33rd AL du Toit Memorial Lecture
After a couple of years of nonexistence, the GSSA Polokwane branch took it upon their sleeves to also be among the hosts of the 33rd AL du Toit memorial lecture, hosted at the University of Limpopo.
There is a noteworthy
disappearance/appearance of these deposits throughout geological record. He attributed
the episodic disappearance/appearance to be relatively dependant on volcanism and
tectono-eustatic sea-level. Tectono-eustatic sea level changes due to glaciations
are plausible hence the stratigraphic occurrence of these deposits with
glaciomarine deposits.
As a young scientist I am inspired to follow
in the steps of these two greatest geologists to go out and discover and
capture the greatest geological phenomenon and add value in the research community
and I hope I share the same sentiments with each and every young scientist who
attended the 33rd AL du Toit memorial lecture.
Dr Alexander Logie Du
Toit (1878-1948) is an eminent South African field geologist, famous for being one
of the supporters of the Alfred Wegner’s theory of continental drift. His work
added a great knowledge on various aspects of geology in South Africa. Travelling
on foot or riding on his bicycle he was able to map most geological boundaries
in South Africa and detailed his geological work in scientific papers and books.
After his death the GSSA instituted a series of memorial lectures across
southern Africa, these are delivered every two years by an admired scientist in
honour of his great work.
This year, the 33rd
AL du Toit memorial lecture was presented by another esteemed South African
geologist, Prof Nic Beukes. His research career focuses on sedimentary basin
analyses with emphasis on manganese(Mn) and iron(Fe) ore deposit formation. The lecture
titled “genesis and paleoenvironmental significance of Precambrian sedimentary
Feand Mn deposits with special reference to the history of free
oxygen in the ocean and atmosphere” is being delivered across 12 places throughout
southern Africa.
My highlights of the
talk were how he addressed the schools of thought which support banded iron formation
(BIF), their environments of formation (anaerobic and aerobic conditions) and
their timing in Precambrian. He showed evidence of free O2 in the
oceans and atmosphere in Neoproterozoic before the Great Oxidation Event (~
2.35 Ga), noticeable by the relative abundance of BIF in the Precambrian record, Isua, W
Greenland (~ 3.8Ga) as an excellent example.
BIFs occur as combinations
of cherts, haematite/ magnetite with carbonates andare usually interbedded with manganese
(MnO2 formed by carbon degradation) as seen in the Hotazel Formation
of the Transvaal SG.
Prof Beukes presented his
findings on the striking similarities between the Transvaal and Hamersley basin
(on the Kaapvaal and Pilbara cratons). He used a basin analysis approach: showing
contrasts or lack thereof sedimentary facies, palaeomagnetics, geochemistry of
these interlayered BIF and manganese (Mn) successions. How these resemble
restricted back –arc basins and possibilities of a single basin, Vaalbara???
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| The audience: the young scientists and professionals |
The lecture presented gave
the audience more than what was expected, the use of micro and macro scale examples suggesting the presence of free O2 in the
atmosphere and oceans in the Archaean and on formation and structure of these interbedded
Mn and Fe deposits.
I was personally
bewildered by an outsized number of young scientists amongst the audience both
from the industry (Anglo Platinum, Bokoni Platinum, and the Council for
Geosciences) and the academic end of the geological spectrum (professional
scientists and students from the University of Venda and the host institution).
The lecture really appealed to both ends of the spectrum.
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| Prof Nic Beukes sandwhiched by the two ladies in the front row with the organising team |
A special thanks to the official sponsors GSSA, Assmang and ofcourse the host institution - University of Limpopo.
