International Geologiical Congress - Oslo 2008

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HPF-07 Rise and fall of the Ediacaran (Vendian) biota

 

Discovery of the first macroscopic carbonaceous algal assemblage in the terminal Proterozoic of Namibia

 

Maxim Leonov, Paleontological Institute RAS (Russian Federation)
Mikhail Fedonkin, Paleontological Institute RAS (Russian Federation)
Patricia Vickers-Rich, Monash University (Australia)
Andrey Ivantsov, Paleontological Institute RAS (Russian Federation)
Peter Trusler, Monash University (Australia)
Karl Hoffmann, Geological Survey of Namibia (Namibia)
 

 

Macroscopic carbonaceous compressions are significant fossils preserved in the Ediacaran fossil assemblages along with soft-bodied metazoans and acritarchs. The most diverse assemblages of such fossils come from two regions: the Eastern European Platform and Southern China. Some macroscopic carbonaceous fossils have been reported also in the Neoproterozoic of South Africa. Dispersed fragments of thalli were described as Vendotaenia sp. from lower Nama Group and also from black shales of Owambo Formation (Mulden Group) (Germs et al., 1986; Germs, 1995). The newly discovered diverse assemblage described in this paper are preserved as carbonaceous films (phytoleimae) on the surfaces of shales . Carbonaceous algal fossils have been found in some abundance within clay layers, which occur in the lower part of the Nama Group, Kliphoek Member of the Dabis Formation, Kuibis Subgroup on Farm Aar, near the town of Aus in southern Namibia.
Channel sands within which Rangea fossils occur lie below the clays bearing the carbonaceous algae and in turn are underlain by mudstones with local concentrations of Ernietta.
The newly described assemblage consists of four distinct taxa: Glomulus filamentum Steiner, 1994; Eoholinia fruticulosa A. Istchenko, 1989; Tyrasotaenia podolica Gnilovskaya, 1971; and Kanilovia sp.
Composition of the macroscopic carbonaceous algal assemblage is mixed in biostratigraphic aspect (when compared with known data algal distribution in the Neoprtoterozoic sequences of Russian platform). Eoholinia fruticulosa is a form with relatively narrow time distribution, a characteristic taxon for the lower part of Redkino regional stage of the Eastern-European Platform. The two other significant forms, Tyrasotaenia podolica and Kanilovia sp., are typical of Kotlin-aged algal assemblages. Such a mixture of taxa is a typical of uppermost part of the Kotlin deposits, the upper part of Kanillovka Series (Podolia, Ukraine). But joint occurrence of such typical taxa with Eoholynia fruticulosa in the newly discovered Namibian assemblage is not typical of the Kotlin assemblages of Eastern-European Platform. Nevertheless, the remaining assemblage suggests that the best stratigraphic correlation of the Namibian sediments bearing this new algal assemblage would be with with the Upper Kotlin deposits of the Russian platform. Further collection in the future may more clearly resolve this dilemma. Research was supported by RFBR grant N 05-05-64825 and grant for leading science schools NSH-1790.2003.5. Field research was funded by a UNESCO grant (IGCP493).

 

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