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

Northwestern Argentina has undergone a complex tectonosedimentary history. From Silurian through Late Jurassic time, sedimentary sequences were deposited in intracontinental basins. The beginning of this stage is linked to a first-order orogenic event, the Ocloyic phase. Above the Ocloyic unconformity, 6 km of sedimentary rocks were deposited during the Silurian-Jurassic interval. This record consists of two major unconformity-bounded sequences separated by the Lower Carboniferous Chanic unconformity. The first sequence, spanning the Silurian-Devonian, contains predominantly marine facies arranged in cycles of different hierarchies that were deposited in an epeiric flexural basin related to the Ocloyic orogen. The less intense Chanic orogeny changed the subsidence style and combined flexural and thermal causes. The low average sea level and variable climatic conditions during the late Paleozoic and early Mesozoic controlled the environmental characteristics of this second sequence, which is represented by predominantly continental facies of glacial and arid origin. This stage of intracontinental evolution ended with rupture and fragmentation of the basins in response to Cretaceous rifting, which marked the Gondwana break-up.

Several of the units deposited during the studied interval produce oil or gas that were generated in the Upper Devonian marine shales. The complex burial history led to the variable thermal maturity of these source rocks. One of the most important control factors of commercial accumulations here is source rock availability because the Devonian rocks were affected by erosive cycles of different ages.