Late Jurassic extensional tectonics in the southwestern Mendoza province, Argentina

MESCUA, J. F.; GIAMBIAGI, L. B.; BECHIS, F.

Niza

Simposio; Seventh International Symposium on Andean Geodynamics (ISAG08); 2008

Institut de Recherche pour le Développement (IRD) y University of Nice - Sophia Antipolis.

We present a study of the Kimmeridgian tectonic setting of the Andean region of south-western Mendoza province, Argentina. The study area is located between 34º and 35º S (fig. 1). At these latitudes the Mesozoic Neuquen embayment, developed south of 37º S, turns into a narrow longitudinal basin (90 km wide) that continues to the north into the San Juan province. The Kimmeridgian fill of the Neuquen basin corresponds to the continental deposits of the Tordillo Formation. This unit is one of the most conspicuous of the basin fill, consisting of sediments deposited in different fluvial systems with associated playa lakes and eolian fields (Legarreta and Uliana, 1999). Towards the west, these sedimentary deposits interfinger with ocoitic lavas and andesitic breccias of the Río Damas Formation. This unit, developed mainly in Chilean territory, corresponds to Kimmeridgian retroarc volcanic activity in an extensional basin (Charrier, 2007). Different methodologies were used to study the Kimmeridgian tectonic setting in the study area. A reconstruction of the thickness variations of the Tordillo Formation was obtained from outcrop and subsurface data. A provenance analisys is being carried out on sandstones of this unit, the first results of which are presented here. These lines of evidence suggested that the deposition of the sediments of the Tordillo Formation was contemporaneous with extensional tectonics. The recognition of syn-sedimentary normal faults in some localities supports this interpretation