Wednesday, June 19, 2013

Hints of the Greenhouse Climate Before the Snowball Earth From Africa

Depositional age, provenance, tectonic and palaeoclimatic settings of the late Mesoproterozoic - middle Neoproterozoic Mbuji-Mayi Supergroup, Democratic Republic of Congo


1. Franck Delpomdor (a)
2. Ulf Linnemann (b)
3. Ariel Boven (c)
4. Andreas Gärtner (b)
5. Aleksey Travin (d)
6. Christian Blanpied (e)
7. Aurélien Virgone (e)
8. Hielke Jelsma (f)
9. Alain Préat (a)


a. Biogeochemistry & Modeling of the Earth System, Université libre de Bruxelles, 1050 Brussels, Belgium

b. Museum für Mineralogie und Geologie, Sektion Geochronologie, GeoPlasma Lab, Senckenberg Naturhistorische Sammlungen, 01109 Dresden, Germany

c. Section of Isotope Geology, Royal Museum for Central Africa, 3080 Tervuren, Belgium

d. United Institute of Geology, Geophysics and Mineralogy, Siberian Branch, Novosibirsk 630090, Russia

e. Total SA, 92078 Paris, France

f. De Beers Exploration, Southdale 2135, Johannesburg, South Africa


The late Mesoproterozoic - middle Neoproterozoic period (ca. 1300 Ma - 800 Ma) heralded extraordinary climatic and biological changes related to the tectonic changes that resulted in the assembly (~ 1.0 Ga) and the break-up of Rodinia (880 Ma - 850 Ma). In the Democratic Republic of Congo, these changes are recorded in the Mbuji-Mayi Supergroup which was deposited in the SE-NW trending siliciclastic-carbonate failed-rift Sankuru-Mbuji-Mayi-Lomami-Lovoy Basin. New LA-ICP-MS U-Pb laser ablation data on detrital zircon grains retrieved from the lower arenaceous-pelitic sequence (BI group) together with C and Sr isotopic data on carbonates from the upper dolomitic-pelitic sequence (BII group) and an 40Ar/39Ar age determination on a dolerite gives a new depositional time frame between 1174 ± 22 Ma and ca. 800 Ma for the Mbuji-Mayi Supergroup. The upper age limit is based on the assumption that the transition between the BIIb and BIIc subgroup recorded the Bitter Springs anomaly. In terms of tectonic and palaeoclimatic settings, the BII group was deposited in the eastern passive margin of the Congo Craton during warm periods interlaced with temporarily dry and wet seasons, suggesting greenhouse conditions during the fragmentation of Rodinia.

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