SUBSÍDIOS GEOLÓGICOS PARA O PLANEJAMENTO URBANO E AMBIENTAL DO MUNICÍPIO DE IGREJINHA/RS

• DOI: 10.22533/at.ed.4421921026

• Palavras-chave: Geologia; Igrejinha; mapeamento geológico; basalto.

• Keywords: Geology, Igrejinha, geological mapping, basalt

• Abstract:

  Igrejinha is a town located in the

  valley of the Paranhana river. The town has a

  history of flood events and large landslides including some with victims and that was

  the reason to carry out a geological mapping of the entire municipality. Three geological

  Formations of interest were identified: Pirambóia Formation (with no outcrops in the

  municipal area), Botucatu Formation and the Serra Geral Formation. Locally were also

  found aluvio-colluvial deposits. The sedimentary packages of the Botucatu Formation

  have average thickness of 70 meters and emerge continuously in the municipal area,

  mainly on the basis of the cliffs of the valleys. The upper contact with the basalts of

  the Serra Geral Formation is discordant. Basic volcanic rocks (Gramado Facies) and

  acidic lavas (Caxias Facies) were identified, with predominance of the first, located on

  the slopes of the region. The acidic lavas are restricted to a small portion in the extreme

  northwest. Basaltic lavas that surface in the central portion of the town were divided into

  two distinct materials, Basalts I (with large mineralogical and textural variability and high

  susceptibility to wheathering, generate thick soils, clayey and red to purple color) and

  Basalts II (generally less whathered and with well-developed columnar discontinuities).

  The colluvial deposits are expressive with important deposits at the base of slopes and

  valley bottoms. There are colluvium deposits in the lava flow contact and in the foothills

  and slope surfaces.

• Número de páginas: 15