Abstract

Carbonate deposits and sedimentary records from lakes in southern Patagonia provides an excellent contribution in the regional environmental register. The Laguna Timone is situated within a maar of the Pali Aike Volcanic Field, a Quaternary volcano-tectonic complex in southernmost South America and represents one of hundreds of pools of brines developed after explosive volcanic eruptions in a periglacial environment. The lake consti-tutes an endorheic hydrological system where processes leading to carbonate precipitation took place under ex-treme physicochemical conditions and biological influences that can be explored. Laguna Timone is recharged by groundwater and sporadic episodes of precipitation (ca. 200 mm/year) and high evaporation rates are controlled by regimes of strong wind (westerlies) and seasonal solar radiation. Carbonate precipitation was studied in microbialite fragments of tufa deposits and carbonate crust located in the edge of the lake, and the mineralogy of all samples is calcite. The clay fraction of the sediment underlying the carbonates was characterized and HRTEM analysis shows that authigenic smectites have influence on calcite crystal precipitation. The positive delta O-18 values (2.28 parts per thousand) in thin crust layers are associated with evaporation processes. In contrast, the negative delta O-18 values (-6.52 parts per thousand) in the microbialites show meteoric and/or groundwater influences. The delta C-13 (-0.43 parts per thousand to 2.50 parts per thousand) values indicate physico-chemical and biochemical processes controlling the precipitation. The carbon-ate precipitation involves the interrelations of hydrogeological properties, climate and biological influences. Laguna Timone provides a natural laboratory for understanding mineral precipitation processes that register continuous climatic and environmental archives. (C) 2022 Elsevier B.V. All rights reserved.