Distribución y caracterización petrográfica de las areniscas de la Formación Allen (Cretácico Superior) en la margen sur del río Negro y su comparación con las unidades infrayacentes del Grupo Neuquén

Abstract

The present work analyzes the distribution and petrographic characterization of the sandstones of the Allen Formation (Malargüe Group – Late Maastrichtian) in the eastern sector of the Neuquén Basin, evaluating their potential as proppants and comparing them with the Anacleto Formation (Neuquén Group – Middle Campanian). The significance of the Allen Formation lies in its record of the first Atlantic transgression and its current strategic role as the primary source of sand for hydraulic fracturing in the region. The methodology integrated the survey of sedimentological logs at Puesto Zinelli and Cantera YPF, the analysis of detrital modes through the Gazzi-Dickinson technique, and the evaluation of textural parameters (sphericity, roundness, and sorting) under the API Standard 19C. The results allowed for the reconstruction of a paleoenvironmental model suggesting an evolution from fluvial channel systems (Anacleto Formation) to marine-marginal environments (Allen Formation). A fundamental finding of this research is the absence of eolian facies in the study area. Unlike previous regional interpretations, it is established that this absence is not due to local paleorelief factors but to a clear chronostratigraphic distinction: the eolian and subaerial exposure records documented in neighboring localities, such as Paso Córdoba, correspond to the Anacleto Formation (Campanian), while the analyzed sections represent the advance of the transgressive front of the Allen Formation during the Maastrichtian. Petrographically, a dissected arc provenance was identified for both units, although the Allen Formation is distinguished by an increase in acidic volcanic and sedimentary lithics. The observed mineralogical stability, characterized by quartz abundance and a low proportion of altered lithic components, suggests that these units possess favorable technical potential for their application as proppants in the industry. Finally, the evaluation of sandstones as proppants revealed high vertical textural heterogeneity at Cantera YPF, contrasting with the greater homogeneity and consistent API standard compliance observed at Puesto Zinelli. These contributions highlight the need for rigorous quality control and open perspectives for identifying new sand beds with more uniform properties within the basin.