Published 1995 as part of Memoir 62
Copyright © 1995 The American Association of Petroleum Geologists.  All Rights Reserved.

Several superimposed tectonic stages distinguished by varying structural styles are recognized in the Andes of northern Argentina (22°-28° S lat). The oldest structures occur in the Precambrian crystalline basement. This basement forms the central core of the region and is made up of several multiply deformed belts. These belts were intruded by several generations of granitoids and were amalgamated during the Panamerican orogeny (Late Brazilian orogeny, 700-600 Ma). A westward-vergent foldbelt containing Ordovician marine sediments shows eastward-dipping axial plane cleavage. It lies along the western border of the crystalline core and acts as host rock to pretectonic intrusives. Development of the folding is assigned to the Late Ordovician Ocloyic orogeny. The sub-Andean ranges and Puna Silurian-Devonian successions were folded during the Late Devonian-Early Carboniferous at the beginning of the Gondwanan cycle (Chañic orogeny). This tectonic cycle is represented in several late Paleozoic basins that surround the study area. The inversion of those basins probably took place during the middle Permian San Rafael orogeny.

The Andean cycle commenced with the opening of rift troughs filled with thick continental deposits during Early Cretaceous-Eocene time. The inversion of these troughs began with the late Eocene Inca movements, but was completed during the Miocene Quechua and Pliocene-Pleistocene Diaguita orogenies. From late Oligocene time onward, continental basins developed, and an extensive Miocene-Pleistocene volcanic arc originated on the western flank of the study area. These Cretaceous-Cenozoic basins were inverted by the Diaguita orogeny. Andean tectonics caused clearly differentiated morphostructural units. The most westerly of these is the Puna Plateau, characterized by Precambrian basement and Paleozoic rocks sheets that were thrust over Tertiary continental successions. East of the Puna, the Eastern Cordillera represents a tectonic stack of Precambrian basement and Paleozoic rock sheets thrust eastward over the sub-Andean ranges. This latter belt forms the outermost unit, made up of large faulted anticlines. South of 27° S lat, a change occurs in the architecture of the Andean foreland. The sub-Andean ranges and the Eastern Cordillera are replaced by faulted blocks of Precambrian crystalline basement and Paleozoic granitic intrusions, which form the Pampean ranges. This paper summarizes the evolution of the oil-bearing basins of northern Argentina.