Dalma Formation

Dalma Fm

Period:

Carboniferous

Age Interval:

Tournaisian – Serpukhovian

Province:
Al Kufrah Basin

Type Locality and Naming

“The name Dalma Formation was applied by Vittimberga & Cardello (1963) to Carboniferous rocks exposed in the Jabal Hawaish.” (Tawadros, 2011, Geology of North Africa).

Synonym: Ounga Sandstone Fm, Ounga Fm and Kurkur Murr Fm are considered to be regional equivalents in this same greater basin area.

References: Le Heron et al., 2009; Le Heron and Howard, 2012

Lithology and Thickness

The Dalma Fm is about 500m thick (Le Heron and Howard, 2012), and it is made up of cross-bedded fluvial to shallow marine sandstones and siltstones (Schmeider et al., 2009).

Lithology Pattern:

Fine-grained sandstone

Relationships and Distribution

Lower contact

It conformably overlies the Binem Fm.

Upper contact

It is unconformably overlain by the Nubian Sandstone (Tawadros, 2001, 2011), used here; although Craig (2006, as used in SEPM summary) suggests it is overlain conformably by the Taiguaentourine Fm.

Regional extent

Only the Al Kufrah Basin.

GeoJSON

{"type":"Feature","geometry":{"type":"Polygon","coordinates":[[[20.913,26.749],[21.87,27.392],[23.008,27.913],[24.311,28.347],[24.806,28.173],[25.234,27.809],[25.597,27.34],[25.845,26.836],[25.977,26.35],[25.96,25.881],[25.812,25.413],[25.614,24.996],[25.399,24.701],[25.185,24.405],[25.036,24.006],[24.987,23.468],[25.069,22.947],[25.35,22.478],[25.647,22.096],[25.96,21.662],[26.125,21.141],[26.141,20.533],[26.026,20.013],[25.812,19.544],[25.399,19.283],[24.905,19.092],[24.459,18.867],[24.212,18.467],[24.113,17.998],[23.948,17.616],[23.503,17.321],[22.975,17.148],[22.431,17.078],[21.919,17.148],[21.441,17.321],[21.029,17.634],[20.649,18.016],[20.287,18.398],[19.891,18.78],[19.462,19.11],[19.066,19.457],[18.753,19.822],[18.637,20.273],[18.67,20.829],[18.786,21.367],[18.934,21.888],[19.116,22.374],[19.347,22.791],[19.61,23.173],[19.874,23.555],[20.089,23.971],[20.27,24.44],[20.435,24.944],[20.518,25.482],[20.501,25.933],[20.567,26.35],[20.913,26.749]]]}}

Fossils

“Its age [in the B1 well] is Tournaisian-Early Middle Visean based on the presence of the palynomorphs assemblage Grandispora balteata, Densosporites variomarginatus, and Spelaeotriletes pretiosus, the last appearance of Vallatisporites vallatus, Raistirckia baculosa, Verrucosisporites nitidus, V. macrogrunosus, Diatomozontriletes fragilis, Apiculiretusispora multiseta, Knoxisporites pristinus, Savitrisporites nux, Radiizonates genuinus, Vallatisporites baffensis, V. ciliaris, Denosporites sp., Pustulatisporites gibberosus, Reticulatisporites canellatus, Spelaeotriletes owensi, S. triangulus, Brochotriletes diversifoveolatus, Apiculiretusispora sp., Krauselisporites ornatus, Cristatisporites sp., Denosporites sp., and Convolutisporites cf. balmei. It correlates with Mrar Fm (Marar Fm) in West Libya” (Tawadros, 2011, Geology of North Africa, p. 322). [Note that the Marar Fm, above the Tahara Fm of Tournaisian, was interpreted as spanning the entire Visean in its Murzuq Basin lexicon entry.]

Age

Craig (2006, as used in SEPM summary) indicates a span from mid-Tournaisian to the base of Gzhelian when it is conformably overlain by the Tiguentourine Fm. However, Tawadros (2011; N. Africa geology book) and Le Heron et al. (2010) vaguely gives a “correlates with Marar Fm (Mrar Fm), which would limit it to only the Lower Carboniferous (used here).

Age Span:

Beginning stage:

Tournaisian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

353.02

Ending stage:

Visean

Fraction up in the ending stage:

1.0

Ending date (Ma):

330.34

Depositional setting

Dominantly continental clastic sedimentation (Le Heron et al., 2009).

Depositional pattern:

Additional Information

Compiler:

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

Tawadros, 2011, Geology of North Africa (book).

Gindre L., Heron D. L., Bjørnseth H. M. (2012). High resolution facies analysis and sequence stratigraphy of the Siluro-Devonian succession of Al Kufrah basin (SE Libya), Journal of African Earth Sciences, 76, pp.8–26.

Schmeider, M., Buchner, E., Le Heron, D. P. (2009): The Jebel Hadid Structure (Al Kufrah Basin, SE Libya) – A Possible Impact Structure and Potential Hydrocarbon Trap? Marine and Petroleum Geology, 26, pp.310-318.