Possible climatic controls on the accumulation of Peru's most prominent alluvial fan: The Lima Conglomerate. Issue 5 (12th December 2018)

• Record Type: Journal Article
• Authors: Litty, Camille; Schlunegger, Fritz; Akçar, Naki; Lanari, Pierre; Christl, Marcus; Vockenhuber, Christof
• Is Part Of: Earth surface processes and landforms. Volume 44:Issue 5(2019)
• Page Start: 991
• Page End: 1003
• Publication Date: 2018-12-12
• Subjects: Lima Conglomerate -- cosmogenic nuclides -- isochron burial dating -- paleo erosion rates -- U–Pb in situ zircon dating -- sediment provenance; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.4548
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: Sediment accumulation can occur in response to a change in either tectonic or climatic driving forces. Here, we explore these controls on the deposition of the Lima Conglomerate, Peru. We use a combination of quantitative methods to explore the age of sediment accumulation, the provenance of the material and the paleo‐erosion rates recorded by these deposits. Isochron burial dating with cosmogenic 10 Be and 26 Al yield an age of c . 500 ka for the base (490 ± 70 ka) and the uppermost sample situated c . 30 m higher upsection (490 ± 80 ka). Results of paleo‐erosion rate estimates with concentrations of in situ 10 Be show a c . 60% increase from 105 ± 10 mm ka ‐1 for the base to 169 ± 14 mm ka ‐1 for the uppermost sample. Finally, provenance tracing with in situ U/Pb ages on detrital zircon implies that the material has been derived from the entire drainage basin. The combination of results suggests that sediment accumulation occurred in response to an erosional pulse, which affected the entire basin within a short time interval. Because 10 Be data represents a large spatial record of erosion, we exclude the possibility where a breakout of a lake or a focused release of material in response to earthquakes, were responsible for the large material flux. Instead, the erosional pulse was likely to have occurred at the scale of the entire basin, supporting the idea of a larger‐scale, most likely climate driven control. In this context, the accumulation age of c . 500 ka falls into an orbital cycle fostering the emerging picture in the literature that sediment routing in the Andes have most likely been driven by climate and cyclic changes. We suggest that the Andean mountain range offers an ideal laboratory to explore the erosional history in relation to climate patterns, at least in Peru. © 2018 John Wiley & Sons, Ltd. Abstract : Results of osochron burial dating, paleo‐erosion rates estimates and provenance tracing studies suggest that sediment accumulation occurred in response to an erosional pulse, which affected the entire basin supporting the idea of a larger‐scale, most likely climate driven control, fostering the emerging picture that sediment routing in the Andes has been driven by climate changes.