Published balanced structural interpretations of the Fuegian thrust‐fold belt (southernmost Andes) fail to address aspects such as basement shortening in the thrust‐fold belt or its structural connection with the central belt of the orogen. We tackle this deficiency by constructing four serial balanced cross sections based on surface geologic information, 2‐D reflection seismic lines, and well logs, which depict the first‐order structural geometry and kinematics from the thrust front to the internal thrust‐fold belt. The interpretation reveals three main tectonostratigraphic packages separated by major detachments: basement (Paleozoic‐Upper Jurassic), Cretaceous, and Paleogene, all variably involved in thrusting along strike. Minimum shortening in the Paleogene cover ranges between 16% and 43%, and significant style changes are observed across and along the thrust wedge. We show that basement thrust sheets have a major role in the construction of the thrust‐fold belt; some of them were emplaced below the thrust front during late Oligocene or early Miocene times. The kinematic evolution of the thrust‐fold belt indicates that the active detachments depended on the existence of high pore pressure to propagate forward. Our model shows that this pore pressure buildup was controlled by overburden, mean rock impermeability, and strain rate; the variable interaction among these factors controlled the propagation and style of the thrust wedge.
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AbstractThe aim of this paper is to emphasize the oil discovery in the pyroclastic deposits of the Precuyano Cycle, in the Valle del Río Grande exploitation block. Since the Precuyano deposits were set in production, these levels have provided considerable wealth of oil, if we compare them to the daily average production of the block. This discovery has brought about a new impulse to the exploration of this kind of reservoirs, which have proved a strong potential in improving the oil production of the zone.This report includes an update of the investigation performed in this unit; it is main purpose of this job was to characterize the reservoir and their oil potential from a series of petrographic, petrophysical and diagenetic analysis. The analysis of the dominant structural styles integrated with the reservoir conditions was essential in order to reduce risk in deep exploration programs and to optimize the field development.Well logs were used as interpretation tools for this nonclassic reservoir; borehole images helped to assess the dominant stress fields; and correlation graphics (cross plots) were used to determine the mineralogy and porosity.
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