Cenozoic

Mesozoic

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AnzaCret Sandstone-Shale Formation

AnzaCret Sandstone-Shale Fm

Period:

Cretaceous

Age Interval:

Berriasian – middle Maastrichtian

Province:
Kenya

Type Locality and Naming

The Anza Basin of north-central Kenya is ca. 560 km long and appears to be deepest towards its northeast side, where the rift spans 130 km. The available information on the Anza basin is largely based on well data from five wells drilled by Amoco Kenya and Total Kenya in the late 1980s (Winn Jr et al., 1993). Stratigraphic subdivision of its sedimentary infill into groups and formations is yet to be completed (Lenhardt et al., 2025).

References: Reeves et al., 1987; Bosworth, 1992; Lenhardt et al., 2025

[Fig. 1: Stratigraphy of the CARS (modified from Schull, 1988; McHargue et al., 1992; Guiraud and Bosworth, 1997; Gani et al., 2009; Wolela, 2009; Dou et al., 2013, 2018, 2023a; Liu and Chen, 2014; Eisawi et al., 2015; Mohammed et al., 2016; Bussert et al., 2018; Yassin et al., 2017; Mohammed Yasin et al., 2019; Gao et al., 2023)]

[Fig. 2: Simplified map of the West and Central African Rift System (WCARS) showing the Anza Basin in Kenya (modified from Genik, 1993).]

Lithology and Thickness

The entire formation is made up of a succession of shaley sandstones (Fig. 9 of Lenhardt et al., 2025). The north-west is characterized by the deposition of coarse clastic fluvial deposits. Coarse fluvial deposits generally dominate within the basin (Lenhardt et al., 2025).

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

Basement Complex

Upper contact

Maikona Fm, unconformably (uppermost Maastrichtian is absent)

Regional extent

Anza Basin

GeoJSON

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Fossils

Age

Age Span:

Beginning stage:

Berriasian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

143.10

Ending stage:

Maastrichtian

Fraction up in the ending stage:

0.75

Ending date (Ma):

67.57

Depositional setting

Depositional pattern:

Additional Information

Compiler:

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

Lenhardt, N., Omietimi, E. J., Edegbai, A. J., Schwark, L., Catuneanu, O., Fairhead, J. D., Gotz, A. E. (2025): Traversing the rift: A review of the evolution of the West and Central African Rift System and its economic potential. Earth-Science Reviews, 261: pp. 1-39