New geomorphological and archaeological evidence for drainage evolution in the Luangwa Valley (Zambia) during the Late Pleistocene

D. Colton, E. Whitfield, A. J. Plater, G. A.T. Duller, M. Jain, L. Barham*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

This is the first systematic investigation of two distinctive geomorphological features recorded in the central Luangwa River valley, Zambia. A series of low hills was found to be capped by thin (~1 m) gravel deposits containing stratified Stone Age artefacts. More widespread gravels occur on the margins of the Luangwa River floodplain lacking stratified artefacts. The previously unreported hilltop deposits are interpreted as remnants of a dissected land-surface, and the valley floor gravels as redeposited clasts from c. 20 m of down-cutting. Clast analysis and drainage basin size analysis support a hypothesis of gravel deposition by unconstrained debris flows from the distant Muchinga escarpment, or from an intermediate zone. Excavation of a perched deposit revealed a coarsely stratified Stone Age record indicating periodic emplacement of artefact-bearing gravels over an extended period. Deposition of these perched gravels continued into the Late Pleistocene (~77 ka), based on OSL dating, after which the current dissected landscape formed. We hypothesize further, based on a regional record of landscape instability and core data from Lake Malawi, that fan formation in the valley was linked to periods of extended aridity and reduced vegetation cover followed by episodic erosional events on the return to wetter conditions. We argue that the subsequent dissection of the land-surface is the end state of a sequence of responses to base-level changes and climate change.

Original languageEnglish
Article number107923
Number of pages20
JournalGeomorphology
Volume392
Early online date03 Sept 2021
DOIs
Publication statusPublished - 01 Nov 2021

Keywords

  • Fan deposits
  • Landscape dissection
  • Late Quaternary
  • Luangwa Valley
  • Stone Age archaeology
  • Zambia

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