Clarens Formation

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Clarens Formation
Stratigraphic range: Pliensbachian-Toarcian
~190–180  Ma
Brandwag rock.JPG
Brandwag Rock in the Golden Gates Highlands National Park
Type Geological formation
Unit of Stormberg Group
Sub-unitsLower Elliot and Upper Elliot
Underlies Drakensberg Group
Overlies Elliot Formation
Thicknessup to 300 m (980 ft)
Lithology
Primary Sandstone, claystone
Other Mudstone, siltstone
Location
Coordinates 30°30′S27°24′E / 30.5°S 27.4°E / -30.5; 27.4
Approximate paleocoordinates 44°06′S1°54′W / 44.1°S 1.9°W / -44.1; -1.9
Region Free State, KwaZulu-Natal & Eastern Cape
CountryFlag of South Africa.svg  South Africa
Flag of Lesotho.svg  Lesotho
Type section
Named for Clarens, Free State
South Africa relief location map.svg
Blue pog.svg
Clarens Formation (South Africa)

The Clarens Formation is a geological formation found in several localities in Lesotho and in the Free State, KwaZulu-Natal, and Eastern Cape provinces in South Africa. It is the uppermost of the three formations found in the Stormberg Group of the greater Karoo Supergroup rocks and represents the final phase of preserved sedimentation of the Karoo Basin. [1]

Contents

Geology

The Clarens Formation is composed nearly entirely of fine to medium-grained, thickly-bedded sandstones that range from pale orange or pinkish to cream in color. It is characterized by its remarkable gross lithological uniformity and that its deposits mainly outcrop as high cliffs. These Clarens Formation cliffs frequently contain shallow caves and overhangs at the contact of the underlying Upper Elliot Formation (UEF) due to processes of erosion. This particular feature of the Clarens Formation lead to the initial naming of these rocks the “Cave Sandstone” in older literature. [2] [3] It is thought that the geographical range of the Clarens Formation was much greater millions of years ago, covering most of southern Africa in a vast sand dune environment which stretched out from the main Karoo Basin westwards into Namibia and into Zimbabwe in the northeast. [4] [5] [6] [7]

There has been very little recent research undertaken on Clarens Formation, [8] but overall, due to the dominant nature of the sandstones, the Clarens Formation is considered to have been deposited in an arid climate where dune fields were abundant. [9] [10] [11] The Clarens Formation deposits have been categorized into three notable sedimentary facies. These are laid out below:

Palaeontology

Paleontological finds of the Clarens Formation are less common than the underlying Upper Elliot Formation (UEF), but this is likely not a true reflection of the species diversity that was present at the time of deposition. Fossils are more well known from its lower facies zones, however, no systematic biostratigraphic mapping of the Clarens Formation has been undertaken to date. This is partly due to the fact that the uppermost sections of the Clarens Formation are difficult and dangerous to access due to these deposits forming steep cliffs. Nevertheless, various vertebrate and invertebrate fossils have been recovered from its lower sections. [13] Vertebrate fossil material generally comprises dis-articulated or isolated bone material of various theropod, sauropodomorph, and ornithischian dinosaurs, crocodylomorphs, and cynodont therapsids; [14] [15] [16] one dinosaur from the Clarens Formation has been named Hortalotarsus skirtopodus . Freshwater fish fossils such as that of Semionotus capensis , and crustaceans have been found in the playa lake facies deposits. The Clarens Formation is also well known for its numerous preserved dinosaur trackways of both large and small theropods, and also of small ornithischian dinosaurs. Petrified wood fragments, rhizoliths, coprolites, and planolites burrows have also been found. [17] [18] [19] [20]

Correlation

The Clarens Formation corresponds with numerous localities in Sub-Saharan Africa. It is currently considered to correlate in age with the Forest Sandstone of Zimbabwe, the Bodibeng Sandstone in the Tuli Basin of Botswana, [21] and the Etjo Sandstone of Namibia. In South Africa, equivalent sedimentary facies to the Clarens Formation are present in the Lebombo Belt, north of Eswatini.

See also

Related Research Articles

<span class="mw-page-title-main">Karoo Supergroup</span> Widespread Mesozoic stratigraphic unit in southern Africa

The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a period of about 120 million years.

<span class="mw-page-title-main">Beaufort Group</span> Third of the main subdivisions of the Karoo Supergroup in South Africa

The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup in South Africa. It is composed of a lower Adelaide Subgroup and an upper Tarkastad Subgroup. It follows conformably after the Ecca Group and unconformably underlies the Stormberg Group. Based on stratigraphic position, lithostratigraphic and biostratigraphic correlations, palynological analyses, and other means of geological dating, the Beaufort Group rocks are considered to range between Middle Permian (Wordian) to Early Triassic (Anisian) in age.

<span class="mw-page-title-main">Ecca Group</span> Second of the main subdivisions of the Karoo Supergroup of geological strata in southern Africa

The Ecca Group is the second of the main subdivisions of the Karoo Supergroup of geological strata in southern Africa. It mainly follows conformably after the Dwyka Group in some sections, but in some localities overlying unconformably over much older basement rocks. It underlies the Beaufort Group in all known outcrops and exposures. Based on stratigraphic position, lithostratigraphic correlation, palynological analyses, and other means of geological dating, the Ecca Group ranges between Early to earliest Middle Permian in age.

<i>Dracovenator</i> Extinct genus of dinosaur from the Jurassic of South Africa

Dracovenator is a genus of neotheropod dinosaur that lived approximately 201 to 199 million years ago during the early part of the Jurassic Period in what is now South Africa. Dracovenator was a medium-sized, moderately-built, ground-dwelling, bipedal carnivore, that could grow up to an estimated 5.5–6.5 metres (18–21 ft) in length and 250 kilograms (550 lb) in body mass. Its type specimen was based on only a partial skull that was recovered.

<span class="mw-page-title-main">Forest Sandstone</span> Geologic formation in Southern Africa

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<span class="mw-page-title-main">Elliot Formation</span> Lithostratigraphic layer of the Stormberg Group in South Africa

The Elliot Formation is a geological formation and forms part of the Stormberg Group, the uppermost geological group that comprises the greater Karoo Supergroup. Outcrops of the Elliot Formation have been found in the northern Eastern Cape, southern Free State, and in the eastern KwaZulu-Natal provinces of South Africa. Outcrops and exposures are also found in several localities in Lesotho such as Qacha's Neck, Hill Top, Quthing, and near the capital, Maseru. The Elliot Formation is further divided into the lower (LEF) and upper (UEF) Elliot formations to differentiate significant sedimentological differences between these layers. The LEF is dominantly Late Triassic (Norian-Hettangian) in age while the UEF is mainly Early Jurassic (Sinemurian-Pliensbachian) and is tentatively regarded to preserve a continental record of the Triassic-Jurassic boundary in southern Africa. This geological formation is named after the town of Elliot in the Eastern Cape, and its stratotype locality is located on the Barkly Pass, 9 km north of the town.

<span class="mw-page-title-main">Kirkwood Formation</span> Cretaceous geological formation in the Uitenhage Group

The Kirkwood Formation is a geological formation found in the Eastern and Western Cape provinces in South Africa. It is one of the four formations found within the Uitenhage Group of the Algoa Basin – its type locality – and in the neighbouring Gamtoos Basin. Outcrops of the Kirkwood are also found along the Worcester-Pletmos, Herbertsdale-Riversdale, Heidelberg-Mossel Bay, and Oudtshoorn-Gamtoos basin lines. At these basins the Kirkwood Formation underlies the Buffelskloof Formation and not the Sundays River Formation.

Notochampsa is an extinct genus of protosuchian crocodyliform. Fossils have been found from the lower Clarens Formation of the Karoo Supergroup in South Africa, dating back to the Pliensbachian stage of the Early Jurassic. Notochampsa comes from a period of relative fossil scarcity, and is the youngest known occurrence of a crocodylomorph from the Karoo Basin of South Africa.

<span class="mw-page-title-main">Molteno Formation</span> Triassic geological formation in the Stormberg Group in Lesotho and South Africa

The Molteno Formation is a geological formation found in several localities in Lesotho and South Africa. It lies mainly south of Maseru, near Burgersdorp, Aliwal North, Dordrecht, Molteno, and Elliot. It extends as far north as Matatiele in the Eastern Cape. The formation's localities lie along the Drakensberg Mountains in Kwazulu-Natal, and near Ladybrand in the Free State of South Africa. The Molteno Formation is the lowermost of the three formations in the Stormberg Group of the greater Karoo Supergroup. The Molteno Formation represents the initial phase of preserved sedimentation of the Stormberg Group.

<span class="mw-page-title-main">Pebbly Arkose Formation</span>

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<span class="mw-page-title-main">Stormberg Group</span> Triassic/Jurassic geological group in the Karoo Supergroup in South Africa

The Stormberg Group is one of the four geological groups that comprises the Karoo Supergroup in South Africa. It is the uppermost geological group representing the final phase of preserved sedimentation of the Karoo Basin. The Stormberg Group rocks are considered to range between Lower Triassic (Olenekian) to Lower Jurassic (Pliensbachian) in age. These estimates are based on means of geological dating including stratigraphic position, lithostratigraphic and biostratigraphic correlations, and palynological analyses.

<span class="mw-page-title-main">Dwyka Group</span> Geological group in the Karoo Supergroup from South Africa

The Dwyka Group is one of four geological groups that compose the Karoo Supergroup. It is the lowermost geological group and heralds the commencement of sedimentation of the Karoo Supergroup. Based on stratigraphic position, lithostratigraphic correlation and palynological analyses, these lowermost Karoo strata range between the Late Carboniferous (Pennsylvanian) to Early Permian in age.

<span class="mw-page-title-main">Lower Karoo Group</span>

The Lower Karoo Group is a sequence of late Carboniferous and Permian sandstone sedimentary rocks of the Karoo Supergroup, found in Botswana, Zambia, Zimbabwe, and Mozambique.

<span class="mw-page-title-main">Uitenhage Group</span> Geological group of post-Karoo Mesozoic rocks in South Africa

The Uitenhage Group is one of three geological groups, which comprise the onshore and offshore post-Karoo middle to lower Upper Mesozoic geological rock units in South Africa. Stratigraphically, the Uitenhage Group overlies the Suurberg Group and is overlain by the Algoa Group. It contains four formations that range in age from late Early Jurassic and late Early Cretaceous in age.

The geology of Lesotho is built on ancient crystalline basement rock up to 3.6 billion years old, belonging to the Kaapvaal Craton, a section of stable primordial crust. Most of the rocks in the country are sedimentary or volcanic units, belonging to the Karoo Supergroup. The country is notable for large fossil deposits and intense erosion due to high rainfall and a rare case of southern African glaciation during the last ice age. Lesotho has extensive diamonds and other natural resources and has the highest concentration of kimberlite pipes anywhere in the world.

<span class="mw-page-title-main">Omingonde Formation</span>

The Omingonde Formation is an Early to Middle Triassic geologic formation, part of the Karoo Supergroup, in the western Otjozondjupa Region and northeastern Erongo Region of north-central Namibia. The formation has a maximum thickness of about 600 metres (2,000 ft) and comprises sandstones, shales, siltstones and conglomerates, was deposited in a fluvial environment, alternating between a meandering and braided river setting.

<span class="mw-page-title-main">Katberg Formation</span> Geological formation in the Beaufort Group of the Karoo Supergroup in South Africa

The Katberg Formation is a geological formation that is found in the Beaufort Group, a major geological group that forms part of the greater Karoo Supergroup in South Africa. The Katberg Formation is the lowermost geological formation of the Tarkastad Subgroup which contains the Lower to Middle Triassic-aged rocks of the Beaufort Group. Outcrops and exposures of the Katberg Formation are found east of 24 degrees on wards and north of Graaff-Reniet, Nieu Bethesda, Cradock, Fort Beaufort, Queensdown, and East London in the south, and ranges as far north as Harrismith in deposits that form a ring around the Drakensberg mountain ranges.

<span class="mw-page-title-main">Middleton Formation</span> Late middle Permian geological formation in the Eastern Cape

The Middleton Formation is a geological formation that extends through the Northern Cape, Western Cape, and Eastern Cape provinces of South Africa. It overlies the lower Abrahamskraal Formation, and is the eastern correlate, East of 24ºE, of the Teekloof Formation. Outcrops and exposures of the Middleton Formation range from Graaff-Reinet in the Eastern Cape onwards. The Middleton Formation's type locality lies near the small hamlet, Middleton, approximately 25 km south of Cookhouse. Other exposures lie in hillsides along the Great Fish River in the Eastern Cape. The Middleton Formation forms part of the Adelaide Subgroup of the Beaufort Group, which itself forms part of the Karoo Supergroup.

<span class="mw-page-title-main">Teekloof Formation</span> Late Permian geological formation that forms part of the Beaufort Group of South Africa

The Teekloof Formation is a geological formation that forms part of the Beaufort Group, one of the five geological groups that comprises the Karoo Supergroup in South Africa. The Teekloof Formation is the uppermost formation of Adelaide Subgroup deposits West of 24ºE and contains Middle to Late Permian-aged deposits and four biozones of the Beaufort Group. It overlies the Abrahamskraal Formation. The Teekloof Formation does not underlie other units other than the younger Karoo dolerites and sills that relate to the emplacement of the Early Jurassic Drakensberg Group to the east. Outcrops and exposures of the Teekloof Formation range from Sutherland through the mountain escarpments between Fraserburg and Beaufort West. The northernmost localities of the Teekloof Formation are found by Loxton, Victoria West and Richmond.

<span class="mw-page-title-main">Drakensberg Group</span> Jurassic geological group in Lesotho and South Africa

The Drakensberg Group is a geological group named after the Drakensberg mountain range where in its uppermost sections the rocks are found. The Drakensberg Group lies over most of Lesotho and localities in the Eastern Cape, KwaZulu-Natal, and Free State provinces of South Africa. It forms part of the greater Karoo Igneous Province, which occurs over an extensive area of southern Africa.

References

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