Akakus Fm
Period:
Silurian
Age Interval:
Ludlow (Gorstian) – Pridoli
Province:
Murzuq Basin, Ghadames Basin, Al Kufrah Basin
Type Locality and Naming
The term "Akakus sandstone" was introduced by Desio (1936a) after Jabal Akakus in the Ghat area. The original description by Desio from a location in the Jabal Akakus, north of Ghat was incomplete, and a replacement type section was established by Klitzsch from an area to the south of Ghat where a complete section is present (Alkhalas, 2006). It is also called Acacus Fm. in the Ghadames and Al Kufrah Basins (Le Heron and Howard, 2011).
Synonym: Acacus Fm; Acacaus Fm (Craig, 2006, used in SEPM summary)
References: Desio, 1936a; Klitzsch, 1969; Castro et al., 1985; Pierobon, 1991; Hallett, 2002; Alkhalas, 2006; Le Heron and Howard, 2011.
Lithology and Thickness
Klitzsch (1969) described section of the formation made up of fine-grained sandstone containing frequent trace fossils, interbedded with dark-grey, graptolitic shales in the lower and middle parts (Pierobon, 1991). At the type locality, the Akakus Formation comprises 240m of fine to medium-grained silty sandstone, thinly bedded, frequently cross-bedded, with ripple and flute marks (Hallett, 2002).
Lithology Pattern:
Clayey sandstone
Relationships and Distribution
Lower contact
It unconformably overlies the Tanezzuft Fm.
Upper contact
It is unconformably overlain by the Tadrart Fm. [Early Silurian is absent.]
GeoJSON
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Age
Ludlow (Gorstian)-Pridoli (according to latest Google Gemini review of literature); but top is base-Pridoli in Al Kufrah Basin
Age Span:
Beginning stage:
Gorstian
Fraction up in beginning stage:
0.00
Beginning date (Ma):
426.74
Ending stage:
Pridoli
Fraction up in the ending stage:
1.0
Ending date (Ma):
419.00
Depositional setting
The Akakus sandstones represent the regressive phase of the Early Silurian transgression pointing out the continental to transitional (nearshore marine) character of the sedimentation in outcrops from Takharkhouri to Al Awaynat. They conclude that deposition of regressive clastics began after the transgressive acme was reached in the Middle Silurian (Fello, 2001).
Depositional pattern:
Clayey sandstone
Additional Information
Compiler:
Enam O. Obiosio, Solomon Joshua Avong and Henry Nasir Suleiman (2024) - Stratigraphic Lexicon compiled from the following books: