Document Detail

Probable calcified metaphytes in the latest Proterozoic Nama Group, Namibia: origin, diagenesis, and implications.
MedLine Citation:
PMID:  11538648     Owner:  NASA     Status:  MEDLINE    
Samples from the Huns Limestone Member, Urusis Formation, Nama Group, at two adjacent localities in southern Namibia contain thin foliose to arched, sheet-like carbonate crusts that are 100-500 micrometers thick and up to 5 cm in lateral dimension. Morphologic, petrographic, and geochemical evidence supports the interpretation of these delicate crusts as biogenic, most likely the remains of calcified encrusting metaphytes. The original sediments of the fossiliferous samples contained aragonitic encrusting algae, botryoidal aragonite cements, and an aragonite mud groundmass. Spherulites within the precursor mud could represent bacterially induced mineral growths or the concretions of marine rivularian cyanobacteria. Original textures were severely disrupted during the diagenetic transition of aragonite to low-magnesian calcite, but some primary structures remain discernible as ghosts in the neomorphic mosaic. Gross morphology, original aragonite mineralogy, and hypobasal calcification indicate that the crusts are similar to late Paleozoic phylloid algae and extant peyssonnelid red algae. Structures interpreted as possible conceptacles also suggest possible affinities with the Corallinaceae. Two species of Cloudina, interpreted as the remains of a shelly metazoan, are also known from limestones in the Nama Group. It is possible, therefore, that skeletalization in metaphytes and animals arose nearly simultaneously near the end of the Proterozoic Eon.
S W Grant; A H Knoll; G J Germs
Related Documents :
9405318 - Effects of incline on speed, acceleration, body posture and hindlimb kinematics in two ...
24317408 - Myometrial physiology -time to translate?
18561148 - Strong association between birth month and reproductive performance of vietnamese women.
18779978 - Which factors regulate the reproduction of ectoparasites of temperate-zone cave-dwellin...
2211538 - Lithium treatment during pregnancy, delivery, and lactation: an update.
18818938 - Pregnancy in chronic renal insufficiency: single centre experience from north india.
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of paleontology     Volume:  65     ISSN:  0022-3360     ISO Abbreviation:  J Paleontol     Publication Date:  1991  
Date Detail:
Created Date:  1996-07-23     Completed Date:  1996-07-23     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  100971397     Medline TA:  J Paleontol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1-18     Citation Subset:  S    
Botanical Museum, Harvard University, Cambridge, Massachusetts 02138, USA.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Algae, Red
Calcium Carbonate / analysis*
Carbonates / analysis
Geologic Sediments / chemistry*
Geological Phenomena
Minerals / analysis
Reg. No./Substance:
0/Carbonates; 0/Minerals; 471-34-1/Calcium Carbonate
A H Knoll / Harvard U, Cambridge, MA, Botanical Museum

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Previous Document:  Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia...
Next Document:  Calculations on the rate of the ion-molecule reaction between NH3+ and H2.