Angélica Fortes Drummond Chicarino Varajão

Universidade Federal de Ouro Preto · Departamento de Geo.ogia

Macromorphological and micromorphological characterization of the alteration facies associated with geomorphological studies are of great importance for understanding the genesis and evolution of ferruginous duricrusts. The study of the ferruginous duricrusts in the Diamantina Plateau (Southern Espinhaço Range, Minas Gerais), a region known worldwi...

This study is the first report of the fossil macroflora of the Paleolagoa Seca, an Upper Quaternary fossil locality of lacustrine origin in central Brazil. Here we present an analysis of well-preserved fossil leaves collected from an argillite level dated at ca. 43,000 cal yr BP and discuss the paleoclimatic implications of this record. We reconstr...

Volcanic oceanic islands host soils that may hold important paleo-environmental proxies, based on vegetation and faunal evidences coupled with pedological and geomorphological indicators. In this regard, the main Brazilian oceanic island of Fernando de Noronha (FNI) still lacks a deeper and more complete analysis of its climatic history and soil ev...

The Quadrilátero Ferrífero (QF), Southeastern Brazil, is a very important tropical highland region in the world’s geological context for its large and diverse Archean and Proterozoic rocks with great reserves of gold, iron, manganese, aluminum and industrial rocks, on a apparently stable geological structure. There, Cenozoic deposits perched on hig...

The pedological studies carried out so far in Trindade Island (TI) have obtained patchy evidences of allophane, without detailed mineralogical and micromorphological studies to confirm the occurrence of Andosols in TI. Therefore, in this study, the mineralogical, micromorphological, physical and chemical characterization of four soil profiles from...

This paper reports the composition and alteration products of pyroclasts in the Holocene Paredão volcano (pyroclast 1) and Late Quaternary Morro Vermelho Formation (pyroclasts 2 and 3) of Trindade Island, South Atlantic, Brazil using combined macromorphological, micromorphological, mineralogical and geochemical techniques. The pyroclasts 1 and 2 ar...

The geochemical behavior of the major, minor, trace and rare earths elements (REEs) in soil profiles from ultramafic volcanoclastic rocks of the Vulcão do Paredão and Morro Vermelho Formation from Trindade Island (TI) was analyzed in this study. Losses and gains of chemical elements were calculated through the mass balance for two profiles along th...

O turismo em Unidades de Conservação (UC) tem se apresentado como uma forma de conservação do patrimônio natural. Os Parques Estaduais do Itacolomi (PEIT) e do Rola-Moça (PESRM) / MG, localizados na área proposta para o Geoparque Quadrilátero Ferrífero, têm solos diferentes ao longo de importantes trilhas: do Pico do Itacolomi e Campo Ferruginoso r...

Trails and their elements, especially soils, tend not to be monitored, whether in urban or natural environments such as protected natural areas. Through tourism in parks, the public uses the trails to access the attractions, thus aff ecting the surface (and subsurface) of the soils. The aim of this study was to identify soil compaction and erosion...

O solo é parte essencial para a vida na Terra. As Geociências, em especial a Pedologia, têm um papel fundamental no balanceamento desta relação biótica-abiótica. Neste sentido propõe-se o pedoturismo como segmento turístico por meio da inventariação e avaliação de “Lugares de Interesse Pedológico” (LIPe) como produtos eco- e geoturísticos. Os métod...

In situ produced cosmogenic ¹⁰Be was used to determine denudation rates and to quantify how evolves the landscape in the Pancas Bomhardt Province, southeastern Brazil. This Province, one of the most remarkable landscapes of the Brazilian Atlantic shield is characterized by three morphological domains (stepped highland hills, bornhardts and smooth l...

Soil provides important support for anthropogenic activities, and earthen trails, which have always been present in the natural landscape, are routes of access to various tourist attractions. In recent decades, trails have been widely used as a method of access and visitation to geotouristic attractions. Because trails are restricted routes, transi...

Natural areas, rather than food sources and shelter from the urban routine, are information that should be better known. The protected areas are useful spaces for the development of the knowledge of nature and of the societies themselves. In the present work it was intended to know the visitor of the National Park of Serra do Cipó-NPSC (MG, Brazil)...

Natural areas, rather than food sources and shelter from the urban routine, are information that should be better known. The protected areas are useful spaces for the development of the knowledge of nature and of the societies themselves. In the present work it was intended to know the visitor of the National Park of Serra do Cipó – NPSC (MG, Brazi...

The alteration of olivine (forsterite) phenocrysts in three soil profiles that were developed on similar pyroclastic rocks from Trindade Island, at different altitudes and degree of development, were investigated in this study. Optical microscopy, Electron Probe Microanalysis (EPMA), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and D...

ABSTRACT Pedological studies using X-ray diffraction (XRD), X-ray fluorescence (XRF), optical microscopy, and scanning electron microscopy (SEM-EDS) showed a Xanthic Ferralsol formed from the degradation of bauxite on a slope in the Caparaó region, in southeastern Brazil. We found a decrease in the number and size of bauxite fragments toward the to...

A origem das depressões fechadas associadas à cobertura laterítica aluminosa nos topos dos morros e ao longo das vertentes na região de Espera Feliz, MG, divisa com Espírito Santo, foi pesquisada através de um levantamento geofísico da cobertura pedológica associado às análises morfológicas (macro e micro) de perfis de solos. O levantamento geofísi...

Adverse natural conditions will, generally, induce gemmulation in freshwater sponges. Because of this environmental dependence, gemmoscleres are given exceptional value in taxonomic, ecological and paleoenvironmental studies. Other spicules categories such as microscleres and beta megascleres have received little attention with regard to their occu...

Ceramic bodies (7.0 cm × 2.0 cm × 1.0 cm) of kaolinite clay and soapstone residuals collected from workshops in Ouro Preto and Mariana, Minas Gerais, Brazil, containing from 2.5 to 97.5 wt% steatite (soapstone) were prepared and firing at 500, 1000 and 1200 °C, for 2 h, in air. The linear shrinkage, compressive strength, water absorption and mass l...

Ceramic bodies composed of steatite residues from workshops from the region of Ouro Preto (MG-Brazil) and 15, 20 and 25% of kaolinite clay were fired at 1000 and 1200 °C for 2hrs in air to evaluate their technological properties. Essays of flexural strength and water absorption showed that ceramic bodies have a performance for their use as commerci...

The Be-10 method was used to investigate the effect of mining activities on the natural denudation rates in alluvial sediments from catchments of the Southern Espinhaco Range (SER) in Minas Gerais State (Brazil). In this region, which is predominantly composed of quartzites, the Be-10 concentrations were measured in alluvial sediments from catchmen...

Petrological studies using X-ray diffraction (XRD) and micromorphological analyses (Optical Microscopy and SEM), were done to understand the role of biological activity in the evolution of Barro Alto bauxite. The results indicated that this influence came through structural (or microstructural) and mineralogical transformations, namely: I — the bio...

No sudeste do Brasil, principalmente no Estado de Minas Gerais, são observados planaltos escalonados drenados por diferentes bacias hidrográficas, muitas vezes separadas entre si por nítidos degraus morfológicos resultantes da diferença no potencial erosivo de suas cabeceiras de drenagem, como resposta à tectônica distensiva cenozoica. Adicionalmen...

The mineralogical, geochemical and micromorphological features of an isalteritic clay facies, which originated from weathering of an anorthosite, were compared to those of clay facies derived from the degradation of a bauxite developed from the same rock. The isalteritic clay was formed by the hydrolytic alteration of plagioclase, whereas the degra...

Siliceous sponge spicules constitute an important siliceous component of lacustrine sediments, together with widespread diatom frustules. In contrast to diatom frustules, siliceous spicules are formed in sponges in an enzymatic way. Previous attempts to use their oxygen isotopic signature (δ18Osilica) as a paleoenvironmental proxy have led to contr...

To investigate denudation rates in the southern part of the Espinhaço Range (central-eastern Brazil) and to understand how this important resistant and residual relief has evolved in the past 1.38 My, cosmogenic 10Be concentrations produced in situ were measured in alluvial sediments from the three main regional basins, whose substratum is composed...

The hydrolytic alteration of anorthosite from the Barro Alto Stratiform Mafic–Ultramafic Complex (Central Brazil) caused the formation of an isalteritic bauxite. Petrological studies using X-ray diffraction (XRD), X-ray fluorescence (XRF), mass balance calculation and micromorphological description via optical microscopy were undertaken to understa...

Due to the poor preservation of old peat formations and the limited research developed on them, the contribution of peat oxidation to the global C cycle at geological scales is poorly understood. Iron duricrusts containing abundant well-preserved plant structures have been reported above Humic Gleysols in the Uberaba Plateau (Brazil). We show that...

The trails in natural areas are recognized as a means of travel between the visitor and tourist attractions. Thus, in protected areas, while providing visitors direct contact with nature, visitation results in environmental changes such as, among others, soil compaction and erosion in the bed of the trails. The objective of this study was to charac...

Topographic relief in southeastern Brazil consists of a sequence of stepped surfaces that formed after the fragmentation of Gondwana during the Cretaceous, Tertiary and Quaternary tectonic pulses. This region is drained by four major rivers within four major river basins, with interfluves that contain denudational escarpments, fault escarpments and...

The pedological horizons of soil profiles developed from pre-cambrian rocks of the municipalities of Alfenas and Areado, MG, Brazil, as well as the alluvial-colluvial sediments associated has been used intensively for ceramic potteries (particularly for bricks) but without a detailed study to rationalize their use in the ceramic industry. However,...

Os interflúvios entre as grandes bacias hidrográficas do Brasil oriental correspondem, muitas vezes, a degraus morfológicos que dividem planaltos escalonados. Esses degraus são feições escarpadas resultantes da diferença de intensidade dos processos erosivos nas cabeceiras dessas grandes bacias. Esse artigo apresenta um estudo da denudação química...

Mineralogical and crystallochemical transformations of representative ferruginous kaolinitic clay samples were investigated in specimens burned at 800, 1000 and 1200 °C. X-ray diffraction and differential thermal and thermogravimetric analyses showed that kaolinite was the predominant mineral in the raw samples. The Mössbauer spectroscopy results s...

Petrological studies using X-ray diffraction (XRD), X-ray fluorescence (XRF), optical microscopy, scanning electron microscopy (SEM-EDS) and electron microprobe analyzer (WDS) showed the mineralogical, micromorphological and geochemical transformations due to the bauxitisation of anorthosite from the Barro Alto Stratiform Mafic–Ultramafic Complex (...

Seven samples from three kaolin deposits of the Quadrilátero Ferrífero were characterized by physical, mineralogical and chemical analyses in order to determine their use in the ceramic industry. Despite the predominant presence of kaolinite, the variations in the Fe2O3 content from 2 to 44%, due to presence of goethite and hematite, resulted in di...

Important erosive processes that took place after the Cretaceous Era were responsible for the evolution of the landscape in the João Pinheiro region where spongillite deposits occur. The progression of these erosive processes on the carbonate rocks led to the development of negative karstic features where the ponds present formed the spongillite de...

O presente trabalho investiga a evolução das terras altas da alta Bacia do Rio das Velhas no Quadrilátero Ferrífero/MG – Bacia do São Francisco. A metodologia adotada se baseia na mensuração da produção do isótopo cosmogênico 10Be em escarpas e superfícies erosivas e na confecção de modelo digital do terreno. Os resultados obtidos demonstraram que...

O presente trabalho investiga a contribuição da denudação geoquímica nos processos erosivos diferenciais do Quadrilátero Ferrífero/MG, área de relevante interesse geomorfológico por possuir, em seu modelado, importantes marcas desse tipo de processo. A fim de cumprir este objetivo foram utilizadas análises físico-químicas e químicas de águas superf...

Spongillite from João Pinheiro, Minas Gerais, Brazil is mainly known for its use in brick production and in the refractory industry. Very few studies have focused on its geological context. Spongillite-rich deposits occur in shallow ponds on a karstic planation surface developed on rocks of the Neoproterozoic São Francisco Supergroup. Cenozoic sili...

The region of Alfenas, in the state of Minas Gerais, Brazil, is predominantly constituted of Pre-Cambrian rocks with well developed alteration profiles in association with colluvial and alluvial sediments. No study to date has examined in detail its potential use in the ceramic industry. The scarce knowledge of its mineralogical and technological p...

A geomorphological overview of the Quadrilátero Ferrífero reveals a conspicuous region where roots of metassedimentary Proterozoic strucutures, displaying young relief features, are in evidence over a sea of hills from the Archean basement. This paper deals with the landscape evolution in the "Quadrilátero Ferrífero" region, based on the integrated...

FRESHWATER SPONGE SPICULES FOUND IN THE CENOZOIC SEDIMENTS OF NORTHWEST MINAS GERAIS, BRAZIL, AS PALEOENVIRONMENTAL INDICATORS. This study relates to the spongillite deposits associated with the Cenozoic detritic cover, occurring in shallow ponds (with a maximum depth of 3.5 m) on a karstic planation surface developed on the rocks of the Sao Franci...

A geomorphological overview of the Quadrilatero Ferrifero reveals a conspicuous region where roots of metassedimentary Proterozoic strucutures, displaying young relief features, are in evidence over a sea of hills from the Archean basement. This paper deals with the landscape evolution in the "Quadrilatero Ferrifero" region, based on the integrated...

This study aims to characterize the facies of alteration developed from the mechanism of bauxitization of the anortosite bodies from the Barro Alto Stratiform Mafic-Ultramafic Complex emphasizing their geomorphological implication. Treated Landsat Images from the field work showed the presence of three domains of superficial formations: i) the doma...

Two samples of calcic bentonite of the Santa Elena Peninsula, Ecuador, were pillared with Al13 ions in the ratio of 10, 15 and 20 meq of Al g-1 of clay, calcinated at 573, 723 and 873 ºK and acid activated with 4, 6 and 8 mol L-1 H2SO4. Analyses by X-ray diffraction, X-ray fluorescence, differential and gravimetric thermal, density, surface area an...

This paper investigates the evolution of the relief within the so-called Iron Quadrangle (Quadrilátero Ferrífero) in Minas Gerais, Brazil, by means of quantification of erosion processes, which affected the principal rock types of the region. The method used is based on measurement of in-situ produced cosmogenic 10Be concentration in fluvial sedime...

The Santa Elena Peninsula, located in the southwest of the Ecuadorian coast, consists of igneous and sedimentary rocks from the Cretaceous to the Quaternary era. The sampled clays originated from the alteration of Andean volcanic ashes found inserted in the clay rocks of the Eocene Medium to Miocene Medium (Ancon Group and, Tosagua and Progreso For...

The Rio Capim kaolin district, located in the north-east of Pará State, Brazil, constitutes one of the world's largest high-whiteness kaolin reserves for the paper coating industry. It contains, at the base of the main ore, a soft kaolin that gradually changes at the top into a ferruginous duricrust followed by a flint kaolin. The flint kaolin is c...

Clays from the Santa Elena Peninsula, south-east of the Ecuador coast, were investigated with a view to identifying their main mineralogical, physical, chemical and textural characteristics as well as their potential for industrial use as adsorbents. Identified as calcic bentonites, two representative samples from the Tosagua Formation (Oligocene t...

Provenance studies carried out on the soft and flint facies of the Capim River kaolin (northern Brazil) trace the possible sources of sediments that host the ore. Pb–Pb evaporation geochronology was applied to four predominant morphologic classes of detrital zircons, and the ages obtained were compared to the main age intervals of the rocks surroun...

The present work quantifies the erosive processes in the two main substrates (schists–phyllites and granites–gneisses) of the upper Maracujá Basin in the Quadrilátero Ferrífero/MG, Brazil, a region of semi-humid tropical climate. Two measuring methods of concentration were used: (i) in situ produced 10Be in quartz veins (surface erosion rates) and...

The Capim Kaolin District (eastern Brazilian Amazon), is one of the largest kaolin deposits in the world; with the kaolin used mainly for paper coating. The kaolin developed at the expense of Cretaceous sandy-clayey sediments of the Ipixuna formation, through intense lateritization from the Mesozoic to Cenozoic times. This work describes the morpho...

The formation of aluminium-substituted iron-minerals is still subject to debate. We report a case study in a Humic Gleysol soil profile, developed on a sedimentary saprolite, from a basin floor on the Uberaba Plateau (Minas Gerais State, Brazil) where iron-phases are crystallized by a ferruginization process. The mineralogical and chemical properti...

The clay studied is taken from Guayaquil, Ecuador. It belongs to the Ancón Group, is Middle to Late Eocene Age and stems from change via Andean volcanic ash neoformation. In 32 collected samples, the three main granulometric fractions contained were quantified. Difraction via X-Ray analysis was carried out and the chemical composition was quantifie...

This paper presents the preliminary results of phytolith analyses of a peat located in the cerrado of the Uberaba municipality, State of Minas Gerais, Brazil. The phytolith soil sequence is discussed by comparison with phytolith assemblages extracted from dominant plants (Cyperaceae and Poaceae). Increasing mean age of phytolith assemblages with de...

The present study deals with the mineralogy and geochemistry of the clayey facies of the Água Limpa kaolin deposit, situated in the Moeda Syncline, Quadrilátero Ferrífero, Minas Gerais, Brazil. Kaolinite, quartz, oxides and iron hydroxides (hematite and goethite) represent the mineral assembly of the five facies of the deposit. White mica, rutile,...

The Capim River kaolin, located in the eastern Brazilian Amazon, constitutes one of the most important kaolin deposits in the world. Known for its high whiteness, its noble application is in the paper industry. Studies were carried out on samples from the six facies of the deposit (sand kaolin, soft kaolin, lower transition facies, ferruginous crus...

This paper investigates the denudation rates in the Quadrilátero Ferrífero, Minas Gerais State (Brazil). The aim is to compare chemical weathering rates from measurements of solute fluxes in rivers and long-term mean erosion rates deduced from in situ-produced cosmogenic 10Be concentrations measured in fluvial sediments. Both water samples and sedi...

O objetivo deste trabalho foi efetuar a caracterização mineralógica dos óxidos de ferro de horizontes B de três perfis de solos desenvolvidos sobre gnaisse do geodomínio do Complexo Bação, no Quadrilátero Ferrífero, em Minas Gerais. As amostras foram coletadas ao longo dos segmentos de alta, média e baixa vertente. As frações de terra fina (diâmetr...

The objective of this work was to characterize iron oxides from B-horizons of three soil profiles developing on gneiss of the Bação Complex geodomain in the Quadrilátero Ferrífero, Minas Gerais, Brazil. Samples were collected from the uppest, middle and lowest segments along the slope. The earth fine fractions (mean diameter, φ = 2 mm) were separat...

Alguns aspectos dos processos de alteração superficial e seus reflexos na pedogeomorfologia Quaternária na sub-bacia do alto Ribeirão Maracujá, no Complexo Bação, Quadrilátero Ferrífero, MG, são aqui caracterizados. São investigados caracteres relativos à dinâmica evolutiva de três vertentes (toposseqüências1, 2 e 3), situadas sobre gnaisses, mas c...

The clay deposit of Caxambu Hill occurs in a NW/SE oriented graben originated by syntectonic sedimentation during Cenozoic. Four facies were identified (fragmentary, nodular, massive and friable) and their differentiation is related to gravity mass-flow processes. The fragmentary facies is composed of extraclast fragments of the local Paleoproteroz...

This work deals with macromorphological, mineralogical, micromorphological and geochemical studies in clayey bodies from Quadrilátero Ferrı́fero in order to define their genesis and formation conditions in this geologic province from Minas Gerais State. Methodologies, based on the description of outcrops and drill cores, using X-ray diffraction (XR...

Vitrinite reflectance and clay mineral composition of shales from five wells in the Lower Cretaceous Barra de Itiúba Formation, Sergipe-Alagoas basin, Brazil, have been examined in order to estimate the thermal conditions of diagenesis and the thickness of the eroded piles using the Sweeney and Burnham [1990] and Velde and Vasseur [1992] kinetic mo...

The illitic end of mixed-layer illite-smectite series (I/S) in shales from Lower Cretaceous Barra de Itiúba Formation, Sergipe-Alagoas basin, was examined with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). A mathematical decomposition of XRD patterns shows different I/S and illite populations. All the samples contain or...

The Precambrian kaolinite and bauxite deposits of Vargem dos Oculos, south of Belo Horizonte, are important economically and scientifically. The mineralogical and geochemical characteristics of the material was investigated, and a genetical correlation among the various facies was established. It was found that an intensive deferruginization has ta...

EPR and Mössbauer spectroscopies were carried out on Capim river's kaolins (Para, Brazil) to identify structural Fe 3+ and electronic defects along a 37 meters logging, and to characterize iron oxydes/hydroxydes. This deposit provides "hard" and "soft" levels, Fe 3+ is mainly concentred in "hard" level. By comparison with results obtained on refere...