Maurício G. M. Santos

Universidade Federal do ABC

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Renato Paes de Almeida

Universidade de São Paulo

Mário Luís Assine

Universidade Estadual Paulista (Unesp)

Lucas V. Warren

Universidade Estadual Paulista (Unesp)

Nigel P. Mountney

University of Leeds

André Marconato

Universidade de São Paulo

Luciano Alessandretti

Universidade Federal de Uberlândia

Antônio Romalino Santos Fragoso-Cesar

Instituto de Geociencias

Adrian J. Hartley

University of Aberdeen

Amanda Owen

University of Glasgow

Jeff Peakall

University of Leeds

Cooperative Institutions

Universidade de São Paulo

Instituto de Geociencias

Universidade Estadual Paulista (Unesp)

Universidade Brasil

Universidade Federal de Uberlândia

Sociedade Brasileira de Geofísica

National Council for Scientific and Technological Development

University of Leeds

Consejo Nacional de Investigaciones Científicas y Técnicas

Hospital Universitário da Universidade de São Paulo

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Meandering rivers in modern desert basins: Implications for channel planform controls and prevegetation rivers

Sedimentary Geology (2019)

Maurício G. M. Santos Adrian J. Hartley Nigel P. Mountney Jeff Peakall Amanda Owen

Meander (mathematics)

10.1016/j.sedgeo.2019.03.011

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Citations (47)

Megafans of the Pantanal Basin, Brazil

Cambridge University Press eBooks (2023)

Maurício G. M. Santos José Cândido Stevaux Mário Luís Assine

The Pantanal Basin (west-central Brazil) is one of the largest alluvial wetlands in the world (> 150,000 km2) formed dominantly by coalescing Quaternary megafans. The Pantanal Basin is an efficient sediment trap: of 25 Mt yr–1 of suspended load that enters by the main river systems, only 10 Mt yr–1 is exported by the trunk river. Sediments are sourced by multiple rivers draining Precambrian lowlands and Paleozoic uplands. The eastern border displays tablelands of Paleozoic rocks of the Paraná Sedimentary Basin, with lowlands of Precambrian rocks on the northern, southern and western borders. The Taquari, Cuiabá, and São Lourenço megafans, tributaries to the Paraguay trunk-river system, are the largest fluvial fans in the Pantanal. The Paraguay River itself has produced two relatively small megafans. The megafans display four main landform assemblages: incised meander belts proximally, active aggradational lobes, abandoned degradational lobes, and mixed-process floodplains. Megafan surfaces display palaeodrainage networks ranging from braided channel planforms to the current meandering and anabranching planforms. Megafan areas seem to be a function of both feeder-basin area and catchment geology: those fed from sedimentary rock outcrops are larger, with more complex barform development than those supplied from Precambrian basement catchments.

Alluvial fan

Aggradation

Alluvial plain

Basement

Outcrop

10.1017/9781108525923.009

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Alluvial-eolian interaction in a Cambrian rift margin: the Pedra das Torrinhas and Pedra Pintada formations (Guaritas Group, RS)

Anais da Academia Brasileira de Ciências (2009)

André Marconato Renato Paes de Almeida Maurício G. M. Santos Jorge E.S. Nóbrega Rogério Brandi de Souza

This work presents a study of selected outcrops from the Pedra das Torrinhas Formation of the Guaritas Group (Cambrian, Camaquã Basin), near the basin bordering Encantadas Fault Zone. The studied succession includes alluvial fan deposits that pass laterally into eolian deposits. Sedimentary facies and architectural element analysis were performed, followed by sedimentary petrography and microscopic porosity analysis, aiming to characterize the porosity of the deposits and its spatial distribution. The main objective was to contribute to a better understanding of the porosity spatial distribution in depositional systems characterized by the interaction between alluvial and eolian processes, with special reference to deposits formed prior to the development of terrestrial plants. Porosity values are related to depositional processes, with higher porosities associated to eolian dune deposits (mean of 8.4%), and lower porosity related to interdunes (mean of 3.4%) and alluvial fans (mean of 4.3%). Architectural elements analysis revealed the spatial relationships of these deposits, a response to the interplay of the eolian and alluvial processes. The integration of porosity data reveals that the interaction of alluvial and eolian processes results in heterogeneous distribution of porosity at the facies association scale. Eolian reworking of alluvial facies increases porosity whereas sheet-flood and other alluvial processes in the interdune areas reduce porosity.

Alluvial fan

Outcrop

10.1590/s0001-37652009000400018

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Citations (17)

Floodplain record of channelized and unconfined flow in a pre-vegetation setting in the Early Cambrian, Southern Brazil

Journal of South American Earth Sciences (2022)

André Marconato Renato Paes de Almeida Liliane Janikian Simone Campos Carrera Bruno Boito Turra

Aggradation

Alluvial plain

Overbank

10.1016/j.jsames.2021.103707

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Citations (6)

Geobotânica por sensoriamento remoto e aerogamaespectrometria aplicados ao mapeamento geológico da Amazônia: um estudo comparativo no vale do Guaporé (MT)

Brazilian Journal of Geology (2008)

Mônica Mazzini Perrotta Teodoro Isnard Ribeiro de Almeida João Batista Freitas de Andrade Carlos Roberto de Souza Filho Gilmar José Rizzotto

Remote sensing geobotany and airborne gamma-ray data applied to geological mapping of the Amazon: a comparative study in the Guapore Valley (Mato Grosso State, Brazil) This paper comprises a comparison between the vegetation response in ASTER multispectral optical imagery and possibly equivalent bedrock/regolith/soil response in airborne gamma-ray spectrometry grids, employing two tropical rainforest areas in the Brazilian Amazon as controls. The applied technique comprised band ratios using a fixed near infrared band (numerator) divided by individual visible and shortwave infrared bands (denominator). These band ratios were subsequently submitted to principal component analysis, and the high frequency information smoothed by low pass filtering. The color compositions selected for interpretation were sharpened by the first principal component of the originalASTER bands through an IHS transform in order to add albedo/ texture information - lost by band rationing - back to the imagery. The products show a plausible coherence with airborne gamma-ray data and field observations, proving that the proposed processing strategy applied to low cost multispectral data can provide useful geologic information in inaccessible vegetaded areas of the Amazon.

10.5327/rbg.v38i1.1351

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Tectônica e sedimentação na Bacia do Camaquã Central (RS): exemplos do Grupo Guaritas e do Grupo Santa Bárbara

Maurício G. M. Santos

10.11606/d.44.2010.tde-01062010-114015

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Citations (2)

Sedimentary evolution of distributive fluvial systems within intraplate tectonic active basins: Case study of the Early Cretaceous Araripina Formation (Araripe Basin, NE Brazil)

Journal of South American Earth Sciences (2021)

Lucas V. Warren André Santiago Martins de Andrade Filipe Giovanini Varejão Paloma Promenzio Maurício G. M. Santos

Paleocurrent

10.1016/j.jsames.2021.103496

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Citations (3)

Distinct styles of fluvial deposition in a Cambrian rift basin

Sedimentology (2013)

Maurício G. M. Santos Renato Paes de Almeida Lucas P. S. Godinho André Marconato Nigel P. Mountney

Abstract Process‐based and facies models to account for the origin of pre‐vegetation (i.e. pre‐Silurian) preserved fluvial sedimentary architectures remain poorly defined in terms of their ability to account for the nature of the fluvial conditions required to accumulate and preserve architectural elements in the absence of the stabilizing influence of vegetation. In pre‐vegetation fluvial successions, the repeated reworking of bars and minor channels that resulted in the generation and preservation of broad, tabular, stacked sandstone‐sheets has been previously regarded as the dominant sedimentary mechanism. This situation is closely analogous to modern‐day poorly vegetated systems developed in arid climatic settings. However, this study demonstrates the widespread presence of substantially more complex stratigraphic architectures. The Guarda Velha Formation of Southern Brazil is a >500 m‐thick synrift fluvial succession of Cambrian age that records the deposits and sedimentary architecture of three distinct fluvial successions: (i) an early rift‐stage system characterized by coarse‐grained channel elements indicative of a distributive pattern with flow transverse to the basin axis; and two coeval systems from the early‐ to climax‐rift stages that represent (ii) an axially directed, trunk fluvial system characterized by large‐scale amalgamated sandy braid‐bar elements, and (iii) a distributive fluvial system characterized by multi‐storey, sandy braided‐channel elements that flowed transverse to the basin axis. Integration of facies and architectural‐element analysis with regional stratigraphic basin analysis, palaeocurrent and pebble‐provenance analysis demonstrates the mechanisms responsible for preserving the varied range of fluvial architectures present in this pre‐vegetation, rift‐basin setting. Identified major controls that influenced pre‐vegetation fluvial sedimentary style include: (i) spatial and temporal variation in discharge regime; (ii) the varying sedimentological characteristics of distinct catchment areas; (iii) the role of tectonic basin configuration and its direct role in influencing palaeoflow direction and fluvial style, whereby both the axial and transverse fluvial systems undertook a distinctive response to syn‐depositional movement on basin‐bounding faults. Detailed architectural analyses of these deposits reveal significant variations in geometry, with characteristics considerably more complex than that of simple, laterally extensive, stacked sandstone‐sheets predicted by most existing depositional models for pre‐vegetation fluvial systems. These results suggest that the sheet‐braided style actually encompasses a varied number of different pre‐vegetation fluvial styles. Moreover, this study demonstrates that contemporaneous axial and transverse fluvial systems with distinctive architectural expressions can be preserved in the same overall tectonic and climatic setting.

10.1111/sed.12074

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Citations (39)

The Quaternary stratigraphy of the São Paulo Basin, southeastern Brazil

Journal of Maps (2022)

Renato Henrique‐Pinto Maurício G. M. Santos

Detailed sedimentological studies of the university main campus of São Paulo city, Brazil, revealed a significant unconformity at the top of the Cenozoic sedimentary deposits of the São Paulo Formation. This unconformity is overlapped by Quaternary sediments which can be traced in 1:20,000 scale and are here named as the Bosque Formation. This unit is characterized by poorly sorted mud deposits and very fine-grained red sand with granule- and pebble-sized clasts of the underlying São Paulo Formation. Furthermore, it overlies topographic highs of the Precambrian basement, and is laterally interfingered with fluvial terraces; it is eroded by the modern river at the lower reaches of the outcrops. The Bosque Formation records sedimentation characterized by a widespread mudflow that overlays old alluviums sediments, and was likely deposited during the beginning of the Holocene.

Outcrop

Pebble

Mudflow

10.1080/17445647.2021.2018367

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Citations (2)

Multi‐scale classification of fluvial architecture: An example from the Palaeocene–Eocene Bighorn Basin, Wyoming

Sedimentology (2017)

Amanda Owen Alena Ebinghaus Adrian J. Hartley Maurício G. M. Santos Gary S. Weissmann

Abstract Fluvial channel geometry classification schemes are commonly restricted in relation to the scale at which the study took place, often due to outcrop limitations or the need to conduct small‐scale detailed studies. A number of classification schemes are present in the literature; however, there is often limited consistency between them, making application difficult. The aim of this study is to address this key problem by describing channel body geometries across a depositional basin to ensure that a wide range of architectures are documented. This was achieved by studying 28 locations over 4000 m of vertical succession in Palaeocene‐aged and Early Eocene‐aged deposits within the Bighorn Basin, Wyoming, USA. Five different channel body geometries have been defined based on the external geometric form, and internal arrangement and nature of storey contacts. These include the massive channel body geometry, semi‐amalgamated channel body geometry, internally amalgamated channel body geometry and offset stacked channel body geometry, which are considered to be subdivisions of the sheet geometry of many other classifications. An isolated channel body geometry has also been recognized alongside splay channel and sheet sandstone geometries in the floodplain facies associations. Field evidence, including the stacking style of storey surfaces, suggests that the different geometries form a continuum. The nature and degree of amalgamation at the storey scale are important in producing the different geometries and are related to the degree of channel migration. It is speculated that this is the result of differences in sediment supply and available accommodation. In contrast to previous schemes, the classification scheme presented here recognizes the importance of transitional geometries. This geometrical range has been recognized because of the basin‐scale nature of the study.

Outcrop

Overbank

Sinuosity

10.1111/sed.12364

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Citations (44)