Jurassic depocenters development, between colorado basin, chelforó sub-basin and neuquén basin

Abstract

Northern Patagonia, to the north of the Somún Cura Massif along the 39°S parallel, is characterized by the development of a series of Jurassic depocenters, initiating in the Andes to the west, across the Neuquén basin and the Pampean sector (Chelforó sub-basin) towards the Atlantic coast near the location of the Pedro Luro −1 well (onshore Colorado basin), and further east over the Argentine shelf, where multiple Jurassic depocenters form the Colorado, Rawson, and Valdés basins.

Using marine and continental gravity data (Free air and Isostatic anomalies respectively), constrained by well and seismic data, an integrated interpretation workflow for the study area was carried out. The southern limit of the Neuquén Basin is controlled by the Huincul High, an E-W directed structure with a positive gravimetric anomaly, interpreted as a basement high limited by relative gravimetric lows to the north and south of the structure. The eastern sector includes a series of isolated depocenters, separated by basement highs (obliquely oriented) and limited to the south by the E-W anomaly of the Huincul High. These depocenters correspond to the Chelforó sub-basin, which was drilled in a recent exploration campaign obtaining Jurassic ages where seismic interpretation pointed out presumably Jurassic deposits. Between Valcheta and Sierra Grande, this positive anomaly turns NW and becomes the southern boundary of the Pedro Luro depocenter, partially drilled by the Pedro Luro- 1 well, with possibly Tithonian palynological records at total depth. Between the Pedro Luro depocenter and the Chelforó sub-basin some features consistent with basement highs with circular morphology have been identified on gravimetric data, located in the area limited between the Colorado and Río Negro rivers. Jurassic rift depocenters have also been interpreted further east, in the Colorado basin where depocenters are controlled by an E-W oriented basement high, and further east by NW trending structures near the position of the SDRs (seaward dipping reflectors on the continental-oceanic crust transition zone).

The common evolution of these Jurassic depocenters is still poorly understood. They extend for more than 1500 km from the Andes to the Atlantic continental shelf and are controlled by structures located to the north of the Somún Cura Massif. The interpretation of seismic lines, and gravimetric data in areas without deep wells allow the identification of new exploration targets increasing the exploration potential of these basins.