Hoanib River flood deposits of Namib Desert interdunes as analogues for thin permeability barrier mudstone layers in aeolianite reservoirs.
Stanistreet IG, Stollhofen H (2002)
Publication Language: English
Publication Type: Journal article, Original article
Publication year: 2002
Journal
Publisher: Wiley-Blackwell
Pages Range: 719-736
Journal Issue: 49
DOI: 10.1046/j.1365-3091.2002.00458.x
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.
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United Kingdom (GB)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.
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