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A biostratigraphic correlation between the Otavi and Nama
Groups in Namibia, to the Cango Caves Group in South Africa;
using Otavia fossils as the chief constraint
S. I. Thompson1
1. Nelson Mandela Metropolitan University, South Africa, [email protected]
ABSTRACT
The South African shallow marine Matjies River Formation of the Cango Caves Group is comprised of intercalated
shale and sandstone with massive limestones. The Cango Caves Group shares lithological and geochronological
similarieties to the Namibian Otavi Group, where recent research has documented evidence for the earliest lifeforms found to date. In February 2012, Brain et al published a significant paper titled “The first animals: ca. 760million-year-old sponge-like fossils from Namibia”. They revealed the significant discovery of the oldest known
animal fossils known to date, and named them Otavia. The Otavi Group rocks are aged between 760 Ma and 550
Ma, implying that Otavia fossils are up to 150 million years older than previously proposed “first life on earth”
fossils. Otavia were mostly found in the organic rich limestone facies of the Otavi Group, but are also present in
the Nama Group. These rocks comprise shallow marine shelfal and slope siliclastic and carbonate rocks up to
several kilometres thick.
This research integrates detailed field work and lab analysis to elucidate the possible presence of Otavia fossils in
the Cango Caves Group rocks in South Africa.
The documentation of these fossils in South Africa would indicate a biostratigraphic correlation between the Otavi,
Nama, and Cango Caves Groups.
The study area for this research is in the area of Oudtshoorn in the Western Cape Fold Belt. Unweathered outcrop
samples of Cango Caves Group limestone have been collected for thin section analysis, and several samples have
been dissolved in acetic acid in order to identify possible Otavia fossils. To date, Otavia fossils have not been
identified, but further analysis and sampling will be performed in the coming months. A more detailed field
campaign is proposed whereby organic rich limestones will be correlated and sampled over a wider aerial
distribution and with greater emphasis on representative facies types. Furthermore, this research will document the
palaeoclimatic, palaeontologic, and palaeogeographical influences of the Cango Caves Group and compare and
contrast them to the Otavi and Nama Groups of Namibia.
KEYWORDS: Otavia, Limestone, Cango Caves Group, Sponge fossils, Oudtshoorn
Inkaba yeAfrica : 9th Annual Workshop, Germany - 2012