Delpomdor, F.,  Schröder, S.,  Blanpied, C.,  Fernandez-Alonso, M. & Préat, A. 2011. ‘Meso- and Neoproterozoic Paleoenvironments of the Mbuji-Mayi Supergorup, DRC’. 23rd colloquium on African Geology - CAG23, Johannesburg. Book of abstracts. Johannesburg : University of Johannesburg.

Conference abstract

MESO- AND NEOPROTEROZOIC PALEOENVIRONMENTS OF THE MBUJI-MAYI SUPERGROUP, DRC Delpomdor, F. 1, Schröder, S. 2, Blanpied, C. 2, Fernandez-Alonso, M. 3, Préat, A. 1 1 Université libre de Bruxelles, Department of Earth and Environmental Sciences, Avenue F.D. Roosevelt 50 CP160/02, B-1050 Brussels, Belgium. Franck.delpomdor@ulb.ac.be 2 Total SA, Avenue Larribau, B-64018 Pau, France. 3 Musée Royal de l’Afrique Centrale, Leuvensesteenweg 13, B-3080 Tervuren, Belgium Keywords: Mbuji-Mayi, carbonates, sedimentology, sequential stratigraphy The Mbuji-Mayi Supergroup is deposited in a NW-SE elongate basin covering a surface of 12,000 km2, extending from Lubudi to Luembe rivers in the Kasai Province in Democratic Republic of Congo. The Mbuji-Mayi sedimentary series is weakly or no affected by regional metamorphism. Lithostratigraphically, this Supergroup is divided from base to top into a siliciclastic succession (550 m) of the BI Group and a carbonate sequence (1000m) with stromatolitic build-ups and ‘black shales’ of the BII Group. Radiometric ages on syngenetic galena for the BI Group (BIe1 Formation) yield 1040 and 1065 Ma (Holmes and Cahen, 1955; Raucq, 1957). Overlying amygdaloidal basaltic pillow lavas from the Sankuru-Bushimay confluence have given K/Ar radiometric ages of 948 ± 20 Ma (Cahen et al., 1974, 1984). In our study five drill cores and numerous handspecimens have been collected, encompassing the top of BIcd to the BIIe Subgroups for sedimentological analysis and sequential stratigraphy. The sedimentological study of thin sections allows recognition of ten microfacies whose succession (from 1 to 10) forms a standard sequence recording a pre-evaporative low-energy subtidal environment with non-branching and branching columnar stromatolites evolving to an evaporative inter- to supratidal environment with lacustrine ponds influenced by a sabhka. A sedimentary model is proposed for the carbonate series. The sequential stratigraphy derived from the lithological curve of the microfacies succession allows recognition of shallowing-upward elementary parasequences of ∼10m in thickness, which allows to establish a quite good correlation between the drill cores. References Cahen, L., Ledent, D. and Snelling, N.J. (1974). Données géochronologiques dans le Katangien inférieur du Kasai oriental et du Shaba nord-oriental (République du Zaïre). Mus. Roy. Afr. Centr., Tervuren, Rapp. Ann. Dépat. Géol. Min., 59-70. Cahen, L., Snelling, N.J., Delhal, J. and Vail, J.R. (1984). Geochronology and Evolution of Africa. Clarendon Press, Oxford, 512 pp. Holmes, A. and Cahen, L. (1955). African geochronology. Colonial Geology and Mineral Resources, 5(1): 3-38. Raucq, P. (1957). Contribution à la reconnaissance