[ Le Sous-groupe de la Mpioka: Témoins de la réactivation des failles post-Schisto-calcaire dans le fossé de la Basse-Sangha ]
Volume 35, Issue 2, January 2022, Pages 367–374
C. M. E. Cibambula1, L. O. Tuema2, K. A. Sekeraviti3, C. L. Mukeba4, and M. N. A. J. Makutu5
1 Université de Kinshasa, Faculté des Sciences, Département des Géosciences, Géologie, Post office Box 190, Kinshasa XI, RD Congo
2 Université de Kinshasa, Faculté des Sciences, Département des Géosciences, Géologie, Post office Box 190, Kinshasa XI, RD Congo
3 Université de Kinshasa, Faculté des Sciences, Département des Géosciences, Géologie, Post office Box 190, Kinshasa XI
4 Université de Kinshasa, Faculté des Sciences, Dép. Géosciences, B.P 190, Kinshasa XI, RD Congo
5 Université de Kinshasa, Faculté des Sciences, Département des Géosciences, Géologie, Post office Box 190, Kinshasa XI
Original language: French
Copyright © 2022 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
In the Lower Sangha through, apart from the glacial deposit of lower and upper Diamictites, detrital sedimentation is represented by the shales and sandstones of Sansikwa and Petite Bembezi formations as well as by conglomerates, shales and sandstones of the Mpioka Subgroup related respectively to the Tonian, the Cryogenian and the Cambro-Ordovician. The carbonate precipitation of Sekelolo and Schisto-Calcaire in the saline waters from the Adamastor paleo-ocean in the Araçuai basin in Brazil are responsible for the interruption of this detrital sedimentation in the entire West Congo basin. In the latter, the erosion of the stepped limestone plateaus, vector of the clasts of the Bangu-Niari conglomerate at the base of the Mpioka Subgroup, sufficiently proves that the releases from the faults of the substratum reactivated in the underlying limestones before the pan-African orogenic thrust had caused the total withdrawal of the sea in the Mayumbe North, Mayumbe South and Lower Sangha throughs. In this aulacogen of the Lower Sangha, the weak accommodation of the Mpioka lake submerging the collapsed median compartment, hardly exceeding the rejection of the border faults, justifies the restriction of the Mpioka deposit only to the Bangu plateau, a collapsed compartment at the both normal and reverse conjugate faults.
Author Keywords: Lower Sangha through, Mayumbe North through, Mayumbe South through, glacial deposit, detrital sedimentation, Mpioka Subgroup, Cambro-Ordovicien, Araçuai basin, West Congo basin, stepped limestone plateaus, faults, withdrawal of the sea, accommodation, Bangu plateau.
Volume 35, Issue 2, January 2022, Pages 367–374
C. M. E. Cibambula1, L. O. Tuema2, K. A. Sekeraviti3, C. L. Mukeba4, and M. N. A. J. Makutu5
1 Université de Kinshasa, Faculté des Sciences, Département des Géosciences, Géologie, Post office Box 190, Kinshasa XI, RD Congo
2 Université de Kinshasa, Faculté des Sciences, Département des Géosciences, Géologie, Post office Box 190, Kinshasa XI, RD Congo
3 Université de Kinshasa, Faculté des Sciences, Département des Géosciences, Géologie, Post office Box 190, Kinshasa XI
4 Université de Kinshasa, Faculté des Sciences, Dép. Géosciences, B.P 190, Kinshasa XI, RD Congo
5 Université de Kinshasa, Faculté des Sciences, Département des Géosciences, Géologie, Post office Box 190, Kinshasa XI
Original language: French
Copyright © 2022 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
In the Lower Sangha through, apart from the glacial deposit of lower and upper Diamictites, detrital sedimentation is represented by the shales and sandstones of Sansikwa and Petite Bembezi formations as well as by conglomerates, shales and sandstones of the Mpioka Subgroup related respectively to the Tonian, the Cryogenian and the Cambro-Ordovician. The carbonate precipitation of Sekelolo and Schisto-Calcaire in the saline waters from the Adamastor paleo-ocean in the Araçuai basin in Brazil are responsible for the interruption of this detrital sedimentation in the entire West Congo basin. In the latter, the erosion of the stepped limestone plateaus, vector of the clasts of the Bangu-Niari conglomerate at the base of the Mpioka Subgroup, sufficiently proves that the releases from the faults of the substratum reactivated in the underlying limestones before the pan-African orogenic thrust had caused the total withdrawal of the sea in the Mayumbe North, Mayumbe South and Lower Sangha throughs. In this aulacogen of the Lower Sangha, the weak accommodation of the Mpioka lake submerging the collapsed median compartment, hardly exceeding the rejection of the border faults, justifies the restriction of the Mpioka deposit only to the Bangu plateau, a collapsed compartment at the both normal and reverse conjugate faults.
Author Keywords: Lower Sangha through, Mayumbe North through, Mayumbe South through, glacial deposit, detrital sedimentation, Mpioka Subgroup, Cambro-Ordovicien, Araçuai basin, West Congo basin, stepped limestone plateaus, faults, withdrawal of the sea, accommodation, Bangu plateau.
Abstract: (french)
Dans le fossé de la Basse-Sangha, hormis le dépôt glaciaire de Diamictites inférieure et supérieure, la sédimentation détritique est représentée par les shales et les grès de Sansikwa et de la Petite Bembezi ainsi que par les conglomérats, les shales et les grès de la Mpioka rattachés respectivement au Tonien, au Cryogénien et au Cambro-Ordovicien. Les précipitations carbonatées de Sekelolo et du Schisto-Calcaire dans les eaux salées en provenance du paléo-océan Adamastor dans le bassin d’Araçuai au Brésil sont responsables de l’interruption de cette sédimentation détritique dans l’ensemble du bassin West Congo. Dans ce dernier, l’érosion des plateaux étagés calcaires, vecteur des clastes du conglomérat de Bangu-Niari à la base du Sous-groupe de la Mpioka, prouve à suffisance que les rejets des failles du substratum réactivées dans les calcaires sous-jacents avant la poussée orogénique pan africaine avaient provoqué le retrait total de la mer dans les fossés de Mayumbe North, de Mayumbe South et de la Basse-Sangha. Dans cet aulacogène de la Basse-Sangha, la faible accommodation du lac de la Mpioka submergeant le compartiment affaissé médian, ne dépassant guère le rejet des failles bordières, justifie la restriction du dépôt de la Mpioka au seul plateau de Bangu, compartiment affaissé à la fois des failles conjuguées normales et inverses.
Author Keywords: Fossé de la Basse-Sangha, fossé de Mayumbe North, fossé de Mayumbe South, dépôt glaciaire, sédimentation détritique, Sous-groupe de la Mpioka, Cambro-Ordovicien, bassin d’Araçuai, bassin West Congo, plateaux étagés calcaires, failles, retrait de la mer, accommodation, plateau de Bangu.
How to Cite this Article
C. M. E. Cibambula, L. O. Tuema, K. A. Sekeraviti, C. L. Mukeba, and M. N. A. J. Makutu, “The Mpioka Sub-group: Witnesses to the reactivation of post-Schisto-limestone faults in the Lower Sangha ditch,” International Journal of Innovation and Applied Studies, vol. 35, no. 2, pp. 367–374, January 2022.
