Late Cretaceous transgression in the Muglad Basin of Central Africa and its implication for oil and gas exploration

doi:10.13745/j.esf.sf.2023.6.19

Abstract

Abstract:

The global transgression during the Late Cretaceous was previously believed to have primarily affected the northern African continent, with the Muglad Basin in the central African region thought to have been unaffected by this event. Within the basin, only one set of organic-rich source rock was known to have formed, namely the lacustrine mudstone of the Lower Cretaceous Abu Gabra Formation. This study collected mudstone samples from both the Upper Cretaceous Darfur Group and the Lower Cretaceous Abu Gabra Formation. Analysis revealed that the mudstones from the Upper Cretaceous Darfur Group exhibit a distinct distribution of dinosteranes and tricyclic terpanes compared to the lacustrine source rocks of the Lower Cretaceous Abu Gabra Formation, showing an abundance of dinosteranes and C₂₃ tricyclic terpanes, which are likely products of transgression. This study suggests that the mudstones from the Upper Cretaceous Darfur Group were influenced by seawater from the Neo-Tethys Ocean, indicating that the global transgression in the Late Cretaceous extended into the Muglad Basin in Central Africa. Furthermore, the presence of organic-rich marine mudstones in the Darfur Group suggests that the basin not only accumulated the lacustrine source rock of the Abu Gabra Formation but also potentially deposited a set of marine source rock. The discovery of marine oil in the K-1 well further confirms the hydrocarbon generation potential of marine source rock in the Darfur Group, pointing to new prospects for petroleum exploration in the Muglad Basin in the future.

Key words: transgression, Late Cretaceous, molecular fossils, dinosteranes, tricyclic terpanes, marine oil

CLC Number:

P618.13

XIAO Hong, LI Meijun, CHENG Dingsheng, LIU Jiguo, LI Jin, XING Xiangrong. Late Cretaceous transgression in the Muglad Basin of Central Africa and its implication for oil and gas exploration[J]. Earth Science Frontiers, 2024, 31(3): 352-359.

Figures/Tables 8

Fig.1 Geological location and stratigraphic column of the Muglad Basin. Adapted from [7,10,12].

Fig.2 Distribution of dinosteranes in the Lower(a) and Upper(b) Cretaceous sediments

Fig.3 Mass spectra of four 4α,23,24-trimethylcholestanes (dinosteranes) isomers

Fig.4 Distribution of tricyclic terpanes in the Lower(a) and Upper(b) Cretaceous sediments

Fig.5 A ternary diagram of relative abundance of C19+20TT, C21TT, and C23TT of the Upper and Lower Cretaceous sediments.Adapted from [35].

Fig.6 Cross plots of 10C23TT/(C23TT+C30H) vs. C24TeT/(C24TeT+C26TT)(a) and C29TT/C30H vs. C28TT/C30H (b) in the Upper and Lower Cretaceous sediments. Adapted from [36].

Fig.7 Cross plots of C19+20TT/C23TT vs. C23TT/C21TT (a) and C19+20TT/C23TT vs. C24TeT/C26TT (b) in the Upper and Lower Cretaceous sediments. Adapted from [42].

Fig.8 Comparative analysis of tricyclic terpanes and dinosteranes distribution in the Darfur Group sediments and K-1 well crude oil

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