Microbialitic deposits of the Yacoraite Formation, NW Argentina: distribution, environments, paleoecology, and economic implications

Abstract

The Yacoraite Formation (NW Argentina) displays important microbialitic deposits of varied features throughout its six sub-basins. With the discovery of important microbialitic hydrocarbon reservoirs and the interest in lacustrine systems due to recent hydrocarbon finds in the presalt Cretaceous series of the South Atlantic, the importance of these organo-sedimentary structures has increased considerably. Because of this, in the past decade, numerous works in Yacoraite Formation have focused on its microbialites. In this study, we provide an updated summary of the existing background and state of knowledge of the microbialites in the Yacoraite Formation, which occupy different stratigraphic positions in diverse sub-basins separated by several kilometers. Due to this, these structures have developed under diverse conditions, giving rise to a great variety of structures and morphologies, useful as reliable and high-resolution proxies for paleoenvironmental studies and to discuss important ecological paradigms. In addition, microbialites of Yacoraite Formation show promising petrophysical conditions to be evaluated as reservoir rocks. Based on the large number of deposits mentioned throughout this work, and the morphological and structural variety of their microbialites, we can highlight Yacoraite Formation as one of the most important microbialite-bearing units in Argentina and South America.

The provenance and persistence of the perennial Río Loa in the Atacama Desert: links between crustal processes and surface hydrology

“…Conceivably correlating with this Formation (Charrier and Reutter, 1994), small inliers of Late Cretaceous-early Paleogene Yacoraite Formation occur >120 km to the SE of El Tatio in Argentina (Rubiolo et al, 2003), and the equivalent Molina Formation some 85 km NE of El Tatio in Bolivia (Pacheco and Ramirez, 1997). Although these may represent a continuous extension of lacustrine/marine conditions underlying the current volcanic arc, both these formations show facies interpreted as lacustrine shorelines (Rohais et al, 2019;Deschamps et al, 2020;Mutti et al, 2023;Villafañe et al, 2023), which might negate any extension to the Loa catchment. The Na-normalized plot of HCO 3 :Ca (Figure 5B) does not indicate any significant carbonate in Salado-Toconce baseflow, other than soil/plant CO 2 generation, nor do the HCO 3 :Cl and Ca:Cl ratios suggest the presence of deep carbonates (Figures 5viii, 5x).…”