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Cited by 23Paleontology and Stratigraphy of FossilsPaleontology and Evolutionary BiologyEvolution and Paleontology Studies

Constraining the onset and environmental setting of metazoan biomineralization: The Ediacaran Nama Group of the Tsaus Mountains, Namibia

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Bowyer, Fred T., Uahengo, Collen-Issia, Kaputuaza, Kavevaza, Ndeunyema, Junias, Yilales, Mariana, Alexander, Ruaridh D., Curtis, Andrew, Wood, Rachel A.·2023·Earth and Planetary Science Letters
DOI 10.1016/j.epsl.2023.118336
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Abstract

The advent of animal (metazoan) biomineralization marks a fundamental transition in Earth's history, facilitating the diversification of novel body plans as well as the biological control of carbonate sediment production, resulting in a permanent restructuring of the global carbon cycle. The oldest known skeletal metazoans, the tubular ‘cloudinids’ e.g., Cloudina, appeared during the terminal Ediacaran of the Nama Group, Namibia, but precisely when, where, and why metazoans first acquired the ability to biomineralize and their timing relative to the regional δ13Ccarb profile is undocumented. Assessing possible environmental triggers for this key event therefore requires accurate constraint of the age, paleoenvironmental setting and the geochemical context of the earliest cloudinids. Here we present new stratigraphic, sedimentological, and geochemical (δ13Ccarb and δ18Ocarb) data from the oldest strata (Dabis Formation) of the Nama Group from the Witputs Sub-basin, exposed in the Tsaus Mountains of the Tsau Khaeb National Park (formerly Sperrgebiet). This constrains the oldest confirmed occurrence of Cloudina to limestones of the lower Kliphoek Member, ca. 551–550 Ma, that were deposited laterally-equivalent to the more proximal fossiliferous Kliphoek quartzite. These limestones have dominantly negative δ13Ccarb values that immediately precede recovery from the basal Nama negative δ13Ccarb excursion (BANE), and were deposited in shallow waters after a transition from semi-restricted, evaporitive-dolomitic to open marine carbonate settings. Regional correlation shows that Cloudina first appeared during an interval of dominantly low oxygen and unstable, regional marine redox conditions. We conclude that data do not support a long-term shift towards more stable, oxygenated conditions as a driver for the first appearance of skeletonization in metazoans, but do suggest that open marine carbonate settings with high carbonate supersaturation were required to support the calcifying Cloudina. In the Nama Group, the appearance of Cloudina also notably coincided with a major sea level lowstand, which we hypothesise may have enabled oxygenation of these more distal settings. Such an expansion of shallow marine oxygen may therefore have provided an evolutionary driver for innovations that were not metabolically costly, such as the onset of Cloudina biomineralization.

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  • The Ediacaran-Cambrian boundary, defined by the first appearance of Treptichnus pedum, has been suggested to coincide with, or immediately postdate, the nadir of the BACE, but both the precise position and the age of onset of the BACE (~538 to 535 Ma) remain uncertain.

    “The Ediacaran-Cambrian boundary, defined by the first appearance of the ichnospecies Treptichnus pedum and the lowest level of the associated T. pedum ichnozone, has been suggested to coincide with, or immediately postdate, the nadir of the “Basal Cambrian negative carbon isotope (δ13C) excursion” (BACE), but both the precise position of this first appearance relative to the BACE nadir and the age”

    From Sea level controls on Ediacaran-Cambrian animal radiations (2024) · cites this paper as [18]

  • The first calcified metazoans appear ~550.5 Ma in shallow marine carbonate rocks globally and increase in diversity substantially in the Cambrian, mainly as small shelly fossils found within shallow marine carbonates.

    “The first calcified metazoans appear ~550.5 Ma in shallow marine carbonate rocks globally (18, 29) and increase in diversity substantially in the Cambrian, mainly as small shelly fossils (SSFs) found within shallow marine carbonates.”

    From Sea level controls on Ediacaran-Cambrian animal radiations (2024) · cites this paper as [18]

  • The absolute timing of the decline of Ediacaran soft-bodied taxa may be related to the fact that the 538- to 533-Ma interval is poorly represented on a global scale due to the sparsity of spatially distributed successions that are currently well constrained in time.

    “The absolute timing of the decline of Ediacaran soft-bodied taxa (temporally constrained only in Laurentia after ~535 Ma) (18, 30) may be related to the fact that the 538- to 533-Ma interval is poorly represented on a global scale due to the sparsity of spatially distributed successions that are currently well constrained in time”

    From Sea level controls on Ediacaran-Cambrian animal radiations (2024) · cites this paper as [18]

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Authors
Bowyer, F. T., Uahengo, C.-I., Kaputuaza, K., Ndeunyema, J., Yilales, M., Alexander, R. D., Curtis, A., & Wood, R. A.
Affiliations
  • University of Edinburgh (GB)
  • University of Namibia (NA)
Corresponding author
  • Bowyer, Fred T.
  • Uahengo, Collen-Issia
ORCID
Venue
Earth and Planetary Science Letters
Publisher
Elsevier BV
Published
2023-10
Volume
620
Pages
118336
ISSN
0012-821X (ISSN-L)
DOI
10.1016/j.epsl.2023.118336
OpenAlex
W4385923483
Cited by
23
References
57
Citations by year
2026: 5 · 2025: 7 · 2024: 9 · 2023: 2
FWCI
4.65
Type
journal article
Language
en
Open access
Licence
Locations
  • Earth and Planetary Science Letters (publishedVersion, cc-by)
  • Edinburgh Research Explorer (University of Edinburgh) (acceptedVersion, cc-by)
Funders
  • Agencia Nacional de Investigación y Desarrollo
  • Natural Environment Research Council (NE/T008458/1)
  • Ministry of Environment and Tourism Namibia
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Evolutionary Biology
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
Keywords
Cloudina, Ediacaran, Nama Group, carbonate oxygen isotopes, marine redox conditions, carbonate supersaturation, sea-level lowstand, early animal evolution, paleoenvironment

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