Deep structure of the Metan-Guachipas region: tectonic inversion in Northwestern Argentina

New deep seismic-reflection data obtained by reprocessing an industrial line from the eastern sector of the Salta rift system, Northwestern Argentina, are examined. An oil well located along the line provides stratigraphic control for the seismic interpretation. The corresponding synthetic seismogram extends this interpretation through the Metán trough. The data show the deep structure of the rift, consisting of a series of half-grabens, filled with Cretaceous red beds of the Pirgua Subgroup. The sag phase deposits consist of limestones, marls, shales and evaporites of the Balbuena and Santa Bárbara Subgroups, deposited in a transitional marine to lacustrine environment. l oblique east-dipping reflectors at 10 to 20–24 km depth, are interpreted as master shears that control the extensional mechanics of the rift system, partially reactivated during Andean compression. The structure of this eastern sector of the rift is integrated through a regional cross-section through the entire rift system. The section clearly shows that troughs and highs may be related to flats and ramps of a regional master shear dipping to the east.