Lakes Formation

Lakes Fm

Period:

Jurassic

Age Interval:

Bajocian-Oxfordian

Province:
Al Kufrah Basin

Type Locality and Naming

“De Lestang (1965, 1968) applied the informal name Lakes Fm (Formation des Lacs) to Mesozoic continental deposits of Ounianga Chebir and Ounianga Sarir in the southwestern Kufrah Basin in northern Chad. … The lower part of the Formation consists of red silty shales which dam the water to form large lakes in the area, hence the name “Lakes” Formation. Since the name of this Formation does not conform to the Code of Stratigraphic Nomenclature, Banerjee (1980) suggested discarding the name without recommending an alternative name. In Tawadros (2011), the Lakes Formation is considered to be the upper part of the Soeka Fm. [upper-Lower formation of the Al Kufra Basin version of the Nubian Sandstone Gr.]

Synonym: upper Soeka Fm

References: Tawadros, 2011

Lithology and Thickness

It is composed of white to brown kaolinitic and well-bedded fine-grained sandstones. The Formation is 200–250 m (656–820 ft) thick. The lower 30 to 40 m (98 to 131 ft) of the Formation consists of red silty shales.

Lithology Pattern:

Clayey sandstone

Relationships and Distribution

Lower contact

It conformably overlies the Soeka Fm.

Upper contact

It is overlain by the Ounianga Fm.

Regional extent

Only the Al Kufrah Basin.

GeoJSON

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Fossils

Age

Shown schematically in Tawadros 2001, and perhaps based on relative thicknesses, as slightly less in span to the underlying Soeka Fm, and top is top of Oxfordian as constrained by the estimate for the Ouniaga Fm. Hence, span of Bajocian-Oxfordian seems appropriate.

Age Span:

Beginning stage:

Bajocian

Fraction up in beginning stage:

Beginning date (Ma):