Chapadas do Alto Vale do Jequitinhonha, MG: II - mineralogia, micromorfologia e evolu??o da paisagem

As veredas s?o forma??es t?picas que ocorrem no Cerrado brasileiro, principalmente nas ?reas aplainadas denominadas chapadas. O objetivo deste trabalho foi caracterizar mineral?gica e micromorfologicamente os solos de uma topossequ?ncia representativa da microbacia da Vereda Lagoa do Leandro, localizada no munic?pio de Minas Novas - MG, situada nas chapadas do Alto Vale do Jequitinhonha, enfatizando aspectos de suas g?neses e da evolu??o da paisagem. A topossequ?ncia est? embasada em rochas do Grupo Maca?bas, com cobertura detr?tica e rochas metam?rficas (xistos diamictitos do Proterozoico). Os solos foram descritos em trincheiras, e amostras deformadas e indeformadas foram coletadas em todos os horizontes, para an?lises mineral?gicas e micromorfol?gicas. As an?lises mineral?gicas da fra??o argila foram determinadas pela t?cnica de difra??o de raios X (DRX), e as micromorfol?gicas, por descri??es de l?minas delgadas em microsc?pio petrogr?fico. Os solos caracterizados da base da vereda para o topo foram Gleissolo H?plico (GXbd), Latossolo Amarelo, de cor cinzenta, aqui denominado Latossolo Acinzentado (LAC), Latossolo Amarelo (LA) e Latossolo Vermelho-Amarelo (LVA). A mineralogia da fra??o argila em todos os solos ? dominada pela caulinita. Nos LVA e LA foram identificadas goethita, gibbsita e anat?sio; no LAC, anat?sio; e no GXbd, ilita, anat?sio e tra?os de vermiculita. A micromorfologia do LVA, LA e LAC ? dominada pela microestrutura do tipo granular ou microagregados e porosidade do tipo empilhamento/empacotamento, t?picos de Latossolos. No GXbd predomina a estrutura maci?a, com a presen?a de cut?s de iluvia??o e ferri-argil?s. Paleogleissolos foram latolizados pela a??o da fauna escavadora e deram origem aos atuais LAC. Os GXbd da base da vereda preservaram atributos f?sicos, mineral?gicos e micromorfol?gicos que tiveram suas g?neses em per?odos secos.Funda??o de Amparo ? Pesquisa do Estado de Minas Gerais (FAPEMIG)Empresa de Pesquisa Agropecu?ria de Minas Gerais (EPAMIG)Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)Palm swanp formations, the so-called veredas, typically occur in the Brazilian biome known as Cerrado (savanna-like vegetation), especially on flattened areas or tablelands (chapadas). The aim of this study was to characterize the mineralogy and micromorphology of soil materials from a representative toposequence of the watershed of the vereda Lagoa do Leandro, located in Minas Novas, state of Minas Gerais, Brazil, on plains in the region of the upper Jequitinhonha valley, emphasizing essential aspects of their genesis and landscape evolution. The toposequence is underlain by rocks of the Maca?bas group and covered with detrital and metamorphic rocks (schists of Proterozoic diamictites). The soil profiles were first pedologically described; samples of the disturbed and undisturbed soils were collected from all horizons for further micromorphological and mineralogical analyses. The mineralogical analysis was mainly based on powder X ray diffractometry (XRD) and micromorphological descriptions of thin sections under a petrographic microscope. The soils from the bottom to the top of this toposequence were classified as: Typic Albaquult (GXbd), Xanthic Haplustox, gray color, here called Gray Haplustox (LAC), Xanthic Haplustox (LA) and Typic Haplustox (LVA). The clay mineralogy of all soils was found to be dominated by kaolinite. In soil of LA and LVA, the occurrence of goethite, gibbsite, and anatase was evidenced; LAC also contained anatase and the GXbd, illite, anatase, and traces of vermiculite. The micromorphological analyses of the LVA, LA and LAC soils showed the prevalence of a microaggregate-like or granular microstructure, and aggregate porosity has a stacked/packed structure, which is typical of Oxisols. A massive structure was observed in GXbd material, with the presence of illuviation cutans of clay minerals and iron compounds. Paleogleissolos, which are strongly weathered, due to the action of the excavating fauna , and resulted in the present LAC. The GXbd at the base of the vereda preserved the physical, mineralogical and micromorphological properties that are typical of a pedogenesis with a strong influence of long dry periods