Hoanib River flood deposits of Namib Desert interdunes as analogues for thin permeability barrier mudstone layers in aeolianite reservoirs.

Journal article
(Original article)


Publication Details

Author(s): Stanistreet IG, Stollhofen H
Journal: Sedimentology
Publisher: Wiley-Blackwell
Publication year: 2002
Journal issue: 49
Pages range: 719-736
ISSN: 0037-0746
Language: English


Abstract


The ephemeral braided Hoanib River of NW Namibia flows for a few days a

year, and only high discharges enable the river to pass through interdunal

depressions within the northern Namib Desert dune field to the Atlantic. The

dune field comprises mainly large transverse dunes resulting from

predominant SSW winds. River flood deposits between aeolian dunes are

analogous to mudstone layers conformably interbedded with ancient

aeolianite dune foresets. Deep floods pond laterally to considerable depths

(metres to >10 m) in adjacent interdunes, depositing mud layers (1–50 cm) to

considerable heights on avalanche and stoss faces of bounding dunes. Fairly

passive flooding only disturbs aeolian stratification minimally. Floodwater

clay infiltrates and settles as an impermeable seal, with a flood pond on top,

perched, above regional groundwater. Flood ponds evaporate slowly for long

periods (>3 years). Early emergence desiccates higher parts of a mud layer.

Subsequent floods can refill a predecessor pond, benefiting from the existing

impervious seal. Potential preservation of such mud layers is lower on the

stoss face, but high on the avalanche face after burial by subsequent dune

reactivation and migration. The leeward (right) Hoanib bank, a dune stoss face,

is river and wind eroded to exhume fossil interdune pond mud layers of an

earlier Hoanib channel. The highly inclined layers are interbedded with dune

avalanche foresets and represent the edges of two successive fossil ponds

exposed in plan. Ancient flood pond mudstones occur in the Permian–Triassic

hydrocarbon reservoir, the Sherwood Sandstone Group of the Cheshire Basin

(Kinnerton Formation) and Irish Sea Basin and were previously used

erroneously to argue against the aeolian origin of cross-bed sets. Hoanib

studies show that primary river interaction with a dune field might preserve

only localized erosional omission surfaces in ancient aeolianites, with little

sandy barform preservation, prone to aeolian reworking. Around the main

fluvial channel locus, however, flood pond mudstone layers should form a

predictable halo, within which fluid permeability will decrease.



FAU Authors / FAU Editors

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


External institutions with authors

The University of Liverpool


How to cite

APA:
Stanistreet, I.G., & Stollhofen, H. (2002). Hoanib River flood deposits of Namib Desert interdunes as analogues for thin permeability barrier mudstone layers in aeolianite reservoirs. Sedimentology, 49, 719-736. https://dx.doi.org/10.1046/j.1365-3091.2002.00458.x

MLA:
Stanistreet, Ian G., and Harald Stollhofen. "Hoanib River flood deposits of Namib Desert interdunes as analogues for thin permeability barrier mudstone layers in aeolianite reservoirs." Sedimentology 49 (2002): 719-736.

BibTeX: 

Last updated on 2018-16-10 at 02:10