Modern Microbialites of Laguna El Peinado: The largest deposit in Argentine Puna (Catamarca province)

VILLAFAÑE, PATRICIO GUILLERMO; LENCINA, AGUSTINA INÉS; FADEL CURY, LEONARDO ; FARÍAS, MARÍA EUGENIA

Dijon

Conferencia; Conference and Workshop. Microbialites: formation, evolution, diagenesis.; 2019

Universite Bourgogne, Total

El Peinado lagoon is located at the southern end of the Salar de Antofalla and at the north ofEl Peinado volcano (Catamarca province), in the Puna region at an average elevation of 3800m asl. This lagoon consists of two main hypersaline water bodies isolated from each other bya salt flat (known as salar) though both contain microbialites arround their entire perimeter.The main purpose of this work is to describe the spatial distribution and architecture ofmicrobialites situated in the smallest water body located at the north of the El Peinado laggon,named as Turquesa lagoon. It is suggested here, that in past times these two water bodiesformed one great lake. Two main microbialites levels were observed on the eastern margin ofthe lagoon. One of the levels is represented by tabular and domal microbialites placed at about0.80 m from the current shoreline. This level has a horizontal continuity, extending fromTurquesa laggon running through the salt flat to the southern margin of El Peinado lagoon.Therefore, this level could represent the paleo-coastline when both water bodies wereconnected. The second level is a modern microbialite one, surrounding the current coastlinewhich has a perimeter of about 1.2 km. Microbialites exhibit platforms and domal externalstructures. As documented by many athours, external morphology appears to be the product ofthe environmental setting. In this case, seasonal fluctuations in water deph and the effects ofcurrents and winds could be the major controlling factors. Platforms structures exhibitbotroidal surface and extends 4 m inland from the shoreline. Besides, platforms wereobserved resembling elongated narrow ridges inside the lagoon and transverselly oriented tothe prevailing winds. These structures could be representing barriers to counteract thehydrodynamic energy of waves (Feldmann & McKenzie, 1997). Domal microbialites exhibitplanar and ring-like surface. The ring-like structures, also described as ?pustular dougnuts?,may be due to subaerial exposure of the upper surface, a feature that restricts microbialitegrowth towards the margins of the structure, thus producing a rim. This rim serves to trapsediments which further will inhibit microbialite growth and help to produce its lower centre(Moore & Burne, 1994). El Peinado and Turquesa lagoons have the largest modernmicrobialite deposits discovered so far in Argentine Puna. Both lagoons are being studied forfuther environmental interpretations.