10Be surface exposure dating reveals unexpected active deformation in the central Andean wedge interior

MARCUS CHRISTL; MARCELA G. YAMÍN; CARLA M. TERRIZZANO; JEREMIAS LIKERMANN; ROLAND ZECH; EZEQUIEL GARCÍA MORABITO; JONATHAN TOBAL

QUATERNARY SCIENCE REVIEWS

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017 vol. 172 p. 131 - 141

0277-3791

Mountainous regions and theirforelands commonly support a suite of landforms sensitive to climate change andtectonics. Alluvial fans in particular, are prominent geomorphological featuresin arid and semiarid regions which provide record for landscape, climate, andtectonic evolution. We applied 10Be surface exposure dating onmoraines and associated fan terraces of the Ansilta range (31.6°S - 69.8°W) inthe Southern Central Andes with the aim of comparing both chronologies andexamining the nature of alluvial fan development. The alluvial fans yieldminimum ages of 19±1 (T1), 120±9 (T2), 185 ±9 (T3), 389±22 (T4) and 768±35 (T5)ka. Minimum ages derived from moraines are 18±1 (M1), 27±1 (M2), 279±23 (M3)and 410±28 (M4) ka. M1-T1 and M4-T4 seem to be geomorphic counterparts during MIS2and MIS11-12. Combining our glacial and alluvial database with that availablefrom other published studies, we recognized further glacial-alluvialcounterparts. The distinct phases of alluvial fan aggradation mainly correlatewith moraines or have a regional extension and fall into local cold and wettimes, so that climate seems to be the main forcing of alluvial fan formationat our study site, even being a region with proofed neotectonic activity. Weinterpret the presence of at least six cold and humid periods of alluvialaggradation which correlate with global MIS 2, 3, 5d-e, 8, 12 and 18-20. Basedon these results, alluvial fans may allow landscape and climate reconstructionsback to ~750 ka in our study region.