Cenozoic

Mesozoic

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Al Gayger Formation

Al Gayger Fm

Period:

Cretaceous

Age Interval:

Barremian-Aptian

Province:
SouthSudan

Type Locality and Naming

Fal-1 well (Dou et al., 2007)

Fal-1 well (Dou et al., 2007) in the Melut Basin (NE South Sudan - W Ethiopia), which is the southeastern basin of the greater White Nile rift basin. Not yet identified in the Rawat Basin of northwestern 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

The combined Al Gayger Fm and the overlying Al Renk Fm has a thickness of 1124m in the type-section – Fal-1 well – and is estimated to be up to 3,000m thick in the depocenter. The lower Al Gayger Fm interval of this combined unit, consists of thin sandstones interbedded by thin claystones (Dou et al., 2007).

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Pre-Cambrian Basement Complex

Upper contact

The Al Renk Fm rests conformably on the Al Gayger Fm

Regional extent

Melut Basin (NE South Sudan - W Ethiopia) is the southeastern basin of the greater White Nile rift basin.

GeoJSON

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Fossils

Sporomorphs (Cupliferoidaepollenites, Tricolpopollenites, Lygodiumsporites, Jiaohepollis),

Age

Barremian-Aptian (Melut Basin)NOTE: Age span as estimated for the Melut Basin used here for graphic and paleogeographic display purposes.

Age Span:

Beginning stage:

Barremian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

126.50

Ending stage:

Aptian

Fraction up in the ending stage:

1.0

Ending date (Ma):

113.20

Depositional setting

Fluvial-deltaic to shallow lacustrine facies that progresses upwards into deep to semi deep lacustrine facies (Dou et al., 2007).

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