Journal of South American Earth Sciences最新文献

{"title":"New archosauromorph remains provide data on the age of a unique Late Triassic assemblage from southern Brazil","authors":"","doi":"10.1016/j.jsames.2024.105046","DOIUrl":"10.1016/j.jsames.2024.105046","url":null,"abstract":"<div><p>The Santa Maria Supersequence, an important stratigraphic unit in the Paraná Basin, yielded a diverse range of Triassic tetrapod assemblages, providing valuable insights into the evolutionary history of southwestern Pangea. This study focuses on the Candelária Sequence of the Santa Maria Supersequence, which includes the <em>Hyperodapedon</em> Assemblage Zone (AZ) and the <em>Riograndia</em> AZ. The <em>Hyperodapedon</em> AZ is characterized by the presence of <em>Hyperodapedon</em> rhynchosaurs alongside a diverse array of other taxa, including dinosaurs, pseudosuchians, and cynodonts. In contrast, the <em>Riograndia</em> AZ preserves mostly small cynodonts, lepidosauromorphs, and sauropodomorph dinosaurs. Whereas biostratigraphic correlations between several localities of the Candelária Sequence have been firmly established, certain sites, like the Niemeyer complex in the Agudo municipality of southern Brazil, present challenges because of their unusual assemblage composition, which result in ambiguous depositional ages. Despite yielding thousands of fossil specimens, the Niemeyer complex lacks index fossils typical of the known Brazilian AZs, making reliable correlation with other sites challenging. This study presents and describes new archosauromorph specimens discovered at the upper portion of the Niemeyer complex. The new materials include a rhynchosaur, a saurischian dinosaur, and a possible silesaurid, which represent the first record of these groups for the site. A phylogenetic analysis of the rhynchosaur material provides insights into its taxonomic affinities, offering valuable data for biostratigraphic comparisons. The new data reinforces an age (early Norian?) that is younger than that of the typical outcrops assigned to the <em>Hyperodapedon</em> AZ. Furthermore, these new specimens contribute to the unique assemblage of the Niemeyer complex, shedding light on its significance within the context of the Santa Maria Supersequence and the broader landscape of southern Brazil during the Triassic Period.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141929848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal thicknesses in Uruguay from joint inversion of receiver functions and surface wave dispersion","authors":"","doi":"10.1016/j.jsames.2024.105062","DOIUrl":"10.1016/j.jsames.2024.105062","url":null,"abstract":"<div><p>The development of a seismic network in Uruguay in recent years has enabled studies of crustal structure in a region with few seismological studies of this type. In this work, we update the crustal thicknesses and Vp/Vs ratios calculated by H-k stack and present S-wave velocity models based on joint inversion of receiver functions and Rayleigh wave group velocity dispersion curves.</p><p>Some interesting results are the presence of a lower crust with a high S-wave velocity of 4.1 km/s below one of the stations located on the Río de la Plata Craton and the existence of a transitional Moho in Uruguay's northernmost station on the Paraná Basin, perhaps suggesting the presence of localized underplated material. A relatively thick crust, 41.8 km, compared to surrounding stations, was found beneath the Sierra Ballena Shear Zone in the Dom Feliciano Belt. We confirm the decrease in crustal thickness when approaching the oceanic coast, reaching a Moho depth of 36.3 km in SE Uruguay. Finally, the calculated Poisson's ratio allows inferring a crust of felsic to intermediate composition beneath most of Uruguay.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142077240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Barrier-lagoon system in the Paraíba do Sul River Deltaic complex (PARNA Jurubatiba, Brazil): Insights into mesoscale behavior and geological influence","authors":"","doi":"10.1016/j.jsames.2024.105047","DOIUrl":"10.1016/j.jsames.2024.105047","url":null,"abstract":"","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141949435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pathology on caudal vertebra of Glyptodon sp. (Xenarthra, Cingulata) from the Upper Pleistocene (Luján Formation) of Buenos Aires province (Argentina)","authors":"","doi":"10.1016/j.jsames.2024.105061","DOIUrl":"10.1016/j.jsames.2024.105061","url":null,"abstract":"<div><p>The paleontological collection of the Museo Municipal de Ciencias Naturales “Carlos Ameghino” (MCA, Mercedes, Buenos Aires Province, Argentina) includes hundreds of mammalian fossil specimens collected from the Luján Formation (Lujanian Stage/Age), bounded to the Late Pleistocene/Early Holocene. Among the specimens of the MCA collection, a caudal vertebra (MCA-117) of <em>Glyptodon</em> sp. (Xenarthra, Cingulata) with pathologies was identified, which are here characterized in order to perform a diagnosis. The main alterations in the vertebra consist of bone erosion and remodeling in the left transverse process, bone erosion in the vertebral centrum, and deformation in the neural arch affecting the prezygapophyses. The features identified in the transverse process were diagnosed as bone remodeling, alterations previously described for Pleistocene xenarthrans. The erosions observed in the vertebral centrum are comparable to spondylosis, Schmorl's node, intervertebral discopathies, or, alternatively, calcium pyrophosphate deposition disease. Nonetheless, these could potentially manifest as secondary complications arising from spondylosis. Regarding characteristics such as low bone density, it is concluded that they are indicative of modifications due to osteoporosis. The alterations present in the specimen can be compared with bone pathologies recognized in elderly individuals with large body mass.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141929849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gravity and magnetic geophysical surveys for exploration of low sulphidation epithermal mining project. Marifil Complex, Chon Aike Igneous Province, Argentina","authors":"","doi":"10.1016/j.jsames.2024.105049","DOIUrl":"10.1016/j.jsames.2024.105049","url":null,"abstract":"<div><p>The Marifil Complex constitutes the early stage of the Chon Aike Igneous Province along eastern North Patagonia, Argentina. Geological, geochronological, and geochemical data indicate that this magmatism consists of two characteristic Lower Jurassic volcanic events (V0 and V1). The epithermal activity takes place in V1 as Au-Ag veins (Pavón Pivetta et al., 2024). Particularly, base metal veins are covered and masked by the important explosive volcanic activity related to the V1 volcanic stage. This makes geophysical exploration a highly recommended tool for interpreting subsurface geological features.</p><p>With this in mind, we have carried out the acquisition and processing of gravity and magnetic data that is supported with drill holes and geochronological data. A series of gravity and magnetic highs and lows were recognized, together with major lineaments. Using Euler deconvolution, the depth of the sources that generate the anomalies was calculated. The analysis of these results allowed us to construct two perpendicular gravity 2D models for the calculation of thicknesses and depth of the rhyolitic <em>coulée</em>. The gravity lows were associated with the major thickness of rhyolitic <em>coulée</em>, reaching 290 m in the drill holes, and interpreted geophysically to have a deeper root. The gravity highs were interpreted in two possible ways: a basement depth decrease and/or the absence of the rhyolitic <em>coulée</em>. The minimum depth estimated for the basement highs is approximately 20 m. These interpretations are consistent with outcrop, drill hole and geochronologic data, and magnetic maps. The RMSE between the calculated and the observed anomalies of the models are about 0.316 and 0.519 mGal. Due to the shape of the anomalies obtained from the gravimetric maps, the structures that generate the anomalies were considered as generated by three-dimensional bodies. For this purpose, we created a 3D model that provides interesting data about the possible location of these non-outcropping gravity lows that are located in the first 200 m depth.</p><p>These results demonstrate that the use of the gravity and magnetic method constitutes a useful, fast, economical, robust, and reliable tool for the identification of these volcanic structures.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141841253","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Palynofacies analysis of a lacustrine succession: The Maracangalha Formation (Lower Cretaceous), Recôncavo Basin, Brazil","authors":"","doi":"10.1016/j.jsames.2024.105050","DOIUrl":"10.1016/j.jsames.2024.105050","url":null,"abstract":"<div><p>A palynofacies analysis was carried out using samples collected from the Manguinhos, Gameleira, Praia da Falha and Penha outcrops of the Lower Cretaceous Maracangalha Formation, Recôncavo Basin, NE Brazil. Qualitative and quantitative analysis of the organic particles, as well as grouping analysis based on the characteristics of the particles found, were conducted to establish the present database. The organic particles were grouped into amorphous organic matter (AOM); opaque phytoclasts; non-opaque phytoclasts and palynomorphs and four distinct palynofacies were recognized. The palynofacies I (P I), present in the Praia da Falha outcrop, is composed of a high abundance of non-opaque phytoclasts (51.22%), followed by palynomorphs (23.61%). The palynofacies II (P II), occurring in the Penha outcrop, shows a high abundance of non-opaque phytoclasts (71.67%), followed by opaque phytoclasts (12%). The palynofacies III (P III), occurring in the Manguinhos outcrop, consists of a high abundance of AOM (48.07%), followed by opaque phytoclasts (32,6%). The palynofacies IV (P IV), occurring in the Gameleira outcrop, also has a high abundance of AOM (47.05%), followed by non-opaque phytoclasts (28.76%). According to the associations of sedimentary organic matter, essentially represented by particles of continental origin, a lacustrine setting is well characterized, corroborating what has been previously suggested in the literature. The palynofacies interpretation also indicates deposition strongly controlled by fluvio-deltaic input. Overall, the Praia da Falha and Penha outcrops suggest proximity to the depositional source in a high-energy environment. In these localities, the predominance of non-opaque phytoclasts indicates deposition under oxic conditions probably near the lake shore. On the other hand, in the Gameleira and Manguinhos outcrops, the predominance of AOM suggests deposition away from the sediment source in a more distal, low-energy environment, with prevalence of suboxic-to-anoxic conditions.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141853595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lithospheric structure of the Paraná, Chaco-Paraná, and Pantanal basins: Insights from ambient noise and earthquake-based surface wave tomography","authors":"","doi":"10.1016/j.jsames.2024.105048","DOIUrl":"10.1016/j.jsames.2024.105048","url":null,"abstract":"<div><p>To investigate the lithospheric seismic structure of southern South America beneath the Paraná, Chaco-Paraná, and Pantanal basins, we measure two distinct sets of dispersion curves of Rayleigh waves: the first corresponds to 25,986 phase velocity dispersion curves in the period range 5–50 s, extracted from cross-correlation of the ambient noise between pairs of stations and thus sensitive mainly to crustal structure; the second set is derived from group velocities extracted from earthquake recordings, resulting in 33,888 dispersion curves with periods ranging from 8 to 200 s, allowing us to probe deeper Earth structure. From these data sets, we derive two independent S-wave velocity models following a two-step inversion procedure, resulting in a crustal and a lithospheric mantle model with depths extending up to 50 and 200 km, respectively. Features imaged in our crustal model include low velocity anomalies in agreement with the surface position of the major sedimentary basins and high velocity anomalies within fold-thrust provinces and the basement of the Pantanal basin. In the uppermost mantle, we identify high velocities in the region of the Paraná basin, São Francisco and Amazonian cratons, and Luiz Alves block, and a low velocity feature beneath the Pantanal basin, which suggests a potentially thinner lithosphere under the basin. We also illuminate a strong velocity gradient boundary between the eastern border of the Pantanal basin with the Paraná basin, from crustal to lithospheric mantle depths, which seems to delineate the western and southern borders of the Paraná basin, coinciding with the Western Paraná Suture. Additionally, we construct a Moho depth proxy map for the study area, which has an overall good agreement with previous results, except for a thicker crust beneath the southern Chaco-Paraná basin. This area, together with a thicker crust counterpart in the Paraná basin, has a remarkable correlation with the position of a volcanic layer related to the Paraná Magmatic Province, which leads us to suggest that magmatic processes played an important role in the south Chaco-Paraná basin as well.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141848282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismotectonic and gravimetric analysis of the central Neuquén Basin","authors":"","doi":"10.1016/j.jsames.2024.105036","DOIUrl":"10.1016/j.jsames.2024.105036","url":null,"abstract":"<div><p>Understanding the seismotectonics in the foreland region of orogenic belts is crucial for several reasons. Firstly, it allows us to infer stress conditions and structural controls in distant orogenic areas. Secondly, because these regions are often densely populated, it becomes essential to assess the associated risks, hazards, and vulnerabilities. In this study, we investigate intraplate seismicity in the foreland region of the Neuquén Basin in the southern Central Andes. Our data were obtained from a local broadband seismic network and high-resolution gravimetric enhancement methods. We analysed three distinct sets of earthquakes associated with major subsurface structural features. We found that seismic events near the Añelo locality may be linked to anthropogenic causes, underscoring the importance of identifying active structures and understanding regional tectonics. The seismicity is mostly aligned with Mesozoic transfer zones, as well as a large laccolithic magmatic intrusion. Focal mechanisms and enhanced gravimetric methods further elucidate previously unidentified structural features related to seismicity and gravity gradients. Reactivation directions coincide with reported Andean E-W maximum stress orientations. To the south of Añelo, seismicity and gravity gradient patterns suggest lineaments within the Huincul System. Notably, NE-SW trending lineaments between 71<span><math><msup><mrow></mrow><mrow><mo>∘</mo></mrow></msup></math></span>W and 70<span><math><msup><mrow></mrow><mrow><mo>∘</mo></mrow></msup></math></span>W align with seismicity possibly associated with the Agrio fold and thrust belt, and the projection of the Valdivia Fracture Zone. At 70<span><math><msup><mrow></mrow><mrow><mo>∘</mo></mrow></msup></math></span>W, E-W trending lineaments correspond to seismic activity near the Chihuidos anticline and Cortaderas lineament. At 69<span><math><msup><mrow></mrow><mrow><mo>∘</mo></mrow></msup></math></span>W, a shorter NE-SW lineament coincides with clustered seismicity, the Añelo anticline, and an eastward shift of the deformation front. Lastly, ESE-WNW trending lineaments at 68<span><math><msup><mrow></mrow><mrow><mo>∘</mo></mrow></msup></math></span>W indicate structural rotations consistent with the complex Mesozoic Huincul System framework. From these results, we propose that the Huincul System exerts strong control over the structural character and seismotectonics of the central foreland region of the Neuquén Basin. This comprehensive analysis underscores the utility of integrating diverse geophysical methods for understanding intraplate seismicity and structural dynamics in foreland basin settings.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141929852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleoclimatic implications of a vascular plant from the lowermost Itararé Group","authors":"","doi":"10.1016/j.jsames.2024.105045","DOIUrl":"10.1016/j.jsames.2024.105045","url":null,"abstract":"<div><p>Plant fossils serve as critical proxies for interpreting past climates and environments, offering insights into the history of biosphere and climatic conditions. Here we describe a large tracheophyte cast, as well as the sedimentological settings in which it is preserved, expanding the paleobotanical database of the Itararé Group and contributing to the understanding of the LPIA in the Paraná Basin. This fossil occurs in Ponta Grossa, Paraná state, Brazil, within sedimentary levels interpreted as glacially dominated and deposited during the Late Paleozoic Ice Age (LPIA). The plant macrofossil is preserved as a cast, and the log is vertically oriented with a slight inclination in relation to the bedding plane. Taphonomic data indicate an allochthonous preservation, suggesting that the log was transported from inland areas to a plain before final burial. The identification of the tracheophyte cast within these glacial beds suggests that even in a dominantly glacial context, there were periods of episodic climatic amelioration. This finding implies that the climatic conditions during the Mississippian were not uniformly harsh, allowing the growth of vegetation as represented by the reported tracheophyta.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141929853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neogene isolated carbonate platform of the Rio Grande rise (southwest Atlantic ocean)","authors":"","doi":"10.1016/j.jsames.2024.105044","DOIUrl":"10.1016/j.jsames.2024.105044","url":null,"abstract":"<div><p>Isolated carbonate platform (ICP) deposits have been extensively studied due to their high sensitivity to sea-level variations and hydrocarbon reservoir potential. Oceanic seamounts/plateaus such as the Rio Grande Rise (RGR) off south-east Brazil, are significant sites for investigating drowned ICPs, as they record the existence of former oceanic volcanic islands. The Geological Survey of Brazil dredged hundreds of samples from the RGR summit, comprising a condensed section with phosphatization, ferromanganese (Fe–Mn) crusts, and associated carbonate rocks. Our study investigates the sedimentary facies of carbonate substrate rocks collected from the borders of the Cruzeiro do Sul Lineament of RGR. Eight facies were identified: Planktonic foraminifera mudstone (Pfm), Planktonic foraminifera wackstone (Pfw), Bioclastic wackstone (Bw), Red algae packstone (Rp), Red algae grainstone (Rg), Foraminifera grainstone (Fg), Red algae bindstone (Rb), and Bioclastic rudstone (Br). Based on facies descriptions and fossil index ages, a paleoenvironmental reconstruction was proposed, indicating the development of a carbonate isolated platform during tectonic quiescence in the Oligocene-Miocene associated with a volcanic island that emerged during the RGR exposure in the Eocene. These deposits likely represent a weakly protected carbonate platform featuring a lagoon associated with barrier coralgal reefs, algal shoals, and patch reefs. A semi-drowning phase during the Pliocene-Pleistocene, characterized by the strong influence of ocean currents and deposition of mixed planktonic and shallow carbonate particles, ensued until complete drowning in the Pleistocene-Recent, marked by pelagic/reworked sedimentation. Platform shrinking and cessation may correlate with the Miocene onset of modern carbonate platforms influenced by currents, leading to the present-day substrate composed of carbonate and Fe–Mn duricrust covered by dunes of winnowed pelagic particles. The RGR's former ICP resembles the south-west Atlantic islands/atolls.</p></div>","PeriodicalId":50047,"journal":{"name":"Journal of South American Earth Sciences","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141847544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}