Argentine Continental Shelf Research Articles

Ontogenetic diet shifts of rough scad Trachurus lathami in the North Patagonian shelf (south-west Atlantic Ocean).

Rough scad Trachurus lathami is a key pelagic fish in the Argentinean continental shelf (ACS, south-west Atlantic Ocean), with recent increases in abundance. It is a main prey of fishes and marine mammals, and shares the environment with commercially relevant pelagic species (Engraulis anchoita and Scomber colias), playing an important role linking lower and upper trophic levels in the ecosystem. This study aims to determine the ontogenetic changes in the diet composition, feeding strategy, trophic niche breadth and trophic level of T. lathami in the North Patagonian Shelf (43°-45°30'S). The stomach contents of adult fish (n=238) were analysed. The results suggest a clear ontogenetic shift in the diet at a size of ~190 mm. Smaller individuals (160-190 mm) were specialized on misidaceans, and showed the highest trophic level, while larger T. lathami (221-230 mm) consumed decapods (Peisos petrunkevitchi) and teleosts (eggs and larvae). Trophic niche breadth was higher at the medium-sized class (191-220 mm), which mainly preyed on copepods (Calanoides carinatus) and chaetognaths (Sagitta spp.), evidencing a more diverse diet and a rather generalist strategy. Updated information on the trophic ecology of T. lathami evidences its extremely plastic feeding behaviour, being able to adapt its trophic niche to the most readily available food items from the mesopelagic community.

Volume Transport Variability on the Northern Argentine Continental Shelf From In Situ and Satellite Altimetry Data

AbstractDirect current observations and satellite altimetry data over the northern portion of the Argentine continental shelf are used to produce an 11‐month long hourly time series and a 25‐year long daily time series of along‐shore volume transport, respectively. At time scales longer than 20 days, the temporal variability of the in situ transport is significantly correlated with the transport inferred from satellite altimetry (r = 0.74). The mean in situ along‐shore transport is 2.65 ± 0.07 Sv (1 Sv = 106 m3 s−1) to the northeast and presents large variability, with a peak‐to‐peak range of 16 Sv. The extended satellite transport presents variability at multiple time scales. The annual cycle is the dominant signal, with a maximum during the austral autumn and a minimum during the austral spring. The interannual component of the transport is significantly correlated (r = −0.5) with the Southern Annular Mode (SAM). SAM‐induced along‐shore wind stress anomalies over the region modulate the cross‐shore pressure gradient that, in turn, modulates the along‐shore transport variability. This mechanism holds also at synoptic scales, highlighting the dominant role of the wind on the along‐shore transport. Satellite altimetry measurements also indicate that the cross‐shore pressure gradient generated by the variability of the Malvinas Current affects the along‐shore transport only in the outer 30 km of the continental shelf.

First data on the age and growth of Brazilian flathead Percophis brasiliensis (Pisces: Perciformes) in San Matías Gulf, northern Patagonia (Argentina)

Brazilian flathead Percophis brasiliensis is a commercially important perciform fish caught as bycatch by trawlers throughout its latitudinal distribution range (from 23° S in Brazil to 47° S in Argentina). It is associated with the catches of Argentine hake Merluccius hubbsi and Patagonian red shrimp Pleocticus muelleri in San Matías Gulf (SMG). The main objective of this study was to describe the first data on the growth of this species in SMG and to compare the results with available information for other areas of the Argentine Continental Shelf (ACS). The study was carried out using 294 specimens (196 females, 97 males and one of indeterminate sex) collected over four non-consecutive years from commercial/recreational fishing and during research cruises. The age of individuals was determined by reading and counting opaque-hyaline rings on the sagittae otoliths. The maximum ages observed were 14 years for females and 12 years for males. Growth parameters were estimated using the von Bertalanffy mode. Significant differences in L∞ parameter between sexes were found (L∞ males = 54.58 cm; L∞ females = 78.31 cm, p < 0.05). Growth parameters were different from those determined in previous studies for the ACS.

Patagonian grouper Acanthistius patachonicus (Jenyns, 1840) forms massive spawning aggregations in the Southwest Atlantic.

Here we describe massive spawning aggregations and seasonal changes in the large-scale distribution of the Patagonian grouper Acanthistius patachonicus in the Southwest Atlantic based on three sources of information: (a) data from bottom trawl research surveys covering the distributional range of the species within the Argentine continental shelf; (b) folk ecological knowledge gathered from experienced captains of the Argentine industrial trawl fisheries; and (c) sampling of an artisanal trap fishery targeting the Patagonian grouper in a specific location off the coast of Buenos Aires Province. The trawl surveys showed a general pattern of aggregation of Patagonian grouper towards the coast during the reproductive period (September-December). Captains described massive aggregations of the species at specific near-shore locations, where trawl catches of up to 15 t in a single haul were registered during the reproductive season. At a local scale, the artisanal trap fishery described operates exclusively during the reproductive period, targeting near-shore aggregations with a high proportion of individuals releasing gametes onboard. These three sources of information provide evidence of the existence of massive transient spawning aggregations of Patagonian grouper in the Argentine shelf. This is the first report of a reef fish spawning aggregation in the southern region of the Southwest Atlantic. Anecdotal information gathered in this study points to the depletion of many of the aggregations targeted during the 1980s and 1990s by the industrial fleet. At the same time, the spawning aggregation site off Buenos Aires Province has been productive for the last 34 years, being exploited exclusively by traps. The Patagonian grouper is classified as Data Deficient by the International Union for Conservation of Nature, which highlights the need for further research to determine its stock status. Mapping its current spawning aggregations should be a priority to inform the design of a targeted monitoring program and management plan for this species.

Legislación e instrumentos de manejo existentes para la protección de los fondos marinos en la Plataforma Continental Argentina

Se presenta un compendio de instrumentos vinculantes y no vinculantes referidos al manejo y protección de los fondos marinos y/o de los invertebrados bentónicos de la Plataforma Continental Argentina (PCA). Se analizaron leyes nacionales y acuerdos internacionales en los cuales Argentina es signataria, así como declaraciones de FAO que establecen principios y normas aplicables a la conservación, ordenación y desarrollo de las pesquerías y ecosistemas asociados. En base a esta selección bibliográfica se analizó la evolución de las medidas a lo largo del tiempo en función del contexto internacional, a fin de esclarecer cuáles son los faltantes y los logros obtenidos en este proceso. Se concluye que Argentina avanzó en la generación de políticas acordes a los lineamientos mundiales que implican un manejo ecosistémico y un mayor resguardo de la biodiversidad, por ejemplo, implementando Áreas Marinas Protegidas, así como con el enunciado de planes de investigación y fomento que involucran el estudio de los fondos marino. Sin embargo, para algunas medidas su efectiva ejecución es parcial a partir de la falta de reglamentación y/o financiamiento. Asimismo, queda pendiente la elaboración de planes de acción concretos referidos al estudio del lecho marino incluido en los nuevos límites exteriores de la PCA.

Circulation and Hydrography in the Western South Atlantic Shelf and Export to the Deep Adjacent Ocean: 30°S to 40°S

AbstractHigh sea surface chlorophyll concentration on the Argentine Continental Shelf frequently extends to the deep ocean in the vicinity of the Brazil/Malvinas Confluence (BMC). The offshore transport of shelf waters likely plays a key role in the biogeochemical balance of the western South Atlantic and promotes the offshore transport of planktonic species. We analyze data from an oceanographic survey carried out in the western South Atlantic shelf between 31°S and 38°S in October 2013. We describe the distribution and circulation of the water masses and focus on the exchanges with the open ocean. On‐shelf subsurface intrusions of oceanic waters and river discharge supply nutrients to the shelf. A low‐salinity tongue of Río de la Plata (RDP) waters extends northward to 32°S. Below these waters Subantarctic and Subtropical Shelf Waters (SASW and STSW) meet to form the Subtropical Shelf Front. The main SASW branch, oversaturated in oxygen and with high‐fluorescence mixes with a detachment of Brazil Current waters at 38°S and is exported offshore along the BMC. A second branch of SASW reaches 33°S mixing along its way with RDP and STSW and returns southward after splitting into an onshore and an offshore branch. The offshore branch is exported to the open ocean through the BMC. These export routes are in overall qualitative agreement with those indicated by a high‐resolution reanalysis. We estimate a net off‐shelf transport (geostrophic [96.2%] plus Ekman [3.8%]) of 3.44 Sv to the open ocean between 32.1°S and 37.7°S. The majority of the offshore flow occurs between 34.7°S and 37.7°S.

Seasonal and spatial variability in condition of age‐0+ Argentine hake Merluccius hubbsi Marini, 1933, in the San Jorge Gulf (Argentina): A bottom‐up perspective

AbstractIn the north Patagonian region of the Argentinean Continental Shelf, the San Jorge Gulf (SJG; 45°‐47°S, 65°30ʹ‐67°30ʹW) is the main nursery ground of age‐0+ Argentine hake Merluccius hubbsi Marini, 1933, one of the most important fishery resources in Argentina. The gulf exhibits strong seasonal and spatial fluctuations in environmental features, which might affect survival of age‐0+ individuals and recruitment to the adult population. Our main goal was to evaluate the seasonal and spatial dynamics of their nutritional status within the SJG in winter 2016, spring 2016 and summer 2017. Condition indices (relative condition factor Kn, hepatosomatic index HSI and liver lipid content %L) and diet information (feeding incidence and relative importance of prey) were combined with physical (temperature and salinity) and biological (satellite chlorophyll‐a concentration; chl‐a) data. Age‐0+ condition indices and prey intake showed significant seasonal variations, with minimum values in winter, intermediate in summer and maximum in spring, strongly coupled to the mean chl‐a concentration in each season. Herbivorous euphausiids Euphausia spp. were the preferred prey along the study period. A bottom‐up effect on condition of age‐0+ hake is suggested, manifested as lower condition values in winter, the less productive season. Spatially, better conditioned individuals matched sectors of the gulf where chl‐a concentrations were higher, coupled to the presence of frontal systems. Monitoring age‐0+ hake nutritional status is relevant in the current global change scenario, which might modify phytoplankton biomass and composition and, consequently, the herbivorous zooplankton abundances.

Ecological study based on the distribution of recent foraminifers from southeast of Buenos Aires province, Argentinean Continental Shelf.

The study about the distribution of benthic foraminifers in relationship with the type of substrate is presented. Samples of surface sediments from 15 to 60 m of depth from the southeast coast of the province of Buenos Aires (40º 30´ - 42ºS), Argentina were analysed. The foraminiferal assemblage was constituted by forty-eight species that belong to 22 genera. It was characterized mostly by the free-living style, epifaunal microhabitats, oxic levels and a detritivore trophic strategy. Based on statistical analysis, three zones were determinated: at 15 m depth , characterized mainly by Buccella peruviana (d´Orbigny), and species of Bolivina reflected a littoral environment with sandy sediments and the most important clay contribution, whereas it also presented the lowest oxygen levels were determinated; between 24-48 m depth, associted by Ammonia parkinsoniana (d´Orbigny), Buccella peruviana and Quinqueloculina seminula (Linné), this zone displayed an oxygenated environment with coarse grainsize from inner shelf where local water circulation may explain the high energy observed; and the last one located between 36 to 58 m of depth was characterized by Buccella peruviana, Ammonia parkinsoniana, Elphidium macellum (Fichtel Moll), Cibicides dispars (d´Orbigny) and Cibicides aknerianus (d´Orbigny) regflecting an inner shelf environment with sandy sediments, the lowest water temperature and the highest oxygen levels.

First evidence of polycyclic aromatic hydrocarbons in sediments from a marine protected area within Argentinean Continental Shelf

This study evaluated for the first time, the distribution, sources, and ecological risk assessment of 16 polycyclic aromatic hydrocarbons (PAHs) in sediments collected along the northern Patagonian shelf in the Argentine Sea –included in a Marine Protected Area (MPA). Total concentration of the PAHs varied from 19.47 to 183.17 ng/g dry weight and low molecular weight compounds, such as Anthracene and Naphthalene were the dominants. The selected PAHs ratios suggested a predominance of petrogenic sources and ecotoxicological risk evaluation based on the sediment quality guidelines model, indicated that some PAHs might cause occasional adverse biological effects in the study area.

Calcareous microorganisms as indicators of oceanographic conditions in South West Atlantic Ocean

Abstract The results of multivariate analysis applied to the associations of benthic foraminifers and ostracods from surface sediments of the north Argentine continental shelf are presented in this study. We evaluated the distribution patterns and ecological preferences of species found in modern sediments from the north Argentine continental shelf, at depths between 15 and 130 m. We identified 61 species of foraminifers corresponding to the orders Rotaliida, Miliolida, Lagenida, Buliminida, Lituolida and Trochamminida, in addition to 18 species of ostracods that belong to the suborder Podocopina. The distribution of the ostracods Bradleya kaeslery Ramos, Coimbra and Whatley was extended to higher latitudes. It was determined that water depth and temperature were the factors that most affected the distribution of both types of microorganisms. Based on these data, we established three physiographical zones, which could be linked to the different water masses. In addition, the western limit of the Malvinas current at 80 m of water depth was corroborated. Our study highlights the potential use of benthic foraminifers and ostracods individuals as bioindicators for identifying oceanographic conditions in the Argentine continental shelf.

Comparative embryonic development patterns in three deep-water skates from the southwest Atlantic

Embryonic development is a vulnerable and key period during the life cycle of an oviparous elasmobranch. Captivity studies are difficult to carry out on non-coastal species; hence, embryonic development can be analysed from samples collected from the seabed. Here, embryonic development of three shelf and deep-water skates from the southwest Atlantic Ocean, Bathyraja brachyurops, B. macloviana and Amblyraja doellojuradoi was studied. Egg cases containing embryos in different stages were collected from 84 to 1006 m depth in the northern part of the Argentinean continental shelf and continental slope (36°S-41°S), including the Mar del Plata Canyon (38° S). Common development patterns were observed among the three species and also with other skate species previously studied. Anatomical structures and embryo features were similar among species in initial, early and middle stages. Advanced and pre-hatching embryos showed species-specific differences regarding pigmentation and spinulation. This study sheds light on the identification of neonates of shelf and deep-water species, which could be useful to recognize specific nursery areas in the deep ocean. In addition, this embryological comparative study expands the existing database on the different chondrichthyan lineages, thus making a step forward towards understanding of their phylogenetic relationships.

Origin and radiogenic isotope fingerprinting of aerosols over the Southwestern Atlantic and corresponding Southern Ocean Sector

Abstract Tracing potential source regions of aerosols/dust is a key factor in understanding the atmospheric circulation regimes. In this context, Nd and Sr isotopes in continental fine sediments have been used as tracers (or fingerprints) of dust found in deep cores retrieved from the Antarctic ice sheets. In order to demonstrate the utility of radiogenic isotopes as dust fingerprint we have conducted atmospheric samplings from latitude 30°S to 64°S, over the Southwestern Atlantic Ocean, the Southern Ocean/Drake passage and coastal waters of the northern Antarctic Peninsula. We aimed at comparing the radiogenic isotope signature of the collected aerosols and their most likely sources as described in the literature. Aerosol samples were collected during oceanographic cruises carried out in 2010, 2011 and 2012 by the Brazilian Antarctic Program. Measured isotope ratios 87Sr/86Sr and 143Nd/144Nd were compared with inventories for Patagonia, Australia and Antarctica. In our study, origins of aerosols over sea were attributed to: (1) the Patagonian influence over the Argentine continental shelf; and (2) in the Southern Ocean where prevails a mix of dust sources from Patagonia, Australia and rock outcrops existing in the Antarctic continent.

Synthetic microfibers in marine sediments and surface seawater from the Argentinean continental shelf and a Marine Protected Area

Abstract In this work, samples were collected from the Argentinean continental shelf –including a Marine Protected Area (MPA) - to assess the occurrence and distribution of synthetic microfibers (MFs), a widespread type of microplastic. MFs were present at 100% of the samples showing an average concentration of 182.85 ± 115.14 particles per Kg of dry sediment and 0.14 ± 0.08 items per m3 of marine water. MFs less than 1 mm were the most abundant (56.4% and 63%, for sediment and surface seawater respectively), followed by 1–2 mm and then 2–3 mm. In regards to the colour, both sediments and water had the major percentage of black MFs (25.6% and 28%, respectively) and the lowest one of green MFs (2.5% and 3%, respectively). Finally, MFs content in sediments was inversely correlated with depth (r = -0.93, p

Revision of Cirratulus (Cirratulidae: Polychaeta) from Argentina, with the description of three new species and a key to identify all species of the area

Introduction: The taxonomy of Cirratulidae is not easy due to the diagnostic characters currently accepted change through ontogeny, in some cases, there are even difficulties to separate juveniles from adults. Among the Cirratulus species cited, described and considered as valid for Argentina are Cirratulus jucundus (Kinberg, 1866), Cirratulus patagonicus (Kinberg, 1866) and Cirratulus mianzanii Saracho Bottero, Elías & Magalhães, 2017. Objetive: This study made a revision of Cirratulus includes material deposited in the Museo de Ciencias Naturales de La Plata (MLP) and specimens collected privately by J.M. Orensanz that was donated to the laboratory of Bioindicadores Bentónicos of the National University of Mar del Plata. Methods: The specimens were examined with optical equipment (microscope and stereomicroscope) and also by a scanning electron microscope (SEM). Results: A complete examination of the material, revealed a higher number of species than those already mentioned. In the present work, three new species are described from the intertidal and subtidal areas of the Argentine continental shelf: Cirratulus orensanzii n. sp.; Cirratulus knipovichana n. sp. and Cirratulus alfonsinae n. sp. Conclusions: The knowledge about the taxonomy of the family as well as the updating of the geographic registries contributes to the biodiversity of the region, which is of great importance to carry out both ecological studies and conservation plans.

Aeolian Dust Provenance in Central East Antarctica During the Holocene: Environmental Constraints From Single‐Grain Raman Spectroscopy

AbstractWe analyzed the single‐grain mineralogical composition of aeolian dust transported to central East Antarctica for provenance purposes. Comparison with data from the last glacial period shows for the first time disappearance of carbonates during the Holocene related to sea level rise and suppressed deflation from the Argentinean continental shelf, exposed during Marine Isotope Stage 2. Zeolites, related to alteration of volcanic glass in the subglacial/periglacial environment of Patagonia, show a similar behavior. The remaining minerals, remarkably similar between the two climatic periods, are compatible with a Pampean and Patagonian provenance, but Holocene data show a more pronounced volcanic and metamorphic imprint and presence of minerals related to warm climate weathering environments compatible with an additional contribution from subtropical latitudes of South America. These results do not imply a major large‐scale reorganization of atmospheric circulation after the last climatic transition.

Effect of nursery ground variability on condition of age 0+ year Merluccius hubbsi

This study examined the southern or Patagonian (41°-55° S) stock of Argentine hake Merluccius hubbsi, the more abundant of the two stocks on the Argentinean continental shelf. Pre-recruits (age 0+ year individuals) of this stock settle and grow in the San Jorge Gulf (45°-47° S, 65° 30' W), a complex habitat with large spatial variability in environmental features. Relative condition factor, hepatosomatic index, lipid content and fatty-acid composition of muscle and liver, and diet information were combined with physical and biological data to evaluate: how nutritional status of age 0+ year hake varies spatially within the nursery ground; whether changes in condition are related to environmental factors and feeding; whether the indices are interchangeable metrics of condition. Both morphometric and biochemical indices showed dissimilar spatial trends; enhanced liver-based condition coincided with low salinity nutrient rich waters, higher chlorophyll-a values and abundances of Euphausia spp., the preferred prey at most stations, suggesting a bottom-up effect on age 0+ year hake condition. Diminished condition at stations where Thermisto gaudichaudii was the main prey could derive from lower prey quality in terms of energy density and essential fatty acids content. Coastal waters of the gulf would be essential habitats for M. hubbsi pre-recruits. Future monitoring of condition with liver-based indices is encouraged in the gulf, where interannual increasing trends of satellite-derived chlorophyll-a values have been observed, which could have implications for recruitment of the species.

Mesoscale distribution and population structure of the chaetognath Serratosagitta tasmanica (Thomson, 1947) from Southwestern Atlantic Ocean

ABSTRACTAlthough Serratosagitta tasmanica is widely distributed, there is little information on how hydrology affects its distribution, abundance and demography. In this study we analyzed the distribution, carbon content and population structure of S. tasmanica in the Southwestern Atlantic Ocean. Samples were collected at 34°–39°S (Northern Argentine Continental Shelf in winters of 1999 and 2000) and at 47°–55°S (Southern Argentine Continental Shelf in spring 2005, summer 2006 and winter 2006). The analysis of more than 8500 individuals showed that its dominance decreased spatially from south to north, whereas biomass (mgC/m2) increased temporally by three orders of magnitude between spring (4.06) and summer (12.7). In the southern area the presence of all maturity stages in all seasons suggests year-round reproduction, with maximum reproductive activity in winter. Body length increased with increasing latitude and decreased with temperature. We detected differences in the morphology of seminal vesicles and ovary length between mature specimens. In the northern area all individuals exhibited short-type ovaries whereas in the southern area individuals had either short or long ovaries, suggesting that some individuals of the latter area had been advected from the Southern Pacific Ocean through the water discharged from the Magellan Strait.

Plankton Multiproxy Analyses in the Northern Patagonian Shelf, Argentina: Community Structure, Phycotoxins, and Characterization of Toxic Alexandrium Strains

The extensive Argentine continental shelf supports high plankton productivity and fish catches. In particular, El Rincon coastal area and the adjacent shelf fronts (38.5–42o S, 58.5–62o W) comprise diverse habitats and hold species of economic and ecological value. So far, studies of the microbial community at the base of the food web remain scarce. Here we describe the early spring plankton (>5-200 µm) structure in terms of abundance, biomass, species composition, functional groups and phycotoxin profiles in surface waters of El Rincon in September 2015. Diatoms were the most abundant and the largest contributors to carbon biomass at most stations. They dominated in coastal and inner-shelf (depths 20 µm) heterotrophic protists, e.g. various ciliates and dinoflagellates species were more abundant offshore. Scanning of phycotoxins in the field disclosed that paralytic shellfish poisoning (PSP) toxins were dominated by gonyautoxins-1/4 (GTX1/4). Lipophilic toxins were detected in low abundance, e.g. domoic acid (DA), although a bloom of Pseudo-nitzschia spp. (up to 3.6 x 105 cells L-1) was detected at inner-shelf stations. Pectenotoxin-2 (PTX-2) and 13-desmethyl spirolide C (SPX-1) were the most abundant in the field. PTX-2 co-occurred with Dinophysis spp., mainly D. tripos, while SPX-1 dominated at middle-shelf stations, where cells of Alexandrium catenella (1 strain) and A. ostenfeldii (3 strains) were isolated. The quantitative PSP profiles of the Alexandrium strains differed significantly from the field profiles. Moreover, the three A. ostenfeldii strains proved to be PSP producers and additionally produced 5 novel spirolides. Phylogenetic analyses of these first strains from the South Atlantic disclosed a new ribotype group suggesting a biogeographical distinction of the population. The plankton survey presented here contributes with baseline knowledge to evaluate potential ecosystem changes and to track the global distribution of toxigenic species.

Fatty acids composition as an indicator of food intake inMerluccius hubbsilarvae

AbstractFatty acids (FA) analysis is a well-established approach for qualitatively studying feeding preferences. In the Argentinean Continental Shelf, Argentine hakeMerluccius hubbsisupports the major demersal finfish fishery. The Patagonian stock of the species spawns and nurses in austral summer in the north Patagonian shelf (NPS, 43°–45°30′S). Previous studies about larval feeding in the NPS have solely focused on gut contents, indicating selectivity upon calanoid copepods. Hence, our main objective was to apply the FA approach to confirm and/or broadenM. hubbsilarval food selection. Hake larvae and copepod FA profiles overlapped significantly, dominated by the saturated FA 16:0, the monounsaturated FAs 18:1n-9 and 22:1n-9, and the polyunsaturated FA 22:6n-3. Moreover, identified markers typical of bacteria (15:0, 17:0) and dinoflagellates (18:4n-3, 22:6n-3) suggest a microbial input at the base of the NPS food web, with the latter probably acting as an intermediate step between bacteria and hake larvae. Possible direct predation upon protozoans by larvae is postulated, broadening the known trophic spectrum derived from classical diet analyses. The FA approach allowed us to clarify feeding preferences in the NPS, with data being relevant in the context of hake recruitment studies.

Application of magnetic method on the Argentine continental shelf between 35ºS and 48ºS

Se analizaron las anomalías del Campo Magnético Total a partir de datos de una red global, con el propósito de contribuir al conocimiento y caracterización de la plataforma continental argentina (35ºS hasta 48ºS). Para ello se utilizaron técnicas de realce, como la señal analítica, el ángulo tilt, y la segunda derivada vertical. Se calcularon las profundidades de las fuentes magnéticas a partir del método de deconvolución de Euler y el modelado de inversión gravimétrica 2D. A partir de los resultados filtrados del TMA se identificaron grandes zonas de fractura de transferencia. La segunda derivada vertical mostró patrones de alta frecuencia en las anomalías G y Tona, así como también en la serie de anomalías M y alineamientos de fondo oceánico, mostrando el carácter volcánico y episódico de los mismos. El método de deconvolución de Euler permitió localizar fuentes magnéticas discontinuas a lo largo del antiguo cinturón Dom Feliciano Lavalleja, cuyas profundidades van desde 5000 a 8000 m. Se obtuvieron pocas soluciones tipo diques, escalones de falla en las zonas de fallas de transferencia y el borde entre corteza continental y oceánica. Se localizaron fuentes en la serie-M a profundidades entre 8000 y 12000 m. También, este método permitió calcular las profundidades de la conspicua anomalía Tona entre 8000 y 20000 m. Además, a partir de un modelo de inversión gravimétrico 2-D aplicado sobre un perfil con dirección NE, se identificó un cuerpo máfico-ultramáfico a lo largo de la sutura Patagonia-Gondwana hasta casi la superficie. Este cuerpo podría ser una imbricación de la sutura emplazada en rocas del basamento.