Dating of alluvial fans from NW Argentina using cosmogenic nuclides and optically stimulated luminescence technique

Alluvial fans are important geomorphic markers and sedimentary archives of tectonic and climatic changes. Hence, basins providing perfect studying conditions can often be found in arid regions due to the low weathering impact and thus well preservation of sedimentary features. Twelve samples for optically/infrared stimulated luminescence (OSL/IRSL) dating and one depth profile for cosmogenic radionuclide dating (10Be) were collected in the Santa Maria Valley in NW Argentina, where the exceptional preservation of several generations of alluvial fans allow exploring the external forcing conditions that led to repeated cycles of incision and aggradation. The results of the OSL/IRSL dating yielded ages ranging between 0.4 ± 0.1 ka and 271.8 ± 24.5 ka. Previous studies next to the study area indicate a depositional age of 1.5-2 Mio years for the oldest generation of alluvial fans, which might still be supported by our ongoing 10Be dating. Due to field observations, sediment provenance, stratigraphic characteristics and the geomorphic pattern of erosion, seven (/eight) generations of alluvial fan deposits were recognized. Comparing my ages with global glaciation cycles as well as linking them to temperature proxies retrieved from a lake on the Altiplano Plateau, a good fit between alluvial fan accumulation phases and global glacial periods (corresponding to cold/wet phases within the central Andes) is observed. This suggests that aggradation occurs during the early stages of glacial periods, while incision is expected at the end of glacial phases. This pattern might be linked to variations in the vegetational cover (controlled by water availability), which will decrease/increase during hot and dry/cold and wet interglacial/glacial phases favoring/limiting sediment production and will increase/decrease during cold and wet/hot and dry glacial/interglacial phases. Even though the eastern Andean margin is showing neotectonic activities and is assumed to be active up to recent times, deformation and seismicity might most probably have played only a minor role in relation to the rather short timescale reflected by the data.

Level thesis:degree_level

master

Grantor dc:publisher

Universität Potsdam

Year

2018

Author dc:creator

• Reger, Carolin

Contributors dc:contributor

• Strecker, Manfred
• Ballato, Paolo

• fan
• alluvial
• argentina
• OSL
• cosmogenic
• nuclides
• Schwemmfächer
• Argentinien
• kosmogen
• Nuklide
• Lumineszenz

Statement dc:rights

• CC-BY-NC-ND - Namensnennung, nicht kommerziell, keine Bearbeitungen 4.0 International

Repository record source_url

https://publishup.uni-potsdam.de/frontdoor/index/index/docId/47147

OAI identifier oai:identifier

oai:kobv.de-opus4-uni-potsdam:47147