Estructuras sedimentarias inducidas por actividad microbiana en la formación Los Molles (Jurásico temprano - medio), Cordillera del Viento, Neuquén, Argentina: implicancias geoquímicas y paleoambientales

Abstract

Microbially induced sedimentary structures in Los Molles Formation (Lower-Middle Jurassic), Cordillera del Viento, Neuquén, Argentina: geochemical and paleoenvironmental implications Sedimentological analyses of the marine sedimentites of Los Molles Formation (Lower Toarcian-Lower Bajocian) in the eastern flank of the Cordillera del Viento, Neuquén basin, allow recognizing the presence of microbially induced sedimentary structures (MISS). These structures were analyzing applying optic and electronic microscopy techniques in order to determine internal features that characterizes them, and in turn, complemented with biomarker analysis to infer sources of organic matter. Prevalent diagnostic features, such as oriented grains, mat-bound small grains, framboidal pyrite and extracellular polymeric substances (EPS) replaced by silica, were identified. The observed MISS developed in an offshore environment and in distal facies of turbidite levee channels, were euxinic (anoxic and sulfidic) conditions at the water-sediment interface promoted its growth and inhibit the establishment of benthic communities. Therefore, MISS constitute important indicators of specific physiochemical conditions at the water-sediment interface, which help refining previous paleoenvironmental interpretations and allow evaluating its possible role in hydrocarbons generation.