Batoka Formation
{{Short description|Geological formation in Southern Africa}}
{{Infobox rockunit
| name = Batoka Formation
| period = Early Jurassic
| age = Early Jurassic
~{{fossil range|180|179}}
| image = Batoka-flows-siyakobvu.png
| caption = Batoka basalt flows at Siyakobvu, Kariba District, Zimbabwe
| type = Geological formation
| prilithology = Basalt
| otherlithology =
| namedfor = Batoka Gorge, Zambezi River
| namedby = G.W. Lamplugh
| region = Zambezi River valley
| country = Botswana
Zambia
Zimbabwe
| coordinates =
| unitof = Upper Karoo Group, Karoo Supergroup
| subunits =
| underlies =
| overlies = Forest Sandstone Formation
| thickness =
| extent =
| area =
| map =
| map_caption =
}}
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.{{cite book |author=David B. Weishampel|display-authors=et al |year=2004 |title=Dinosaur distribution (Early Jurassic, Africa) |work=Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria |edition=2nd |publisher=University of California Press |location=Berkeley |pages=535–536 |isbn=978-0-520-24209-8}} 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.{{Cite journal|last1=Viglietti|first1=Pia A.|last2=Barrett|first2=Paul M.|last3=Broderick|first3=Tim J.|last4=Munyikwa|first4=Darlington|last5=MacNiven|first5=Rowan|last6=Broderick|first6=Lucy|last7=Chapelle|first7=Kimberley|last8=Glynn|first8=Dave|last9=Edwards|first9=Steve|date=January 2018|title=Stratigraphy of the Vulcanodon type locality and its implications for regional correlations within the Karoo Supergroup|journal=Journal of African Earth Sciences|volume=137|pages=149–156|doi=10.1016/j.jafrearsci.2017.10.015|issn=1464-343X|bibcode=2018JAfES.137..149V}}
Geology
= Description =
The formation is a volcanic unit, consisting mainly of high-titanium, low-potassium tholeiitic basalt flows.{{cite journal |doi=10.1007/BF01820167 |title=Karoo basalts from western Zambia and geochemical provinces in central and southern Africa |year=1981 |last1=Ridgway |first1=John |last2=Money |first2=N. J. |journal=Geologische Rundschau |volume=70 |issue=3 |pages=868 |bibcode=1981GeoRu..70..868R|s2cid=128474657 }}{{cite journal |doi=10.1007/s10040-007-0191-z |title=Geophysical and hydrogeologic investigation of groundwater in the Karoo stratigraphic sequence at Sawmills in northern Matabeleland, Zimbabwe: a case history |year=2007 |last1=Danielsen |first1=Jens E. |last2=Dahlin |first2=Torleif |last3=Owen |first3=Richard |last4=Mangeya |first4=Pride |last5=Auken |first5=Esben |journal=Hydrogeology Journal |volume=15 |pages=945 |issue=5 |bibcode=2007HydJ...15..945D|s2cid=2059067 |url= http://portal.research.lu.se/ws/files/2951758/4934450.pdf}}{{cite journal |author=G. Bond |year=1973 |journal=Rhodesia Geological Survey Bulletin |volume=70 |title=Palaeontology of Rhodesia}}{{cite report |author=B.J. Wahl |date=1971 |title=An Investigation of the Interbasaltic Sandstones in the Sibilobilo Islands, Kariba |publisher=Unpublished B.Sc. Special Honours project, Department of Geology, University of Rhodesia, Harare, Zimbabwe}}
File:Batoka-basalt-siyakobvu.png
The lavas are dark, vesicular and porphyritic or massive basalts, with occasional pillows,{{cite journal |author=G.W.Lamplugh |doi=10.1144/GSL.JGS.1907.063.01-04.14 |title=The Geology of the Zambezi Basin around the Batoka Gorge (Rhodesia) |year=1907 |journal=Quarterly Journal of the Geological Society |volume=63 |issue=1–4 |pages=162–216 |s2cid=131664930 |url=https://zenodo.org/record/2112374 }}{{cite journal |author=B. Lightfoot |year=1914 |title=The Geology of the North-western part of the Wankie Coalfield |journal=Southern Rhodesia Geological Survey Bulletin |volume=4}}{{cite journal |author=B. Lightfoot |year=1929 |title=The geology of the Central Part of the Wankie Coalfield |journal=Southern Rhodesia Geological Survey Bulletin |volume=15}}{{cite journal |author=B. Barber |year=1994 |title=Notes on the isotopic dating of Karoo and younger lavas from the Zambezi valley, and implications for sedimentation |journal=Annals of the Zimbabwe Geological Survey |volume=17 |pages=19–23}} although rare dacites and rhyolites have been reported from some areas of north-eastern Botswana.{{cite report |title=The lithostratigraphy of the Karoo Supergroup in Botswana |author=R.A. Smith |publisher=Geological Survey Department, Ministry of Mineral Resources and Water Affairs, Republic of Botswana}} The vesicular and massive basalts occur in alternating bands, with the vesicular bands usually being the top and base of each flow. 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, though zeolites, such as stilbite, mesolite and laumontite, are dominant towards Victoria Falls and in the lower Deka valley, and are common in north-eastern Botswana.
The basalt lavas are related to carbonatite intrusions in the Zambezi valley.{{cite journal |title=Major and trace element geochemical characteristics of Karoo basaits in Zimbabwe, providing evidence for the origin of spatially related carbonatites |author1=K.L. Walsh |author2=P. Hall |author3=D.J. Hughes |journal=Journal of African Earth Sciences |issue=4 Suppl 1 |pages=84 |volume=28 |doi=10.1016/S0899-5362(99)00028-7 |year=1999 |bibcode=1999JAfES..28....1.}}
= Extent =
The Batoka Formation is found in Botswana, Zambia, Zimbabwe, in the Mid-Zambezi, Mana Pools and Cabora Bassa Basins.{{cite journal |doi=10.1029/2000GC000110 |title=Age of the Batoka basalts, northern Zimbabwe, and the duration of Karoo Large Igneous Province magmatism |year=2001 |last1=Jones |first1=D. L. |last2=Duncan |first2=R. A. |last3=Briden |first3=J. C. |last4=Randall |first4=D. E. |last5=MacNiocaill |first5=C. |journal=Geochemistry, Geophysics, Geosystems |volume=2 |issue=2 |pages=n/a |bibcode=2001GGG.....2.1022J|doi-access=free }}
= Age =
= Stratigraphy =
The Batoka Formation is the uppermost formation in the Upper Karoo Group of the Karoo Supergroup, lying above the Forest Sandstone Formation.{{cite journal |doi=10.1016/S0899-5362(97)00081-X |title=Stratigraphy and palynostratigraphy, Karoo Supergroup (Permian and Triassic), mid-Zambezi Valley, southern Zambia |year=1997 |last1=Nyambe |first1=Imasiku A. |last2=Utting |first2=John |journal=Journal of African Earth Sciences |volume=24 |issue=4 |pages=563 |bibcode=1997JAfES..24..563N}}
The Batoka Formation has been correlated to the Drakensberg Group of the Great Karoo Basin, South Africa,{{cite journal |doi=10.1016/j.jafrearsci.2005.07.007 |title=The Karoo basins of south-central Africa |year=2005 |last1=Catuneanu |first1=O. |last2=Wopfner |first2=H. |last3=Eriksson |first3=P.G. |last4=Cairncross |first4=B. |last5=Rubidge |first5=B.S. |last6=Smith |first6=R.M.H. |last7=Hancox |first7=P.J. |journal=Journal of African Earth Sciences |volume=43 |issue=1–3 |pages=211–253 |bibcode=2005JAfES..43..211C}} and the basalts of the Tuli Basin in Botswana and Zimbabwe.{{cite journal |doi=10.1016/j.jafrearsci.2004.11.004 |title=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 |year=2004 |last1=Rogers |first1=Raymond R. |last2=Rogers |first2=Kristina Curry |last3=Munyikwa |first3=Darlington |last4=Terry |first4=Rebecca C. |last5=Singer |first5=Bradley S. |journal=Journal of African Earth Sciences |volume=40 |issue=3–4 |pages=147 |bibcode=2004JAfES..40..147R|url=http://doc.rero.ch/record/14568/files/PAL_E1780.pdf }}
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References
{{Portal|Geology}}
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Category:Geologic formations of Botswana
Category:Geologic formations of Zambia
Category:Geologic formations of Zimbabwe