Postglacial alluvial fan dynamics in the Cordillera Oriental, Peru, and palaeoclimatic implications

authored by

Kevin Ratnayaka, Ralf Hetzel, Jens Hornung, Andrea Hampel, Matthias Hinderer, Manfred Frechen

Abstract

Alluvial fans record climate-driven erosion and sediment-transport processes and allow reconstructing past environmental conditions. Here we investigate the sedimentation history of two alluvial fans located in formerly glaciated valleys of the Cordillera Oriental, Peru. ¹⁰Be exposure ages from the fan surfaces and radiocarbon ages from the fan interiors constrain the final stages of fan formation. The ¹⁰Be and ¹⁴C ages cluster mainly between 13.3-9.3 ka and 11,500-9700 cal yr BP, respectively. Our age data set indicates that - after deglaciation - large amounts of fan sediment were deposited until ∼10 ka, when sedimentation rates declined rather abruptly. This pattern is supported by ¹⁰Be erosion rates for the fan catchments, because under the assumption of constant erosion the time needed to Erode the material stored in the fans significantly exceeds their age. Correlating our ages with regional climate records indicates that precipitation exerts the primary control on fan sedimentation. Two periods with elevated lake levels and increased precipitation between 18 and 14.5 ka and from 13 to 11.5 ka resulted in rapid deposition of large fan lobes. Subsequently, lower precipitation rates decreased erosion in the catchments and sediment delivery to the fans, which have remained largely inactive since ∼9.5 ka.

Organisation(s)

Institute of Geology
Leibniz Research Centre FZ:GEO

External Organisation(s)

University of Münster
Technische Universität Darmstadt
Leibniz Institute for Applied Geophysics (LIAG)

Type

Article

Journal

Quaternary Research (United States)

Volume

91

Pages

431-449

No. of pages

19

ISSN

0033-5894

Publication date

01.01.2019

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Arts and Humanities (miscellaneous), Earth-Surface Processes, General Earth and Planetary Sciences

Sustainable Development Goals

SDG 13 - Climate Action

Electronic version(s)

https://www.repo.uni-hannover.de/handle/123456789/11692 (Access: Open)
https://doi.org/10.1017/qua.2018.106 (Access: Closed)