Resumo

SELLES-MARTINEZ, José  e  AZCURRA, Diego. Lower Paleozoic microestructures in the headwaters of Río Jachal, San Juan Province: their description and interpretation. Rev. Asoc. Geol. Argent. [online]. 2010, vol.66, n.1-2, pp.94-101. ISSN 0004-4822.

group of microstructures present in the Ordovician Yerba Loca and Los Sombreros Formations (cropping out in the vicinity of Road 150, between cuesta del Viento and Los Túneles), are described and interpreted. Cleavage, joints and fractures, shear zones, planar and sigmoid (en echelon) veins and kink bands are most common among them. Folded and domino faulted quartz veins, resulting from pressure solution contraction during formation of axial plane cleavage, are an outstanding feature and allowed calculation of contraction associated to cleavage development. The assemblage of minor structures shows coherency with the major structures hosting them and evidences a systematic displacement and stacking of rock masses from west to east. They also show the important participation of pressure solution and re-crystallization processes during deformation, along with progressive deformation due to rotation of local structures in the regional stress field.

Palavras-chave : Precordillera; Jáchal River; Palaeozoic; Minor structures; Yerba Loca Formation.

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