Digital processing and geological interpretation of TM-LANDSAT images of the area east of the Camaquã mine in Rio Grande do Sul State, Southern Brazil

Abstract

RlBEIRO DE ALMEIDA, T.I. ct al. (1997) Digital processing and geological interpretation of TM-LANDSAT images of the areas east of1he Camaqu3. mine in Rio Grande do SuI State, Southern Brazil. Bol.IG-USP. Sir.Cielll . • 28:101 -118 . ABSTRACT The Camaqull basin was formed during the closing stages of the accretion of Gondwanaland. The sediments were deposited over myloni!es of the Porongos Complex. Two !oCquences of silici-clastic sediments are present, the lower Santa Barbara Formalion and the upper Guaritas Formation. which is intruded by the Rodeio Velho calc-alkaline rocks. Relief is strongly controlled by lithology and structure, with an overall reailinear drainage panern. Vegetation is formed by grasses together with subordinate bushes and trees which are either scanered over the countryside or form small woods and dominates the spectral response. Soil cover is thin and rock outcrops are common, although subordinate. Based on fieldd3la, statistical paramelers for atrnosphere-corrected bands 2, 3, 4, 5 and 7 were sel up, and scrved as abase for the digital processing. Greater lithological eontraslswereoblainedby Principal Component Analysis (PCA) through comparison of results of statistical analysis of the transformed parameters and of the original bands. A preliminary analysis of the images thus obtained led 10 the identificalion of different spectral panems. ~ component PC I reflects textural patterns related to the relief and the different albedos. In PC2, the spectral response ofuus highlighted the Porongos Complex and the Rodeio Velho andesites, while grasses accentuated areas of fine-grained sandstones of the Santa Barbara and Guaritas Formations. In PC4, the sandstones and conglomerates of the two sequences. logether with quartzite hills of the basement complex, are prominent RESUMO A Bacia do Camaqul originou-se nos estagios finais da acre~lio do Supercontinente Gondwana. Os sedimentos fonnados depositaram.-se sobre 0 embasamento do Complexo Porongos Destacam-se duas seqll~ncias sedimentares siliciclisticas, na base, a Fonna~i'lo Santa Barbara, e a su-perior. Formayi'lO Guaritas, na qua! OCOJTem as intruSOes cldcio-akalinas Rodeio Velho. A seqUencia superior (Formayi'lo Guaritas) compo!le-se de duas unidades, na po~o basal, de arenitos e6licos, e arenitos e conglomerados fluvio-deltaicos na pane superior. Os diversos corpos intrusivos d lcio-alcalinos Rodeio Velho (rochas andesi-basAllicas),maisjovens, instalaram-sc, preferencialme nle, na interface entre essas