Early evolution of the southern margin of the Neuquén Basin, Argentina: Tectono-stratigraphic implications for rift evolution and exploration of hydrocarbon plays

LEANDRO D´ELIA; ANDRÉS BILMES; JUAN FRANZESE; GONZALO D. VEIGA; MARIANO HERNANDEZ; MARTIN MURAVCHIK

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2015 vol. 64 p. 42 - 57

0895-9811

Long-lived rift basins are characterized by a complex structural and tectonic evolution. They presentsignificant lateral and vertical stratigraphic variations that determine diverse basin-patterns at differenttiming, scale and location. These issues cause difficulties to establish facies models, correlations andstratal stacking patterns of the fault-related stratigraphy, specially when exploration of hydrocarbonplays proceeds on the subsurface of a basin. The present case study corresponds to the rift-successions ofthe Neuquen Basin. This basin formed in response to continental extension that took place at the western margin of Gondwana during the Late TriassiceEarly Jurassic. A tectono-stratigraphic analysis of the initialsuccessions of the southern part of the Neuquen Basin was carried out. Three syn-rift sequences were determined. These syn-rift sequences were located in different extensional depocentres during therifting phases. The specific periods of rifting show distinctly different structural and stratigraphic styles:from non-volcanic to volcanic successions and/or from continental to marine sedimentation. The resultswere compared with surface and subsurface interpretations performed for other depocentres of thebasin, devising an integrated rifting scheme for the whole basin. The more accepted tectono-stratigraphicscheme that assumes the deposits of the first marine transgression (Cuyo Cycle) as indicative of the onsetof a post-rift phase is reconsidered. In the southern part of the basin, the marine deposits (lower CuyoCycle) were integrated into the syn-rift phase, implying the existence of different tectonic signatures forCuyo Cycle along the basin. The rift climax becomes younger from north to south along the basin. Thepost-rift initiation followed the diachronic ending of the main syn-rift phase throughout the NeuquenBasin. Thus, initiation of the post-rift stage started in the north and proceeded towards the south,constituting a diachronous posterift event. This arrangement implies that the lower part of Cuyo Cycle,traditionally related to regional thermal subsidence, may be deposited during either mechanical subsidenceor thermal subsidence according to its position within the basin.