Veins of solid bitumen (asphaltite) have been commercially exploited in the Neuquen basin, Argentina, for over 100 yr. Veins are up to 5 m wide and several kilometers in length, over a region of 15,000 km². These veins were emplaced in fractures both parallel and at high angles to bedding, in close proximity to their source rocks in the Vaca Muerta and Agrio formations (Late Jurassic-Early Cretaceous). Two or more phases of bitumen emplacement can be recognized in several localities; structures bearing viscous oil are younger than structures having solid bitumen.

Bitumen emplacement was vigorous and caused brecciation and spalling of the host rocks. The bitumen was also viscous, and supports rock debris ranging in size from sand grains up to meter-scale slabs. Brecciation, bedding-parallel injection, and wall rock impregnation suggest high fluid pressures during emplacement. High fluid pressure may have been engendered by substantial hydrocarbon generation from rich source rocks in a low-permeability sequence, and probably caused the fractures into which the bitumen migrated. The bedding-parallel veins facilitated decollement during thrusting that took place during and after bitumen emplacement. The timing of emplacement relative to thrusting and oil migration constrains bitumen emplacement to the Eocene-Oligocene.