Facies and sequence stratigraphy of the Katangan Basin in Zambia

The Neoproterozoic (ca. 840 – ca. 560 Ma) Katangan Basin hosts the Zambian Copperbelt, part of the world's largest sediment-hosted copper province: the Central African Copperbelt. Many detailed descriptions of Katangan stratigraphy exist, but predominantly on a sub-basin or mine-scale. This work, based on 10 deep drill-holes across the Katangan Basin of Zambia, builds on the mine-centric literature by proposing a comprehensive facies scheme and sequence stratigraphic correlation to better understand the basin's tectonostratigraphic evolution. The proposed facies scheme covers the Katangan Supergroup in Zambia, and is intended primarily for use on drill core. 36 facies and sub-facies form 17 facies associations attributed to 5 gross depositional environments: terrestrial, deltaic, coastal, shelf, and slope. The facies successions and the stacking patterns of the interpreted depositional environments are consistent with those of an archetypal rift basin. Stratigraphic evidence supports two phases of extension and thermal subsidence, punctuated by two widespread glacial events. Facies counts support this, and allow for the stratigraphic evolution of the basin to be more quantitatively constrained. The Lower Roan Group is dominated by coarse siliciclastic syn-rift fill responding to fault-controlled subsidence. A post-rift sequence boundary marks a clear reversal in facies trends between the Lower and Upper Roan Groups, from siliciclastic-dominated to carbonate-dominated. The Upper Roan is interpreted to represent an epicontinental sea with extensive coastal regions and sabkhas deposited as the basin thermally subsided. The Mwashia Group is demarcated at its base by a maximum flooding surface, and records a second, magmatic, phase of extension, causing the basin to deepen and widen. The Nguba Group can be defined at its base by a maximum flooding surface, and is associated with extensive Sturtian diamicite successions. The basin mostly remained deep during Nguba times. The Kundelungu Group overlies a regionally correlatable sequence boundary and associated Marinoan diamictites, likely representing the distal portion of a flexurally subsiding basin prior to inversion during the Lufilian orogeny. • An integrated facies scheme for the Neoproterozoic Katangan Basin of Zambia is proposed. • Facies analysis provides a robust framework for a sequence stratigraphic correlation of the Katangan Supergroup in Zambia. • Quantifying facies abundances can aid in discriminating syn- and post-rift phases of the basin's evolution. • Facies and stratigraphic architecture are compatible with a two-phase Tonian rift interpretation for the Katangan Basin.