Batoka Formation

Batoka Formation
Stratigraphic range: Early Jurassic ~180–179  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Batoka basalt flows at Siyakobvu, Kariba District, Zimbabwe
Type	Geological formation
Unit of	Upper Karoo Group, Karoo Supergroup
Overlies	Forest Sandstone Formation
Lithology
Primary	Basalt
Location
Region	Zambezi River valley
Country	Botswana Zambia Zimbabwe
Type section
Named for	Batoka Gorge, Zambezi River
Named by	G.W. Lamplugh

The Batoka Formation is a geological formation in the Zambezi valley in Botswana, Zambia and Zimbabwe. It is predominantly a volcanic unit comprising mainly basalts. ^[1] It was formerly thought to contain sand stones containing the dinosaur Vulcanodon , however this was shown to be in error resulting from interpreting folding of the rocks as separate layers, with the sandstone layers actually being from the underlying Forest Sandstone. ^[2]

Geology

Description

The formation is a volcanic unit, consisting mainly of high-titanium, low-potassium tholeiitic basalt flows. ^{[3] [4] [5] [6] [7]}

Pillow lavas in Batoka Basalt, Siyakobvu, Kariba District, Zimbabwe

The lavas are dark, vesicular and porphyritic or massive basalts, with occasional pillows, ^{[8] [9] [10] [11]} although rare dacites and rhyolites have been reported from some areas of north-eastern Botswana. ^[12] The vesicular and massive basalts occur in alternating bands, with the vesicular bands usually being the top and base of each flow. ^{[10] [12]} The basalt mineralogy consists of mainly of plagioclase, augite, magnetite, some ilmenite and volcanic glass. In the Hwange area, vesicles consist mostly of quartz, chalcedony or calcite, ^[10] though zeolites, such as stilbite, mesolite and laumontite, are dominant towards Victoria Falls and in the lower Deka valley, ^[8] and are common in north-eastern Botswana. ^[12]

The basalt lavas are related to carbonatite intrusions in the Zambezi valley. ^[13]

Extent

The Batoka Formation is found in Botswana, Zambia, Zimbabwe, in the Mid-Zambezi, Mana Pools and Cabora Bassa Basins. ^{[3] [14] [15]}

Age

Lavas of the Batoka Formation have been dated at 180 to 179 Ma. ^[3]

Stratigraphy

The Batoka Formation is the uppermost formation in the Upper Karoo Group of the Karoo Supergroup, lying above the Forest Sandstone Formation. ^[14]

The Batoka Formation has been correlated to the Drakensberg Group of the Great Karoo Basin, South Africa, ^[15] and the basalts of the Tuli Basin in Botswana and Zimbabwe. ^[16]

References

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1. David B. Weishampel; et al. (2004). Dinosaur distribution (Early Jurassic, Africa) (2nd ed.). Berkeley: University of California Press. pp. 535–536. ISBN   978-0-520-24209-8.{{cite book}}: |work= ignored (help)
2. Viglietti, Pia A.; Barrett, Paul M.; Broderick, Tim J.; Munyikwa, Darlington; MacNiven, Rowan; Broderick, Lucy; Chapelle, Kimberley; Glynn, Dave; Edwards, Steve (January 2018). "Stratigraphy of the Vulcanodon type locality and its implications for regional correlations within the Karoo Supergroup". Journal of African Earth Sciences. 137: 149–156. Bibcode:2018JAfES.137..149V. doi:10.1016/j.jafrearsci.2017.10.015. ISSN   1464-343X.
3. Jones, D. L.; Duncan, R. A.; Briden, J. C.; Randall, D. E.; MacNiocaill, C. (2001). "Age of the Batoka basalts, northern Zimbabwe, and the duration of Karoo Large Igneous Province magmatism". Geochemistry, Geophysics, Geosystems. 2 (2): n/a. Bibcode:2001GGG.....2.1022J. doi: 10.1029/2000GC000110 .
4. Ridgway, John; Money, N. J. (1981). "Karoo basalts from western Zambia and geochemical provinces in central and southern Africa". Geologische Rundschau . 70 (3): 868. Bibcode:1981GeoRu..70..868R. doi:10.1007/BF01820167. S2CID   128474657.
5. Danielsen, Jens E.; Dahlin, Torleif; Owen, Richard; Mangeya, Pride; Auken, Esben (2007). "Geophysical and hydrogeologic investigation of groundwater in the Karoo stratigraphic sequence at Sawmills in northern Matabeleland, Zimbabwe: a case history" (PDF). Hydrogeology Journal. 15 (5): 945. Bibcode:2007HydJ...15..945D. doi:10.1007/s10040-007-0191-z. S2CID   2059067.
6. G. Bond (1973). "Palaeontology of Rhodesia". Rhodesia Geological Survey Bulletin. 70.
7. B.J. Wahl (1971). An Investigation of the Interbasaltic Sandstones in the Sibilobilo Islands, Kariba (Report). Unpublished B.Sc. Special Honours project, Department of Geology, University of Rhodesia, Harare, Zimbabwe.
8. G.W.Lamplugh (1907). "The Geology of the Zambezi Basin around the Batoka Gorge (Rhodesia)". Quarterly Journal of the Geological Society. 63 (1–4): 162–216. doi:10.1144/GSL.JGS.1907.063.01-04.14. S2CID   131664930.
9. B. Lightfoot (1914). "The Geology of the North-western part of the Wankie Coalfield". Southern Rhodesia Geological Survey Bulletin. 4.
10. B. Lightfoot (1929). "The geology of the Central Part of the Wankie Coalfield". Southern Rhodesia Geological Survey Bulletin. 15.
11. B. Barber (1994). "Notes on the isotopic dating of Karoo and younger lavas from the Zambezi valley, and implications for sedimentation". Annals of the Zimbabwe Geological Survey. 17: 19–23.
12. R.A. Smith. The lithostratigraphy of the Karoo Supergroup in Botswana (Report). Geological Survey Department, Ministry of Mineral Resources and Water Affairs, Republic of Botswana.
13. K.L. Walsh; P. Hall; D.J. Hughes (1999). "Major and trace element geochemical characteristics of Karoo basaits in Zimbabwe, providing evidence for the origin of spatially related carbonatites". Journal of African Earth Sciences . 28 (4 Suppl 1): 84. Bibcode:1999JAfES..28....1.. doi:10.1016/S0899-5362(99)00028-7.
14. Nyambe, Imasiku A.; Utting, John (1997). "Stratigraphy and palynostratigraphy, Karoo Supergroup (Permian and Triassic), mid-Zambezi Valley, southern Zambia". Journal of African Earth Sciences. 24 (4): 563. Bibcode:1997JAfES..24..563N. doi:10.1016/S0899-5362(97)00081-X.
15. Catuneanu, O.; Wopfner, H.; Eriksson, P.G.; Cairncross, B.; Rubidge, B.S.; Smith, R.M.H.; Hancox, P.J. (2005). "The Karoo basins of south-central Africa". Journal of African Earth Sciences. 43 (1–3): 211–253. Bibcode:2005JAfES..43..211C. doi:10.1016/j.jafrearsci.2005.07.007.
16. Rogers, Raymond R.; Rogers, Kristina Curry; Munyikwa, Darlington; Terry, Rebecca C.; Singer, Bradley S. (2004). "Sedimentology and taphonomy of the upper Karoo-equivalent Mpandi Formation in the Tuli Basin of Zimbabwe, with a new 40Ar/39Ar age for the Tuli basalts" (PDF). Journal of African Earth Sciences. 40 (3–4): 147. Bibcode:2004JAfES..40..147R. doi:10.1016/j.jafrearsci.2004.11.004.