Cretaceous–Quaternary seismic stratigraphy of the Tanga offshore Basin in Tanzania and its petroleum potential

Abstract

In this study, the available 2D seismic lines have been interpreted to understand the basin development and petroleum potential of the Late Cretaceous–Quaternary stratigraphy of the Tanga offshore Basin in Tanzania. Conventional seismic interpretation has delineated eight sedimentary fill geometries, fault properties, stratal termination patterns and unconformities characterizing the studied stratigraphy. The Late Cretaceous was found to be characterized by tectonic quiescence and uniform subsidence where slope induced gravity flows that resulted during the Miocene block movements was the major mechanism of sediment supply into the basin. The Quaternary was dominated by extensional regime that created deep N-S to NNE-SSW trending graben. The graben accommodated thick Pleistocene and Holocene successions deposited when the rate of tectonic uplift surpasses the rate of sea level rise. Thus, the deposition of lowstand system tracts characterized by debris flow deposits, slope fan turbidites, channel fill turbidites and overbank wedge deposits, known for their excellent petroleum reservoir qualities, especially where charged by Karoo Black Shales. Subsequent tectonic quiescence and transgression lead to the emplacement of deep marine deposits with characteristic seismic reflection patterns that indicate the occurrence of Quaternary shale sealing rocks in the study area. The occurrence of all the necessary petroleum play systems confirms the hydrocarbon generation, accumulations and preservation potential in the Tanga Basin.

Timing of the Miocene-Quaternary magmatic intrusions in the Tanga offshore basin: correlation to age equivalent deposits in the Eyasi-Wembere basin and their implications for petroleum potential

“…Fig. 2; Mvile et al, 2021). Seismic interpretation revealed that the sea bottom has been dissected by several faults that have been active during different periods to recent time.…”

“…Ebinger et al, 1997;Foster et al, 1997) but recent studies have reported a third component, the offshore branch of EARs (e.g. Franke et al, 2015) which is evident in the Tanga offshore basin (Mvile et al, 2021). Both onshore and offshore compartments of the sedimentary basins that their development were partly in uenced by the EARs have been dissected by more or less near vertical faults (Ebinger et al, 1997;Foster et al, 1997…”

“…Possible traps include localized force folds (Fig. 20) and the Quaternary extensive fault system in the basin (Mvile et al, 2021; Fig. 10).…”

“…;Mvile et al, 2021). Here correlation is made between sedimentary successions in the offshore branch of the EARs within the Tanga Basin and the Eyasi-Wembere basin, a south-eastern arm of the eastern branch of the EARs for a better understanding of the Miocene-Quaternary successions of the Tanga offshore basin.…”