Pyroclastic facies and diagenesis of Río Blanco formation, Tupungato depocenter, Cuyana Basin Related to important petroleum accumulations, a well-known record of Triassic has been preserved in Cuyana Basin. Main rifting faults trend and delineate the Tupungato depocenter, located on the Southwest flank of Cacheuta sub-basin. The most remarkable feature in this sector is the uncoupling effect recognized in 3D subsurface data between the faulted Triassic strata and the folded Meso- Cenozoic deposits. In this area of study the most important reservoirs are allocated on Río Blanco formation (Late Triassic). Integrated subsurface information is herein presented in order to discuss the importance of pyroclastic products in the constraint of the sedimentary infilling of this depocenter, during the deposition of Río Blanco formation. Based on an unconformity, two different sedimentary units are proposed: Lower Rio Blanco (RBI) and Upper Rio Blanco (RBS) sequences. We suggest that RBS sequence is the result of a proximal volcanic system interacting with a lacustrine system. It is also considered analcime as the most important diagenetic product that determines reservoir quality. We suggest that the current location of Chañares Herrados oil field, Anchayuyo-Chañares Sur transfer zone and Puesto Pozo Cercado-Cruz Negra complex were part a an important Triassic volcanic system reactivated during Jurassic and Cretaceous times.