Modern terrestrial microbial mats from hypersaline lakes in the Puna, Andean Range, Argentina.

DANIEL G. POIRE, MARIA E. FARIAS, VERÓNICA LOPEZ-AGOSTI , VIRGINIA H. ALBARRACIN, JULIA ARROUY, LUBOS POLERECKY

Mendoza

Congreso; 18 th International Sedimentological Congress; 2010

International Asssociation of Sedimentologists

High-Altitude Lakes at the northwest of Argentina in the Puna and Andean regions are considered extreme environments of biotechnological interest, where microbial mats are living and producing different organomineralization products. Microbial mat ecosystems were recorded so far in three locations in Argentine Puna: Socompa Lake, Tolar Grande and Diamante Lake. The aim of this contribution is to discuss why similar microbial mat communities produce different microbialite structures with varied mineral composition. The Puna has a clear plane relief, with occasional mountains crossing the area that allow to demarcate close basins. In fact, most Puna region represent a big arreic basin, fragmented in a system of minor basins interrelated among each other. At the bottom of those basins, big lakes are developed, with variable limits due to the alternance of inter- annual irregular precipitations. Occasionally, the lakes get dry and give birth to large salars due to the high concentration of minerals in the water. The climate is dominated by arid and desertic conditions with daily temperatures ranging from 20 to -10ºC in summer and 10 to -15 ºC in winter. Precipitations in the area are scarce, less than 350 mm per year. The high altitude and low latitude geographical position of the Puna expose these are to high solar irradiance (i.e. 165% higher than at sea level) with instantaneous UV-B flux reaching 17 Wm-2 (UV-flux is twice the amount of present-day equatorial Mars, while UV-B is half the amount on Mars). It is apparent that the characteristics which dominated the high-altitude lakes such as residual volcanic activity associated with sulphur availability, hypersalininty and high Ultraviolet (UV) irradiation promotes the formation of microbial mats associated with mineral precipitation. Modern stromatolites found in other parts of the world are not under too much stress or extreme conditions. In these cases, the modern stromatolite-like ecosystems herein described are developing under conditions that remains to the one imparating in the Early Earth with high UV, low O2 pressure and low nutrient