Spatio-temporal patterns of alluvial deposition at the Skeleton Coast of Namibia

Autor(en)

Joel Mohren, Janek Walk, Dominik Brill, Wolfgang Römer, Julian Krieger, Alicia Medialdea, Anna Nguno, Frank Lehmkuhl

Abstrakt

The timing and spatial extent of alluvial deposition and the processes causing post-depositional alterations of alluvial landforms are governed by a variety of environmental factors, which can be summarised in the domains of climate and tectonics. The significance and magnitude of the individual factors in shaping topography can depend on the spatial and/or temporal scales being considered, often blurring an interpretation of the sediment successions as climate archives. In contrast, landscapes situated in tectonically quiescent environments may host valuable climate archives, in particular in long-term (hyper-)arid settings. Such conditions can help to preserve alluvial landforms indicative for climate-controlled pulses of sediment aggradation. The (hyper-)arid Skeleton Coast of Namibia generally appears to provide such conditions, including the climate-controlled presence of a dune belt affecting oceanward sediment transport. Many alluvial deposits have been studied in detail in this region, but analyses largely focused on sedimentological and/or morphometric characteristics, while fewer attempts were made to date these landforms. Consequently, the region is still lacking a spatially extensive geochronological framework necessary to relate alluvial deposition dynamics to climatic fluctuations during the Quaternary. Here, we present first results of a combined approach investigating landform ages inferred from optically stimulated luminescence (OSL) and cosmogenic 10Be data. In alluvial deposits located to the east of the dune belt, we find OSL ages to reflect Holocene sediment accumulation, while surfaces are dated to the Middle Pleistocene, as inferred from 10Be concentrations. Middle Pleistocene (~100-500 ka) 10Be ages are also obtained for other alluvial surfaces sampled in the vicinity of the erg, potentially reflecting the impact of orbital forcing on topography formation. An exception makes alluvial sediments sampled in the coastal Uniabmond area (~20.2°S). These sediments have OSL ages ranging ~20-40 ka and minimum 10Be ages of ~20-30 ka, likely reflecting Last Glacial Maximum-related aggradation at the Skeleton Coast.

Organisation(en)

Institut für Geographie und Regionalforschung

Externe Organisation(en)

Rheinisch-Westfälische Technische Hochschule Aachen, Universität zu Köln, Geological Survey of Namibia

Publikationsdatum

2023

ÖFOS 2012

105404 Geomorphologie, 105127 Geochronologie

Sustainable Development Goals

SDG 13 – Maßnahmen zum Klimaschutz

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/2a83a034-e5da-42b9-9a42-a2ed30ed515d