The Nama Group is a megaregional

Vendian The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and the ...

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

group of stratigraphic sequences deposited in the Nama

foreland basin A foreland basin is a structural basin that develops adjacent and parallel to a mountain belt. Foreland basins form because the immense mass created by crustal thickening associated with the evolution of a mountain belt causes the lithospher ...

in central and southern

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

. The Nama Basin is a peripheral foreland basin, and the Nama Group was deposited in two early basins, the Zaris and Witputs, to the north, while the

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

n Vanrhynsdorp Group was deposited in the southern third. The Nama Group is made of fluvial and shallow-water marine sediments, both siliciclastic and carbonate. La Tinta Group in Argentina is considered equivalent to Nama Group.

Description

The group extends from the

Gariep Belt The Orange River (from Afrikaans/Dutch: ''Oranjerivier'') is a river in Southern Africa. It is the longest river in South Africa. With a total length of , the Orange River Basin extends from Lesotho into South Africa and Namibia to the north ...

in the south to outcrops of pre- Damara

basement A basement or cellar is one or more floors of a building that are completely or partly below the ground floor. It generally is used as a utility space for a building, where such items as the furnace, water heater, breaker panel or fuse box, ...

in the north.Meert et al., 1997, p.639 Thrombolite-

stromatolite Stromatolites () or stromatoliths () are layered sedimentary formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). The ...

reefs in the Nama Group are best developed in the Kuibis Subgroup of the Zaris subbasin, and in the Huns platform of the Witputs subbasin. The Nama Group is a series of interbedded shallow marine carbonates and siliciclastics deposited in a storm-dominated ramp setting.Wood & Curtis, 2015, p.114 "Nama-type preservation" is an

Ediacaran type preservation Ediacaran type preservation relates to the dominant preservational mode in the Ediacaran period, where Ediacaran organisms were preserved as casts on the surface of microbial mats. Exceptional preservation All but the smallest fraction of the ...

that presents sandstone castings of fossil creatures in which organisms are preserved in three dimensions, within fine-grained beds that were deposited in single storm or mudflow events: an example is ''

Ausia fenestrata ''Ausia fenestrata'' is a curious Ediacaran period (630 – 539 million years ago) fossil represented by only one specimen 5 cm long from the Nama Group, a Vendian to Cambrian group of stratigraphic sequences deposited in the Nama foreland ...

''. Analysis performed in 2018 on ''

Namacalathus ''Namacalathus'' is a problematic metazoan fossil occurring in the latest Ediacaran. The first, and only described species, ''N. hermanastes'', was first described in 2000 from the Nama Group of central and southern Namibia. A U–Pb zircon age ...

'' and '' Cloudina'' skeletons from the Ediacaran Omkyk Member of the Nama Group demonstrates that both organisms originally produced

aragonitic Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...

skeletons, which later underwent diagenetic conversion to

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

.Pruss et al., 2018, p.763

Stratigraphy

The Nama Group is subdivided into:

Ages

The lower and upper part of the Spitskop Member of the Urusis Formation, Schwarzrand Subgroup, had originally been dated on the basis of

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the r ...

s to 545.1 ± 1 Ma and 543.3 ± 1 Ma respectively. Recalibration of the Spitskop radiometric data indicates revised dates of 542.68 ± 1.25 Ma (terminal Ediacaran) and 540.61 ± 0.67 Ma (within error of the Ediacaran–Cambrian boundary), respectively. An ash bed from the Hoogland Member towards the base of the Nama Group (Zaris Formation, Kuibus Subgroup) has yielded an age of 547.4 ± 0.3 Ma, in 2018 slightly modified to 547.32 ± 0.31 Ma. The lower part of the Nomtsas Formation has yielded an age of 539.4 ± 1 Ma, in the same year recalibrated to 538.18 ± 1.11 Ma.Buatois et al., 2018

Fossil content

Nama-type Ediacaran fossils found in the group include: * ''

'' * '' Bergaueria'' - Kuibis SubgroupCrimes & Germs, 1982, p.890 * '' Brooksella'' - Schwarzrand Subgroup * '' ?Chondrites'' - Schwarzrand Subgroup * '' Cloudina'' - Zaris Formation * '' ?Diplichnites'' - Nomtsas Formation * '' Neonereites biserialis'', '' N. uniserialis'' - Nomtsas Formation * ''

Diplocraterion ''Diplocraterion'' is an ichnogenus describing vertical U-shaped burrows having a spreite (weblike construction) between the two limbs of the U. The spreite of an individual ''Diplocraterion'' trace can be either protrusive (between the paired ...

'' - Schwarzrand Subgroup * '' Enigmatichnus africani'' - Fish River Subgroup * ''

Ernietta ''Ernietta'' is an extinct genus of Ediacaran organisms with an infaunal lifestyle. Fossil preservations and modeling indicate this organism was sessile and “sack”-shaped. It survived partly buried in substrate, with an upturned bell-shaped ...

'' - Naldaus & Dabis Formations * '' Namacalathus hermanastes'' - Zaris FormationThrombolite Reef, Schwarzrand Subgroup
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.org * '' Namalia villiersiensis'' - Kuibis Quartzite * '' Namapoikia rietoogensis'' - Dabis Formation * ''

Nereites ''Nereites'' is a genus of trace fossil. Modern tracemakers of incipient ''Nereites'' include worm-like organisms,Seilacher, A., 2007. Trace Fossil Analysis. Springer, Berlin, Heidelberg (226 pp.) horseshoe crabsMartin, A.J., Rindsberg, A.K., 20 ...

'' - Schwarzrand Subgroup * '' Protechiurus edmondsi'' - Kuibis Quartzite & Dabis Formation * '' Pteridinium carolinaense'', '' P. simplex'' - Naldaus & Dabis FormationsVendian fauna, Kuibis Formation, - Glaessner 1979
at

.orgFarm Swartpunt
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.org * '' Rangea schneiderhoehni'' - Naldaus & Dabis FormationsNiederhagen Member, Naldaus Fm., - Jenkins 1985
at

.orgKliphoek Member, Dabis Fm., - Jenkins 1985
at

.org * ''

Skolithos ''Skolithos'' (formerly spelled ''Scolithus'' or ''Skolithus'') is a common trace fossil ichnogenus that is, or was originally, an approximately vertical cylindrical burrow. It is produced by a variety of organisms in shallow marine environment ...

'' - Fish River & Schwarzrand Subgroups * '' Streptichnus narbonnei'' - Urusis Formation * '' Swartpuntia germsi'' - Urusis Formation * ''

Treptichnus pedum ''Treptichnus'' (formerly named ''Phycodes'', ''Manykodes'' by J. Dzik, and also known as ''Trichophycus''See e.gfossiilid.info: paleodiversity in Baltoscandia: Trichophycus pedum/ref>) is the preserved burrow of an animal. As such, it is regar ...

'' - Nomtsas FormationSonntagsbrunn Farm, Nomtsas Fm., Valley Fill 2, Visionarium
at

.org

Gallery

File:Swartpuntiagermsi.png, Reconstruction of '' Swartpuntia germsi'' File:Namacalathus.svg, Reconstruction of '' Namacalathus hermanastes'' File:Cloudina.svg, Reconstruction of '' Cloudina''

References

Bibliography

* * * * * * * {{Cite journal , last=Wood , first=R. , last2=Curtis , first2=A. , year=2015 , title=Extensive metazoan reefs from the Ediacaran Nama Group, Namibia: the rise of benthic suspension feeding , url=https://www.geos.ed.ac.uk/homes/acurtis/Wood_Curtis_2015.pdf , journal=

Geobiology Geobiology is a field of scientific research that explores the interactions between the physical Earth and the biosphere. It is a relatively young field, and its borders are fluid. There is considerable overlap with the fields of ecology, evolutio ...

, volume=13 , issue=2 , pages=112–122 , access-date=2018-08-25, doi=10.1111/gbi.12122 , pmid=25556318 , hdl=20.500.11820/5f33c6b7-a2ac-4d1b-9f8d-a0ee6409af28 , hdl-access=free