Stormberg Lava Gr

Period:

Jurassic

Age Interval:

Middle Jurassic (Toarcian)

Province:
SouthAfrica-Namibia-Botswana

Type Locality and Naming

Kalahari Basin (Central), Kalahari Basin (NE). Historically named after the Stormberg region in the Eastern Cape, South Africa, by early geologists to describe the volcanic rocks capping the Karoo sequence. In modern formal South African stratigraphy, this massive volcanic succession is officially designated as the Drakensberg Group.

Synonym: Drakensberg Gr

Lithology and Thickness

Currently preserved up to approximately 1,400 meters thick in the Lesotho Highlands (though originally much thicker prior to Cretaceous/Cenozoic erosion). It is composed of stacked, horizontal flows of massive, subaerial tholeiitic flood basalts. The lowermost successions frequently feature pillow lavas, volcanic ash (tuffs), and thin lenses of aeolian sandstone.

Lithology Pattern:

Lava

Relationships and Distribution

Lower contact

Conformably overlies the Stormberg Gr (Ntane Fm) in Kalahari Basin (Central), i.e., Clarens Fm

Upper contact

Forms the present-day erosional surface, creating the highest mountain peaks in southern Africa (the Drakensberg Escarpment and Maloti Mountains).

Regional extent

Drakensberg Gr (South Africa/Lesotho); Karoo Volcanics. Regionally corresponds to the Batoka Basalts (Zambia/Zimbabwe) and the Kasane/Kwitane Volcanics (Botswana). Dominates the high-altitude core of Lesotho and the surrounding escarpment in South Africa. As part of the Karoo Large Igneous Province (LIP), equivalent flood basalts were poured out across vast tracts of Gondwana, from Antarctica to Botswana.

GeoJSON

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Fossils

Age

Middle Jurassic (Toarcian)

Age Span:

Beginning stage:

Toarcian

Fraction up in beginning stage:

0.0

Beginning date (Ma):

184.20

Ending stage:

Toarcian

Fraction up in the ending stage:

0.2

Ending date (Ma):

182.30

Depositional setting

A massive continental flood basalt province (Large Igneous Province).

Depositional pattern:

Additional Information

The Stormberg Lavas / Drakensberg Group represent the dramatic volcanic culmination of the Karoo Supergroup's history, bringing the continuous ~120-million-year sedimentary cycle of the Karoo Basin to a sudden end.

Compiler:

From the O. Catuneanu et al. / Journal of African Earth Sciences 43 (2005) 211–253; Johnson, M.R., et al. (2006): Sedimentary Rocks of the Karoo Supergroup. In: The Geology of South Africa; Jourdan, F., et al. (2005): Karoo large igneous province: Brevity, origin, and relation to mass extinction question.