Cenozoic Evolution of the Intramontane Santa María basin, Pampean Ranges, northwestern Argentina

BOSSI, GERARDO; GEORGIEFF, SERGIO M.; GAVRILOFF, IGOR; IBAÑEZ, LUCÍA M.; MURUAGA, CLAUDIA M.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2001 vol. 14 p. 725 - 734

0895-9811

The Cenozoic of the Santa María Valley is composed of four Sequences defined by regional discontinuities. The two lower sequences are related to arching upward and shallow extension of the upper crust composed of Precambrian-Cambrian crystalline rocks (Sierras Pampeanas) and the two upper ones to compression related to thickening of the lithosphere and mountain uplift. Sequence I reflects the and consists of reddish fine sandstones, shales and local conglomerates older than 13 Ma. Sequence II was divided in two units. The lower one (Sequence IIa or initial rift stage) is composed by fine paralic deposits related to the Paraná marine ingression. The upper one (Sequence IIb or rift climax stage, 7 to 5.2 Ma) is composed of several lacustrine (fresh to saline) episodes and medium to coarse-grained fluvial sandstones. Sequence III started (around 5.2 Ma) with a change of tectonic style from extensive to compressive, reflected in the intra-Andalhuala unconformity. This sequence is the initial compressive stage (5.2 to 2.9 Ma) and involves a coarsening-up succession of conglomerates and sandstones. Progressive aridity is evident in the facies association and is related to the rise of eastern mountain barriers. Sequence IV, The climax compressive stage (2.9 Ma) is represented by local coarse conglomerates.