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The International Symposium on Andean Geodynamics (ISAG) is an international conference that was held, on average, every 3–4 years in different European cities between 1990 (Grenoble) and 2008 (Nice). These symposia usually offer an opportunity for researchers from Latin American countries and Europe as well as other countries to review the state of knowledge in geosciences on the Andes. After a long period without an edition, the 8th ISAG was organized for the first time in a Latin American country, Ecuador, from 24th to 26th September 2019. The organizing committee led by Pablo Samaniego relied heavily on the Instituto Geofísico of the Escuela Politécnica Nacional (IG-EPN) and the Institut de Recherche pour le Développement (IRD), in particular through its office in Quito, and through the Laboratoire Mixte International in France and Ecuador: "Seismes et Volcans dans les Andes du Nord" (LMI-SVAN); and the French Embassy in Ecuador. Field trips in tectonics, seismotectonics and volcanology at emblematic sites in Ecuador were organized by researchers from the IRD (Isterre and LMV), the Institut de Radio Protection Nucléaire (IRSN), IG-EPN and the University of Geneva. Four invited speakers gave presentations: Peter Molnar (University of Boulder) on the mechanisms of the Andes uplift, Suzanne Kay (Cornell University) on its magmatism, Victor Ramos (University of Buenos Aires) on the scientific approaches developed through time for the Andean orogeny and Eric Calais (Ecole Normale Supérieure de Paris) on the difficulty of dialog between seismic risk specialists and the authorities in Haiti. The symposium also provided an opportunity for more than 250 participants to meet, with more than 80 oral presentations and over 150 posters. As a result of this conference, the Editor of the Journal of South American Earth Sciences proposed to the organizing committee to publish a special issue on the contours of these presentations. Following the peer review process, 19 papers are published in this special issue. These manuscripts reflect the various disciplinary fields, geophysics and deep imaging, tectonics, volcanism, geomorphology and seismic hazard, from the local scale to the Andes as a whole. Not surprisingly, a higher density of works is found in Ecuador and the northern Andes (Figure 1). As this collection of articles reflects the outlines of a symposium and not a specific scientific question, our aim here is not to develop a synthesis of current knowledge on the Andes. We therefore present these articles in sequence, by discipline, although this categorization may appear subjective since some articles are multidisciplinary. [ABSTRACT FROM AUTHOR]

Villaseñor and Olóriz (2019) present a comprehensive review of latest Jurassic to earliest Cretaceous ammonites from Mexico, which previously were ascribed to the genus Kossmatia , and provides evidence that these fossils should be referred to other genera. However, descriptions of two new genera provided by Villaseñor and Olóriz (Burckhardtieia and Aguilerites) are lacking indication of their type species that make these genera unavailable following to ICZN articles 13.3 and 67.4.1. Discussed paper also includes figures of the new species Burckhardtieia westermanni , which is lacking formal description, although illustrated by few figures and its holotype is clearly indicated. The genus Burckhardtieia Villasenor and Oloriz can be considered as a junior synonym of the genus Fierrites Cantu Chapa. The latter genus is suggested to be invalid by Villaseñor and Olóriz (2019), but without strong background in support of this statement. Here the author is follow the proposal by Enay (2009) and consider the genus Fierrites as a correct name, which can be used for all American " Kossmatia ". Discussed article is also lacking detailed biostratigraphic data concerning the range of the Burckhardtieia , although clear indication of its range (and ranges of species included in this taxon) seems to be necessary. [ABSTRACT FROM AUTHOR]

M. Rogov refers to [5], Treatise Online) to accept Fierrites as proper name for American "Kossmatia", following these authors without any other argumentation to add to the brief text of [5], Treatise Online). Unfortunately, neither [5] nor [13] became aware from their respective contributions, but the occurrence of Mexican "Kossmatia" in Lower Tithonian horizons is known since [8], as reported in [12], [13] but overlooked by M. Rogov. Concerning the first formal mention to the new taxon Buckhardtieia gen. nov. in [13], p. 12), it was preceded by the precise revision, with citations, of all the available information about topics related to the use of genus Kossmatia elsewhere and, especially, in Mexico. [Extracted from the article]

In their paper: U–Pb geochronology of intrusive rocks of northwestern Mesa Central province and Sector Transversal of Sierra Madre Oriental, Mexico: Time and space distribution of inland Cretaceous-Paleogene magmatism during the Mexican orogeny, Díaz-Bravo et al. (2022) present a database of geochronological ages reported in literature and seven generated by themselves, with which they adapt a model of flat-slab subduction to explain the geographical distribution of the Cretaceous-Paleogene magmatism in north-central Mexico. In our opinion, the paper contains limited bibliographic documentation, since it omits previously published zircon U–Pb ages, whose relationship with the Mexican orogeny has been discussed in several previously published papers. Furthermore, an important approach on the distribution of plutons is that the effects of contractional deformation during pluton emplacement and younger extensional tectonics in the studied area were not evaluated. We propose that the syntectonic relationships with the Mexican Orogeny for some of the plutons imply that the magmas were emplaced in rocks undergoing shortening and eastward-NE translation during the development of the Mexican fold and thrust belt. Therefore, they are not in their original position and must be carefully studied to establish the magmatic model presented in this work. • The Cretaceous plutons in the Mesa Central and Sector Transversal of the Sierra Madre Oriental are syntectonic to the development of the Mexican Fold and Thrust Belt. • The Cretaceous syntectonic plutons are allochthonous, so they do not represent a fixed position to model the subduction angle of the Farallon plate. • Pico de Teyra and El Peñuelo plutons show evidence of mylonitic recrystallization, S-C structures, and cleavage, congruent with northeastward tectonic transport of the Mexican Fold and Thrust Belt. [ABSTRACT FROM AUTHOR]

Climate change has increased the frequency of extreme weather events and, consequently, the number of occurrences of natural disasters. In Brazil, among these disasters, floods, flash floods, and landslides account for the highest number of deaths, the latter being the most lethal. Bearing in mind the importance of monitoring areas susceptible to disasters, the REMADEN/REDEGEO project of the National Center for Monitoring and Natural Disaster Alerts (Cemaden) has promoted the installation of a network of soil moisture sensors in regions with a long history of landslides. This network was used in the present paper as a base to develop a system for moisture forecasting in those critical zones. The time series of rainfall and moisture were used in an inversion algorithm to obtain the geotechnical parameters of the soil. Then the geotechnical model was used in a forward calculation with the rainfall prediction to obtain the soil moisture forecast. The landslide events of March 2020 and May 2022 in Guarujá and Recife, respectively, were used as study cases for the developed system. The obtained results indicate that the proposed methodology has the potential to be used as an important tool in the decision-making process for issuing landslide alerts. • This paper presents a novel system aimed at predicting soil moisture conditions based on rainfall forecast data. [ABSTRACT FROM AUTHOR]

Alkaline rocks of prevailing sodic composition form major ring complexes and stocks along a seismically active N–S structural lineament parallel to the Paraguay river course. All these occurrences are encompassed by the Alto Paraguay Province, their rocks corresponding to the oldest known alkaline magmatic activity in the Paraná Basin, with a Middle Triassic age of 241.5 ± 1.3 Ma. Intrusive rocks ranging from silica-undersaturated (nepheline and/or sodalite syenites) to silica-oversaturated (quartz syenites and alkali granites) and their fine-grained counterparts constitute the most abundant rock-types. Clinopyroxenes, associated amphiboles and varying amounts of biotite are the main mafic minerals present. Alkali feldspar (mainly mesoperthites and subordinate sanidine and anorthoclase) and feldspathoids (nepheline and/or sodalite) are widespread. A late-stage magmatic to metasomatic/deuteric mineral assemblage is mostly typical of miaskitic to agpaitic rocks of the Cerro Boggiani complex, whereas rare accessory silicate minerals are found in peralkaline syenites of the Cerro Siete Cabezas major intrusion. Positive Nb–Ta and Zr–Hf anomalies and negative Sr, P, and Ti spikes are common features to the whole province. REE behavior shows enrichment in LREE and strong LREE/HREE fractionation with various parallel subtrends. This paper addresses petrological aspects of the origin and evolution of these alkaline rocks. • The paper reviews knowledge about the Alto Paraguay Alkaline Province (border between Brazil and Paraguay). • The main rock types vary from undersaturated (nepheline and sodalite syenites) to silica-oversaturated (quartz syenites and alkali granites) and their fine-grained equivalents. • The intrusion of the alkaline bodies took place along an N–S-oriented structure that marks the boundary of the Pampia and Rio Apa cratonic blocks. • The rocks are dated from the Middle Triassic and constitute the oldest alkaline magmatic event on the edge of the Paraná Basin. [ABSTRACT FROM AUTHOR]

Cetina et al. (2019) presented new geochronological, geochemical and isotopic data obtained from volcanic and sub-volcanic rocks exposed in the northern segment of the Western Cordillera of Colombia, which are interpreted as related to a Cretaceous island arc-plateau system. These data are used to come up with a paleogeographic model for the circum-Caribbean realm that may account for the presence of old (Paleozoic – Proterozoic) xenocrystic zircons in the analyzed units. Nevertheless, the authors ignored previously published geological, geochemical, geochronological, thermochronological and provenance constraints from Cretaceous rocks of northwestern Colombia, which refuse the plausibility of their proposed models. Particularly, the occurrence of Cretaceous subduction-related metamorphism, magmatism and construction of marginal sedimentary basins, documented by several published papers in the last decade, renders the paleogeographic reconstructions of Cetina et al. (2019) to be unlikely. We demonstrate that when considering the ignored geological evidences, alternative explanations for the origin of pre-Mesozoic xenocrystic zircons are required. • We comment the recently published paper by Cetina et al. (2019). • Several ignored geological evidences are recalled and discussed. • Paleogeographic models of Cetina et al. (2019) are not plausible. • Alternative explanations for the origin of pre-Mesozoic xenocrystic zircons are required. [ABSTRACT FROM AUTHOR]

One of the challenges in the unification of the global vertical datum is to determine the vertical offset between the local vertical datum and the global vertical datum. Since 2015, the scientific community has been working on the unification of the global vertical datum, following the publication of the resolution for the definition and realization of an International Height Reference System. This paper aims to estimate the vertical offset in Brazil (Imbituba and Santana Data) by combining a regional gravity field model, using the Geodetic Boundary Value Problem approach applying the Remove-Compute-Restore procedure, and GNSS/leveling data. In the Imbituba vertical datum 1271 stations were used and 66 stations were connected to the Santana tide gauge. The results showed that the geopotential value of Imbituba was 62,636,849.87 ± 0.224 m2s-2, and the vertical offset concerning the reference surface (W 0) was 0.358 ± 0.023 m. In Santana, the geopotential value was 62,636,836.88 ± 4.108 m2s-2, and the vertical offset was 1.689 ± 0.420 m. The offset between Imbituba and Santana was computed once the physical connection between Brazil's two local vertical data is a challenge. The estimated value was 1.331 ± 0.421 m. This means the Santana vertical datum is 1.331 m higher than the Imbituba vertical datum. • Improving the Brazilian height system. • Using GNSS/leveling data to estimate the vertical offset in Brazil. • Connecting the Brazilian local vertical data to the International Height Reference Frame. [ABSTRACT FROM AUTHOR]

Turritelline gastropod-dominated assemblages (TDAs) are common in siliciclastic facies from the mid-Cretaceous to the Recent, but their distribution in carbonate facies has been thought to be limited to the Cretaceous and Paleogene, except for "cool-water" carbonates from the Miocene of Australia. This paper describes a TDA in a Pliocene limestone in northern Chile, the only known Neogene TDA limestone from outside Australia. This Chilean TDA probably formed in conditions of relative low temperatures and high productivity, and thus appears to support the hypothesis that TDAs largely disappeared from warm waters after the Oligocene. It is also possible, however, that it formed in conditions of warmer temperatures associated with upwelling during the Early Pliocene warm interval. • A turritelline gastropod-dominated assemblage from Chile is Early or Late Pliocene. • The limestone assemblage is a rarity in the Neogene, when most are in siliciclastics. • The assemblage formed under high-productivity conditions. • If Late Pliocene, conditions were cool water upwelling, unusual for a limestone. • If Early Pliocene, they were non-uniformitarian warm water upwelling in a warm ocean. [ABSTRACT FROM AUTHOR]

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 Afonso Cláudio Intrusive Complex (ACIC) is a typical post-collisional intrusion from Araçuaí-West Congo orogen (AWCO). The ACIC intruded allanite-bearing orthogneisses from AWCO pre-collisional tectonic stage (Rio Doce arc related rocks) and paragneisses from Nova Venécia Complex and it is composed of two lowered off-centered monzogabbroic and monzodioritic cores surrounded by quartz monzonite high hills, showing intense magma mingling and mixing between these domains. Xenoliths attributed to the enclosing gneisses have been commonly found widespread in the quartz monzonitic rocks, while are occasional in the monzogabbroic and monzodioritic domain. This paper presents the first detailed investigation of the xenoliths hosted by an AWCO post-collisional intrusion, focusing on petrography, major and trace element geochemistry and U–Th–Pb monazite dating of the main xenolith types. For comparison, major and trace element data investigation of the ACIC enclosing rocks has also been conducted. The correlated xenoliths and ACIC enclosing rocks show partially similar geochemical features, however both show different REE and multi-element normalized patterns compared to the ACIC main rocks. These results suggest that correlated xenoliths and enclosing rocks are cogenetic, however both could not represent the main sources of magmas that generated the ACIC. Geochemical modeling of igneous processes of previous ACIC dataset considering the investigated xenoliths and enclosing rocks as the main assimilant material suggests that mixing was responsible for both ACIC main rocks similar geochemical patterns and linear trends in the bimodal diagrams. This modeling also indicates that the evolution of the ACIC main rocks was ruled by different processes. Fractional crystallization with minor influence of assimilation of enclosing rocks controlled the magmatic evolution of monzogabbro and monzodiorite related to an enriched mantle source, while coupled assimilation and fractional crystallization ruled the evolution of quartz monzonite possibly associated to lower crust magmas mainly contaminated by enclosing rocks. U–Th–Pb monazite dating of two xenoliths showed that these rocks preserved similar main ages related to different stages of ACIC and AWCO post-collisional evolution. Both xenoliths showed main older ages of 478 and 477 Ma which are related to ACIC intrusion during AWCO post-collisional stage, while younger ages of 431 and 427 Ma are probably related to the intrusion of syenogranite dykes that crosscut the ACIC, representing an extension of AWCO post-collisional magmatism or a later unrelated thermal event. Due to the similarities between the typical AWCO post-collisional intrusions, the insights brought about the evolution of ACIC magmas could be considered to the typical AWCO post-collisional mantle and crustal magmas. This first investigation of xenoliths hosted by an AWCO post-collisional intrusion has showed that these strange rock pieces could bring new and important insights about the AWCO evolution, which shows an amazing and long-lasting magmatism with common occurrence of poorly investigated xenoliths. • The ACIC is formed by the interaction between mantle and crustal contrasting magmas. • The contrasting magmas evolved ruled by different processes. • Assimilation of enclosing country rocks is an important process in ACIC evolution. • The xenoliths preserved two main ages related to ACIC and AWCO evolution. [ABSTRACT FROM AUTHOR]

Fossils from natural tanks can contribute to the paleoenvironmental interpretation of the Brazilian Intertropical Region (BIR), an important study area for the Quaternary in South America. In this paper we present results of δ13C and δ18O for Eremotherium laurillardi (δ13C = −4.6 ‰, δ18O = 33.0 ‰), Toxodon platensis (δ13C = −3.8 ‰, δ18O = 35.5 ‰), and Notiomastodon platensis (δ13C = −2.9 ‰, δ18O = 31.6 ‰) from Zabelê tank, compared to other localities, suggesting that these taxa had a mixed-feeder diet with a higher consumption of C 4 plants (p i > 60%), living in a transition zone between woodland savannah and open savannah. The Zabelê tank, northeastern Brazil, presents Optically Stimulated Luminescence ages ranging from 41.2 to 30.4 ky (Lujanian Stage/Age; Late Pleistocene). The origin of the fossiliferous layer through debris flow suggests short periods of intense rainfall under drier climatic conditions. Compared to other locations in the BIR, Zabelê documented a drier climate (δ18O = 31.6–33.4 ‰), which preceded the last glacial maximum. These new isotopic data to OSL ages associated with previous data from the BIR contribute to the understanding of the paleoecology and paleoenvironment dynamics of South America. • New δ13C and δ18O for the three most studied taxa from the Quaternary of the BIR. • These taxa had a mixed-feeder diet with higher consumption of C 4 grasses. • These taxa inhabited a transition zone between arboreal to open savanna. [ABSTRACT FROM AUTHOR]

The Salares Norte (SN) Au–Ag belt is here defined as an Upper Miocene-Pliocene metallogenic area, extending for nearly 200 km, located NE of the northern end of the Upper Oligocene-Lower Miocene Maricunga Belt in the central Andes of northern Chile. The belt is located just east of the main reverse NS fault systems which are part of the Sierra Castillo, Potrerillos Mine and Claudio Gay Cordillera faults, limited to the north and south by the NW-striking oblique to the arc Imilac and Wheelwright-Incahuasi regional faults systems. The epithermal deposits within the SN belt are intimately associated with the occurrence of Middle Miocene volcaniclastic basins and Middle to Upper Miocene phreatomagmatic vents and their related high-sulfidation hydrothermal systems. The volcanostratigraphy of the SN epithermal belt comprises volcaniclastic sequences, subvolcanic and volcanic rocks ranging between the Lower Miocene and the Pliocene. High-angle NS reverse faults involving Paleozoic and lower Cenozoic units form the western-southwestern limit of the belt. Folded and faulted Middle Miocene volcaniclastic and volcanic sequences form the main host rock of at least 4 phreatomagmatic events that generated maar-diatreme fields and discrete maar vents, with their related subvolcanic facies, within the widespread Upper Cenozoic volcanic arc, ranging in age between ca. 15 and ca. 4 Ma. These four phreatomagmatic events are spatially and temporarily associated to 4 main high-sulfidation hydrothermal events which have altered both the phreatomagmatic rocks and the Cenozoic country rock of the explosive activity. These hydrothermal systems have formed dozens of discrete hydrothermally altered areas where argillic, advance argillic, silicification and steam-heated alteration are common. Most of the maar fields and the hydrothermal alteration systems are emplaced within a strike-slip tectonic regime with NE-trending shortening which is accommodated in the NW-striking sinistral-normal faults and NE-striking extension structures. These fault systems crosscutting interaction favor the hydrothermal fluid circulation and migration, as well as mineral precipitation on structural and/or primary lithological traps and on NE-striking tension cracks. In summary, the SN epithermal belt is an almost 200 km long and 60 km wide area, mainly NNE-oriented, where epithermal deposits have formed during the Upper Miocene and Pliocene (ca. 13-4 Ma), emplaced within Middle to Upper Miocene volcanic and volcaniclastic sequences associated to small volcanotectonic basins oriented in NS, NE-SW and NW-SE directions, in which most of the high-sulfidation systems are associated to discrete or repetitive structurally-controlled Upper Miocene-Pliocene phreatomagmatic vents and maar fields. • This paper defines a new Au–Ag epithermal belt in the Central Andes of northern Chile. • Novel results in terms of age, volcanic stratigraphyand hydrothermal alteration. • The relationships between Upper Cenozoic HS epithermal areas, local tectonics and phreatomagmatic volcanism are discussed. [ABSTRACT FROM AUTHOR]

This paper presents sedimentological, stratigraphic, and palynological data from borehole PBAT-15-43, in which a 230 m long continuous core was sampled in the central portion of the Amazonas Basin, where it was possible to define the contact relationship between Paleozoic deposits of the Andirá and Arari Formations (Tapajós Group). The drilling hole is located in the southern portion of the municipality of Autazes (Amazonas State) and was made available by the Potássio do Brasil Company. Six sedimentary facies were identified in the borehole and grouped into two associations, informally referred to as I and II, representing the Andirá (upper part) and Arari (lower part) formations, respectively. Association I was interpreted as a fluvial environment with channel deposits, flood barriers, and crevasses splay. Association II, on the other hand, represents an alluvial fan environment with predominantly gravitational flow deposits. The facies of association II proved to be sterile for palynomorphs, whereas facies I contain a rich palynoflora, including especially the species Lueckisporites virkkiae , Corisaccites alutas , Hamiapollenites andiraensis , H. karooensis , Vittatina costabilis , V. saccata , V. subsaccata , and Tornopollenites toreutos ; secondarily by species of the genera Punctatisporites , Verrucosisporites , Limitisporites , Cycadopites and Stratopodocarpites , which are considered as belonging to the Permian age. The fact that no marine palynomorphs were detected supports the present interpretations regarding the age and the depositional environments previously predicted for these formations as predominantly fluvial deposits. • Sedimentological, stratigraphic, and palynological data from the central portion of the Amazonas Basin-Tapajós Group. • Six sedimentary facies were identified and grouped into two associations. • Arari Formation - Association I represent a fluvial environment with channel deposits, flood barriers, and crevasses splay. • Andirá Formation - Association II represents an alluvial fan environment with predominantly gravitational flow deposits. • Identification of the Tornopollenites toreutos palynozone Upper Permian in age. [ABSTRACT FROM AUTHOR]

Magnetotelluric (MT) data from 49 broadband and 23 long period stations, covering periods between 10−3 and 104 s, were measured along a NNW-SSE profile of approximately 470 km, crossing the Parnaíba Basin, Borborema Province and São Francisco Craton in northeastern Brazil. The geotectonic scenario of the study region comprehends a complex structural framework formed during the Brasiliano orogenic collage. The MT data were processed to obtain the impedance tensor estimates for each MT site using a robust technique and then followed by a dimensional analysis via both the rotational invariants (WAL invariants) of the magnetotelluric tensor and the phase tensor. The two approaches indicated a three-dimensional nature of the region, allowing to proceed to 3D inversion, despite the data distribution along a profile. Several inversion trials of the full impedance tensor, tipper and tipper combined with impedance tensor resulted in a final 3D resistivity model, which suggests a division of the profile into three major zones. A sub horizontal resistive crustal block, interpreted as being part of the Parnaíba block, characterizes the western zone. A mosaic of resistive and conductive zones, which integrates the extended fold belt of the Borborema Province, composes the central zone. In the interface between the central and the eastern zones, there is a sub vertical conductive region limiting two resistive blocks, interpreted as a suture zone. This suture divides tectonic provinces and is supposed to be related with a Neoproterozoic collisional system. The 3D MT imaging recovered the structural framework under the Parnaiba Basin and marked the main lineaments. The paper suggests a distinct tectonic evolution for the complex assemblage of blocks in Northeast Brazil. • The 3D MT imaging allowed drawing a crustal model that recovers existing structures in great depth along the study region. • The 3D MT imaging recovered the structural framework under the Parnaiba Basin and marked the main lineaments. • The paper suggests a distinct tectonic evolution for the complex assemblage of blocks in Northeast Brazil. [ABSTRACT FROM AUTHOR]

Abstract This paper explores microbially induced sedimentary structures (MISS) preserved in Late Paleozoic Ice Age deposits to evaluate the potential microbe-substrate physical interactions in ancient glacial settings. MISS have been recorded worldwide in different modern and ancient settings, mostly in tidal flats. However, their record in ancient glacial settings is still underrepresented. The reported MISS are preserved in the siltstone-claystone glacigenic rhythmites in Trombudo Central region of the Rio do Sul Formation (Paraná Basin, Pennsylvanian, southern Brazil). The recorded structures in these deposits are composed of wrinkle structures, dome structures, mat fragments, mat microfabrics, sinoidal structures, laminated leveling structures, oriented grains and mat-layer bound small grains, kinneyia structure, discoidal microbial colony, elongated filaments, and drab-haloed filaments. They represent the development of endobenthic and epibenthic microbial mats, as well as microbial earths. Endobenthic mat structures predominate in the siltstone beds, suggesting less time for development of microbial mat during deglaciation events and meltwater input. Epibenthic mat structures preserved in the claystone layers indicate episodic quiescence periods that allowed the mat achieve maturity and that cyanobacteria and sulfate-reducing bacteria composed a significant part of the microbial community. The set of MISS observed in the studied rhythmites have been commonly reported in tidal settings, and the presence of microbial earths structures indicate periods of drainage of the water bodies, at least partially. Thus, the microbial communities played an important role in ancient glacial settings during climatic amelioration periods, opening the colonization window for macroorganisms in outwash plains and marginal marine settings. This paper provides a characterization of different sorts of preserved MISS, and evaluate the physical interactions between microbial mats and the substrate, in the ancient glacigenic deposits from the Itararé Group. Highlights • Preserved MISS in glacigenic rhythmites of Pennsylvanian Paraná Basin in southern Brazil. • Preserved records represent the development of endobenthic and epibenthic microbial mats, as well as microbial earths. • The microbial communities enhancing the colonization window for macroorganisms during climatic amelioration periods. [ABSTRACT FROM AUTHOR]

Abstract The Dom Feliciano Belt (DFB), part of the Mantiqueira Province in southern Brazil and Uruguay, results from multiple Neoproterozoic collisions leading to the construction of the Gondwana supercontinent. Therefore, complex structural relations are expected, as it is the case for the Porongos Metamorphic Complex (PMC) and Várzea do Capivarita Complex (VCC). Several papers have described structural features from both complexes, and some evolution models were proposed for them. However, very few papers have tried to correlate them, and recent geochronological and provenance studies carried out in both complexes pointed out some inconsistencies in these models. Such studies demonstrate that part of the protoliths of metasedimentary and metaigneous rocks of PMC and VCC, of different metamorphic grades, could have been deposited in the same sedimentary environment. The geological meaning of such data is still poorly explained and requires a better understanding of the original geometrical relations between PMC and VCC. This paper focuses on the metavolcanic rocks from two subareas near the northeastern tip of the Porongos Metamorphic Complex area, and on the previously published data for the VCC. In order to investigate the structural and kinematic history of this part of PMC, detailed structural mapping, petrography, whole-rock and mineral chemistry studies were carried out in selected subareas. Metavolcanic rocks from Subarea 1 and Subarea 2 are metadacites and metarhyolites bearing a geochemical imprint of arc magmatism at ca. 790 Ma. Structural investigation of the area reveals that the main deformation phase D 1 is mostly compressive and reached the metamorphic peak at amphibolite facies conditions. D 2 and D 3 are late deformation phases which develop open folds and axial plane cleavages. The most conspicuous D 1 structure is an alternation of non-mylonitic S 1 and mylonitic-S 1 , developed over an originally horizontal foliation, which suggests strain concentration in sub-horizontal shear zones interpreted as related to a fold and thrust belt evolution. The scattering of stretching lineation (L 1) measurements along a great circle in stereoplots is interpreted to result from shearing along S 1 planes, similar to what is described for the progressive deformation of VCC nearby. The present dataset supports the interpretation that PMC and VCC have shared a single volcano-sedimentary basin which subsequently achieved different crustal levels. A W-directed collisional event at 650 Ma metamorphosed the rocks and generated thrust-folds in both complexes. As indicated by recent studies in the local literature, deformed metavolcanics rocks of ca. 578 Ma magmatic age form concordant sheets in the PMC. Such data suggest a metamorphic-deformational event younger than ca. 578 Ma, which, in our view, is probably related to the reactivation of the contractional structures generated at ca. 650 Ma. This younger event must have folded the eastern part of the PMC generating shallow-level folds, and thrusted the rocks onto the eastern side to place them on top of the PMC western-side rocks. Thus, it is possible that PMC rocks register two thrusting episodes, one during peak metamorphic conditions (ca. 650 Ma) and one under retrograde metamorphic conditions (ca. 578 Ma). Graphical abstract Image 1 Highlights • Studied metavolcanic rocks bearing a geochemical inprint of arc magmatism. • Three deformations phases affected the studied rocks. • Two contractional stage occurred in the Porongos Metamorphic Complex. • The studied rocks reached the metamorphic peak at amphibolite facies conditions. • Porongos and Várzea do Capivarita Complexes possibly shared a single basin. [ABSTRACT FROM AUTHOR]

Due to its high efficiency and zero direct greenhouse gas emissions, the direct utilization of geothermal energy could play a crucial role in addressing climate change. Low-enthalpy geothermal projects, such as geothermal heat pumps (GHPs), have the potential to contribute to greenhouse gases reduction and replace polluting systems like wood burning, which are extensively used in countries such as Chile. The implementation of this technology presents various challenges, encompassing not only economic and technical aspects but also cultural and social factors. This paper addresses the latter two, providing empirical findings from a social and qualitative perspective by examining three GHP projects in educational spaces in Chilean Patagonia. An inductive approach was employed to describe the social perception of GHP projects in three public buildings, specifically educational facilities, located in the Aysén region of Chile. The questions that guided the research were how users interact with technology in these environments and what factors influence their acceptance. Data were collected through various methods, including in-depth interviews and participant observation, with a focus on social perceptions and everyday practices. The paper argues that there is a general lack of information regarding GHP technology. This type of system is often perceived as an 'elegant' and almost 'untouchable' technology. Nevertheless, motivational factors such as preventing deforestation and reducing air pollution were identified as the primary drivers supporting this type of initiative. One of the cases studied, which demonstrated sustainability over time, revealed that the participants' main motivation was to see themselves as agents of change. This allowed them to build a coherent narrative around the project. Consequently, the cultural meaning attached to the new practice became central for change and sustained adoption of social practices. • There is a social distance between GHP technology and local communities. • There is a low level of information about geothermal energy. • Sustainable adoption of GHP requires cultural and social changes. • GHP projects require the development of new skills and monitoring activities. [ABSTRACT FROM AUTHOR]

This work presents a comment on the paper "Spatio-temporal analysis of shoreline changes and future forecast using remote sensing, GIS and Kalman filter model: A case study of Rio de Janeiro, Brazil". Results obtained by Palanisamy et al. (2023) differ from other works on the coastline of Rio de Janeiro. Images from the Landsat 1–3 Multispectral Scanner (MSS) satellite and Landsat 5–9 images were inappropriately used in the detailing to delimit the shoreline variations. The lack of information about tides and waves at the time of image acquisition compromised the research results. Oceanographic - meteorological data relating to the month, day and time of the satellite's passage are fundamental in studies of this nature. These forcings are capable of temporarily modifying the morphology and position of coastline. The article proposed by Palanisamy et al. (2023) underestimated the rates of accretion and coastal erosion along the coastline of Rio de Janeiro city by neglecting the issues addressed here. • Results obtained by Palanisamy et al. (2023)on the shoreline variations in Rio de Janeiro city are questioned here. • Methodological procedures used to delimit the historical shoreline variations of Rio de Janeiro city presented inconsistencies. • Results obtained by Palanisamy et al. (2023) on the shoreline of Rio de Janeiro city are incompatibles with other work carried out in the study area. • Comments presented here aim to contribute to the evolution of knowledge about the coastal erosion process (geological hazard) on the shoreline of Rio de Janeiro - Brazil. [ABSTRACT FROM AUTHOR]

The La Rinconada Terrane comprises the core of Margarita Island, Venezuela; it is a composite unit composed of rocks of both continental and oceanic affinity that were brought together and metamorphosed at high-pressure and low- to medium-temperature conditions in a collision zone along NW South America in Albian to Cenomanian time. Details of the ensuing three-stage exhumation path and concomitant eastward translation until Miocene oblique collision of Margarita with central and eastern Venezuela have remained the subject of discussion. In this paper we integrate the results of published age dating and the details of extensive Rb-Sr, K-Ar, 40Ar/39Ar and fission track dating that have been only superficially presented to date. Initial exhumation from high-pressure conditions into ductile mid-crustal levels occurred at 90-80 Ma, followed by essentially isobaric, isothermal conditions for ca. 30 Myr during which the La Rinconada Terrane was subjected to continual ductile penetrative shearing and recrystallization. Partial to total recrystallization with concomitant partial to total isotopic re-equilibration, especially of quartz-rich rocks, was widespread during this time interval. The youngest Rb-Sr, K-Ar and 40Ar/39Ar ages cluster at ca. 50 Ma. Zircon fission track ages of 50–40 Ma corroborate exhumation into brittle levels of the crust at this time. An apatite fission track age of 23 Ma indicates the attainment of shallow depths in Miocene time. This discontinuous history of exhumation fits tectonic models of the Caribbean well. As the Caribbean Plate led by the Antilles Arc entered the gap between the Americas, strongly dextral, transpressive subduction in the SE Caribbean drove shear deep within the forearc. The La Rinconada Terrane of Margarita was exhumed to mid-crustal depths in the Late Cretaceous and is suggested to have occupied high-angle forearc shear zones above the primary Benioff Plane. As the arc migrated past the Guajira promontory and became extensional due to roll-back of Proto-Caribbean oceanic crust north of the Falcón re-entrant of the South American margin, the La Rinconada Terrane formed the footwall of an Eocene lithospheric rift that opened by late Eocene into the Grenada (oceanic intra-arc) Basin, effecting exhumation into the brittle crust. The progressive obduction of the SE Caribbean Plate onto the South American continental margin during prolonged dextral oblique collision completed most of Margarita's exhumation history by middle Miocene time (17–12 Ma). [Display omitted] • High-pressure rocks of Margarita show a discontinuous 70 Myr exhumation path. • Rb-Sr, K-Ar, 40Ar/39Ar, zircon/apatite fission-track data allow sequential tracking. • A 20–30 Myr mid-crustal hiatus is marked by strong ductile penetrative shearing. • Shearing causes partial/total isotopic resetting/recrystallization of many rocks. • Exhumation path correlates well with Caribbean tectonic history. [ABSTRACT FROM AUTHOR]

The Porteirinha Block (PB) provides an important record of the origin and evolution of South American crust. The PB records the generation of Paleoarchean TTG, Mesoarchean anatexis, and Paleoproterozoic crustal reworking. It is exposed as a basement inlier in the Araçuaí Orogen as a result of a tectonic involvement of the continental margins of São Francisco Congo Paleocontinent (PSFC) during the collisional processes of Gondwana amalgamation at the Neoproterozoic. The PB basement unit is the Porteirinha Complex (PC), which consists of TTG orthogneisses, migmatites, amphibolites, metaultramafics rocks and Neoarchean granitoids. In this paper, we discuss the evolution of the TTG orthogneisses and migmatites from PC based on field, geochronological and whole-rock geochemistry data. Zircon U–Pb ages (LA-ICP-MS) show a complex and polycyclic evolution of these rocks. Concordant ages were obtained for crystallization of TTG magma at ca. 3.4 Ga and the geochemical signature supports the idea of TTG generation by partial melting of hydrated mafic crust under garnet-amphibolite facies conditions. Zircon U–Pb ages also suggest crustal reworking events at 3.1 Ga. Metatexite and diatexite domains related to partial melting of TTG orthogneisses are individualized. The migmatites record processes of crustal anatexis and melt generation that occurred between 2.8 and 2.9 Ga (LA-ICP-MS, U–Pb in zircon) and are linked to crustal reworking and heat generation events recognized regionally. The new data presented in this work allow us to establish correlations between Archean and Paleoproterozoic units of the PB and those that occur regionally, particularly those related to Gavião block, where a series of stages and events of early crustal evolution are shared. • Archean crustal evolution of TTG orthogneisses from the São Francisco Congo Paleocontinent. • Zircon U–Pb geochronology shows igneous ages of 3.4 Ga for the precursor TTG magma of the Porteirinha Complex orthogneisses. • The orthogneisses show a typical TTG signature and were generated by partial melt of thickened lower crust. • Meso-Neoarchean crustal anatexis are recorded in metatexites and diatexites domains. • Successive stages of magmatism and crustal reworking have been identified since the Paleoarchean. [ABSTRACT FROM AUTHOR]

An approach involving data on wave-induced sediment transport estimates is essential for managing coastal environments. Numerical models are powerful tools to understand and investigate many processes responsible for longshore sediment transport (LST) in a systematic way, since direct measurement of LST is a difficult task. This paper presents estimates of longshore sediment transport through numerical modeling of wave-induced sediment dispersion patterns in the Formosa Bay, State of Rio de Janeiro - Southeast Brazil. The analysis was conducted using the computational package Coastal Modeling System/SMC-Brazil and mathematical formulations proposed by Cerc (1984). The results suggest average residual solid discharge (Qsr avg) in the order of 131,442.745 m3/yr in northern sector, −151,908.32 m3/yr in central sector, and 71,987.69 m3/yr in southern sector of investigated area. In addition, it is important to highlight that minor variations in the wave incidence angle may cause changes in the longshore sediment drift, promoting the convergence and divergence zones throughout the investigated area. The results presented contribute to the advancement of knowledge on the topic addressed here and will be useful in future engineering projects related to beach nourishment and the management of coastal areas subject to erosion processes. • Data are presented on simulations of wave-induced longshore sediment transport rates in Baia Formosa Bay, southeastern Brazil. • The Coastal Modeling System SMC/Brazil were used. • Results suggest different solid outflow rates for each sector of investigated area. • The model may provide a basis for planning actions and environmental management in coastal zones. [ABSTRACT FROM AUTHOR]

This work presents facies analysis of pyroclastic and effusive deposits present in areas of the Fernando de Noronha Archipelago (FNA), South Atlantic Ocean. A detailed stratigraphic study was carried out for the Remédios Formation at the Caieira beach and the Quixaba Formation at the Capim-Açu Edge, Americano, and Bode beaches. The lithofacies association for the deposits of the Remédios Formation characterizes non-welded ignimbrites of phonolitic composition generated by concentrated ground-hugging density currents originated from collapses of a buoyant eruption column. Possibly, this phase was followed by a caldera collapse and the exposition of a complex system of dikes at Caieira Beach. For the deposits of the Quixaba Formation, the lithofacies association characterizes scoria and ash flow/grain avalanching deposits, proximal fallout deposits, and Pahoehoe lava flows. The Quixaba volcanism shows evidence of pulses of Strombolian and possibly Violent Strombolian activity alternated with effusive Hawaiian activity. A later stage of magma-water interaction during the Quixaba volcanism led to the formation of a sustained eruption column and fallout deposits with ash aggregates formed through wet aggregation. This paper is the first ever written about aspects of the Physical volcanology of the Fernando de Noronha Archipelago, Brazil. It contributes to the understanding of the evolution of the volcanism that occurred in the Archipelago between ∼12 and ∼1.2 Ma, and of the South Atlantic Ocean. The conclusions of our study are: The stratigraphic study of specific areas of the Archipelago through field observations complemented with laboratory-based pyroclastic and lava flow descriptions allowed us to propose the following evolutionary model: • Explosive magmatic eruptions formed buoyant eruption columns that collapsed and originated ground-hugging concentrated density currents represented by the lithic-rich non-welded ignimbrites. • Volcanic and subvolcanic manifestations generated domes of phonolitic and trachytic composition; i) and ii) might be concurrent. Possibly this phase was followed by a caldera collapse with the exposition of a complex system of dikes at Caieira Beach. • A hiatus in the geological record of about 3 Ma, characterized as a period of quiescence and erosion. • Effusive Hawaiian eruptions with the emplacement of olivine nephelinitic pahoehoe lava flows. Alternated to the effusive eruptions, Strombolian and possibly Violent Strombolian pulses led to mass ejections of juvenile ash, lapilli, bombs, and cognate lithic fragments, forming grain-avalanching scoria deposits, and scoria-and-ash flow deposits. • Stage of dominant water-magma interaction and the formation of a water-rich volcanic cloud, which led to the formation of planar-stratified bedforms, fall-dominated with mixed deposition of ash aggregates in the shape of massive ash pellets, layered and complexly layered accretionary ash pellets, armored and complexly layered armored ash pellets, formed through wet aggregation. [ABSTRACT FROM AUTHOR]

The structure and nature of the crust underlying the Northeast Brazilian margins have been investigated based on the interpretation of 12 wide-angle seismic profiles acquired during the SALSA (Sergipe ALagoas Seismic Acquisition) experiment in 2014. In this study, we present the coincident analyses of 2 marine seismic reflection and refraction data, SL07 and SL 08, that have been acquired using 15 and 13 ocean-bottom-seismometers along each profile, offshore the Jacuipe Basin. The SL07 has a 270-km long inland continuation with 46 land-seismic-stations crossing the South Tucano and Reconcavo Basins. Wide-angle seismic forward modellings reveal a narrow necking zone, an intermediate domain with anomalously high crustal velocities interpreted as intruded lower continental crust, and a sharp continent to ocean transition zone, greatly different from the adjacent segments (see companion paper of Evain et al., 2023). Below the Tucano half-grabens, the Moho shows no rise, displaying a flat reflector throughout the landward part of the profile. The high seismic velocities areas in the lower continental crust are interpreted as intrusions that provide an overloading allowing the necessary subsidence for the deposition of the thick sedimentary sequences. Together with the recent information obtained by the analysis of continental basins and aborted rifts, and similar wide-angle experiments on other margins and geodynamic contexts, we propose new paradigm for the thinning process which confirms the crucial role of the lower continental crust and its relation with the upper mantle. We postulate a phase of overloading of the lower continental crust, an exhumation phase of the lower continental crust, and a phase of proto-oceanic crust which involved the lower continental crust and the upper mantle, before the emplacement of a more typical oceanic crust. • This study is part of the SALSA project (S ergipe AL agoas S eismic A cquisition), led by IFREMER (France) and Petrobras (Brazil). • This article focuses on two E-W profiles offshore the Jacuipe Basin, crossing onland the South Tucano and Reconcavo Basin. • Below Tucano half-grabbens, the moho shows no rise, displaying a flat reflector throughout the landward part of the profile. • Offshore, a strong E-W-segmentation is described with a very abrupt thinning and a sharp continent ocean-boundary, greatly different from the adjacent segments • The intermediate domain has anomalously high crustal velocities ans is interpreted as intruded lower continental crust. • The lower continental crust and its interactions with the mantle play a crucial role, giving rise to a new paradigm. • 3 phases implying the lower continental crust are described : overloading and subsidence, exhumation, proto-oceanic crust. [ABSTRACT FROM AUTHOR]

This paper presents the geomorphological features of four areas of subtropical, southernmost Brazil displaying striking landforms developed upon Precambrian Camaquã Basin conglomerates in the southern Brazilian shield areas. The distinctive and unique features of the Serra do Segredo cuesta, the Rincão do Inferno canyon, the Casa de Pedra inselberg, and the Pedra da Cruz cap-shaped hills are important examples of such conglomerate geomorphology in South America and in Brazil, where few occurrences were available so far. They are the first documented conglomerate landforms in southernmost Brazil, widening the distribution of such terrains in South America and in the subtropical, southern hemisphere areas, considering recent global reviews. Besides the high scientific relevance for geomorphology as a whole, such features are important also for (1) evidencing the decisive role of lithology, structure, and water flows in the formation of such landforms; as well as (2) ecology and tourism, being distributed within and in the vicinity of the Caçapava UNESCO Global Geopark of southernmost Brazil. • Novel description of conglomerate geomorphology developed upon Ediacaran alluvial/fluvial deposits of the Camaquã Basin in subtropical, southernmost Brazil. • Different landforms developed according to bed tilting and arrangement, as well as to tectonic structures "pre-design". • Decisive role of lithology and water in shaping ranges and hills. • Contribution to a global distribution of conglomerate landforms, especially in humid, subtropical areas. • Geological heritage potential, features within and in the surroundings of the Caçapava UNESCO Global Geopark. [ABSTRACT FROM AUTHOR]

The hard rock aquifer systems of Crystalline Aquifer System II (CBASII) and Crystalline Aquifer System III (CBASIII) in Rio Grande do Sul (RS) State, Brazil, were characterized qualitatively and quantitatively through remote sensing, gis-analysis, aeromagnetometry and structural geology analysis. The methods were applied to understand the relationship between the structures and the well capacities in both aquifer systems. Analysis of 139 structures provided a basis for a conceptual model for municipality of São Lourenço do Sul, in Rio Grande do Sul Coastal Plain, scaling systematic and a connection to preexisting structures. Python programming language script are used for statistical analysis can be download to reproduce statistical analysis of this paper with structural data bank. São Lourenço do Sul, is underlain by Pelotas Batholith, a geological complex affected by deformational events related to the Dom Feliciano orogeny. The models provided NW-SE extensions fractures with higher densities in depth for CBASII and CBASIII. Nevertheless, only CBASII is productive due to interconnectivity with preexisting structures WNW-ESE and generated by D 1 and D 2 deformational events of the Pelotas Batholith. CBASIII decreases its permeability as it was affected by the youngest brittle D 3 event an extensional/strike-slip tectonic regime. The regional structures mapping with remote sensing and aeromagnetic ENE-WSE are mostly present in CBASIII. Structures mapping in remote are the same but vary in density. The relationship between oriented magnetic gradients and productive wells suggests fault zones with low hydraulic conductivity in areas with higher anomalies values. Fault damage zones are identified around these anomalies and characterized as the best areas for drilling. [ABSTRACT FROM AUTHOR]

Highlands form one of the essential links ensuring the good performance of the hydrological cycle on Earth, and significant amounts of good-quality water are concentrated in these areas and distributed to lowlands. These resources are indispensable for arid/semi-arid regions such as NE Mexico, where water is scarce and sometimes lacks good quality. In the state of Coahuila, the Serranía del Burro is one of the most important hydrogeological systems, and at least seven aquifers show some type of relationship with this system or benefit from its recharging. In this paper, data from 50 well and spring samples are presented with the goal of identifying the effect of the range on the chemical composition of the surrounding aquifers and the mechanism of recharging. The results show that in this area, the waters are mostly of the type Ca2+-Mg2+-HCO 3 -, with minor contributions from more saline and mixed waters. The main processes responsible for the chemistry of the waters are water-rock interactions, mixing and, cationic exchange, in which, the weathering of silicates and, the dissolution of carbonates through karst processes predominates. Recharging is characterized as fresh and deep, due to the influence of karst and tectonic phenomena throughout the geology of the Serranía del Burro and the adjacent areas. Limited shallow meteoric percolation occurs in the NO of the Serranía del Burro due to the presence of conglomerates and caliche sequences, resulting in low permeability. This study highlights the need to take care of good-quality water resources located in the mountains; adequate exploration work must be carried out in these areas, since waters of questionable quality prevail throughout the state, mainly due to natural salinization processes in lowland areas. • The karstic mountain systems in NE Mexico play an important role in maintaining good quality water resources in arid/semi-arid climate conditions. • Ca2+-Mg2+-HCO 3 - waters are dominant in the Serrania del Burro ranges and surrounding aquifers. • The occurrence of local storms, effective recharge and active tectonism allows infiltration processes over the mountains to be efficient. [ABSTRACT FROM AUTHOR]

Reservoir characterization is extremely important for understanding and determining the behavior of hydrocarbon reservoirs. The geophysical well logging, widely applied in the oil industry, helps to obtain essential physical properties (acoustic, electrical, mechanical, radioactive and thermal) by deploying measurement devices in the drilled well. This project aims to carry out the geological characterization of hydrocarbon reservoirs in the Amazonas Basin through the analysis of well geophysical logs. Despite the oil-producing potential of the basin, there are few published papers that use geophysical well logging for reservoir characterization. For this study, composite log data publicly provided by ANP were used. Six exploratory wells drilled in AM-T-84 and AM-T-85 exploratory blocks in the Amazonas Basin were selected. By analyzing the geophysical logs of gamma ray, resistivity, density and neutron from these wells, it was possible to identify the hydrocarbon reservoir interval within the Monte Alegre formation and obtain estimates of thickness, shale volume and porosity. The identified reservoir is relatively thin, with an average thickness of 16 m. The obtained shale volume values were relatively high, due to the influence of shale layers present in the Monte Alegre formation. The effect of clay content affected the interpretation process of the well logs; however, it did not significantly impact the reservoir porosity estimation, which ranged between 10.4 and 23.4 %. • The analysis and interpretation of well logs can provide petrophysics properties of the petroleum reservoir. • The Amazonas Basin is one of the pioneering areas for hydrocarbon exploration in northern Brazil. • Despite the clay content present in the formation, relatively good porosity values were obtained for the reservoir. • The temperature values obtained range from 70 to 95 °C. They are contained in the oil generation range (65–165 °C). [ABSTRACT FROM AUTHOR]

The present paper shows a mineral chemistry study in chromites found in serpentine-talc schists of the Arroio Grande Ophiolite, located in the southeastern Dom Feliciano Belt, near the Brazil/Uruguay border. Using electron microscope scanning and electron microprobe techniques, this study found a supra-subduction zone signature in the chromites, together with evidence of metasomatism. It corroborates previous hypothesis that suggested a supra-subduction zone origin for the protoliths of the Arroio Grande meta-igneous rocks and a metasomatic origin for the chromite-bearing magnesian schists. The studied chromites present high Cr# (0.65–0.77) and Fe 2+ # (0.88–0.95), low MgO (0.85–2.47 wt%) and TiO 2 (0.01–0.19 wt%) and anomalous high concentration of ZnO (up to 1.97 wt%). The results were compared with chemical data from detrital chromites from the Schwarzrand and Fish River Subgroups of the Nama Group (Namibia), demonstrating that they are compositionally similar with those found in the latter. These chromites, in turn, are believed to have been derived from the oceanic Marmora Terrane (Gariep Belt) in the west (present-day coordinates). Taking into consideration that oceanic metamafites from both the latter and the Arroio Grande Ophiolite share common bulk-rock geochemical features (in this paper interpreted as fragments of the same paleo-ocean floor – the Marmora back-arc basin), it is possible to raise the hypothesis that detrital material derived from the studied ophiolite might also be found in Nama Group. It is reinforced by the fact that sediments (related to the Pelotas-Aiguá Batholith granitoids) derived from the easternmost Dom Feliciano Belt, i.e. the region where Arroio Grande Ophiolite is located, is found in both Schwarzrand and Fish River Subgroups. Thus, we suggest that Arroio Grande Ophiolite detrital sediments might also have contributed to the Nama Basin infilling during Late Ediacaran-Lower Cambrian. [ABSTRACT FROM AUTHOR]

dos Santos Teixeira et al. evaluated the effectiveness of three different sensors, portable X-ray fluorescence (pXRF) spectrometry, visible near-infrared (Vis-NIR), and NixPro TM color sensor, in predicting six soil properties including sum of bases (SB), effective cation exchange capacity (eCEC), potential cation exchange capacity (CEC), base saturation (BS), soil organic matter (SOM) content, and soil pH, and compared their performance when used alone or in combination. Preprocessing methods and other variables were also analyzed. In this comment paper, some misuses of Kappa statistic in the original paper by dos Santos Teixeira et al. are discussed. The authors calculated Cohen's kappa coefficient to make categorical predictions for soil fertility classes. However, using Cohen's Kappa to estimate the intra-rater reliabilities (IRRs) is not appropriate on the condition of ordinal categorical variables in four or five categories in the original paper. We briefly introduce the Kappa statistic for evaluation of IRR between two raters and propose to use weighted Kappa to compute IRRs under such conditions. To conclude, we recognize that this does not significantly alter the conclusions of this paper, but it is necessary to ensure that the appropriate statistical tools are used. • Cohen's Kappa assesses IRR for 2 or ≥3 unordered categorical variables categories. • Weighted Kappa measures IRR for ordered categorical variables with ≥3 categories. • QWK reveals more inconsistencies than LWK. [ABSTRACT FROM AUTHOR]

One of the most debated volcanic areas along the eastern coast of Mexico is Los Tuxtlas Volcanic Complex located in the south of the Veracruz state. This volcanic province stands out as an isolated massif between the Trans-Mexican Volcanic Belt to the NW and the Chiapanecan Volcanic Belt to the SE. Los Tuxtlas complex is surrounded by two large alluvial plains formed by the Papaloapan and Coatzacoalcos rivers, and include the active volcano San Martín Tuxtla, the last eruption of which occurred in 1793. The ages, distribution, morphology and geochemistry of the volcanic vents and lavas, particularly the co-existence of the alkaline and subalkaline suites, offer an excellent opportunity to understand, in space and time, the tectono-magmatic history of Los Tuxtlas in comparison with other similar volcanic complexes in the eastern Trans-Mexican Volcanic Belt. Most of the volcanic centers of Los Tuxtlas show NW-SE alignments. This vent arrangement is associated with a left-lateral fault system known as the Veracruz fault, the northwestern expression of which are the submarine volcanoes that form the Anegada High. This fault might be a reactivation of the ancient Tamaulipas-Oaxaca fault related to the opening of the Gulf of Mexico. Based on geomorphological, geochemical, petrographical, and 40Ar/39Ar data, we propose three different stages of volcanic activity for Los Tuxtlas: The older Montepío-El Vigía (7–1.4 Ma), the intermediate Santa Marta (1–0.5 Ma), and the younger San Martín Tuxtla (50 ka to present). The main focus region of this paper is the stratovolcanoes of the Sierra de Santa Marta, formed by at least four major NW-SE aligned volcanic edifices, which from NW to SE are Encanto (950 m.a.s.l; identified and named in this work for the first time), Yohualtajapan (1450 m.a.s.l), Santa Marta (1685 m.a.s.l), and San Martín Pajapan (1250 m.a.s.l). The geological map, the 40Ar/39Ar dates, and the geochemistry data indicate a NW-SE migration of the volcanic activity of the four stratovolcanoes that have created the sierra de Santa Marta. Petrography and chemistry of rocks suggest that the subalkaline rocks of the three magmatic stages were fed by subduction activity of the Cocos Plate. The alkaline suite is likely associated with asthenosphere upwelling and slab edge melting, facilitated by a slab tear of the south Cocos plate evolved since the Early Miocene. • This paper provides new data in the evolution of a controversial volcanic complex in southern Mexico. The ages, distribution, morphology and geochemistry of the volcanic vents and lavas, particularly the co-existence of the alkaline and subalkaline suites, offer an excellent opportunity to understand, the tectono-magmatic history of the Los Tuxtlas Volcanic Complex in comparison with other similar volcanic complexes in the eastern Trans Mexican Volcanic Belt. [ABSTRACT FROM AUTHOR]

Centroid moment tensor (CMT) determination in intraplate regions like Brazil can be very difficult, because earthquakes are often recorded just at few and distant stations. This paper introduces a methodology for datasets like that. The methodology is based on waveform inversion in which each source-station path has its own velocity model. The 1-D path-specific velocity models are derived from the Rayleigh- and Love-wave dispersion curves. The waveform inversion is accompanied by posterior check of numerous P-wave first-motion polarities. An important innovation is the use of so-called frequency range test. The test basically consists in calculating CMT's for many different frequency ranges to assess the stability and uncertainty of the solution. The method is validated on two Brazilian earthquakes and a well-known Greek event. An offshore event (mb 5.2) in SE Brazil is inverted with four stations, at epicentral distances 300–400 km. The other Brazilian earthquake (mb 4.8 in Central Brazil) is even more challenging – only two broadband stations at 800–1300 km are at disposal for waveform inversion. The paper unambiguously demonstrates that the path-specific velocity models significantly increase the reliability of the CMT's. While standard models (e.g. IASP91) typically allow waveform modeling up to epicentral distances of the order of a few (∼10) minimum shear wavelengths (MSW), using the path-specific velocity models we successfully inverted waveforms up to > 20 MSW. Single-station waveform inversions are thoroughly tested, but multi-station joint inversions are shown to be preferable. The new methodology of this paper, providing a reasonable estimate of focal mechanisms and their uncertainties in case of highly limited waveform data, may find broad applicability in Brazil and elsewhere. [ABSTRACT FROM AUTHOR]

A detailed sedimentological analysis of the so called “Chachil Limestones” at its type locality around the Mirador del Chachil area, southwestern Neuquén province, Argentina, is presented in this paper for the first time. It is based on a macro/microfacial analysis and their environmental interpretation by means on texture, fabric, bioclasts, intrabasinal and extrabasinal grain amounts, sedimentary structures, bioturbations and hydro-dynamism. Because of the recognition of different facies associations, but no pure limestones, it is more suitable to refer these sediments as the Chachil Formation. The depositional environment of this unit is interpreted to correspond to an internal platform dominated by tides, with carbonate sedimentation disturbed by repeated explosive volcanic episodes, which reduced the sedimentation space, causing retrogradation of the sedimentary system and coastal onlap. In addition, a new recalibration of the U-Pb zircon dating used for the geochronological analysis reveals a small change with regard to previous information that has been used to recalculate the data, is presented in this paper. [ABSTRACT FROM AUTHOR]

This paper documents an investigation on the use of full waveform inversion to retrieve focal mechanisms of 11 micro-earthquakes (Mw 0.8 to 1.4). The events represent aftershocks of a 5.0 m b earthquake that occurred on October 8, 2010 close to the city of Mara Rosa in the state of Goiás, Brazil. The main contribution of the work lies in demonstrating the feasibility of waveform inversion of such weak events. The inversion was made possible thanks to recordings available at 8 temporary seismic stations in epicentral distances of less than 8 km, at which waveforms can be successfully modeled at relatively high frequencies (1.5–2.0 Hz). On average, the fault-plane solutions obtained are in agreement with a composite focal mechanism previously calculated from first-motion polarities. They also agree with the fault geometry inferred from precise relocation of the Mara Rosa aftershock sequence. The focal mechanisms provide an estimate of the local stress field. This paper serves as a pilot study for similar investigations in intraplate regions where the stress-field investigations are difficult due to rare earthquake occurrences, and where weak events must be studied with a detailed quality assessment. [ABSTRACT FROM AUTHOR]

Kimberlitic rocks are known in the São Francisco Craton, Brazil, since the 1980s when the De Beers started a prospective work in the Itapicuru River Greenstone Belt. However, 40 years later, the scientific knowledge about these occurrences is still very restricted. This paper presents new geological and petrographical data for the pipes of the "Brauna Kimberlitic Field". These rocks are exposed in a strongly eroded cratonic area of Northeastern São Francisco Craton and as expected, represent the deepest parts of these bodies, showing textural aspects and components typical of coherent volcanic rocks emplaced at deep crustal levels. The kimberlitic magmatic event resulted not only in the emplacement of macrocrystalline hypabyssal olivine archetypal kimberlites, here represented by the B3 (678–682 Ma) and B4 pipes (s.s. Former type 1 kimberlites), but also in hypabyssal macrocrystalline pyroxene-phlogopite- lamproite intrusions, as exposed in the B7 (641 Ma) pipe of the Brauna Field. Both magmas are rich in mantle-xenoliths and have potential for diamond ores. The observed features suggest the presence of multiple magmatic pulses – which acted as deep samplers, recorded in the diversity of xenoliths and xenocrysts – thus demonstrating the potential of these rocks for the comprehension of the first stages of evolution of the Early Earth as well as for understanding the formation of the metasomatized lithospheric mantle below the São Francisco Craton. The new data for these hypabyssal facies, macrocrystic pulse of kimberlitic rocks in the Brauna Field, São Francisco Craton, Brazil, can be used to characterize the petrographic and mineralogical heterogeneities of a Neoproterozoic alkaline-ultrapotassic magmatic event that shows a kimberlite-lamproite transitional nature. The petrogenetic knowledge presented for the São Francisco Craton kimberlites and lamproites – accordingly to the most recent classifications for these rocks – include textural-genetic data, geotectonic environment, and intrusive-spatial context, setting these rocks at the stage 5 of present-day kimberlite classification scheme. Moreover, the integration of such data and the close spatial associations of kimberlites, lamproites, lamprophyres, syenites and shoshonites allowed to create a solid interpretation of the rock formation processes that correlates these Neoproterozoic alkaline ultrapotassic magmas to the reactivation of ancient mantle conduits in a thick lithosphere that overlies a previously metasomatized mantle and intrude a metal-rich craton environment. • Current models and nomenclature of kimberlite-lamproite rocks highlight the importance of detailed petrogenetic studies. • Detailed petrographic studies points to the usefulness of deepening the discussion on kimberlite rocks nomenclature. • The pipes of the BKF present textural characteristics and components typical of massive coherent rocks emplaced at deep crustal levels. • B3/B4 are classified as coherent coarse-grained, macrocrysts-rich, hypabyssal-facies, mega-graded, diamondiferous-olivine-kimberlite. • Otherwise, B7 is interpreted as an intrusive plug of a massive coherent coarse-grained, hypabyssal, diamondiferous-phlogopite-lamproite. • The petrogenetic and textural classification of BKF, presented in this paper, contribute to understanding of kimberlite and lamproite magmas. • BKN petrogenesis contribute to understand the metasomatized mantle and ore deposits of the Sao Francisco Craton. [ABSTRACT FROM AUTHOR]

This paper describes the lithological and micropaleontological characteristics of a new record corresponding to the last interglacial for Buenos Aires province. Foraminifera were analyzed from an artificial outcrop 4 m thick (36°34′0.97″ S and 57°22′54.43″ W), from the quarry situated in the town of General Conesa, Buenos Aires province at an approximate elevation of 4 m a.s.l. Benthic foraminifera fauna was constituted by a predominance of calcareous forms represented mostly by the species Buccella peruviana and Ammonia parkinsoniana. The micropaleontological and lithological characteristics of all the sedimentary units involved in this locality suggest deposits associated with a transition from a low-energy shallow intertidal or subtidal zone to a higher-energy beach or supratidal environment. Although, the topographic height does not enable conclusive assignment of the age of this coastal deposit (>79.500 kyr), the environmental conditions could be correlated with the penultimate transgressive event that occurred at the beginning of the Late Pleistocene (MIS 5), which would have occurred in a shallow environment with changes in the marine influence. These findings provide new information that contributes to better understanding of the paleoenvironmental evolution of this region where two marine transgressions and two wind deposits have been recognized. • Paleoenvironmental changes during the Late Pleistocene from General Conesa Site, Argentina. • Transgressive event from the beginning of the Late Pleistocene (MIS 5), South America. • Fossil Foraminifera from Buenos Aires province and their paleoenvirnmental implications. [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 Mosasauridae underwent a major radiation early in the Late Cretaceous, with the subfamilies Plioplatecarpini and Tylosaurini appearing in the Turonian. Here we report an almost complete mosasaur skull assigned to the plioplatecarpine genus Yaguarasaurus. The specimen was discovered southwest of Vallecillo in the northeastern Mexico state of Nuevo Leon, about 80 km north of Monterrey, in a laminated limestone layer of the upper member of the Agua Nueva Formation (Upper Turonian - ?Lower Coniacian). The specimen is referred to as a new species, Y. regiomontanus. This is the first report of Yaguarasaurus from Mexico and the most complete of the Americas. At roughly 5 m in length, it is one of the earliest large mosasaurids. Along with Yaguarasaurus columbianus , Russellosaurus coheni , and an unnamed plioplatecarpine from Texas, it documents the rapid diversification and expansion of plioplatecarpines in the marine realm in the Turonian. • The Highlight of the paper is that is a new species of mosasaurus described for Mexico. [ABSTRACT FROM AUTHOR]

This paper presents a novel Stratigraphic and Tectonic Framework for the Mesozoic Register of the Parecis Basin, using the concept of Supply Generated Sequences. The tectonic evolution of the South American Platform during the Mesozoic was utilized to establish the significance and correlations of the proposed Parecis Sequences 1 to 4 and their bounding surfaces. Parecis Sequence 1 exhibits a complete Transgressive Regressive Climatic Induced Clastic Behavior, with a depositional age from the Juro-Triassic period, related to localized deposition in an extensional regime caused by the CAMP event. A non-depositional/erosional gap of 90 million years between Parecis Sequence 1 and 2 is attributed to regional uplift associated with the Juruá Orogeny until the Late Cretaceous. Parecis Sequence 2 displays a complete Transgressive Regressive Climatic Induced Clastic Behavior and is associated with the Mochica phase of the Andean Orogen. Parecis Sequence 3 displays a complete Transgressive Regressive Climatic Induced Clastic Behavior correlated with the Peruvian phase of the Andean Orogeny. Parecis Sequence 4 considers the Rio Tapirapé Formation as a probable fourth sequence, with lake register and age defined by Coniacian notosuchian fossils. The Parecis Supersequence comprises Sequences 2 to 4, representing a trend of basin fill from Albian to Coniacian in a back-bulge foreland basin. • Supply Generated Sequences are used to explain climatic control clastic behavior in the Mesozoic register of the Parecis Basin. • The novel sequence stratigraphy framework defines four third transgressive-regressive sequences. • Parecis Sequence 1 registers the triassic-jurassic sequence related to CAMP and Penetecaua magmatism. • Parecis sequences 2 to 4 conforms the Parecis Supersequence, registering fluvial-aeolian deposits with attributed age from Albian to Coniacian. [ABSTRACT FROM AUTHOR]

Every year, Brazil grapples with the destructive impact of landslides, typically during the summer season. The National Centre for Monitoring and Alerts of Natural Disasters (Cemaden) places significant emphasis on studying these phenomena to understand their processes and causes more deeply. One key challenge faced in this endeavour is the procurement of geotechnical properties of the soil in high-risk areas, with soil moisture being a crucial factor. Collecting point samples for acquiring these geotechnical parameters is not only costly but also limited in providing a comprehensive two-dimensional or three-dimensional coverage. Therefore, the primary aim of the proposed project is to validate the method of acquiring soil moisture data through geophysical surveys in both 2D and 3D scenarios. Data was gathered from soil moisture stations within Cemaden's network and various collected samples to confirm the results. To generate more controlled yet realistic conditions, a sequence of field infiltration experiments was conducted. The findings, related to the ability of the geoelectric method to define soil moisture, derived from this project form an invaluable foundation for future investigations spearheaded by the Geodynamics Group and its collaborating institutions. • This paper presents a series of experiments to understand the method of acquiring soil moisture through the DC method. [ABSTRACT FROM AUTHOR]

The Argentinean Andean foreland region between latitudes 31°S to 33.5°S presents an intense crustal and upper mantle seismic activity that was recorded by a local seismological network called CHARSME (Chile Argentina SeisMic Experiment), and was used to obtain new velocity determinations. In a first moment, from 4 P-wave velocity (V P) models proposed by other authors, the detail in the layers was increased, resulting in better models used as initial model in the investment. Finally, by carefully selecting a set of earthquakes, a simultaneous velocity inversion, hypocentre determination and station correction were performed using the VELEST code. In order to obtain better velocity models (V P and V S) and V P /V S ratio, different tests were carried out in all processes. The final V P model presented in this paper incorporates considerations made in other seismological studies. This model accurately determined velocities between 10 and 65 km depth. The upper mantle velocity (V P) was defined in 8.05 km/s. From the Wadatti diagram, which represents a line whose slope is related to the wave velocities and the Poisson's coefficient, a V P /V S value of 1.732 was obtained. Alternative V P /V S values were also considered to invert V P , V S and V P /V S simultaneously. The minimum detailed model of V P , V S and V P /V S decreased the RMS by 25% relative to the initial models, implying an improvement in the uncertainty of locations. The new and precise locations of crustal earthquakes allowed defining clusters within Cuyania, a tectonic terrain that collided to Gondwana in the Early Paleozoic. Although it is known that foreland seismicity is mainly concentrated in this terrain, this work shows that there are well-defined zones within Cuyania that are more seismically active. Earthquakes of intermediate depth (upper mantle) are strongly agglomerated in the flat-slab zone of the subducting Nazca Plate. The discontinuities present in our model suggest upper, middle and lower crustal structuring, as well as a marked contrast between the sediments and the underlying basement. It was possible to interpret an upper crust consisting of sediments and basement to a depth of 25 km, a middle crust between 25 and 45 km and a lower crust between 45 and 55 km. We also defined the Mohorovičić (Moho) discontinuity at 55 km depth. The crustal velocities are in agreement with previous seismological studies. • The minimum detailed model of VP, VS and VP/VS reduced the RMS by 25% compared to the initial models. • Minimal one-dimensional models allowed us to obtain more precise locations of the hypocentres. • Our locations show that the crustal earthquakes there are located in well-defined seismically active sectors. • Upper mantle earthquakes are strongly agglomerated in the flat-slab zone of the subducting Nazca Plate. [ABSTRACT FROM AUTHOR]

Focal-mechanism determination of weak events recorded in sparse networks is challenging. First-motion polarities are often available at relatively distant stations, and waveforms only at a few near stations can be modeled. A two-step approach of how to combine such data has been suggested recently (Cyclic Scanning of the Polarity Solutions, or CSPS method; Fojtíková and Zahradník, 2014). It starts with creating a suite of first-motion polarity solutions, which is often highly non-unique. The next step consists of repeating full waveform inversion for all polarity solutions. Even few stations may efficiently reduce the non-uniqueness of the polarity solutions. Centroid depth, time, scalar moment and uncertainty estimate of the well-fitting double-couple solutions are obtained. The CSPS method has been extended in this paper by adding a new feature, i.e. repeated inversions using multiple first-motion polarity sets. The polarity sets are created by projecting the stations on focal sphere in several available velocity models, thus accounting for the takeoff angle uncertainty. The multiple polarity sets provide assessment of the CSPS solution stability. These ideas are demonstrated on a comprehensive analysis of a rare event in central Brazil. It is the Mw ∼4 mainshock of the Mara Rosa 2010 earthquake sequence (Barros et al., 2015, Carvalho et al., 2015). We employ polarities at 11 stations (distances < 730 km) and invert full waveforms at two stations (CAN3 and BDFB at distances ∼120 and 240 km), for 0.1–0.2 and 0.05–0.125 Hz, respectively. Six polarity sets reflect the takeoff angle uncertainty. The obtained CSPS results are very stable across all the polarity sets (in terms of depth, Mw, and strike/dip/rake angles). It is found that the Mara Rosa mainshock mechanism deviated from the composite solution of the whole sequence by 38°. The paper also includes a test simulating situations at which just a single waveform is used, and how it negatively affects the solution stability. [ABSTRACT FROM AUTHOR]

This work presents a few comments on the paper "Relative sea-level curve during the Holocene in Rio de Janeiro, Southeastern Brazil: A review of the indicators - RSL, altimetric and geochronological data". Surprisingly the authors omitted in this review a former discussion on the interpretation of paleo-sea level indicator and paleo-sea level reconstructions on the Rio de Janeiro coast that questions their results. Therefore, at this present work we resume the previous discussion. We conclude that although at the commented paper the altitudes of the paleo-sea level indicators were determined precisely, they did not consider the vertical distance between a given a paleo-sea level indicator and its current homologous one, and thus do not indicate paleo-sea levels. [ABSTRACT FROM AUTHOR]

This paper presents the first mapping of bedform morphological features on the Trindade Island shelf, with the goal of identifying and defining them. By using a side scan sonar, collecting seabed samples, and taking submarine photographs, five different morphological types were identified on this shelf: an erosive type: (i) characterized by the dispersion of rocks and rock blocks; and four depositional types: (ii) one formed by calcareous algal reefs, (iii) one composed by rhodoliths, (iv) one formed by medium sands with large symmetrical wave ripples, (v) and the last one formed by fine sands with asymmetrical wave ripples. The main result is a morphological map of the Trindade Island shelf, which shows the occurrence of these five seabed units. To further understand the sedimentological factors that affect the island shelf, we also examined the sediments that were collected for this study. Our results show that the amount of carbonate-formed grains on the collected sand sediments is higher than the amount of grains formed by the volcanoclastic ones, generated by the disaggregation of the main building on Trindade Island. The sediments formed by bioclastic grains are more frequently found in the coarser fractions than in the finer fractions when compared to lithic ones. • First seabed characterization on the Trindade Island shelf. • Boulders and rock outcrops occur at shallow depths, near the shoreline. • Rhodoliths and algal reefs are the main shelf seabed types. • Bioclasts are the main component that forms sandy deposits. [ABSTRACT FROM AUTHOR]

This paper aims at analyzing the Ordovician–Silurian (Hirnantian–early Llandoverian) Transition in the Central and Eastern Precordillera of San Juan Province based on stratigraphic relationships, diagnostic deposits and sedimentary, paleobiologic and isotope data. At the Central Precordillera, three sections have been examined and sampled: (a) Los Baños de Talacasto, (b) Poblete Norte in the Talacasto area, and (c) northward the Cerro La Chilca section. At the Eastern Precordillera, only the Don Braulio section at the Villicum Range has been considered. These four sections have been selected because they include significant brachiopod assemblages related to the three Transitional Benthic Faunas (TBF 1–3), Hirnantian and Rhuddanian graptolites zones and palynomorph assemblages, in addition to isotope data as a useful tool for dating and correlations. The analysis of these sections has allowed recognizing the timeline of four events that span early Hirnantian–early Llandoverian. Event 1 is linked to the early Hirnantian postglacial transgression, in accordance with TBF 1 and Metabolograptus extraordinarius Zone correlation. Event 2 developed in the middle-upper Hirnantian, is witnessed in a transgressive shallow-water succession, coeval with the Hirnantia Fauna and Metabolograptus persculptus Zone. Event 3 is widely represented by the basal cherty pebbly conglomerate of La Chilca Formation and its correlatives Los Bretes and lower Tambolar formations in the Central Precordillera. This conglomerate is thought to be a lag deposit, which erosively overlies Ordovician strata, as a result of the Hirnantian postglacial transgression, but it is absent in the Eastern Precordillera. Finally, Event 4, at the Villicum section, spans the late Hirnantian–early Llandoverian, standing out a shallow-water, bioturbated mudstone succession, of 12 m thick with no diagnostic fossils, indicating upwelling processes and probably including the Ordovician–Silurian Boundary. However, in the Los Baños de Talacasto and Poblete Norte sections, this succession is composed of a graptolite-rich pelite succession 12 m thick, exhibiting at the base Fe-phosphate strata, and bearing graptolite assemblages of the Hirnantian Metabolograptus persculptus Zone, and the Rhuddanian Parakidograptus acuminatus Zone, indicating the Ordovician–Silurian boundary. It should be noted that the A. ascensus Zone has not been registered to date in the Precordillera. • A timeline of events across Ordovician-Silurian Transition of San Juan Precordillera is proposed. • Litho-biostratigraphic, isotope data and unconformities considered for global correlations. • Paleoenvironmental changes are based on benthic faunas, palynomorphs and graptolite biozones. • Conglomerate, phosphate lags, ironstone and upwelled mudstone, are considered for correlations and environmental analysis. • Tambolar and Villicum-Zonda archs are thought as structural elements during the Ordovician-Silurian. [ABSTRACT FROM AUTHOR]

The paper focuses on the sedimentological, stratigraphic, and climatic implications of silicified fossil trunks found in the Missão Velha Formation (MVF) of the Araripe Basin in Northeastern Brazil. The rich fossiliferous plant assemblages in the MVF are primarily dominated by conifers, specifically a group known as Agathoxylon, and are associated with coarse sandstone and conglomerate fluvial beds. The MVF represents a late Jurassic-early Cretaceous formation deposited during the Early Rift phase of the basin. Silicified fossil trunks and woods from the MVF have been known since 1863, and previous studies have discussed their morphology, internal structure, and paleogeographic implications. Taphonomically, these macrofossils have been interpreted as hypautochthonous, meaning they originated from their growth sites. However, some authors have suggested an allochthonous origin for these fossils. Despite their significance, the sedimentological and stratigraphic characteristics of these fossil associations have received limited attention in previous research. We have collected the fosil trunks exclusively in the MVF, and they are restricted to the upper parts above an internal unconformity. Two main taphofacies were identified: T1 comprises coarse-to medium-sandstones, locally conglomeratic, with planar and trough cross-stratifications, with abundant fossil wood and trunks, and T2 defined as well-stratified pebbly conglomerates, with horizontal to cross bedding, with larger common fossil wood and trunks fragments. T1 taphofacies occur in most of the cross-stratified sandstones of the upper part of the MVF, T2 taphofacies (larger wood logs) are primarily concentrated in a coarse sandstone to conglomeratic bed strata at the top of the MVF. The preservation of the trunks is characterized by uncompressed fragments with poorly rounded edges. The cell walls are preserved by permineralization, with the spaces filled by silica, indicating short transport and rapid burial. The silicified fossil woods are found in foresets of planar and trough cross-stratifications, associated with coarse-grained to conglomeratic sandstones. These sandstones are highly abundant, sometimes forming anomalous concentrations, such as in the Grota Funda outcrop. The dimensions of the fossil trunks range from 5 cm up to 2 m in length, with some exceptionally large trunks measuring approximately 1.70 × 1.40 m. The investigated trunks exhibit various orientations, with some concordant and others dissenting from the surrounding strata. However, the majority of the fossil trunks do not show a preferential orientation. Orientation analysis of more than twenty logs suggests a predominant south paleocurrent direction trend, likely resulting from monsoon storms originating from a source area to the north. The assemblages were likely formed through putrefaction processes and late fragmentation, followed by size-selection through fluvial transport. The relatively short transport distance is indicated by the preserved edges, lack of preferential position, and the size of the trunks. Consequently, it is inferred that the trunks originated within the basin itself rather than being transported from the basement area, supporting their hypautochthonous character. The MVF and the associated plant remains bear resemblance to deposits of similar age in other Northeast Brazilian basins, such as the Recôncavo-Tucano-Jatobá, Sergipe-Alagoas, and Camamu-Almada basins, as well as the Gabon Basin in Western Africa. Evidence from the trunk taphofacies, stratigraphy and sedimentology of the MVF is consistent with a warm, seasonal, hot, and humid climate, indicative of a monsoon climate similar to other conifer forests in Gondwana during the Mesozoic era. • The rich fossiliferous plant assembly is dominated by conifers restricted to Agathoxylon and relates only to coarse sandstone and conglomerate beds deposits of the upper portion of the Missão Velha Formation. • The sandstone strata that hosts the fossil woods denotes subaqueous dune deposits. • High energy channels in shallow braided fluvial channels carried heavy logs. • Channels could be sudden causing great damage, carrying heavy logs in a short path. • Evidence from the fossil trunks and woods, stratigraphy and sedimentology of the Missão Velha Formation is consistent with a warm, seasonal, hot and humid climate, suggestive for monsoon climate [ABSTRACT FROM AUTHOR]

The bioregionalization of the Devonian fauna in southwest Gondwana has been extensively studied, focusing on the occurrences of brachiopods and trilobites, however, little attention has been given to Conulariids. The main goal of this paper is to propose a bioregionalization for the Conulariids (Conularia albertensis , C. quichua , C. sp., Paraconularia africana , P. ulrichana , and Reticulaconularia baini) from the Lower-Middle Devonian in southwest Gondwana. After a clustering analysis and diversity tests we have identified two distinct bioregions for Conulariids: the Amazon and southwest Gondwana, in the Amazon region the diversity is low, and can be attributed to scarcity of palaeontological data on the area. On the other hand, in the southwest Gondwana bioregion, diversity ranges from moderate to relatively high, which helps define a second-order bioregion, the Andeo-South Africa and Interior Gondwana. The first includes areas where diversity has higher values bordering southwest Gondwana (Bolivian Chaco-Peru, Zorritas-NOA-South Bolivia, South Africa and Malvinas areas). Further, in the Interior Gondwana bioregion are the Parnaíba (Parnaíba Basin), Alto Garças (north and northwest of Paraná Basin), Paraná (south of Paraná Basin, Uruguay and Paraguay) areas, where the diversity is slightly lower when compared to the Andeo-South Africa bioregion. • Paleobiogeography of Devonian Conulariids from southwest Gondwana. • During the Devonian, the inland seas of Gondwana hosted similar fauna of Conulariids. • The seas bordering Gondwana had a high diversity of Conulariids during the Devonian. • Cluster analyzes show different bioregions in Gondwana during the Devonian. [ABSTRACT FROM AUTHOR]

Only a few studies on Quaternary continental mollusks of Uruguay have been published over the last few decades. Despite the high occurrence of this group in many of the Late Pleistocene outcrops of the country, all of them are better known for their classic Ice Age mammal assemblages. To overcome this situation, 23 localities were sampled from two lithostratigraphic units: the Sopas and Dolores formations. The identified species are included in the families Sphaeriidae, Cyprinidae, Mycetopoda, Acridae (freshwater bivalves); Ampullariidae, Cochliopidae, Tateidae, Chilina, Physidae, Planorbidae (freshwater gastropods); Scolodontidae, Succineidae, Charopidae and Bulimia (terrestrial gastropods). As a result of these new samplings, the Sopas Formation mollusk species count increased from 20 to 29 species, and the Dolores Formation from six to 29 species. Seventeen of these species are new records for the Quaternary of Uruguay , and eight for the Quaternary of South America. Two bivalves, five freshwater gastropods, and a new terrestrial gastropod were added for the Sopas Formation; and for the Dolores Formation, four new bivalves, 14 new freshwater gastropods, and five new terrestrial gastropods. The Dolores Formation has been the most understudied unit until now, increasing here its biodiversity to 23 species. These new records of freshwater and terrestrial gastropods, increase the biodiversity and biogeographical range of the continental mollusks of the Late Pleistocene-early Holocene of the region. In addition, new AMS 14C ages were obtained for both lithostratigraphic units, framing the age of the mollusk assemblages for both formations in the a maximum range of 13,000–48,000 years before the present. • This paper is a comprehensive study of the continental mollusks species composition of two Quaternary stratigraphic units from Uruguay. • In this work, 17 new species of freshwater and terrestrial mollusks are described for the first time for the Late Pleistocene of Uruguay. Of those species, nine are new for the Quaternary of South America. • Comparing with the Pampean Region, the assemblages of Uruguay can be related with the Quaternary Assemblages from Pampean Argentina and Rio Grande do Sul (Brazil). [ABSTRACT FROM AUTHOR]

Analysis of ancient animal bone fractures can provide insights into ecological and behavioral aspects, as well as death processes and bone preservation modes. This paper describes and interprets the cause of a bone fracture observed in the fossil remains of a juvenile Myrmecophaga tridactyla (giant anteater) recovered from a limestone cave in Brazil. We identified an indirect bone trauma with a curved or spiral fracture line and a well-formed bone callus in the left ulna through a macroscopic and radiological examination. These features indicate that the giant anteater fell from a great height with an outstretched hand. • Presence of bone fracture in the ulna of a juvenile Myrmecophaga tridactyla caused by indirect bone trauma. • Presence of a well-formed bone callus, indicating that the animal survived the injury and underwent an advanced healing process. • The giant anteater likely fell from an elevated location and sought shelter in the cave after sustaining the injury. [ABSTRACT FROM AUTHOR]