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Abstract The sedimentary basins in the Continental Rift of Southeastern Brazil (CRSB) provide an opportunity for ichnological analyses due to its well-known facies relationships and paleoenvironmental interpretations. This study reports invertebrate trace fossils from the Neogene fluvial deposits (Floriano Formation) and applies integrated ichnological and facies analyses to reconstruct the environmental conditions recorded in this lithostratigraphic unit. Fieldworks revealed a rich ichnofauna in the Floriano Formation, whose facies associations have been interpreted as indicative of meandering river environments. Four sedimentary facies were identified, including bioturbated sandstone, horizontally stratified sandstone, laminated sandstone, and mudstone. Six ichnogenera were identified, Arenicolites, Beaconites, Camborygma, Palaeophycus, Skolithos, and Taenidium. Those ichnogenera occur as Skolithos, Taenidium, and Beaconites ichnocoenoses. The Skolithos ichnocoenosis is primarily represented within sand bar deposits, indicating arthropod colonization in abandoned channels. The Taenidium ichnocoenosis, which is observed within mudstone layers and presents Camborygma burrows, suggests transitional environments between aquatic and subaerial conditions, locally with high water table levels. The Beaconites ichnocoenosis indicates changes in substrate consistency associated with progressive desiccation and extended exposure time. Therefore, the identified ichnocoenoses, combined with the analysis of physical sedimentary structures, suggest generally humid conditions during colonization by invertebrates of the meandering river deposits of the Floriano Formation.

Abstract A worldwide revision of the Cretaceous record of Neornithes (crown birds) revealed that unambiguous neornithine taxa are extremely scarce, with only a few showing diagnostic features to be confidently assigned to that group. Here we report two new neornithine specimens from Vega Island (López de Bertodano Formation). The first is a synsacrum (MN 7832-V) that shows a complex pattern of transversal diverticula intercepting the canalis synsacri, as in extant neornithines. Micro-CT scanning revealed a camerate pattern of trabeculae typical of neornithines. It further shows the oldest occurrence of lumbosacral canals in Neornithes, which are related to a balance sensing system acting in the control of walking and perching. The second specimen (MN 7833-V) is a distal portion of a tarsometatarsus sharing with Vegavis iaai a straight apical border of the crista plantaris lateralis. Osteohistologically the tarsometatarsus shows a thick and highly vascularized cortex that lacks any growth marks, resembling Polarornis gregorii. The cortex is osteosclerotic as in other extinct and extant diving neornithines. These new specimens increase the occurrences of the Cretaceous avian material recovered from the Upper Cretaceous strata of the James Ross Sub-Basin, suggesting that a Vegaviidae-dominated avian assemblage was present in the Antarctic Peninsula during the upper Maastrichtian.

A Bacia Bauru congrega um dos mais ricos conjuntos de somatofósseis de tetrápodes do território brasileiro, sendo cerca de 70% dessa paleodiversidade procedente de seus depósitos em São Paulo. Com registros conhecidos desde o início do século XX, tais fósseis foram coletados em todas as unidades estratigráficas da Bacia que afloram no estado, i.e., formações Santo Anastácio, Araçatuba, Adamantina (alternativamente dividida em formações Vale do Rio do Peixe, Presidente Prudente e São José do Rio Preto) e Marília. Os grupos registrados incluem raros anuros, mamíferos e escamados, um importante conjunto de testudinos, dinossauros terópodes (incluindo aves) e saurópodes, além de uma das mais diversas faunas de crocodiliformes conhecidas para o registro fóssil global. Tal conjunto congrega mais de cinquenta entidades taxonômicas distintas, incluindo 42 espécies formalmente descritas. A partir de dados de cunho bioestratigráfico, incluindo correlação com base em tetrápodes, e em poucas datações absolutas, a totalidade dos depósitos da Bacia Bauru em São Paulo parece estar cronologicamente restrita ao Neocretáceo, mas um maior detalhamento de tais inferências se faz extremamente necessário. Por fim, o histórico das pesquisas com tais fósseis de tetrápodes evidencia a importância da interiorização do ensino universitário e do financiamento público à pesquisa para o desenvolvimento das ciências.

Abstract Carbonate deposits are numerous and have undeniable economic appeal for the oil industry. However, there are many uncertainties associated with different aspects of these lithologies. Understanding carbonate factories and their global distribution has been a subject of discussion in recent decades, especially concerning the products expected from different carbonate systems, their response to sea‐level variations and the transition between different depositional environments. Therefore, the goal of this study was to understand the role of sea‐level variations, and geodynamics in factories and the evolution of Albian depositional sequences on the south‐east continental margin of Brazil. Fifteen lithofacies consisting of seven facies associations and five third‐order sequences were identified. Sequence boundaries are unconformities formed by erosion or non‐deposition surfaces, representing either exposure periods or drowning events, and their correlative condensed sections. The first sequence, deposited in a shallow lagoon environment, recorded the onset of the T‐factory and the start‐up phase of the shelf. The second sequence represents a period of broad carbonate deposition in the basin, related to the catch‐up phase of the platform. The third sequence was established during a sea‐level rise and recorded the keep‐up phase of the platform and the transition from tropical to cool waters. The fourth sequence, was deposited in a deep marine environment and the fifth and last, recorded the shelf drowning. The succession typifies the beginning, the pinnacle and the end of carbonate deposition, spanning the initial and final highstand system tracts. The whole succession is part of a first‐order transgressive cycle that led to a factory transition and culminated with the definitive drowning of the depositional system.

Abstract We present the analysis of airborne and ground gamma-ray spectrometry signatures of the Araguainha impact structure, located in central Brazil, the largest impact structure in South America with ~ 40 km diameter. The airborne data are total gamma-ray counts per second collected along flight lines spaced 1 km apart. The ground gamma-ray data are concentrations of potassium, uranium, and thorium isotopes calculated from radiations measured in three individual channels. The objectives are to distinguish lithologies within the structure, which have naturally distinctive radiogenic signatures, and identify potential post-impact hydrothermal alteration zones, as indicated by high K concentrations. Based on results obtained by numerical modeling of the crater formation, we infer the locations of potential occurrences of target rocks that may have undergone hydrothermal alteration as a result of the impact. The deviations from the background potassium concentration show significant anomalous K values at the center and in the northwestern crater rim, where high concentrations of U are also observed. The numerical model shows that ideal temperature conditions for hydrothermal fluid circulation were attained right after pos-impact gravitational stabilization.

Abstract Tectonic rejuvenation has been widely described in ancient rifting areas of intraplate settings, despite extensive active tectonics being discontinued long ago. Various models have been invoked to justify such tectonic rejuvenation, suggesting that the long-term deformation in intraplate interiors may be more complex than once supposed. Inherited weakness zones, e.g., pre-existing faults are stress concentrators. However, not all weakness zones in plate interiors show tectonic rejuvenation and recognizing intraplate fault reactivation remains puzzling. Bedrock channels play an essential role in tectonically unstable landscapes and therefore they may unveil which pre-existing structures have been rejuvenated. Here we explore the Cinzas Catchment in order to investigate the interactions between tectonic rejuvenation, bedrock inheritance and geomorphic river signatures in an important Brazilian rifting feature, the Ponta Grossa Arch. We perform a geomorphic analysis combined with fieldwork, dating techniques and existing data to evaluate whether the geomorphic responses of the major rivers show perturbations related to the bedrock inheritance and post-rift rejuvenation. We also show that the interactions between river signatures and the bedrock fault zones are responses to post-rifting rejuvenation coupled with bedrock inheritance. This post-rifting rejuvenation is consistent with a mosaic of superimposed mechanisms which have been invoked by previous studies.

The sedimentary basins in the Continental Rift of Southeastern Brazil (CRSB) provide an opportunity for ichnological analyses due to its well-known facies relationships and paleoenvironmental interpretations. This study reports invertebrate trace fossils from the Neogene fluvial deposits (Floriano Formation) and applies integrated ichnological and facies analyses to reconstruct the environmental conditions recorded in this lithostratigraphic unit. Fieldworks revealed a rich ichnofauna in the Floriano Formation, whose facies associations have been interpreted as indicative of meandering river environments. Four sedimentary facies were identified, including bioturbated sandstone, horizontally stratified sandstone, laminated sandstone, and mudstone. Six ichnogenera were identified, Arenicolites, Beaconites, Camborygma, Palaeophycus, Skolithos, and Taenidium. Those ichnogenera occur as Skolithos, Taenidium, and Beaconites ichnocoenoses. The Skolithos ichnocoenosis is primarily represented within sand bar deposits, indicating arthropod colonization in abandoned channels. The Taenidium ichnocoenosis, which is observed within mudstone layers and presents Camborygma burrows, suggests transitional environments between aquatic and subaerial conditions, locally with high water table levels. The Beaconites ichnocoenosis indicates changes in substrate consistency associated with progressive desiccation and extended exposure time. Therefore, the identified ichnocoenoses, combined with the analysis of physical sedimentary structures, suggest generally humid conditions during colonization by invertebrates of the meandering river deposits of the Floriano Formation. [ABSTRACT FROM AUTHOR]

O presente trabalho tem como objetivo discutir a aplicabilidade e as limitações do uso de estimativas de paleoprecipitação e paleotemperatura em paleossolos da Formação Marília, Neocretáceo da Bacia Bauru. Foram descritas três seções (A1, A2 e A3), compreendendo nove perfis. Os elementos maiores, menores e traços foram determinados por Espectrometria de Fluorescência de Raios-X e as estimativas se basearam em equações exponenciais e regressões lineares. Na Formação Marília, os paleossolos desenvolvimentos sobre arenitos apresentam horizontes argílicos (Btk e Bt) e carbonáticos (Bk) com distintos graus de cimentação, constituindo-se calcretes em sua maioria. Os paleossolos com Bk apresentaram valores médios de 420 e 500 mm/ano, respectivamente para as seções Botucatu (A1) e Garça (A3). Nos paleossolos com Bt, a média de paleoprecipitação foi 881 mm/ano e a média anual de paleotemperatura foi de 10 ºC. Paleossolos com Btk revelaram valores médio de precipitação de 605 mm/ano. As variações de precipitação, tomadas individualmente e indutivamente, proporcionaram a definição de três intervalos paleoclimáticos para o Maastrichtiano da Bacia Bauru. No entanto, a variabilidade dos atributos verticais e horizontais dos solos, bem como o uso excluso dessa técnica como principal método, inviabilizaram a utilização das climofunções, que não alcançaram consenso, em estudos paleoclimáticos.

Geochemistry of major and trace elements has been used as an important tool for the study of provenance and tectonic and climatic evolution of sedimentary basins. The São Carlos Formation is an Upper Cretaceous unit that lies on the eastern border of the Bauru Basin. Despite the paleontological and paleodepositional studies performed in this unit in the last years, little is known about the correspondence between tectonic and climatic conditions acting during the first stages of sedimentation. The hypothesis of this paper is to evaluate São Carlos and Araçatuba formations and understand the evolution of the eastern border of the basin. Thus, were conducted geochemical studies using X-ray fluorescence on sandstones, siltstones, and shales from the São Carlos Formation. According to the chemical weathering index, which presented values ranging from 57.12 to 71.58%, the oxides of major elements indicate that moderate weathering processes affected the source area, possibly associated with the arid-semiarid climate. Alkaline rocks, granites, gneisses, and metasediments were the main lithotypes of the source area. Ternary diagrams show that the tectonic environment was equivalent to the passive continental margin, coinciding with the Serra do Mar and, secondarily, Alto Paranaíba Uplift regions. Based on major and trace elements, their ratios, and published data on the basin, was elaborated a paleogeographic model of the eastern border of the Bauru Basin, concluding that the source area of the sediments was constituted by intermediate and felsic rocks, sometimes recycled by sedimentary processes.

Este trabalho reúne e discute as principais técnicas de estudo de indicadores geomórficos desenvolvidas por diversos pesquisadores ao longo do tempo e, correntemente, aplicadas à investigação de deformação tectônica/neotectônica/tectônica ativa. A drenagem é um dos elementos mais sensíveis a modificações do relevo, sobretudo àquelas relacionadas a manifestações tectônicas e/ou mudanças climáticas, a oscilações do nível do mar, ou ainda à ação antrópica. Esta sensibilidade dos rios frente a modificações do relevo reflete, não somente, em sua rápida resposta morfológica/morfométrica e sedimentar, mas também no rápido ajuste a um estágio de quase-equilíbrio em curtos períodos de tempo geológico. Isto permite inferir atividade tectônica recente, mediante identificação de regiões em desequilíbrio erosional em áreas de grande extensão, independentemente de províncias geológicas ou geomórficas. Tal característica singular dos rios reforça a importância de identificação de comportamentos anômalos destes em investigações de atividade tectônica e da evolução de ambientes modernos ou reconstituição paleogeográfica. Desta forma, a revisão apresentada considera os índices relacionados a características quantificáveis do relevo, tais como altimetria, hipsometria e declividade, e, sobretudo, a indicadores relacionados a respostas geomórficas e de sedimentação de rios frente a deformação tectônica (desvios, capturas e decapitação; sinuosidade; mudança de padrão de drenagem; migração e avulsão; deformação de perfis longitudinais e índice SL; assimetria e forma da bacia hidrográfica; sinuosidade de rios e padrão de canal, Sinuosidade de front de montanha (Smf); Índice de atividade tectônica relativa (Iat) e carga sedimentar e fluxo, entre outros). Para tal objetivo, o presente estudo envolveu revisão bibliográfica e leitura dos autores proponentes de tais técnicas, enriquecida pela exemplificação de alguns estudos de caso, como no rio Aiuruoca (Serra da Mantiqueira, MG) e rios das Cinzas e Laranjinha (bacia do rio das Cinzas, norte do estado do Paraná). Distante de uma pretensão de totalizar ou encerrar o assunto, este trabalho propõe auxiliar na estratégia de investigação e no processo de escolha das diversas técnicas existentes, bem como contribuir para um melhor entendimento e aplicação destas.

O presente trabalho tem como objetivo determinar o índice de intemperismo médio (m), de alteração geoquímica (CIA-K) e de morfologia (MI) para avaliar o grau de evolução dos paleossolos da Formação Marília, Maastrichtiano da Bacia Bauru. Foram descritas três seções da Formação Marília (A1, A2 e A3), compreendendo nove perfis. Na caracterização das seções, horizontes carbonáticos (Bkm) e argílicos (Btkm e Bt) foram identificados nos paleossolos da área de estudo. Os índices de intemperismo médio, de alteração geoquímica e de morfologia foram determinados para os horizontes dos paleossolos, de acordo com a literatura especializada.Os paleossolos com horizonte Bt foram os mais intemperizados, indicativos de períodos com maiores taxas de precipitação e lixiviação no Maastrichtiano da Bacia Bauru. Os paleossolos com horizonte Bkm apresentaram os menores índices sendo, portanto, testemunhos, vestígios de momentos de maior semiaridez da Formação Marília. No entanto, apesar de apresentarem baixos índices, os paleossolos com Bkm podem ser considerados evoluídos em condições semiáridas, pois apresentaram estágios de cimentação carbonática III e V.

In the last three decades, records of tribosphenidan mammals from India, continental Africa, Madagascar and South America have challenged the notion of a strictly Laurasian distribution of the group during the Cretaceous. Here, we describe a lower premolar from the Late Cretaceous Adamantina Formation, São Paulo State, Brazil. It differs from all known fossil mammals, except for a putative eutherian from the same geologic unity and Deccanolestes hislopi, from the Maastrichtian of India. The incompleteness of the material precludes narrowing down its taxonomic attribution further than Tribosphenida, but it is larger than most coeval mammals and shows a thin layer of parallel crystallite enamel. The new taxon helps filling two major gaps in the fossil record: the paucity of Mesozoic mammals in more northern parts of South America and of tribosphenidans in the Cretaceous of that continent. In addition, high-precision U-Pb geochronology provided a post-Turonian maximal age (≤87.8 Ma) for the type stratum, which is overlain by the dinosaur-bearing Marília Formation, constraining the age of the Adamantina Formation at the site to late Coniacian–late Maastrichtian. This represents the first radioisotopic age for the Bauru Group, a key stratigraphic unit for the study of Cretaceous tetrapods in Gondwana.

Tectonic rejuvenation has been widely described in ancient rifting areas of intraplate settings, despite extensive active tectonics being discontinued long ago. Various models have been invoked to justify such tectonic rejuvenation, suggesting that the long-term deformation in intraplate interiors may be more complex than once supposed. Inherited weakness zones, e.g., pre-existing faults are stress concentrators. However, not all weakness zones in plate interiors show tectonic rejuvenation and recognizing intraplate fault reactivation remains puzzling. Bedrock channels play an essential role in tectonically unstable landscapes and therefore they may unveil which pre-existing structures have been rejuvenated. Here we explore the Cinzas Catchment in order to investigate the interactions between tectonic rejuvenation, bedrock inheritance and geomorphic river signatures in an important Brazilian rifting feature, the Ponta Grossa Arch. We perform a geomorphic analysis combined with fieldwork, dating techniques and existing data to evaluate whether the geomorphic responses of the major rivers show perturbations related to the bedrock inheritance and post-rift rejuvenation. We also show that the interactions between river signatures and the bedrock fault zones are responses to post-rifting rejuvenation coupled with bedrock inheritance. This post-rifting rejuvenation is consistent with a mosaic of superimposed mechanisms which have been invoked by previous studies. [ABSTRACT FROM AUTHOR]

RESUMO Com uma área de 1.600.000 Km2 na região sudeste do Brasil, a Bacia Sedimentar do Paraná tem posição de destaque mundial com relação sua potencialidade para recursos hídricos, por abrigar estratos rochosos com características de permo-porosidade adequadas ao armazenamento de água. A partir da análise de bacia sedimentar integrada, utilizando informações de afloramentos e poços tubulares profundos, foi feita a caracterização de três sistemas de aqüíferos (Botucatu, Serra Geral e Bauru) para uma região que abrange o extremo oeste do Estado de Minas Gerais (Triângulo Mineiro), e áreas adjacentes nos estados de São Paulo, Goiás e Mato Grosso do Sul. As informações obtidas subsidiaram a confecção de mapas de distribuição de fácies reservatórios, isoespessuras, contorno estrutural e lineamentos estruturais. Dessa forma, foi possível avaliar características dos sistemas de aqüíferos, tais como, espessuras médias, cota topográfica de topo das formações, bem como suas vazões médias, apontando áreas favoráveis a execução de projetos para explotação das águas, de acordo com as necessidades de cada região. ABSTRACT Basin Analysis Applied To The Mesozoic Units Of Triângulo Mineiro (Southeast Of Brazil): A New Strategy Of Groundwater Exploration. The Paraná Basin has been occupied an important position in the world because of the groundwater potential in their geological units, distributed in area with 1.600.000 Km2 in the southeast portion of Brazil. Based on surface and sub-surface data, the basin analysis applied to the western portion of the Minas Gerais (Triângulo Mineiro area), and adjacent portions in the states of São Paulo, Mato Grosso do Sul and Goiás, has allowed to characterize the groundwater systems (Botucatu, Serra Geral and Bauru units). The information has shown as reservoirs facies, structural contorn and structural lineaments maps. Thus it was possible to define characteristic like median thick of reservoir, topographic level of the top units, median outflow, that has allowed to select the better areas to groundwater exploration projects. Because of the increase in the waters waste in the Triângulo Mineiro region, the basin analysis method applied in the Mesozoic units suggest the Botucatu groundwater system should be the mainly target of groundwater exploration projects.

Carbonate deposits are numerous and have undeniable economic appeal for the oil industry. However, there are many uncertainties associated with different aspects of these lithologies. Understanding carbonate factories and their global distribution has been a subject of discussion in recent decades, especially concerning the products expected from different carbonate systems, their response to sea‐level variations and the transition between different depositional environments. Therefore, the goal of this study was to understand the role of sea‐level variations, and geodynamics in factories and the evolution of Albian depositional sequences on the south‐east continental margin of Brazil. Fifteen lithofacies consisting of seven facies associations and five third‐order sequences were identified. Sequence boundaries are unconformities formed by erosion or non‐deposition surfaces, representing either exposure periods or drowning events, and their correlative condensed sections. The first sequence, deposited in a shallow lagoon environment, recorded the onset of the T‐factory and the start‐up phase of the shelf. The second sequence represents a period of broad carbonate deposition in the basin, related to the catch‐up phase of the platform. The third sequence was established during a sea‐level rise and recorded the keep‐up phase of the platform and the transition from tropical to cool waters. The fourth sequence, was deposited in a deep marine environment and the fifth and last, recorded the shelf drowning. The succession typifies the beginning, the pinnacle and the end of carbonate deposition, spanning the initial and final highstand system tracts. The whole succession is part of a first‐order transgressive cycle that led to a factory transition and culminated with the definitive drowning of the depositional system. [ABSTRACT FROM AUTHOR]

The Marília Formation is a lithostratigraphic unit positioned at the top of the Bauru Group of Maastrichtian age. The present work presents a provenance study of the Marília Formation sandstones through the combined dating of the fission‐track method (FTM) and U–Pb, in which individual zircon grains are simultaneously dated by these two methods. Thirty‐one zircons were dated in the C5 sample and 26 in the C7 sample for a total of 57 grains. The data demonstrated a wide range of U–Pb ages, presenting maximum and minimum ages, respectively: 2,905 ± 11 and 128 ± 1 Ma for the C7 sample and 2,676 ± 10 and 455 ± 5 Ma for the C5 sample. Regarding the fission‐track (FT) ages, they have been grouped into three time intervals, which are associated to geological events relatively well recognized in the published literature: ages younger than 250 Ma (Wealdenian Reactivation); between 250 and 470 Ma (Palaeozoic orogenesis—Ocloyic, Precordilleran, Chanic, and Sanrafaelic); and older than 470 (Precambrian collisions—Brasiliano I, II, and III). There is a predominance of results of Precambrian age using the U–Pb dating, mainly in the Neopalaeoproterozoic, and with FT dating corresponding to the Ocloyic, Precordilleran, Chanic, and Sanrafaelic orogeneses. From the comparison of the results between the two dating methods, the age variations suggest that the zircons originated during the main south‐western orogenesis of Gondwana and were reworked during the Palaeozoic and Mesozoic geological episodes. The ages associated to the Upper Cretaceous are related to the tectonic and magmatic activity of the Alto Paranaiba Uplift. [ABSTRACT FROM AUTHOR]

The Late Cretaceous Marília Formation located in the central-southern portion of Brazil is characterized by a succession of sandstones, conglomerates, and paleosols. The paleosols constitute more than 60% of this formation, providing significant information about pedogenetic processes as well as paleoenvironmental and paleoclimate implications. The paleosols of the Marília Formation have been studied principally from a stratigraphical, sedimentological and paleopedological point of view; however, there are no studies addressing in detail the geochemical behavior of the paleosols. Therefore, we used a robust geochemical dataset combined with stratigraphical and macromorphological interpretations as well as clay mineralogy to conduct a paleoenvironmental and paleoclimate analysis of the Marília Formation in the western portion of the state of Minas Gerais in Brazil. The results indicate that the paleosols of the Marília Formation can be divided into three pedotypes and pedochemical units based on their geochemical variations and are limited at the base and top by pedochemical markers. Moreover, X-ray diffraction identified quartz and calcite as primary minerals associated with montmorillonite, smectite, illite and palygorskite, indicating wet periods combined with dry stages associated principally with dry and arid environments. The paleosol distribution and weathering index allow us to interpret the paleoenvironmental evolution of the Late Cretaceous Marília Formation, suggesting an increase in humidity from east to west in the study area. • A new approach using pedochemistry analysis was used. • Three pedochemical units and geochemical markers were identified. • Seasonal variations based on weathering indexes were observed. • Paleoenvironmental and paleoclimate conditions indicate arid to semiarid climate. [ABSTRACT FROM AUTHOR]

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The Upper Cretaceous Bauru Group in south‐east Brazil consists of alluvial strata whose characteristics and distribution indicate a fluvial system developed in a semi‐arid to arid climate. Sections exposed within a 90 000 km2 study area in Minas Gerais State (in south‐eastern Brazil) were evaluated using facies and palaeosol analysis to formulate depositional and pedogenic models that may account for geomorphic and climate features. From east to west, the study succession records a gradual decrease in grain size, an increase in the width/thickness ratio in channels, a decrease in the lateral and vertical connectivity of channel deposits, and an increase in overbank deposits. The fluvial architecture indicates a braided channel belt, ephemeral ribbon–channels, and an unconfined fluvial facies from east to west in the study area. The lateral and vertical distribution of facies, stratigraphic architecture and palaeocurrent data suggest proximal, medial and distal portions of a progradational distributive fluvial system. The sedimentary dynamics were marked by the building and abandonment of channels related to processes of aggradation, vegetation growth and palaeosol generation. Macromorphological and micromorphological analyses have identified pedological and mineralogical features that indicate an arid to semi‐arid climate with a provenance from the north‐eastern part of the basin (Alto Paranaiba Uplift). From the proximal to the distal portions of the distributive fluvial system, the palaeosol development is different. In the proximal portion, the palaeosols are absent or poorly developed, allowing a possible general comparison with the present soil order: Inceptisols and Aridisols. In the medial portion of the fluvial system, the palaeosols are well‐developed and characterized by Bt, Btk, C and Ck horizons (Alfisols, Aridisols, Inceptisols and Entisols). Poorly drained to well‐drained palaeosols from the base to the top in the distal plain (Aridisols and Inceptisols) are associated with geomorphic and hydromorphic changes in the fluvial system due to progradational evolution. The genetic relationship between the fluvial architecture and the palaeosols enhances the understanding that the sedimentation and pedogenesis that occurs in different portions of the distributive fluvial system are related to the tectonic and climatic evolution of the basin. [ABSTRACT FROM AUTHOR]

Abstract Rhizoliths are organosedimentary structures produced by plants and are an important proxy for paleoenvironmental reconstructions because the differences in the morphology of rhizoliths and their rooting depths can be used to interpret soil humidity regimes, overall biomass at the soil surface, and the behavior of the water table. With the objective of advancing knowledge on rhizoliths, a study was performed on the macromorphological and micromorphological characterizations of the rhizoliths preserved in the thirty-one paleosols of the Marília Formation in Minas Gerais, southeastern Brazil. Based on the topological and architectural attributes of rhizoliths, and on their possible functional adaptations, such as mycorrhizal associations, three different types of rhizoliths are described in this study and represent at least three different plants: rhizohaloes, root casts and rhizocretions. Well-developed paleosols with nodular horizons contain the higher density of long root casts, indicating a seasonally dry environment, because the root casts present two meters in length. These adaptations are associated with an exploitation of a lowered water table during most times of the year. The higher density of rhizoliths indicates an area with agglomerated arboreous arbustive vegetation cover. Paleosols with chalky horizons also show a high density of root casts, indicating a landscape with high plant density that is adapted to drained soils, but with a seasonally elevated water table or the influence of ephemeral flows, given the proximity to the flow channels. The poorly drained paleosols with redoximorphic features show the lowest density of rhizoliths, thus indicating an incipient vegetation in response to near-surface water table and waterlogged soils in a distal floodplain. The rhizogenic laminar horizons have developed near fluvial channels with frequent sedimentary input, resulting in a sequence of laminar horizons composed of rhizocretions that are separated by sandy deposits or poorly developed pedogenic horizons. The micromorphological analysis on the rhizogenic laminar calcretes showed biogenic features, such as alveolar septal structures, calcified filaments, microcodium, calcified cells and pisoliths. Despite the scarce paleobotanical findings in the Marília Formation, the results obtained indicate an ecosystem that was composed of plants varying from herbaceous to arboreous, with an environment similar to modern semiarid shrublands. Graphical abstract Unlabelled Image Highlights • The architecture and geometry of rhizoliths indicate different types of paleosols. • The preservation of rhizoliths are linked to the paleosols characteristics. • A link between the type of rhizolith and paleotopography was established. [ABSTRACT FROM AUTHOR]