Palaeoclimatic implications of Mio–Pliocene sedimentation in the high-altitude intra-arc Lauca Basin of northern Chile

Abstract

This paper examines the Late Miocene to Pliocene sedimentary succession in the high-altitude, intra-arc Lauca Basin of northern Chile, and discusses the palaeoclimatic evidence recorded within the basin fill. Sedimentological and geochronological data allow the reconstruction of four stages of the fluvial to lacustrine basin fill from the Late Miocene (>6.4 Ma) to the Late Pleistocene. We interpret the sedimentary evolution to reflect changes in precipitation during a time interval of general aridity. Climatic changes exerted the dominant control on sediment accumulation. Volcanism, tectonism, changes in morphology, and sediment supply were factors of subordinate importance. Stage 1 comprises a clastic red bed sequence developed during the Late Miocene under relatively humid conditions. An abrupt change in depositional style occurred around 6.4 Ma, when ephemeral saline lake sedimentation prevailed (stage 2). This change in depositional style is considered to document the begin of a phase of desiccation, that lasted until the Early Pliocene (3.7 Ma), and which was succeeded by less arid climatic conditions during the Late Pliocene and Pleistocene (stages 3 and 4). The transition between stages 1 and 2 and the subsequent dry period is assumed to coincide with a global cooling event during the latest Miocene to Early Pliocene. Comparable sedimentary responses to this climatic change can be expected in adjacent basins of the Central Andes.