DOI: http://dx.doi.org/10.5027/andgeoV48n2-3292

Las Quínoas oncoids: a new deposit of microbialites in the Salar de Antofalla (Catamarca, Argentina)

Patricio Guillermo Villafañe, Agustina Inés Lencina, Mariana Soria, Luis Alberto Saona, Fernando Javier Gómez, Guido Ezequiel Alonso, María Eugenia Farias

Abstract


The Salar de Antofalla (salt flat) is located in the Puna region of Catamarca, in northern Argentina. In this paper we report and provide the first descriptive data of Las Quínoas, a modern system of oncoids located in the western margin of the salt flat. Oncoids were studied by insitu logging, polished and thin sections analysis. In addition, the 16s rRNA genes of microbial mats associated with these oncoids were amplified and sequenced to characterize the microbial biodiversity. Oncoids present discoidal to subrounded morphologies and sizes up to 15 cm in diameter. They are scattered along channels, which originate from the groundwater springs of a wetland and enter the salt flat. Its macrostructure is concentric and composed by three zones: 1. A nucleus zone built by clastic material in a carbonate matrix. 2. A well-laminated zone around the nucleus that shows two types of mesostructures: concentrically stacked spheroids (SS-C) and randomly stacked hemispheroids (SS-R), both showing an alternation of dense and dark micritic laminae with light micritic to microsparitic laminae. 3. A poorly-laminated zone, in the outermost sector of oncoids, with two types of mesostructures too: a laminated mesostructure composed also of an alternation of dense and dark micritic laminae with light micritic to microsparitic laminae, and a non-laminated mesostructure composed of agglomerated and cemented clastic material within a calcareous matrix (wackestones-packstones). Regarding the microbial diversity, the analyzed oncoids in this work are mainly inhabited by Proteobacteria (ca. 37.5%), Bacteroidetes (ca. 25.0%), and in less proportion Planctomycetes, Actinobacteria and Cyanobacteria.

Keywords


Oncoid; Microbialite; Salt flat; Holocene; Catamarca

How to cite this article Villafañe, P.; Lencina, A.; Soria, M.; Saona, L.; Gómez, F.; Alonso, G.; Farias, M. 2021, Las Quínoas oncoids: a new deposit of microbialites in the Salar de Antofalla (Catamarca, Argentina). Andean Geology 48 (2): 281-302. [doi:http://dx.doi.org/10.5027/andgeoV48n2-3292]