Resumen de Late Quaternary Lacustrine Deposition in the Chilean Altiplano (18°-28°S)

Blas Lorenzo Valero Garcés, Martin Grosjean, Bruno Messerli, Antje Schwalb, Kerry Kelts

• We summarize the Holocene sedimentary infilling of four high-altitude (>4000 m a.s.l.) lacustrine basins in the subtropical Chilean Altiplano (Central Andes, northern Chile): Laguna Chungara (18 5), Laguna Miscanti and Laguna Lejia (23 5)/ and Laguna del Negro Francisco (27 5) (Figure 1). These lakes are located within the active Andean convergent margin and formed by tectonic and volcanic activity during the Pliocene-Pleistocene. The Central Andes consists of several north-south mountain ranges and intermontanebasins that resulted from the sub duction of the Pacific Nazca plate from the Permian to the present.The Andes in northern Chile are characterized by a high fore-arc region (Coastal range, Longitudinal Valley, Chilean Precordillera, and Preandean Depression),an active magmatic arc (Western Cordillera and Altiplano), and a retro-arc belt (Eastern Cordillera and Chaco Foreland basin) (Borgel Olivares, 1983) (Figure1). The Altiplano is a high ignimbrite plateau of some100,000 km from about 15 5 to 28 5 at an average altitude of 3800 m. The evolution of this complex unit is the result of the Miocene (Quechua tectonic phase) torecent volcanic and tectonic activity. Large, faultboundedtopographically closed basins developed in the Altiplano, including Titicaca and saline lake Poopo, the large Uyuni and Coipasa salares, andnumerous small salares (Montti and Henriquez, 1970;Chong Diaz, 1988). The evolution of these alluvial and 625 lacustrine depositional systems has been strongly controlled by the synsedimentary tectonic and volcanicactivity.