CLIMATIC AND TECTONIC IMPLICATIONS OF A MID MIOCENE LANDSCAPE: EXAMINATION OF THE TARAPACA PEDIPLAIN, NORTHERN ATACAMA DESERT, CHILE

The history and relationship between uplift and climate change along the western flank of the Central Andes is not well understood. Documenting the nature and timing of regional climate change and the transition to arid conditions in the Atacama Desert is important, as these events may be directly linked to the uplift of the Central Andean system. Arid soils containing various soluble salt minerals preserve information about the environmental conditions present during soil formation and have been useful here to determine past climate since the mid-Miocene. Multiple soluble salt-rich soils developed on mid-Miocene to younger ancient landscapes in the northern Atacama are preserved regionally, as a result of surface incision and modern day aridity, making them suitable for characterizing climate change. In this study, multiple landscapes capped with distinct arid soils have developed since desertification (mid-Miocene) and have been analyzed here to constrain the nature and timing of climate change in the northern desert region. Relict soils and paleosols formed on various landscape surfaces denote periods of surface stability have been mapped across the northern Atacama. Soil soluble salt geochemistry (DCP, HPLC) and microstructure (LM, SEM) evidence environmental contributions impacting soils during their formation on stable landscape surfaces over time. While mid-Miocene soils are thick, indurated and well developed, younger soils are less developed. Detrital U-Pb zircon (LA-ICP MS) dating of different paleosols, relict surfaces, and surrounding stratigraphy, places temporal constrains on soils and land surfaces and allow for the development of a regional climate record and geomorphic record since initial desertification.

The relict soil- and paleosol-derived paleoclimate record produced from this study is directly compared to well-constrained climate proxies across the dry western flank of the Central Andes and the wet eastern flank to constrain the timing and degree of climatic change and possibly degree of uplift.