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)

André Marconato

Universidade de São Paulo

Nigel P. Mountney

University of Leeds

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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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)

Microbially induced pseudotraces from a Pantanal soda lake, Brazil: Alternative interpretations for Ediacaran simple trails and their limits

Geology (2020)

Lucas V. Warren Luís A. Buatois M. Gabriela Mángano Marcello Guimarães Simões Maurício G. M. Santos

Abstract Despite the absence of metazoans, structures resembling animal traces are common in a soda lake from the western Brazil Pantanal wetland. Pantanal soda lakes are ecologically extreme environments that preclude complex life, allowing extremophiles to flourish. Direct observation indicates that these structures are pseudotraces, representing groove marks that result from the interaction of wave-transported floating rafts of epibenthic microbial mat fragments with the substrate. Variations in wind/wave direction and intensity result in marks of different size and morphology. The most common pseudotraces are simple and slightly curved, narrow grooves (type 1), whereas others are straight and present raised lateral ridges (type 2). Both are V-shaped in cross section. Type 3 comprises long, sinuous, shallow grooves, displaying internal crescentic laminated infill and U-shaped cross section. The similarity of these pseudotraces to Ediacaran structures usually interpreted as animal trace fossils suggests that care should be exercised in their analysis. A set of criteria is proposed to differentiate microbially induced pseudotraces from trace fossils. Analysis of Ediacaran structures needs to be performed on a case-by-case basis, taking into account morphology, orientation, and preservation style of the structure, sedimentary environment, and presence or absence of microbial mats.

Microbial mat

Infill

10.1130/g47234.1

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Citations (9)

Tracking triggering mechanisms for soft-sediment deformation structures in the Late Cretaceous Uberaba Formation, Bauru Basin, Brazil

Brazilian Journal of Geology (2020)

Luciano Alessandretti Lucas V. Warren Maurício G. M. Santos Matheus Carvalho Virga

Soft-sediment deformation (SSD) structures are widespread in the sedimentary record, and numerous triggering mechanisms can induce its development, including glaciation, earthquakes, overloading, ground-water fluctuations, and wave movement. The Late Cretaceous Uberaba Formation preserves SSD structures as small- and large-scale load casts and associated flame structures, pseudonodules, and convolute laminations observed in the contact of three well-defined intervals among fine- to coarse-grained lithic and conglomeratic sandstone with fine-grained arkose and mudstone beds. Based on the morphology of the SSD structures, sedimentary facies of the Uberaba Formation, and similarities with previous observations in the geological record and laboratory models, these features are assigned to liquefaction-fluidization processes as the major deformational mechanism triggered by seismic and aseismic agents. We propose that a deformation occurred just after the sedimentation triggered by seismic shock waves and overloading, induced by the sudden deposition of coarse-grained sandy debris on fine-grained sediments. Some of these structures can be classified as seismites, providing evidence of intraplate seismicity within the inner part of the South American Platform during the Late Cretaceous. This seismic activity is likely related to the uplift of the Alto Paranaíba High along reactivations of regional structures inherited from Proterozoic crustal discontinuities and coeval explosive magmatism of the Minas-Goiás Alkaline Province.

10.1590/2317-4889202020190100

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Citations (8)

Tectonic and environmental controls on Palaeozoic fluvial environments: reassessing the impacts of early land plants on sedimentation

Journal of the Geological Society (2016)

Maurício G. M. Santos Nigel P. Mountney Jeff Peakall

The apparent increase in occurrence of meandering fluvial channel systems in the Middle Palaeozoic has long been related to the effects of land-plant colonization. However, evidence for meandering channels in non-vegetated settings is shown by pre-vegetation successions on Earth, from the prevalence of meandering channels on Mars, from physical modelling of meandering channels, and from non-vegetated channels in modern desert basins. In addition, early land plants had small dimensions, were limited in their occurrence, and were dependent on environmental factors. Here, we question the capacity of early land plants to impose the major impacts suggested by current models. We propose that the sudden widespread occurrence on Earth of fluvial deposits indicative of the accumulation of meandering river systems in the Middle Palaeozoic was primarily an effect of environmental and tectonic conditions that prevailed during this period. These conditions induced a worldwide increase in the proportion of meandering rivers, which in turn helped favour the appropriate environment for land-plant colonization of the continents. We propose that land plants opportunistically took advantage of an appropriate global environment, which enabled them to thrive in continental environments. Fluvial environments characterized by single-channel systems and stable floodplains facilitated the greening of the land.

Sedimentation

10.1144/jgs2016-063

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Citations (49)

Reply to Discussion on ‘Tectonic and environmental controls on Palaeozoic fluvial environments: reassessing the impacts of early land plants on sedimentation’ Journal of the Geological Society, London , https://doi.org/10.1144/jgs2016-063

Journal of the Geological Society (2017)

Maurício G. M. Santos Nigel P. Mountney Jeff Peakall Robert E. Thomas Paul B. Wignall

Sedimentation

10.1144/jgs2017-031

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Citations (8)

Recurring extensional and strike-slip tectonics after the Neoproterozoic collisional events in the southern Mantiqueira province

Anais da Academia Brasileira de Ciências (2012)

Renato Paes de Almeida Maurício G. M. Santos Antônio Romalino Santos Fragoso-Cesar Liliane Janikian Gélson Luís Fambrini

In Eastern South America, a series of fault-bounded sedimentary basins that crop out from Southern Uruguay to Southeastern Brazil were formed after the main collisional deformation of the Brasiliano Orogeny and record the tectonic events that affected the region from the Middle Ediacaran onwards. We address the problem of discerning the basin-forming tectonics from the later deformational events through paleostress analysis of more than 600 fault-slip data, mainly from the Camaquã Basin (Southern Brazil), sorted by stratigraphic level and cross-cutting relationships of superposed striations, and integrated with available stratigraphic and geochronological data. Our results show that the Camaquã Basin was formed by at least two distinct extensional events, and that rapid paleostress changes took place in the region a few tens of million years after the major collision (c.a. 630 Ma), probably due to the interplay between local active extensional tectonics and the distal effects of the continued amalgamation of plates and terranes at the margins of the still-forming Gondwana Plate. Preliminary paleostress data from the Castro Basin and published data from the Itajaí Basin suggest that these events had a regional nature.

Orogeny

Extensional tectonics

10.1590/s0001-37652012005000034

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Citations (44)

How Ground Penetrating Radar helps to understand the Nhecolândia lakes landscape in the Brazilian Pantanal wetland

Brazilian Journal of Geology (2021)

Fábio Taioli Maurício G. M. Santos Mário Luís Assine Déborah Mendes

The Pantanal wetland is an active sedimentary basin representing a relevant depositional setting for alluvial sedimentation studies. However, sedimentation homogeneity and the lack of outcrops makes sedimentary analysis more difficult. The Lower Nhecolândia is located at the Southern edge of the Taquari river megafan, whose genetic origin has been disputed as fluvial or eolian deposition. GPR analysis was used to characterize the subsurface stratigraphy and understand the region’s geomorphic evolution. The 100 MHz GPR provided continuous good quality sections up to a depth of 8 m. Two continuous reflections are disconformities that bound three depositional sequences characterized by distinct radar facies. The lower facies presents an upper erosional truncation followed by reflections presenting ∼1.5 m deep channelized forms and concave-up low amplitude reflections. The intermediate facies (∼4 m thick) presents a base with erosional truncation followed by concave-upward forms, ∼10 m wide, 1–3 m deep, separated by 1–2 m, and offlapping geometry. The upper facies has a flat base and thickness of 2–4 m, with parallel reflections; it shows a strong correlation between the radar facies and the forms preserved in the landscape, suggesting that channelized fluvial streams did not form them. The results obtained indicate that GPR use in the Pantanal is an important method to elucidate its geologic evolution.

Ground-Penetrating Radar

Alluvial fan

Bedform

Outcrop

10.1590/2317-4889202120200021

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Citations (2)

Uplifting mountains and shaking deserts: volcano-tectonic earthquakes revealed by soft-sediment-deformation structures in Upper Cretaceous aeolian deposits

Journal of Sedimentary Research (2023)

Luciano Alessandretti Lucas V. Warren Filipe Giovanini Varejão Raul Rassi Maurício G. M. Santos

ABSTRACT During the last stages of Gondwana fragmentation, large regions of the newly formed South American continent were covered by extensive deserts. Some parts of this continental landmass were synchronously affected by pronounced tectonism and magmatism, which were responsible for reshaping the regional topography. In this context, the southwestern part of the Sanfranciscana Basin in central Brazil is a key area for understanding this particular period in the geodynamic evolution of the South American continent. Aeolian deposits of the Posse Formation in the basin occur in direct association with volcanic rocks of the Upper Cretaceous Mata da Corda Group. Here, we report evidence of synsedimentary magmatism in direct association with soft-sediment-deformation structures, including flame structures, load casts and pseudonodules, water-escape structures, convolute lamination, faults, breccias, and clastic dikes, developed exclusively in aeolian sandstone and siltstone facies. The deformation features are interpreted as indicative of liquefaction, fluidization, and brittle behavior of the loose to partially lithified, wet sandy–silty sediments. The Late Cretaceous aeolian sedimentation is contemporaneous with the uplift of the Paranaíba High and associated magmatism in the Minas–Goiás Alkaline Province. In this context, these significant volcano-tectonic activities are considered to have triggered ductile to brittle deformation in the reported aeolian deposits.

Siltstone

10.2110/jsr.2021.143

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The Quaternary alluvial systems tract of the Pantanal Basin, Brazil

Brazilian Journal of Geology (2015)

Mário Luís Assine Éder Renato Merino Fabiano do Nascimento Pupim Hudson de Azevedo Macedo Maurício G. M. Santos

ABSTRACT The Pantanal Basin is an active sedimentary basin in central-west Brazil that consists of a complex alluvial systems tract characterized by the interaction between different river systems developed in one of the largest wetlands in the world. The Paraguay River is the trunk river system that drains the water and part of the sediment load received from areas outside of the basin. Depositional styles vary considerably along the river profiles throughout the basin, with the development of entrenched meandering belts, anastomosing reaches, and floodplain ponds. Paleodrainage patterns are preserved on the surface of abandoned lobes of fluvial fans, which also exhibit many degradational channels. Here, we propose a novel classification scheme according to which the geomorphology, hydrological regime and sedimentary dynamics of these fluvial systems are determined by the geology and geomorphology of the source areas. In this way, the following systems are recognized and described: (I) the Paraguay trunk-river plains; (II) fluvial fans sourced by the tablelands catchment area; (III) fluvial fans sourced by lowlands; and (IV) fluvial interfans. We highlight the importance of considering the influences of source areas when interpreting contrasting styles of fluvial architectures in the rock record.

Alluvial fan

Aggradation

Ephemeral key

10.1590/2317-4889201520150014

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Citations (86)

Seismites as a tool in the palaeoenvironmental reconstruction of fluvial deposits: The Cambrian Guarda Velha Formation, southern Brazil

Sedimentary Geology (2012)

Maurício G. M. Santos Renato Paes de Almeida Nigel P. Mountney Antônio Romalino Santos Fragoso-Cesar

10.1016/j.sedgeo.2012.07.006

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Citations (34)