Cenozoic

Mesozoic

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Jimidi Formation

Jimidi Fm

Period:

Neogene

Age Interval:

Late Oligocene-Early Miocene

Province:
SouthSudan, Sudan S

Type Locality and Naming

Melut Basin (NE South Sudan - W Ethiopia), and the Rawat Basin (SE Sudan), which are the southeastern and the northwestern basins of the greater White Nile rift basin. The name and age of the formation were assigned by Robertson Research International “RRI” (1991); and it is found in Rawat Basin Wells M-1, M-2, M-3 (Hassan, 2016).

Reference: Dou et al., 2007; Dou et al., 2023 (Melut Basin); Mohammed et al, 2017 (Rawat Basin)

[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: Comprehensive stratigraphic columns in the Melut Basin (from Dou et al., 2023)]

[Fig. 3: Rawat Basin- Block 25 in southern Sudan (after Ministry of Petroleum & Gas-OEPA, 2015, Extracted from Mohammed et al., 2017).]

[Fig. 4: Summary of Tectono-stratigraphy of the Rawat Basin (from Mohammed, 2016).]

Lithology and Thickness

In Melut Basin, it is to 213m of massive sands that upwards are interbedded with more thin claystones (Dou et al., 2007). In Rawat Basin, it is made up of equally interbedded sequences of sand/sandstone and mudstone. The sand is dominantly medium-coarse, whereas the sandstone is medium grained and well sorted (Mohammed, 2016). The cementing material is kaolinitic and siliceous. The mudstone is light grey and occasionally greyish red in color, hard to moderately hard, occasionally sandy and non-calcareous (Mohammed, 2016). At well M-1, the total thickness of the Jimidi Fm is placed by Mohammed (2016) at 139m, and a total thickness of 538m in well M-2

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

Jimidi Fm unconformably overlies a Lau Fm unit of clayey sandstone in the Melut Basin; but overlies the upward continuation of the Adar Fm claystone in the Rawat Basin.

Upper contact

Miadol Fm conformably rests on the Jimidi Fm

Regional extent

Melut Basin (NE South Sudan - W Ethiopia), and the Rawat Basin (SE Sudan), which are the southeastern and the northwestern basins of the greater White Nile rift basin.

GeoJSON

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Fossils

In Rawat Basin, it has Spores-Pollen (Magnastriatites howardii, Cyathidites congoensis, Triplanosporites microsinuosus, Leiotriletes maxoides, Deltoidospora delicate, Dictyophyllidites trilobiformis, Leiotriletes microsinuosides, Laevigatosporites discordatus, Laevigosporites josensis, Verrucatosporites favus) (Mohammed et al., 2017)

Age

Late Oligocene-Early Miocene (estimated Aquitanian-Burdigalian in Melut Basin; but an older Chattian to mid-Burdigalian in Rawat Basin)NOTE: Age span as estimated for the Melut Basin used here for graphic and paleogeographic display purposes.

Age Span:

Beginning stage:

Aquitanian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

23.04

Ending stage:

Burdigalian

Fraction up in the ending stage:

1.0

Ending date (Ma):

15.99

Depositional setting

In Melut Basin, it is interpreted as shallow lacustrine to fluvial environments (Dou et al., 2007); but in Rawat Basin, it is interpreted as marginal marine (Mohammed, 2016).

Depositional pattern:

Additional Information

Compiler:

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

Dou L., Xiao K., Cheng D., Shi B., Li Z. (2007): Petroleum Geology of the Melut Basin and the Great Palogue Field, Sudan. Marine and Petroleum Geology, 24, pp.129-144

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

Mohammed H. Z. A., Awad M. Z., Eisawi (2017): Upper Cretaceous to Neogene Palynology of the Rawat Basin, White Nile State, Sudan. Journal of Earth Science & Climatic Change. 08 (04)

Robertson Research International “RRI”, Geological Research Authority of Sudan “GRAS” (2016): The Geology and Petroleum Potential of Southern, Central, and Eastern Sudan. Unpublished Report. Vol. 1-4