Cenozoic

Mesozoic

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Melut Formation

Melut Fm

Period:

Cretaceous

Age Interval:

Campanian – Maastrichtian

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.

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 the Melut Basin, the thickness of this formation averages 1,303m, and is characterized by the dominance of thick sandstones interbedded with thin claystones (indicating a progressive shallowing) (Dou et al., 2007). In the Rawat Basin, the formation is composed mainly of claystone, siltstone and occasional sandstone. The claystone is greyish red to pale red, occasionally greyish brown to moderately brown, moderately hard to hard, occasionally sandy, rare carbonaceous material, washable in part, non to slightly calcareous. The sandstone is poorly to moderately consolidated, subrounded to rounded, well to moderately sorted, very fine to medium grained, poor to fair porosity (Mohammed et al., 2017). The thickness of the formation is estimated at 324m in the well M-1 and 538 in well M-2 (Mohammed et al., 2017).

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Melut Fm conformably rests on the Galhak Fm (or the Upper Galhak Fm in the sub-divided terminology of the Rawat Basin)

Upper contact

Samma Fm unconformably rests on the Melut Fm in the Melut Basin; but the equivalent interval to the Samma Fm is a Paleocene hiatus in the Rawat Basin; where the Melut Fm is unconformably below the Tabus Fm of Eocene.

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 the Rawat Basin, it has Spore-Pollen (proteacidites sigalii, Zivisporis cf. blanensis, Scabratriporites annellus, Deltoidspora balinkaense, Dicyophyllidites sp.) (Mohammed et al., 2017)

Age

Campanian – Maastrichtian (Melut Basin; but interpreted as only Maastrichtian in Rawat Basin)NOTE: Age span as estimated for the Melut Basin used here for graphic and paleogeographic display purposes.

Age Span:

Beginning stage:

Campanian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

83.65

Ending stage:

Maastrichtian

Fraction up in the ending stage:

1.0

Ending date (Ma):

66.04

Depositional setting

Deep lacustrine influenced by distributary channels; lacustrine-deltaic during the initiation of the regional subsidence and extension in the Maastrichtian Syn-rift stage (Mohammed et al., 2017).

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