Morphology and fluvio-aeolian interaction of the tropical latitude, ephemeral braided-river dominated Koigab Fan, north-west Namibia.

Article in Edited Volumes
(Original article)


Publication Details

Author(s): Krapf C, Stanistreet IG, Stollhofen H
Editor(s): Blum, M., Marriott, S., Leclair, S.
Title edited volumes: Fluvial Sedimentology VII
Publication year: 2005
Title of series: IAS Special Publication
Volume: 35
Journal issue: 35
Pages range: 99-120
Language: English


Abstract


The Koigab Fan is the largest of the active fan systems formed by some of the

west-south-west flowing ephemeral river systems of the Skeleton Coast area,

north-west Namibia. Issuing from the volcanic Etendeka Plateau, the Koigab

River flows towards the Atlantic Ocean across a considerable climatic gradient

from semi-arid summer rainfall in the mountainous catchment, to hyperarid in

the coastal depositional setting.

The morphology of channels can be discerned over the whole fan surface

(gradient 1.011), the majority of which appears as a vast deflation surface on

which lithic and heavy mineral grains are concentrated by aeolian removal of

fines. The Koigab catchment restricts source-rock lithologies to flood basalts and

interleaved quartz latites of the Etendeka Plateau, so components that unequivocally

relate to a volcanic source (e.g. volcanic lithics, Ti-magnetite, pyroxenes)

indicate fluvial transport, whereas grains reflecting a metamorphic basement

source (e.g. garnet, muscovite, staurolite) must be aeolian derived. Both heavy

mineral and grain-size data were used to estimate the amount of fluvio-aeolian

interaction at the Koigab Fan surface. This aspect is significant because it comprises

not only winnowing of the fan surface and of ‘fresh’ sandy channel

deposits but also fluvial recycling of aeolian material. The contribution of

aeolian-derived grains to river deposits increases from 5% in the fan apex area

to as much as 50% in the distal fan reaches.

In the spectrum of fan types, the Koigab Fan takes an intermediate position

both in size and in terms of the braided river style between debris flow and low

sinuosity meandering fan systems. Within the braided fluvially dominated fan

class itself the Koigab Fan is also intermediate in size, but its ephemeral channels

contrast sharply with those of perennial glacial outwash fans previously

described from the sub-Arctic. Within low-latitude fan systems, the Koigab also

contrasts with other highly vegetated fans in the tropics, for example the subaerial

portion of the Yallahs Fan-delta, Jamaica. Thus, the Koigab Fan is important

as a potential analogue for Precambrian and early Palaeozoic low-latitude

fan systems that lacked surface vegetation prior to the evolution of land plants.



FAU Authors / FAU Editors

Stollhofen, Harald Prof. Dr.
Lehrstuhl für Geologie (Exogene Dynamik)


External institutions with authors

Julius-Maximilians-Universität Würzburg
The University of Liverpool


How to cite

APA:
Krapf, C., Stanistreet, I.G., & Stollhofen, H. (2005). Morphology and fluvio-aeolian interaction of the tropical latitude, ephemeral braided-river dominated Koigab Fan, north-west Namibia. In Blum, M., Marriott, S., Leclair, S. (Eds.), Fluvial Sedimentology VII. (pp. 99-120).

MLA:
Krapf, Carmen, Ian G. Stanistreet, and Harald Stollhofen. "Morphology and fluvio-aeolian interaction of the tropical latitude, ephemeral braided-river dominated Koigab Fan, north-west Namibia." Fluvial Sedimentology VII. Ed. Blum, M., Marriott, S., Leclair, S., 2005. 99-120.

BibTeX: 

Last updated on 2019-28-01 at 07:08