Significantly enhanced mid Holocene fluvial activity in a globally important, arid-zone wetland: The Okavango Delta, Botswana
dc.contributor.author | Tooth, Stephen | |
dc.contributor.author | McCarthy, Terence S. | |
dc.contributor.author | Duller, Geoff A. T. | |
dc.contributor.author | Assine, Mario L. [UNESP] | |
dc.contributor.author | Wolski, Piotr | |
dc.contributor.author | Coetzee, Grace | |
dc.contributor.institution | Aberystwyth University | |
dc.contributor.institution | University of the Witwatersrand | |
dc.contributor.institution | Universidade Estadual Paulista (UNESP) | |
dc.contributor.institution | University of Cape Town | |
dc.date.accessioned | 2022-04-28T19:49:05Z | |
dc.date.available | 2022-04-28T19:49:05Z | |
dc.date.issued | 2022-03-15 | |
dc.description.abstract | Information on past dryland environments is commonly derived from geomorphological landforms and sediments (‘geoproxies’). The Okavango Delta in the middle Kalahari, Botswana, has been subject to a long history of arid–humid transitions but its potentially rich archive of fluvial geoproxies is largely untapped. Previous palaeoenvironmental studies in the Delta region have focused mainly on aeolian dunes, lacustrine beach ridges, and rare pollen sequences in surrounding locations, and the Delta's channel dynamics have remained poorly constrained, both chronologically and in quantitative palaeohydrological terms. Focusing on the Delta's Xugana region, we present the first optically stimulated luminescence ages for palaeochannel fills and scroll bars, revealing significantly enhanced fluvial activity in the ~7–4 ka interval. Along 120–150 m-wide, sand-bed, sinuous palaeochannels, lateral migration and bend cutoffs were driven by palaeodischarges up to ~350–450 m3 s−1, at least nine times those of the present-day channels. These palaeochannels represent the last major phase of meander activity in the middle and lower Delta. The palaeodischarges imply significantly higher rainfall over the catchment in the mid Holocene, possibly resulting from a southwards shift of the African tropical rainbelt. Over the last few thousand years, diminished fluvial activity in the Xugana region has continued; <20 m-wide channels with discharges typically <40 m3 s−1 have been more laterally stable, albeit subject to local avulsions. These findings provide the ‘missing link’ between evidence for past intervals of enhanced rainfall in the Delta's tributary catchments in the northwest and west and the filling of large lacustrine basins to the southeast and east. The findings contribute to improved understanding of changing Kalahari hydroclimates and support growing evidence indicating that the mid to late Holocene was a time of significant fluvial transformation across many of the world's drylands. | en |
dc.description.affiliation | Department of Geography and Earth Sciences Aberystwyth University | |
dc.description.affiliation | School of Geosciences University of the Witwatersrand | |
dc.description.affiliation | Department of Geology São Paulo State University | |
dc.description.affiliation | Climate System Analysis Group University of Cape Town | |
dc.description.affiliationUnesp | Department of Geology São Paulo State University | |
dc.description.sponsorship | National Research Foundation | |
dc.description.sponsorship | Aberystwyth University | |
dc.format.extent | 854-871 | |
dc.identifier | http://dx.doi.org/10.1002/esp.5289 | |
dc.identifier.citation | Earth Surface Processes and Landforms, v. 47, n. 3, p. 854-871, 2022. | |
dc.identifier.doi | 10.1002/esp.5289 | |
dc.identifier.issn | 1096-9837 | |
dc.identifier.issn | 0197-9337 | |
dc.identifier.scopus | 2-s2.0-85122329131 | |
dc.identifier.uri | http://hdl.handle.net/11449/223181 | |
dc.language.iso | eng | |
dc.relation.ispartof | Earth Surface Processes and Landforms | |
dc.source | Scopus | |
dc.subject | Holocene climate | |
dc.subject | Kalahari | |
dc.subject | luminescence dating | |
dc.subject | Okavango Delta | |
dc.subject | palaeodischarge | |
dc.subject | scroll bar | |
dc.title | Significantly enhanced mid Holocene fluvial activity in a globally important, arid-zone wetland: The Okavango Delta, Botswana | en |
dc.type | Artigo | |
unesp.author.orcid | 0000-0001-5714-2606[1] |