Assessing the origin of pisoids within a travertine system in the border of Puna Plateau, Argentina

MORS, R. AGUSTIN; GOMEZ, FERNANDO J.; ASTINI, RICARDO A.; CELESTIAN, AARON J.; CORSETTI, FRANK A.

SEDIMENTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2021

0037-0746

The origin of pisoids in a diversity of environments has been recently discussed.While traditionally considered physico-chemical sedimentary productsdeveloped in turbulent environments, or even grown in situ, new resultsshow that microbes may influence their development. In the Terma Los Hornostravertine system, two types of actively forming pisoids were recognized:(i) laminated pisoids with a concentrically laminated crust surrounding anucleus; and (ii) dendriform radial pisoids with no distinct nucleus. Laminatedpisoids form in turbulent pools at the base of waterfalls, while dendriticpisoids develop within small depressions between terracettes, and they canoccur superposed as a result of episodic transport and recycling within the travertinesystem (for example, dendritic textures as nucleus of laminatedpisoids). The laminated pisoids are characterized by laterally constant laminaethickness with high inheritance and low amounts of randomly distributedorganic matter and microbial remains, suggesting a predominantly abiogenicorigin. In contrast, the dendritic pisoids exhibit an intimate relationship withdiatoms and filamentous bacteria suggesting a stronger biotic influence in theirformation. Thus, both abiogenic and biogenic carbonate structures can coexistin the same hydrothermal system. Pisoids found in the stratigraphic record ofTerma Los Hornos allowed to test the preservation potential of the primary signalsand reconstructing early diagenetic overprints.