A multidisciplinary study of the Cacheuta Basin, Mendoza, Argentina

URIEN, C.M.; ZAVATTIERI, A.M.; SCHIEFELBEIN, C.; LIMARINO, O.

Mendoza

Congreso; 18th International Sedimentological Congress; 2010

The present study utilized a multidisciplinary approach, 3G (Geology, Geophisics, Geochemestry), Paleontology and Sedimentology to evaluate and predict the occurrence and distribution of petroleum systems active in this important area. Oil and source rock geochemistry and paleoentological data are integrated within a geological and geophysical framework, and combined with recent 2.5D thermal modeling results to understand facies and thermal variability across the basin resulting in a realistic evolutionary model. The Cuyo Basin is a pericratonic landlocked intermountain rift basin covering an area of about 40,000 km2 and containing about 6 km of sediment. It is situated on the southwest flank of the Pampean Massif, east of the Andean Cordillera, and northeast of Precordillera foothills. The basin is formed by several smaller rift formed during the Triassic as a result of post-orogenic relaxation and extension that continued into the early Jurassic. Waxy oils produced from Triassic and Tertiary strata constitute one of the oldest and most important petroleum resources in Argentina and are primarily derived from organic-rich shales of the Late Triassic Cacheuta and Potrerillos formations deposited in freshwater lacustrine and fluvial-lacustrine environments. Significant hydrocarbon generation only occurred during the last 10 Ma. following a rapid subsidence episode with thick Tertiary sediments. More than 150 different species of palynomorphs including variegate floras rich in “Dicroidium” characterize the Potrerillos and Cacheuta formations and coeval equivalents. These highly diversified associations are dominated by austral forms (Gondwanide), but also contain cosmopolitan and boreal elements that have been attributed to Middle to Late Triassic age.