The Nama Group is a megaregional Ediacaran group of stratigraphic sequences deposited in the Nama foreland basin in central and southern Namibia. 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 African Vanrhynsdorp Group was deposited in the southern third.Gresse, P. G., G. J. B. Germs. The Nama foreland basin: sedimentation, major unconformity bounded sequences and multisided active margin advance. 1993, Precambrian Research, 63(3-4):247-252, 259-272 The Nama Group is made of fluvial and shallow-water marine sediments, both siliciclastic and carbonate.Saylor, Beverly Z., John P. Grotzinger, Gerard J. B. Germs. Sequence stratigraphy and sedimentology of the Neoproterozoic Kuibis and Schwarzrand Subgroups (Nama Group), southwestern Namibia. 1995 Precambrian Research 73:153-171. La Tinta Group in Argentina is considered equivalent to Nama Group.
Description
The group extends from the Gariep Belt in the south to outcrops of pre-Damara basement in the north.Meert et al., 1997, p.639 Thrombolite-stromatolite 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.Grotzinger, 2000, p.252 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 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. Analysis performed in 2018 on Namacalathus and Cloudina skeletons from the Ediacaran Omkyk Member of the Nama Group demonstrates that both organisms originally produced aragonitic skeletons, which later underwent diagenetic conversion to calcite.Pruss et al., 2018, p.763
Stratigraphy
The Nama Group is subdivided into:Winterleitner et al., 2015 Subgroup Formation Member Fish River Schwarzrand Vergesig Formation Nomtsas Formation Urusis Formation Spitskop Naldaus/Nudaus Formation Huns Niederhagen Kuibis Zaris Formation Urikos & Hoogland Omkyk Dabis Formation Kliphoek Kanies
Ages The lower and upper part of the Spitskop Member of the Urusis Formation, Schwarzrand Subgroup, had originally been dated on the basis of zircons 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:
Ausia fenestrataHahn, G.; Pflug, H. D. (1985). "Polypenartige Organismen aus dem Jung-Präkambrium (Nama-Gruppe) von Namibia". Geologica et Palaeontologica. 19: 1–13 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 - Schwarzrand Subgroup Enigmatichnus africani - Fish River Subgroup Ernietta - Naldaus & Dabis Formations Namacalathus hermanastes - Zaris FormationReefal biostrome, Kuibis Subgroup at Fossilworks.orgThrombolite Reef, Schwarzrand Subgroup at Fossilworks.org Namalia villiersiensis - Kuibis Quartzite Namapoikia rietoogensis - Dabis FormationRietoog, Driedoornvlagte pinnacle reef complex at Fossilworks.org Nereites - Schwarzrand Subgroup Protechiurus edmondsi - Kuibis Quartzite & Dabis FormationAar Farm at Fossilworks.org Pteridinium carolinaense, P. simplex - Naldaus & Dabis FormationsVendian fauna, Kuibis Formation, - Glaessner 1979 at Fossilworks.orgFarm Swartpunt at Fossilworks.org Rangea schneiderhoehni - Naldaus & Dabis FormationsNiederhagen Member, Naldaus Fm., - Jenkins 1985 at Fossilworks.orgKliphoek Member, Dabis Fm., - Jenkins 1985 at Fossilworks.org Skolithos - Fish River & Schwarzrand Subgroups Streptichnus narbonnei - Urusis FormationFarm Swartpunt, Urusis Formation at Fossilworks.org Swartpuntia germsi - Urusis Formation Treptichnus pedum - Nomtsas FormationSonntagsbrunn Farm, Nomtsas Fm., Valley Fill 2, Visionarium at Fossilworks.org
Gallery
See also
List of fossiliferous stratigraphic units in Namibia Geology of Namibia Puncoviscana Formation Sierra Bayas Group
References
Bibliography
Further reading 2009 - Cohen, Phoebe A., Alexander Bradley, Andrew H. Knoll, John P. Grotzinger, Soren Jensen, John Abelson, Kevin Hand, Gordon Love, Joannah Metz, Nicola McLoughlin, Patrick Meister, Rebekah Shepard, Mike Tice, and Jonathan P. Wilson - Tubular compression fossils from the Ediacaran Nama Group, Namibia. Journal of Paleontology 83, no. 1: 110-122 M. F. Glaessner. 1979. An echiurid worm from the Late Precambrian. Lethaia 12(2):121-124 D. Grazhdankin and A. Seilacher. 2002. Underground Vendobionta from Namibia. Palaeontology 45(1):57-78 J. P. Grotzinger, W. A. Watters, and A. H. Knoll. 2000. Calcified metazoans in thrombolite-stromatolite reefs of the terminal Proterozoic Nama Group, Namibia. Paleobiology 26(3):334-359 R. J. F. Jenkins. 1985. The enigmatic Ediacaran (Late Precambrian) genus Rangea and related Forms. Paleobiology 11(3):336-355 S. Jensen and B. N. Runnegar. 2005. A complex trace fossil from the Spitskop Member (terminal Ediacaran–? Lower Cambrian) of southern Namibia. Geological Magazine 142(5):561-569 G. M. Narbonne, B. Z. Saylor, and J. P. Grotzinger. 1997. The youngest Ediacaran fossils from southern Africa. Journal of Paleontology 71(6):953-967 J. P. Wilson, J. P. Grotzinger, W. W. Fischer, K. P. Hand, S. Jensen, A. H. Knoll, J. Abelson, J. M. Metz, N. Mcloughlin, P. A. Cohen, and M. M. Tice. 2012. Deep-water incised valley deposits at the Ediacaran-Cambrian boundary in Southern Namibia contain abundant Treptichnus pedum. Palaios 27:252-273 R. A. Wood, J. P. Grotzinger, and J. A. D. Dickson. 2002. Proterozoic Modular Biomineralized Metazoan from the Nama Group, Namibia. Science 296(5577):2383-2386