Abstract

SCHENCMAN, Laura Jazmín; COLOMBI, Carina; SANTI MALNIS, Paula  and  LIMARINO, Carlos Oscar. Diagénesis y procedencia de la Formación Los Colorados (Noriano), Cuenca de Ischigualasto- Villa Unión, Noroeste de Argentina. Rev. Asoc. Geol. Argent. [online]. 2015, vol.72, n.2, pp.219-234. ISSN 0004-4822.

This paper deals with the diagenetic history, and the source areas of the Los Colorados Formation, a red bed sequence that records the final filling of the Triassic Ischigualasto-Villa Unión Basin. Forty-five unaltered sandstone were selected for thin section analysis, six by scanning electron microscopy investigation and eight for chemical analysis. From the diagenetic point of view, were considered two different situations due to the depositional environment strongly influenced the subsequent diagenetic processes: 1. Early cemented sandstones (for gypsum) probably linked to small ephemeral water bodies, and 2. Sandstones showing much more complex diagenetic patterns, probably related to fluvial environments with water table below the depositional surface. In this last case, four diagenetic stages were recognized, comprised between the eogenesis and the early mesogenesis. The reduction of the intergranular space was widely dominated by physical compaction. The sandstones showed maximum porosity values slightly higher than 10 %, predominating the intergranular secondary porosity. Considering the morphology, conectivity, size and type of porel, three major porous patterns were identified. In relation to the provenance areas, the detrital modes of sandstones as well as chemical analysis indicated that the source areas corresponding both, the metamorphic-igneo basement of the Sierra de Valle Fértil and the granitic rocks of the Sierras de Sañogasta. Moreover, the Precordillera was discarded as source area during the deposition of the Los Colorados Formation in the studied area.

Keywords : Triassic; Diagenesis; Sandstone detrital modes; Ischigualasto Basin.

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