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Tectonic Control on the Deposition of the Tihonian-Berriasian Sequences (Vaca Muerta-Quintuco Fm), Eastern Neuquen Basin, Argentina


The Huincul High has historically been considered as an east-west structural boundary separating the Neuquén Basin into two sub-basins (Picun Leufú and Neuquén sub-basins). According to previous ideas, Vaca Muerta −Quintuco (VM-Q) sequences did not have a south-north connection at the time of their deposition as a result of the existence of this paleo-high. Recently, a new studied showed that during Tithonian times the Huincul High was inactive implying that there was not an east-west tectonic barrier disrupting the northwestward prograding VM-Q sequences. In this study, we document the timing of the Huincul High and how the different tectonic pulses controlled sequence geometries and their areal distribution. The initial depositional stage of the organic-rich shales (Vaca Muerta Fm.) are characterized by high amplitude, continuous, parallel reflections which represent the first Tithonian anoxic flooding event of the basin. The top of these continuous, mainly aggrading seismic reflections is a downlap surface interpreted as a maximum flooding surface (MFS). The northwestward downlapping clinoforms are interpreted as mixed carbonate-siliciclastic system. Mapping of these sequences shows continuity and lack of major thickness changes interpreted as being deposited during times of tectonic quiescence. On top of these prograding sequences, there are aggrading, continuous reflections (lithostratigraphically known as Quintuco Formation), showing onlap and truncation geometries which are interpreted as being coeval with intermittent tectonic pulses. Main deformation direction, linked to compression, was oblique (s1 ∼45°) relatively to the pre-existing E-W Triassic hemigraben structures, generating different compressive structures from E-W verging anticlines to NW-SE strike-slip related structures. Understanding the tectonic growth history of the Huincul High during the Late Jurassic Early Cretaceous has significant impact on the characterization of tectono-stratigraphic traps for conventional and unconventional reservoirs within the Neuquén basin.