Microbialites of Balbuena IV Sequence (Danian), Salta Basin, Argentina: intrabioarchitectural characterization and definition of microcycles

Abstract

Microbialites produced in lacustrine environment exhibit a wide range of internal structures and textures. The organization and the characterization of the arrangement formed by these attributes are denominated as intrabioarchitectures. This work sought to identify the main types of intrabioarchitectural patterns in the microbialites of Balbuena IV Sequence (Danian, Salta Basin, Argentina) in mesoscopic scale (10⁰ – 10^-2 m) and the cyclical interpretation for the recurrence of the components that build these intrabioarchitectures, in microscopic scale. Seven main intrabioarchitectural types were recognized, and denominated as: coarse grain agglutinated microbialite (MA-gg); fine grain agglutinated and sparite fan crust, banded microbialite (MBFA-gf); micrite agglutinated, pseudo-microcolumnar microbialite (MPMA-m); fine grain agglutinated, grumous, shrubby microbialite (MArbMA-gf); fine grain agglutinated grumous, dendriform microbialite (MDMA-gf); fine grain agglutinated with esferulites, sparite fan crust, banded microbialite (MBFA-gf,esf); coarse grain agglutinated, grumous, stromatolite (EMA-gg). These intrabioarchitectures were grouped and related to three types of microcycles. The microcycles allow organizing the microbial record in a meso- and microscopic scale. That cyclic organization is related to climatic variations that affect the base level, the input of siliciclastics sediments, the biotic and geochemical processes in lake system. Therefore, it was possible to associate the formation of microbialites to phases of higher or lower aridity in the depositional environment.