Significantly enhanced mid Holocene fluvial activity in a globally important, arid-zone wetland: The Okavango Delta, Botswana

dc.contributor.authorTooth, Stephen
dc.contributor.authorMcCarthy, Terence S.
dc.contributor.authorDuller, Geoff A. T.
dc.contributor.authorAssine, Mario L. [UNESP]
dc.contributor.authorWolski, Piotr
dc.contributor.authorCoetzee, Grace
dc.contributor.institutionAberystwyth University
dc.contributor.institutionUniversity of the Witwatersrand
dc.contributor.institutionUniversidade Estadual Paulista (UNESP)
dc.contributor.institutionUniversity of Cape Town
dc.date.accessioned2022-04-28T19:49:05Z
dc.date.available2022-04-28T19:49:05Z
dc.date.issued2022-03-15
dc.description.abstractInformation 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.affiliationDepartment of Geography and Earth Sciences Aberystwyth University
dc.description.affiliationSchool of Geosciences University of the Witwatersrand
dc.description.affiliationDepartment of Geology São Paulo State University
dc.description.affiliationClimate System Analysis Group University of Cape Town
dc.description.affiliationUnespDepartment of Geology São Paulo State University
dc.description.sponsorshipNational Research Foundation
dc.description.sponsorshipAberystwyth University
dc.format.extent854-871
dc.identifierhttp://dx.doi.org/10.1002/esp.5289
dc.identifier.citationEarth Surface Processes and Landforms, v. 47, n. 3, p. 854-871, 2022.
dc.identifier.doi10.1002/esp.5289
dc.identifier.issn1096-9837
dc.identifier.issn0197-9337
dc.identifier.scopus2-s2.0-85122329131
dc.identifier.urihttp://hdl.handle.net/11449/223181
dc.language.isoeng
dc.relation.ispartofEarth Surface Processes and Landforms
dc.sourceScopus
dc.subjectHolocene climate
dc.subjectKalahari
dc.subjectluminescence dating
dc.subjectOkavango Delta
dc.subjectpalaeodischarge
dc.subjectscroll bar
dc.titleSignificantly enhanced mid Holocene fluvial activity in a globally important, arid-zone wetland: The Okavango Delta, Botswanaen
dc.typeArtigo
unesp.author.orcid0000-0001-5714-2606[1]

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