Cenozoic

Mesozoic

Information provided by geoscience team at Ahmadu Bello University, Zaria, Nigeria --see About

Mimosa Formation

Mimosa Fm

Period:

Cretaceous

Age Interval:

Hauterivian

Province:
Chad S

Type Locality and Naming

Bongor Basin (SW Chad).

Reference section: Chen et al., 2018; Wang et al., 2022; Dou et al., 2023

[Fig. 1: Simplified map of the West and Central African Rift System (WCARS) showing the major features discussed in the text and the location of the Melut Basin in South Sudan (modified from Genik, 1993)]

[Fig. 2: Stratigraphic chart for the Bongor Basin showing the positions of producing reservoirs, source rocks and seals (from Dou et al., 2020)]

Lithology and Thickness

The Mimosa Formation is made up of thick –bedded, dark grey and grey-green mudstones intercalated with medium- to thick-bedded, fine- to medium-grained sandstones and pebbly sandstones interbedded with diabase (Chen et al., 2018; Wang et al., 2022). The Mimosa Formation is the most important source rock in the basin, with a maximum thickness of 2500 m and mainly consists of a large set of dark mudstone shale intercalated with siltstone and fine sandstone deposits, with local reverse cycle deposits of fine sandstone to gritstone. (Dou et al., 2023).

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

The Mimosa Fm conformably rests on the Prosopsis Fm

Upper contact

Kubla Fm conformably rests on the Mimosa Fm

Regional extent

Bongor Basin (SW Chad).

GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[19.4,9.82],[17.92,9.36],[17.18,9.44],[15.36,9.97],[14.78,10.73],[15.25,11.38],[16.26,11.23],[17.7,10.81],[19.4,9.82]]]]}}

Fossils

Ostracod (Cypridea cf. prognata, C.cf. subconcina, Mantel-liana sp., Lycopterocypris sp.), Pollen (Leiotriletes, Concavisporites, Cycadopites, Classopollis, Chasmatosporites)

Age

Hauterivian

Age Span:

Beginning stage:

Hauterivian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

132.60

Ending stage:

Hauterivian

Fraction up in the ending stage:

1.0

Ending date (Ma):

126.50

Depositional setting

Fan delta – deep to semi-deep lake (Chen et al., 2018; Wang et al., 2022).

Depositional pattern:

Additional Information

Compiler:

Enam O. Obiosio, Solomon Joshua Avong and Henry Nasir Suleiman (2024) - Stratigraphic Lexicon compiled from the following books:

Chen L., Ji H., Dou L., Du Y., Xu Z., Zhang L. (2018): The Characteristics of Source Rock and Hydrocarbon Changing Time of Precambrian Granite Reservoirs in the Bongor Basin, Chad. Mar. Petroleum Geol. 97, pp. 323-338

Wang Y., Xu G., Zhou W., Liang J., He S. (2022): Predicting Granitic Buried-Hill Reservoirs Using Seismic Reflection Data – A Case Study From the Bongor Basin, Southwestern Chad. Frontiers in Earth Science, pp. 1-13

Dou L., Xiao K., Wang J. (2023): Petroleum Geology and Exploration of the Bongor Basin. Petroleum Industry Press.