# Huab Formation

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The **Huab Formation** is an [Early Permian](/source/Early_Permian) ([Artinskian](/source/Artinskian) to [Kungurian](/source/Kungurian)) geologic [formation](/source/Formation_(geology)) correlated with the [Ecca Group](/source/Ecca_Group) and designated "Ecca" Group, because it does not belong to the [Karoo](/source/Karoo), in the southwestern [Kunene Region](/source/Kunene_Region) and northern [Erongo Region](/source/Erongo_Region) of northwestern [Namibia](/source/Namibia). The Huab Formation represents the oldest sedimentary unit of the [Huab Basin](/source/Huab_Basin), overlying the [basement](/source/Basement_(geology)). The [oil shales](/source/Oil_shale) within the formation were deposited in a shallow [lacustrine](/source/Lacustrine) [environment](/source/Depositional_environment), and the formation marks the transition from terrestrial deposits under [glacial](/source/Glacial) climatic circumstances towards a warmer fluvial and marine deltaic environment.

The Huab Formation is correlated with a series of formations in the [Pelotas](/source/Pelotas_Basin) and [Paraná Basins](/source/Paran%C3%A1_Basin) in southeastern Brazil, deposited in a larger basinal area, 150 million years before the break-up of [Pangea](/source/Pangea). The abundance of *[Glossopteris](/source/Glossopteris)* and *[Mesosaurus](/source/Mesosaurus)* fossils are characteristic of the [Gondwanan](/source/Gondwana) correlation across present-day South America, Africa, Antarctica and Australia.

## Description

The Huab Formation is a lithological unit with an approximate maximum thickness of 190 metres (620 ft), deposited in the eponymous [basin](/source/Huab_Basin) where it underlies the [Gai-As Formation](/source/Gai-As_Formation), separated by a significant hiatus,[1] and overlies the [basement](/source/Basement_(geology)).[2] The formation crops out south of the [Huab River](/source/Huab_River),[3] extending from the [Atlantic coast](/source/Atlantic_Ocean#Southern_Atlantic) to [Twyfelfontein](/source/Twyfelfontein). The thickness in the coastal area is about 75 metres (246 ft).[4]

### Lithologies

Part of the formation in the west is composed of [carbonates](/source/Carbonate) (domal [stromatolites](/source/Stromatolite) with an east to west orientation and thin laminae of less than 1 millimetre (0.039 in)). The stromatolites occur in a 35 kilometres (22 mi) wide zone, reaching from 3 kilometres (1.9 mi) east of the [Uniab Fault](/source/Uniab_Fault) to 2 kilometres (1.2 mi) east of the [Bergsig Fault](/source/Bergsig_Fault) system.[5] The eastward sections comprise [oolitic](/source/Oolite) [conglomeratic](/source/Conglomerate_(geology)) horizons of up to 50 centimetres (1.6 ft) thick. The carbonates ([mudstones](/source/Mudstone) and [marls](/source/Marl)) are overlain by silty, partly calcareous [shales](/source/Shale). The shales interfinger with [sandstones](/source/Sandstone) and in certain parts [coal](/source/Coal) beds are found. In the eastern domain around the [Doros crater](/source/Doros_crater), dark iron-oxide cements occur in the upper conglomerate horizons.[5] In virtually all lithological units, bones of the amphibious reptile *[Mesosaurus tenuidens](/source/Mesosaurus)* can be encountered in concretions.[6] The laminated mudstones and marls contain a diverse [ichnofauna](/source/Ichnofossil) including *[Skolithos](/source/Skolithos)*, *[Planolites](/source/Planolites)*, and large exemplars of *[Rhizocorallium irregulare](/source/Rhizocorallium)*.[7]

### Depositional environments

The depositional environment is interpreted as ranging from [glacial](/source/Glacial) ([tillite](/source/Tillite)) at the very base,[2] followed by a glacio-[fluvial](/source/Fluvial) setting, and a warmer climate fluvial environment.[8] The sequence higher up is formed by a [fan deltaic](/source/River_delta) setting,[9] with a lateral shallow lake with increased [salinity](/source/Salinity) where stromatolite bioherms were formed.[6][10][11] The uppermost section of the Huab Formation, underlying the Gai-As Formation, was deposited in an [estuarine](/source/Estuary) environment.[12]

The depositional environments have been described in detail by Wanke in 2000 as follows:[13]

**Western and central domain**

Stromatolitic bioherms acted as a barrier towards the open sea in the west. Their preferred E-W orientation coincides with tidal- and wave induced currents perpendicular to the palaeo-coastline. [Lagoonal](/source/Lagoon) environments were established landwards of the bioherm belts, in which laminated shales developed. The lamination is due to suspension fallout in slightly agitated water. Erosive based interbeds of coarse to gritty sandstones formed during storm events and are therefore interpreted as [tempestites](/source/Tempestite). West of the bioherm belts, the fair weather wave basis reached the ground, expressed in oscillation-rippled surfaces.

Channels between bioherm ridges have been interpreted as tidal channels. They host flat-pebble conglomerates, which are characterized by a high ooid content. These ooid bearing flat-pebble conglomerates support the facies concept of shallow, wave dominated water in the vicinity of the bioherms: Ooids form in very shallow, fairly agitated, carbonate saturated water probably under warm climate. The flat pebbles derived from desiccated layers of unlithified cohesive fine clastics that had been reworked, preferentially under the influence of storm waves. Tidal flats or lagoons provide the conditions for the generation of both, ooids and flat-pebble conglomerates.

**Eastern domain**

Shales and mudstones besides algal laminites represent deposition in a slightly agitated, shallow water body with relatively intensive carbonate production. Oscillating water-levels resulted in the formation of [paleosols](/source/Paleosol), which were reworked in flat pebble conglomerates after flooding. Autochthonous [breccias](/source/Breccia) give clear evidence for frequent sea level fluctuations, that refer to palustrine soils, which underwent periodically subaerial exposure. Coarse sandstones, partly channelized, reveal fluvial influence. The coarser material was probably sourced by a nearby delta that was temporarily flooded during storm events. The dominance of those coarse sandstones towards the top of the eastern flat-pebble facies association might indicate delta progradation. The iron-oxide cements are interpreted as ferricretes, that either formed autochthonous or derived from adjacent reworked ferricrete crusts. An early uplift of the eastern [hinterland](/source/Hinterland) might be indicated by coarse, westwardly prograding deltaic deposits of the upper Huab Formation in the eastern Huab area.[14]

### Correlations

See also: [Paraná Basin](/source/Paran%C3%A1_Basin) and [Pelotas Basin](/source/Pelotas_Basin)

The upper part of the formation is correlated with the [Irati Formation](/source/Irati_Formation) of the [Paraná](/source/Paran%C3%A1_Basin) and [Pelotas Basins](/source/Pelotas_Basin) in [Rio Grande do Sul](/source/Rio_Grande_do_Sul), [Brazil](/source/Brazil), and with the [Whitehill Formation](/source/Whitehill_Formation) in the [Karoo Basin](/source/Karoo_Basin) of southern Namibia and the [Eastern](/source/Eastern_Cape), [Northern](/source/Northern_Cape) and [Western Cape](/source/Western_Cape), [South Africa](/source/South_Africa).[6] The lower section correlates with the [Palermo](/source/Palermo_Formation) and [Rio Bonito Formations](/source/Rio_Bonito_Formation) of the Paraná Basin and the [Prince Albert Formation](/source/Prince_Albert_Formation) of the Karoo.[15] The Permian sequence in the Huab Basin is much thinner than those of the Paraná and Karoo Basins.[16] The fossil assemblages of *[Glossopteris](/source/Glossopteris)* and *Mesosaurus* are known from other parts of [Gondwana](/source/Gondwana); the [Vryheid Formation](/source/Vryheid_Formation) of South Africa and coal deposits of the Lower Permian in Australia.[8]

## See also

- [List of fossiliferous stratigraphic units in Namibia](/source/List_of_fossiliferous_stratigraphic_units_in_Namibia)
- [Geology of Namibia](/source/Geology_of_Namibia)
- [Ganigobis Formation](/source/Ganigobis_Formation)
- [Gondwanide orogeny](/source/Gondwanide_orogeny)

## References

1. Wanke, 2000, p.25

1. Horsthemke et al, 1990, p.68

1. Duncan et al., 1989, p.5

1. Wanke, 2000, p.20

1. Wanke, 2000, p.21

1. [Section 2, Cycle 2, Unit 5](https://paleobiodb.org/classic/displayCollResults?collection_no=28468) at [Fossilworks](/source/Fossilworks).org

1. Wanke, 2000, p.23

1. Horsthemke et al., 1990, p.69

1. Horsthemke et al., 1990, p.70

1. Horsthemke et al., 1990, p.72

1. [Stromatolitic bioherm of the Huab Formation](https://opus.bibliothek.uni-wuerzburg.de/opus4-wuerzburg/frontdoor/deliver/index/docId/271/file/Plate-I-1.pdf)

1. Horsthemke et al., 1990, p.73

1. Wanke, 2000, pp.22–23

1. Wanke, 2000, p.38

1. Horsthemke et al., 1990, p.74

1. Holzförster et al., 2000, p.255

### Bibliography

- Duncan, A.R.; Newton, S.R.; van den Berg, C.; Reid, D.L. (1989), ["Geochemistry and petrology of dolerite sills in the Huab River Valley, Damaraland, north-western Namibia"](http://www.mme.gov.na/files/publications/354_Duncan%20et%20al_Dolerite_Huab%20area.pdf), *Communications of the Geological Survey of Namibia*. **5**: 5–18, retrieved 2018-08-26
- Holzförster, Frank; Stollhofen, Harald; Stanistreet, Ian G. (2000), ["Early Permian deposits of the Huab area Namibia: a continental to marine transition"](http://www.mme.gov.na/files/publications/05b_Holzforster%20et%20al_Lower%20Permian_Huab%20Area.pdf), *Communications of the Geological Survey of Namibia*. **12**: 247–257, retrieved 2018-08-26
- Horsthemke, E.; Ledendecker, S.; Porada, H. (1990), ["Depositional environments and stratigraphic correlation of the Karoo Sequence in northwestern Damaraland"](http://www.mme.gov.na/files/publications/d95_Horsthemke%20et%20al_Karoo%20Sequence_Huab%20Basin.pdf), *Communications of the Geological Survey of Namibia*. **6**: 67–77, retrieved 2018-08-26
- Wanke, Angsar (2000), ["Karoo-Etendeka Unconformities in NW Namibia and their Tectonic Implications (PhD thesis)"](https://opus.bibliothek.uni-wuerzburg.de/opus4-wuerzburg/frontdoor/deliver/index/docId/271/file/Diss-wanke.pdf), [Julius-Maximilians-Universität Würzburg](/source/University_of_W%C3%BCrzburg), pp. 1–114, retrieved 2018-08-26

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Adapted from the Wikipedia article [Huab Formation](https://en.wikipedia.org/wiki/Huab_Formation) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Huab_Formation?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.