Petrogenesis of Late Archaean Flood-Type Basic Lavas from the Klipriviersberg Group, Ventersdorp Supergroup, South Africa

1992 ◽  
Vol 33 (4) ◽  
pp. 817-847 ◽  
Author(s):  
J. S. MARSH ◽  
M. P. BOWEN ◽  
N. W. ROGERS ◽  
T. B. BOWEN
Keyword(s):  
South Africa ◽  
Late Archaean

scholarly journals Palaeoclimates: the first two billion years

2006 ◽  
Vol 361 (1470) ◽  
pp. 917-929 ◽  
Author(s):  
James F Kasting ◽  
Shuhei Ono
Keyword(s):  
South Africa ◽  
Oxygen Isotopes ◽  
Natural Explanation ◽  
Witwatersrand Basin ◽  
Late Archaean ◽  
Bacterial Sulphate Reduction ◽  
Climatic Constraints ◽  
The Mean ◽  
High Concentrations ◽  
Earth’S Climate

Earth's climate during the Archaean remains highly uncertain, as the relevant geologic evidence is sparse and occasionally contradictory. Oxygen isotopes in cherts suggest that between 3.5 and 3.2 Gyr ago (Ga) the Archaean climate was hot (55–85 °C); however, the fact that these cherts have experienced only a modest amount of weathering suggests that the climate was temperate, as today. The presence of diamictites in the Pongola Supergroup and the Witwatersrand Basin of South Africa suggests that by 2.9 Ga the climate was glacial. The Late Archaean was relatively warm; then glaciation (possibly of global extent) reappeared in the Early Palaeoproterozoic, around 2.3–2.4 Ga. Fitting these climatic constraints with a model requires high concentrations of atmospheric CO 2 or CH 4 , or both. Solar luminosity was 20–25% lower than today, so elevated greenhouse gas concentrations were needed just to keep the mean surface temperature above freezing. A rise in O 2 at approximately 2.4 Ga, and a concomitant decrease in CH 4 , provides a natural explanation for the Palaeoproterozoic glaciations. The Mid-Archaean glaciations may have been caused by a drawdown in H 2 and CH 4 caused by the origin of bacterial sulphate reduction. More work is needed to test this latter hypothesis.

Raindrop imprints in the Late Archaean-Early Proterozoic Ventersdorp Supergroup, South Africa

1989 ◽  
Vol 61 (3-4) ◽  
pp. 303-309 ◽  
Author(s):  
W.A. van der Westhuizen ◽  
N.J. Grobler ◽  
J.C. Loock ◽  
E.A.W. Tordiffe
Keyword(s):  
South Africa ◽  
Late Archaean ◽  
Early Proterozoic
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