Hamra Formation

Hamra Fm

Period:

Ordovician

Age Interval:

Floian.

Province:
Illizi Basin, Ghadames Basin

Type Locality and Naming

Synonym: Hamra Quartzites, and Unit III-2/3 in Illizi Basin

References: Klett, 2000; Benvegnù, 2020; Kwakman, 2020.

Lithology and Thickness

It is made up of basal transgressive lag above which there are repetitions of graptolitic shales and highstand sandstone facies, representing an alternation between tidal deposits and continental shelf strata (Benvegnù, 2020). The Hamra Fm contains meter thick beds of clean, highly cemented quartz-sandstone in the Chotts Basin (Kwakman, 2020). Corresponds to the Hamra Quartzite Fm of the SW Algeria basins of Paleozoic, which is a major reservoir.

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

In the Oued Mya (or Triassic) and Chotts Basins, it conformably overlies the El Atchane Fm. But, in the Illizi Basin, it conformably overlies the In Kraf Fm, which is the lateral equivalent of the El Atchane Fm and El Gassi Fm (see Klett, 2000).

Upper contact

In the Oued Mya (or Triassic) Basin, it is conformably overlain by the Ouargla Fm, while it is unconformably overlain by the Edjeleh Fm in the Illizi Basin (see Klett, 2000). In the Chotts Basin of Tunisia, it is conformably overlain by the Azzel Fm.

Regional extent

Widespread. It extends from the Oued Mya to Illizi Basin to the Chotts and Ghadames Basins.

[Just Illizi-Ghadames merger given in this GeoJSON pending making a larger one.]

GeoJSON

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Fossils

Graptolites

Age

Floian

Age Span:

Beginning stage:

Floian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

477.08

Ending stage:

Floian

Fraction up in the ending stage:

1.0

Ending date (Ma):

471.26

Depositional setting

Shallow marine (Benvegnù, 2020)

Depositional pattern:

Additional Information

Compiler:

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

Benvegnù I. (2020): Thermal Evolution of Paleozoic and Triassic Reservoir Rocks in the Ghadames-Illizi Basin (Algeria). An unpublished MSc thesis at Universita’ degli Studi di Padova.

T.R. Klett (2000): Province, Algeria, Tunisia, and Libya - The Tanezzuft-Oued Mya, Tanezzuft-Melrhir, and Tanezzuft-Ghadames. U.S. Geological Survey Bulletin, 2202-C.