Soft sediment deformation structures in the Neoproterozoic Kansuki formation (Katanga Supergroup, Democratic Republic of the Congo): Evidence for deposition in a tectonically active carbonate platform

摘要

The Neoproterozoic Kansuki Formation in the Katanga Supergroup (Katanga Copperbelt, Democratic Republic of the Congo) mainly consists of platform carbonates with pyroclastic beds and mafic layers. Lithological and sedimentological investigation in the central part of the Katanga Copperbelt (Tenke Fungurume Mining District) evidenced peritidal facies for the carbonate. It also evidenced the presence of Soft Sediment Deformation Structures (SSDS). Small-scale load structures, multiple successions of load cast and flame structures are attributed to discrete sedimentary processes such as overloading and rapid deposition. Tepee-like structures are indicative of a subaerial exposure of the carbonate that was deposited in relatively shallow water. Major SSDS such as boudinage within water escape structures, load cast with attached pseudonodules, tepee-like structures with sheet cracks, small-scale mass displacement, and brecciation are interpreted as triggered by seismicity and indicative of active tectonics during sedimentation in the Katanga basin. This is consistent with the presence of pyroclastic beds and mafic layers within the Kansuki Formation, pointing to carbonate platform deposition in a paleorift.