Hofra Formation

Hofra Fm

Period:

Cambrian, Ordovician

Age Interval:

Fortunian?-Hirnantian? (see Barr and Weeger, 1972).

Province:
Sirte Basin

Type Locality and Naming

Synonym: Equivalent to the Amal Fm in the eastern part of the basin.

References: Barr and Weeger, 1972; Ahlbrandt, 2001.

Lithology and Thickness

The pre-rift Hofra Fm is the lateral lithological equivalent of the Gargaf Gr and Amal Fm throughout the Sirte Basin, and it is made up of sandstones (Ahlbrandt, 2001).

Lithology Pattern:

Sandstone

Relationships and Distribution

Lower contact

It unconformably overlies the Precambrian Basement Complex.

Upper contact

It is unconformably overlain by the Nubian Sandstone Fm. The Sirt Basin was a permanent high from the Middle Paleozoic until the Early Mesozoic (from SEPM overview).

Regional extent

“It is frequently correlated with the surface-exposed Gargaf Group (specifically the Hasawnah Fm) of western Libya, representing the vast siliciclastic blanket deposited across North Africa before the Sirte Basin rifting events occurred.” (Google Gemini, Aug’26, citing the SEPM overview)

GeoJSON

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Fossils

Age

Very vague “Cambrian-Ordovician” or simply “pre-Upper Cretaceous”. The age of the Hofra Fm. was tied to that of its lateral equivalent – the Gargaf Fm. whose age was estimated to be from the Cambrian to the early Ordovician (Barr and Weeger, 1972). Here, we accept that it might be the equivalent of the Hasawnah Fm, then a base-Drumian to base-Tremadocian age is used here.

Age Span:

Beginning stage:

Drumian

Fraction up in beginning stage:

0.00

Beginning date (Ma):

504.50

Ending stage:

Tremadocian

Fraction up in the ending stage:

0.0

Ending date (Ma):

486.85

Depositional setting

Depositional pattern:

Additional Information

Compiler:

T. S. Ahlbrandt (2001): The Sirte Basin Province of Libya—Sirte-Zelten Total Petroleum System, U.S. Geological Survey Bulletin 2202–F

R.C. Selley (1997): The Sirte Basin of Libya. In: African Basins. Sedimentary Basins of the World, 3, edited by R.C. Selley (Series Editor: K.J. Hsu), Elsevier Science B.V., Amsterdam, pp. 27-37.

Abugares, Miloud M. (2007): Deposition, Diagenesis, and Reservoir Development of the Cretaceous Lidam Formation, SE Sirt Basin, Libya. Durham e-Theses. http://etheses.dur.ac.uk/2599/

Elkanouni, I. E. D. (2014). Sedimentology, Sequence stratigraphy and Spatial-temporal Patterns of the late Paleocene Succession, western Sirt Basin, Libya, Durham e Theses. http://etheses.dur.ac.uk/10538/