The Palermo Aike Formation equivalent to surface Río Mayer Formation, in the Austral-Magallanes Basin is a proven source rock and an emerging frontier in southern South America for unconventional shale exploration. This study presents an integration of field data, Rock-Eval pyrolysis, vitrinite reflectance, organic petrology, optical-electron microscopy and U-Pb zircon geochronology from four outcrop profiles in the northern margin of the basin, in order to evaluate the source rock properties and define potentials sweet spots. At the study area, this Lower Cretaceous marine unit is in the oil window and can be subdivided in two sections. The lower Río Mayer Formation, a 60 m thick organic-rich mudstone succession, is interpreted to represent offshore settings in oxygen-deficient conditions. The data obtained show very good present-day total organic carbon contents (mean: 2.08%), and predominance of amorphous organic matter (type II kerogen). This lower section is characterized by both inorganic and organic porosity. The upper section of Río Mayer Formation is composed of ca. 250 m thick mudstones and very fine sandstones, that represent a more oxygenated and dynamic paleoenvironment influence by deltaic systems. The upper section presents poor present-day total organic carbon content (mean: 0.63%), type III to II/III kerogen, associated with the preservation of inorganic porosity. In Puesto Bajo Comisión sector, the upper interval is affected by Eocene mafic igneous intrusives that enhanced the maturity and generated changes in the microstructure of shales. The results of this study suggest a possible landing zone for future exploration activities in the top interval of the lower Río Mayer Formation, based on the organic geochemical characteristics.
Giunta et al. (Tue,) studied this question.