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- Title
Sequence stratigraphy in the Algoa and Gamtoos basins (South Africa): a shoreline’s journey since the Middle Mesozoic.
- Authors
Makhubele, Marvel H.; Bordy, Emese M.
- Abstract
Basin evolution models are dependent on high-quality subsurface data, normally obtained during hydrocarbon exploration activities. The limited exploration, to-date, has impeded the understanding of the geological evolution of the offshore Algoa and Gamtoos half-graben basins in the southern Cape region of South Africa. To reconstruct the main geological events of the area since the Early Jurassic, vintage borehole and seismic data as well as key outcrop observations were integrated. Using this combined dataset, we generated contemporary gross depositional environment models, as well as tested the applicability of different sequence stratigraphic models for these late Gondwana basins. The studied stratigraphic interval contains syn- and post-rift systems that were impacted by marine processes, especially in the distal hanging walls of these compartmentalized half-graben basins. Sedimentation within these depocenters primarily occurred above the hanging walls, while the footwalls formed regions of basement highs. The geological characteristics of the studied succession prevent the application of the depositional sequence or tectonic system tracts models in the syn-rift succession. Because subaerial unconformities (SUs) in the distal syn-rift sequence are not detectable, a diachronous, northward advancement of the shoreline (relative sea level rise) until the late Valanginian can be postulated. The observations in the syn-rift sequence, which is bound by a basal SU, followed by third- and fourth-order transgressive and regressive cycles and a second-order maximum flooding surface at the top, can be explained with a modified genetic sequence model. In the transitional to drift phase interval, from Hauterivian to Holocene, the successions are bound by SUs and their correlative conformities. In the successions without evidence for subaerial exposure, flooding surfaces could be used as sequence-bounding stratigraphic contacts. This study reaffirms the notion that while the sequence stratigraphic concept is model-independent, sequence models are sensitive to depositional scale.
- Publication
Geo-Marine Letters, 2021, Vol 41, Issue 4, p1
- ISSN
0276-0460
- Publication type
Article
- DOI
10.1007/s00367-021-00721-8