Calcified Metazoans in Thrombolite-stromatolite Reefs of the Terminal Proterozoic Nama Group, Namibia

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Calcified Metazoans in Thrombolite-stromatolite Reefs of the Terminal Proterozoic Nama Group, Namibia

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dc.contributor.author Watters, Wesley A.
dc.contributor.author Grotzinger, John P.
dc.contributor.author Knoll, Andrew Herbert
dc.date.accessioned 2010-02-16T21:48:16Z
dc.date.issued 2000
dc.identifier.citation Grotzinger, John P., Wesley A. Watters, and Andrew H. Knoll. 2000. Calcified metazoans in thrombolite-stromatolite reefs of the terminal Proterozoic Nama Group, Namibia. Paleobiology 26, no. 3: 334-359. en_US
dc.identifier.issn 0094-8373 en_US
dc.identifier.uri http://nrs.harvard.edu/urn-3:HUL.InstRepos:3638444
dc.description.abstract Reefs containing abundant calcified metazoans occur at several stratigraphic levels within carbonate platforms of the terminal Proterozoic Nama Group, central and southern Namibia. The reef-bearing strata span an interval ranging from approximately 550 Ma to 543 Ma. The reefs are composed of thrombolites (clotted internal texture) and stromatolites (laminated internal texture) that form laterally continuous biostromes, isolated patch reefs, and isolated pinnacle reefs ranging in scale from a meter to several kilometers in width. Stromatolite-dominated reefs occur in depositionally updip positions within carbonate ramps, whereas thrombolite-dominated reefs occur broadly across the ramp profile and are well developed as pinnacle reefs in downdip positions. The three-dimensional morphology of reef-associated fossils was reconstructed by computer, based on digitized images of sections taken at 25-micron intervals through 15 fossil specimens and additionally supported by observations of over 90 sets of serial sections. Most variation observed in outcrop can be accounted for by a single species of cm-scale, lightly calcified goblet-shaped fossils herein described as Namacalathus hermanastes gen. et sp. nov. These fossils are characterized by a hollow stem open at both ends attached to a broadly spheroidal cup marked by a circular opening with a downturned lip and six (or seven) side holes interpreted as diagenetic features of underlying biological structure. The goblets lived atop the rough topography created by ecologically complex microbial-algal carpets; they appear to have been sessile benthos attached either to the biohermal substrate or to soft bodied macrobenthos such as seaweeds that grew on the reef surface. The phylogenetic affinities of Namacalathus are uncertain, although preserved morphology is consistent with a cnidarian-like bodyplan. in general aspect, these fossils resemble some of the unmineralized, radially symmetric taxa found in contemporaneous sandstones and shales, but do not appear to be closely related to the well-skeletonized bilaterian animals that radiated in younger oceans. Nama reefs demonstrate that biohermal associations of invertebrates and thrombolite-forming microorganisms antedate the Cambrian Period. en_US
dc.description.sponsorship Organismic and Evolutionary Biology en_US
dc.language.iso en_US en_US
dc.publisher Paleontological Society en_US
dc.relation.isversionof http://dx.doi.org/10.1666/0094-8373(2000)026<0334:CMITSR>2.0.CO;2 en_US
dc.relation.hasversion http://stuff.mit.edu/people/watters/grotz_etal_paleobio_2000.pdf
dash.license META_ONLY
dc.title Calcified Metazoans in Thrombolite-stromatolite Reefs of the Terminal Proterozoic Nama Group, Namibia en_US
dc.type Journal Article en_US
dc.description.version Version of Record en_US
dc.relation.journal Paleobiology en_US
dash.depositing.author Knoll, Andrew Herbert
dash.embargo.until 10000-01-01

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  • FAS Scholarly Articles [7495]
    Peer reviewed scholarly articles from the Faculty of Arts and Sciences of Harvard University

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