacier studies since the late 19th century. However, no systematic attempts to characterize the specific research trends and the scientific community focused on Patagonian cryosphere have been conducted so far. To fill this gap, we analyzed the metadata associated to 305 articles compiled from the Web of Science database following a bibliometric approach covering the period between 1976 and 2020. Our results point to an irregular but net increase on the number of contributions on Patagonian (paleo)glaciers. Mass balance analyses based on satellite data of present-day glaciers and the reconstruction of past glacier activity by dating glacial landforms formed during the Last Glacial Termination, were the most addressed topics during the analyzed period. Patagonian (paleo)glacier studies are mostly published in generic Earth Sciences publications, followed by Quaternary and glaciological journals. Most of the studies were led by scientists from the United Kingdom, followed by Chile, Argentina and United States. In terms of collaborations, these studies can be divided into two main clusters, one composed by researchers from United States, Chile and Argentina institutions, and another mostly composed by British researchers. So far, the most prolific authors are nearly equally distributed in nationality, yet gender inclusion and international collaborations are still caveats that must be solved. Even though our query on the Web of Science missed highly influential (so-called) grey literature, such as local scientific journals and technical reports, the reviewed scientific literature unambiguously indicates that Patagonia is a privileged location for (paleo)glaciers studies worldwide and that it will continue offering vast opportunities to tackle critical questions related to global cryosphere and past-to-present climate changes. • Patagonia is a privilege site for studying present and past glacier dynamics and the evolution of climate changes at hemispheric and global scale. • Glacier dynamics during the 20th century and and the Last Glacial Termination are the most common topics addressed in past decades in the WOS. • Patagonian (paleo)glacier studies has contributed to the development or improvement of diverse analytical techniques. • United Kingdom, United States, Chile and Argentina produced the largest number of WOS-listed papers on (paleo)glaciers in past decades. • The related scientific community is fairly heterogeneous. Although, inclusion and international collaboration issues still need to improve. [ABSTRACT FROM AUTHOR]

The PANG 0003 well records a siliciclastic sedimentary succession corresponding to the Tunas Formation (Permian) in the Claromecó Basin area (Buenos Aires province, Argentina). The aim of this paper is to establish a relationship between fracture frequency in the PANG 0003 exploration well and AMS parameters, as it is a novel research topic that would contribute to the knowledge of the Claromecó basin. Opening-mode I and mode II/III fractures were found in 729 m of unoriented core between 901 m and 170 m recovered. Fracture attributes: inclination, aperture, height, and cement presence are represented by four fracture sets according to the inclination angle; representative kinematic aperture data range from 0 to 5 mm and height constrain by core dimensions. Cement presence is represented by quartz, calcite, and minor pyrite. Fracture description were distributed in lower, middle and upper section of the well according to their fracture frequency (number of fractures per meter). Lower section is represented by a high fracture frequency (13 fractures/meter), which notably diminishes to the middle and upper section of the well (3 fractures/meter). The results indicate that the fracture frequency increases in depth and has a direct relationship with AMS parameters, such as degree of anisotropy (Pj) and magnetic foliation (F). According to previous studies in Sierras Australes outcrops and subsurface for Tunas Formation, tectonic imprint decreases its expression from base to top of the unit and has a positive correlation with fractures studies on cores. This relationship could be used as an alternative methodology to distinguish intervals of high number of fractures in subsurface, in this particular case, for the Claromecó Basin. • The PANG 0003 well records the Tunas Formation (Permian) in the Claromecó Basin area (Buenos Aires province, Argentina). • Fracture frequency increases in depth and has a direct relationship with AMS parameters, such as degree of anisotropy (Pj) and magnetic foliation (F). • Relationship between the parameters of anisotropy of magnetic susceptibility and fracture frequency could be used as an alternative methodology to distinguish intervals of high number of fractures in subsurface, in this particular case, for the Claromecó Basin. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to analyze the morphology of the Quaternary relict features and bedforms that characterize the outer zone of an extensive mesomareal system, which is part of the Bahía Blanca estuary (Argentina), and to estimate the prevailing hydro-sedimentological conditions on the continental shelf adjacent to the estuary. Surveys with a multibeam bathymetric system, side-scan sonar and a high-resolution seismic system (3.5 kHz) were carried out and bottom sediment samples were collected. In general, the seafloor presents a varied configuration, marked by changes in its physiography. The Quaternary relict features are composed of two terraces (12–14 m and 18–22 m deep), with steeply sloping escarpments, that are oriented approximately parallel to the current coastline. Associated with these terraces, wide abrasion platforms develop with irregular and plateau-like structures up to 4 m high, together with large rocky blocks up to 6 m in diameter. Here, the predominant sediment corresponds to a gravel-sized material composed of quartzite boulders, siltstone fragments of up to 7 cm, and biogenic remains with different degrees of fragmentation. These sedimentological data, together with the bathymetric and seismostratigraphic information, indicate that the terraces and abrasion platforms are ancient shorelines that originated in an environment with high wave energy, corresponding to periods of stabilization of sea level rise during the final stage of the last postglacial transgression (late Pleistocene-Early Holocene). On the other hand, asymmetric dunes of different sizes (0.5 m < height < 5 m, 5 m < wavelength < 200 m), sand ribbons (length > 300 m) and comet marks originated in equilibrium with the present-day hydro-sedimentological conditions. The availability of sandy material mobilized as bedload is the determining factor for the generation of the varied bedforms. Thus, sand ribbons and comet marks are generated especially in the northern sector of the area, with mobile sediment thicknesses ≤ 0.5 m. With larger thicknesses the formation of dunes occurs. Their size and asymmetry show an intense transport of sand as bedload towards the continental shelf, the southern sector of the area being the main route of the sediment that leaves the estuary. This sediment is the supply source of the sandy shoals that are part of the great ebb delta developed on the continental shelf in the external area of the Bahía Blanca estuary. • Quaternary relict features coexist with current bedforms. • Terraces and abrasion platforms associated with ancient coastlines are recognized. • Transition between comet marks, sand ribbons and dunes is evident. • The sediment availability determines the generation of different types of bedforms. [ABSTRACT FROM AUTHOR]

Buenos Aires, the capital and largest city of Argentina, is located on the southern shore of the Río de la Plata, hundreds of kilometers away from the seismically active areas in the west of the country. For this reason, and despite evidence from both historical and recent events, earthquake hazards in this area have been traditionally neglected. Based on a series of unprecedented ground motions recorded in the city, this paper presents a review of the seismic hazard in the city of Buenos Aires. In order to do so, a site-specific probabilistic seismic hazard assessment is conducted considering (i) the higher rate of moderate local intraplate earthquakes observed in this area compared to the rest of Argentina's stable region, (ii) the significant site amplification produced by the soil deposit, and (iii) the influence of long-distance earthquakes. The results suggest that site-specific seismic design criteria are needed in Buenos Aires. A series of uniform hazard spectra are recommended for such purpose. • Earthquake hazards should not be neglected in the city of Buenos Aires, Argentina. • Very long-distance earthquakes play an important role because of site amplification. • Site-specific ground motions prediction equations are needed. • Site-specific seismic design provisions should be considered. [ABSTRACT FROM AUTHOR]

This paper presents the first study of nonmarine ostracods recovered from the Danian of the upper Yacoraite Formation (Balbuena IV sequence) Salta Basin. Six species were identified: Ilyocypris triebeli , Ilyocypris argentiniensis , Neuquenocypris (Alleniella)? sp. 1; Neuquenocypris (Alleniella)? sp. 2; Penthesilenula sp. and four indeterminate species. The ostracod fauna shows fluctuations in abundance, diversity, and preservation associated with different phases of the paleolake evolution. This distribution, clearly delineated by the depositional facies, corroborates previous geochemical analyses and high-resolution sequence stratigraphy developed for the section. In general, the most abundant occurrences of ostracods coincide with high-frequency transgressive tracts of the lake system, which form long-term wettest interval of the upper Yacoraite Formation. • First study with ostracods for the Balbuena IV sequence of the Yacoraite Formation, Salta Basin, Argentina. • Six nonmarine ostracods species are identified. • Temporal distribution of ostracods is in agreement with U/Pb radiometric dating. • Ostracod abundance is correlated with the climatic fluctuations of the dry and wet periods of the paleolake. [ABSTRACT FROM AUTHOR]

Gastropods and ostracods are widely used in Quaternary paleoenvironmental reconstructions but the taphonomic studies that should precede them are not as common. In this paper we compare the taphonomic information obtained from assemblages recovered in Holocene fluvial sequences of the Salado River basin (Buenos Aires, Argentina) and analyze the changes or similarities between species, localities and stratigraphic units. Using taphonomic grades, gastropod shells were cataloged based on three attributes: fragmentation, discoloration and dissolution. For ostracods, discoloration and dissolution together with the population structure (adults-juveniles A/J, valves-carapace V/C and male-female ratios) were analyzed. For gastropods, Heleobia parchappii , Biomphalaria peregrina and Succinea meridionalis showed similar preservation patterns, and Miradiscops brasiliensis showed least evidence of alteration. In ostracods, these patterns varied among species. For V/C ratio, 7% of assemblages were formed only by valves, 82% were dominated by valves and 11% were dominated by carapaces. Fragmentation and population structure allowed autochthonous and allochthonous associations to be distinguished. Gastropod assemblages with low levels of fragmentation were recovered mainly from the uppermost levels of the stratigraphic profiles. For ostracods, the A/J ratio showed that 52% of the assemblages were dominated by adults with most ontogenetic stages represented and 29% retained their original population structure suggesting they would be autochthonous associations, whereas 19% of the assemblages were dominated by juvenile valves therefore assuming allochthonous associations. Our results indicate that taphonomic analysis is an effective tool that allows identifying autochthonous assemblages, which are the most reliable for robust paleoenvironmental reconstructions. • First taphonomic study combinating ostracods and gastropods in Argentina. • The most abundant species of gastropod showed similar preservation pattern. • In ostracods, the preservation states varied among the most abundant species. • Ostracod population structure allows recognizing autochthonuos or allochtonous assemblages. [ABSTRACT FROM AUTHOR]

Apart from Vaca Muerta's case history in Argentina, the unconventional exploration in South America is still underdeveloped, and one of the causes is the scarcity of geological studies. The present paper enlightens the embryonic unconventional exploration in the Sergipe-Alagoas Basin by introducing a seismic interpretation workflow to map thin shale layers and the natural fracture system, a challenge in unconventional reservoir explorations. Fracture and faults are critical elements in exploring ultra-low permeability shale oil/gas reservoirs. Identifying and locating these structures influence modeling fluid flow, hydraulics, and simulation models to improve horizontal well-drilling plans. The workflow comprises four main steps: data pre-conditioning, well-to-seismic tie, seismic spectral blueing (for frequency enhancement), and, finally, spectral decomposition and advanced fault attributes. The proposed workflow was applied to a seismic dataset from the onshore Brejo Grande oilfield focusing on the source rocks of the Coqueiro Seco Formation, the main unconventional reservoir candidate in the basin. That approach allowed mapping the lateral continuity, truncation, faults, and fractures in these thin shale layers previously below seismic resolution. The mapped structures belong to the complex natural fracture system with faults distributed to all trend directions. These faults are distributed along two zones with distinct fault densities with a possible sweet spot outline. • We present an interpretation workflow implemented to unconventional reservoirs. • The workflow combines seismic-resolution enhancing techniques and fault attributes. • As a result, thin-shale layers and fault zones were identified at Coqueiro Seco Fm. [ABSTRACT FROM AUTHOR]

In this paper, first and last occurrences of conodont species and petrographic thin sections are used for detection of systems tracts in the San Juan Formation. After analysis of 16,432 conodont elements from Cerro La Silla and Cerro Viejo of Huaco (Los Gatos Creek), Precordillera, Argentina, two transgressive systems tracts (TST) and two highstand systems tracts (HST) are recognized in the San Juan Formation (Lower−Middle Ordovician), including the location of the maximum flooding surface corresponding to each depositional sequence. This study includes the analysis of 32 thin sections of limestones. The maximum flooding surface of the first depositional sequence is recorded in deposits of the lower Floian Prioniodus elegans Zone, whereas the second depositional sequence is located in lower Darriwilian rocks (Lenodus variabilis Zone). At Cerro La Silla and Cerro Viejo of Huaco, the global transgressions of the middle−upper Prioniodus elegans Zone (Billingen transgression) and the lower Oepikodus evae Zone (Evae transgression) are identified. In order to get contrasting results on sea-level changes from the analysis of first and last occurrences of conodont species, it is necessary to account for a high amount of conodonts from most productive samples. Conodont specimens have been recovered from average weight samples and analyses are undertaken including lithology and petrographic sections. • Systems tracts of the San Juan Formation (Ordovician), Argentina. • Systems tracts from the Lower-Middle Ordovician, Argentine Precordillera. • Systems tracts from the Ordovician, Central Precordillera, Argentina. [ABSTRACT FROM AUTHOR]

This paper documents calcareous nannofossil assemblages and the bioevents recorded in the Austral basin of Tierra del Fuego, Argentina. Fifty samples from the type section of the Cerro Colorado Formation were analyzed. Nannoflora is moderately preserved and indicates a late Eocene to early Oligocene age for sedimentary rocks of this formation. Biostratigraphic results are based on distribution patterns of calcareous nannofossils assemblages, permitting comparison with the Southern Ocean zonations and some correlations with standard schemes. Our biostratigraphic interpretation shows an almost complete stratigraphic section spanning from the Priabonian to Rupelian Stages and calcareous nannofossil Chiasmolithus oamaruensis to Blackites spinosus zones, or the low latitude zones of Martini NP18 to NP21. The oldest fossiliferous rocks from the type locality of the Cerro Colorado Formation contain Chiasmolithus oamaruensis indicating nannofossil Zone NP18. The Eocene/Oligocene boundary was placed between the last occurrence (LO) of Reticulofenestra oamaruensis and the increasing in abundance (IB) of Reticulofenestra daviesii. Samples taken from the top of the section belong to the Estancia María Cristina Beds have Cyclicargolithus abisectus. During the late middle to late Eocene a hiatus is suggested between the Cerro Colorado and Leticia formations evident by a 39 Ma detrital zircon age dating, and the first occurrence (FO) of D ictyococcites bisectus. Furthermore, the presence of C. abisectus in the Estancia María Cristina Beds suggests an unconformity with the underlying Cerro Colorado Formation as previously inferred by stratigraphic relationships. • Calcareous nannofossils confirm a late Eocene to early Oligocene age. • The E/O boundary is placed in Tierra del Fuego, Austral basin. • The nanofossil bioevents are correlated with those of the Southern Ocean zonation. • The section spanning from the Chiasmolithus oamaruensis to B. spinosus Zones. [ABSTRACT FROM AUTHOR]

This paper includes a detailed sedimentologic and stratigraphic analysis of the fill of the western part of the Neogene Northern Patagonian extra-Andean foreland basin of Argentina. Using facies analysis, stratigraphic relationships, independent age indicators and physical correlation between sections, the depositional history of the basin is reconstructed and linked to regional climatic and tectonic events. The fill of the basin comprises the El Sauzal, Barranca de los Loros, El Palo, Bayo Mesa and Río Negro formations and it reaches up to 60 m thick in outcrop. On the basis of fourteen detailed sedimentologic logs located in the western side of the basin, a total of nine facies associations are recognized: braided permanent fluvial channel belt, pedogenized floodplain, shallow floodplain lakes, eolian dune field, alkaline lake, saline lake, shallow freshwater lake, and permanent braided gravelly channel belt facies associations. Basin sediments were deposited on an erosive unconformity on Late Cretaceous/Paleocene to early Eocene sedimentary rocks and are divided into five depositional episodes. The first depositional episode is represented by a shallow freshwater lacustrine system of local occurrence, tentatively assigned to the late Miocene. The second depositional episode is represented by permanent braided sandy fluvial system that occurred in the late Miocene-early Pliocene in a depression from the center and south of the study area. The large rivers of this episode flowed toward the east and northeast. The third depositional episode is represented from south to north by ephemeral fluvial, eolian dune and saline-alkaline lacustrine deposits that were recorded in all sections and is tentatively assigned to the Pliocene. Eolian dunes migrated toward the northeast and east. The fourth depositional episode is composed of permanent sandy braided fluvial deposits occurring only in the center of the study area. The fifth depositional episode (early Pleistocene?) is represented by permanent braided gravelly fluvial deposits that rests on a regional erosive unconformity interpreted as a large fluvial fan sourced from the south. These deposits resulted calcretized prior to the middle Pleistocene. The paleoclimatic evolution suggest a wetter period (depositional episodes 1 and 2) tentatively linked to the middle member of the Río Negro Formation and the Paranense transgression, followed by a progressive aridization during the Pliocene and Pleistocene. • Stratigraphic analysis of the Northern Patagonian Andean foreland basin of Argentina. • The basin fill includes late Miocene to early Pleistocene continental deposits. • Sedimentation occurred on Late Cretaceous/Paleocene to early Eocene sedimentary rocks. • A wet initial period linked to the Paranense sea followed by progressive aridization. • A tentative basin wide correlation is proposed. [ABSTRACT FROM AUTHOR]

This paper aims to better comprehend the crustal structure of the Precordillera and the Iglesia Valley. Located in the northern sector of the Pampean flat-slab (San Juan, Argentina), this region was the epicenter of the historical 1894, M > 7 earthquake (intensity IX on the modified Mercalli scale) and thus considered as a region of particularly high seismic hazard. The structure and deformation style associated with such events remain poorly understood. In this study, we analyze 4 months of regional seismic records from national and international stations in order to characterize a sequence of 74 crustal events that followed the occurrence of an intermediate magnitude (M W = 4.8 and M L = 5.2) earthquake on October 28th, 2019 for which we constrain the source parameters using regional moment tensor inversion. The analysis also includes the determination of 11 focal mechanisms from P-wave polarities and P–S waves amplitude ratios. Most of the focal mechanisms indicate reverse motion solutions. Seismological results are then integrated with other geophysics (gravity and seismic reflection profiles) as well as geological data, to build a 3D structural model that allows a better understanding of the crustal deformation mechanisms of the study area. Our results suggest that the seismic deformation is mostly concentrated in the basement of the Western Precordillera, at the transition with the Frontal Cordillera. This deformation seems respond to compressional stresses. The proposed model provides evidence of ongoing seismic activity related to the interaction between the thick-skinned deformation of the Frontal Cordillera with the thin-skinned fold and thrust belt of the Western Precordillera. • We analyzed the crustal seismicity in the Western Precordillera and Iglesia Basin. • We modeled the source parameters for the October 28, 2019 earthquake. • We located 74 crustal earthquakes mainly distributed between 10

The South Atlantic coast in Argentine Patagonia is an area where semi-arid to arid conditions predominate and coastal populations present serious water supply problems. The aim of the work was to evaluate the factors that condition the salinization processes of coastal aquifers from a hydrochemical and isotopic analysis of the groundwater located in Pleistocene and Holocene littoral ridges in the northern sector of Patagonia in Bahía San Blas. A geomorphological characterization of the area was carried out using digital elevation models, satellite image interpretation and field surveys. Groundwater chemistry was analyzed in 40 shallow wells and 2 tidal water samples. At each point, electrical conductivity, temperature and pH of water were measured and samples were taken for analysis of major ions and stable isotopes. The salinization processes were analyzed by means of ionic and isotopic relationship graphs and were subsequently modeled using free software. The results obtained allowed the identification of the factors that determine the salinization of coastal aquifers. Particularly in the Pleistocene coastal ridges, the cementation of the most superficial sediments reduces permeability conditioning rainwater infiltration. This, together with the presence of soluble salts on the surface and the mixing with sea water, determines the salinization of the groundwater. In contrast to these, in the Holocene coastal ridges without cementation, rainwater infiltrates forming freshwater lenses where salinization processes occur only at the edges of the lenses where the saltwater wedge is located. The data provided in this paper are useful in prospecting freshwater sources along the arid coast of Patagonia where freshwater availability is scarce. They can also be extrapolated to other sectors worldwide with similar geological and climatic environments. • Water supply problems exist in the arid coastal zone of Patagonia Argentina. • Freshwater lenses are formed in Pleistocene and Holocene littoral ridges. • Groundwater salinization is recognized in lenses of Pleistocene littoral ridges. • Salinization processes are due to cementation, salts dissolution and marine intrusion. [ABSTRACT FROM AUTHOR]