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
sedimentaryfacies. These are laid out below:
Basal Zone 1: This
facies is located in the lower or older sections of the Clarens Formation, and always have eroded bases at their contact with the underlying Upper
Elliot Formation (UEF). The
sandstones in this
facies zones are thickly-bedded, massive, are fine-grained and are
silt-rich. Minor
mudstonelenses are also found within the
sandstone layers and often exhibit
desiccation cracks. These are interbedded with
lenticularsandstones that contain various
ripple structures,
calcareous concretions and clay-pellet
conglomerates. These have been interpreted as
loess deposits. Various
trace fossils are found in the
mudstone layers of the Basal Zone 1.
Middle Zone 2: The middle section of the Clarens Formation exhibit either massive or large-scale planar or cross trough bedding structures, and in some instances minor herringbone cross bedding. The
sandstones are well sorted and the grain size is coarser than that found in the lower deposits. The sandstones from this
facies and up are composed either of
quartzarenites or
greywackes. Scour and fill structures, and scour marks are also commonly observed in the upper
sandstone deposits. These
sedimentaryfacies have been interpreted as preserved sheet flood and ephemeral stream deposits, as well as
playa lakes that were formed in a proper
desert environment.
Upper Zone 3: In the upper sections of the Clarens Formation,
siltysandstones reappear which grade laterally into fine-grained, massive, and immature
sandstone beds. These massive sandstones contain
quartz-rich
feldspathicwackes and subordinate
arkosicarenites. Other minerals identified - which are found in all
sandstones across the entire Clarens Formation - are
zircons,
garnets,
agates,
riebeckite,
spinel,
sphene, and
hornblende. Thin, lenticular
sandstones also reappear in the uppermost Clarens Formation, as do
ripple marks and clay-pellet
conglomerates, which reveals that the environment where these
sedimentary rocks were formed was similar or the same as that of Basal Zone 1. Minor
basalts begin to appear in the uppermost sections of the Clarens Formation which are interpreted as the commencement of the
magmatic activity associated with the Drakensberg Group. The appearance of the
basalts signals the termination of the
sedimentation of the
Karoo Basin. Extremely rare occurrences of shallow water structures have been found in the basaltic deposits.[12]
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.
^Broom, R. 1948. A contribution to our knowledge of the vertebrates of the Karroo Beds of South Africa. Transactions of the Royal Society of Edinburgh, 61, 577–629.
^Beukes, N.J., 1970. Stratigraphy and sedimentology of the Cave Sandstone stage, Karoo System. In: S.H. Haughton (Editor), Proceedings and papers of the 2nd Gondwana symposium. Council for Scientific and Industrial Research, Pretoria, 321-341.
^Head, H. V.; Bordy, E. M. (2018-03-01). "Lithostratigraphy of the Clarens Formation (Stormberg Group, Karoo Supergroup), South Africa". South African Journal of Geology. 121 (1): 119–130.
Bibcode:
2018SAJG..121..119B.
doi:
10.25131/sajg.121.0009.
ISSN1012-0750.
^Meiklejohn, K.I., 1997. The role of moisture in the weathering of the Clarens Formation of the KwaZulu-Natal Drakensberg: implications for the preservation of indigenous rock art. South African Geographical Journal, 79, pp.199-206.
^Beukes, N.J., 1969. Die sedimentologie van die Etage Holkranssandsteen,sisteem Karoo. Unpublished MSc thesis, University of the Orange Free State,Bloemfontein, 138pp. [Online] Available at
hdl:11660/7671
^Eriksson, P.G., 1981. A palaeoenvironmental analysis of the Clarens Formationin the Natal Drakensberg. Transactions of the Geological Society of SouthAfrica, 84, 7-17.
^Eriksson, P.G., 1986. Aeolian dune and alluvial fan deposits in the Clarens Formation of the Natal Drakensberg. Transactions of the Geological Societyof South Africa, 89, 389-393.
^Smith, R.M.H., Eriksson, P.G., Botha, W.J. (1993-01-01). "A review of the stratigraphy and sedimentary environments of the Karoo-aged basins of Southern Africa". Journal of African Earth Sciences (and the Middle East). 16 (1–2): 143–169.
Bibcode:
1993JAfES..16..143S.
doi:
10.1016/0899-5362(93)90164-L.
ISSN0899-5362.{{
cite journal}}: CS1 maint: multiple names: authors list (
link)
^Bordy, E.M., Bumby, A.J., Catuneanu, O. and Eriksson, P.G., 2004. Advanced early Jurassic termite (Insecta: Isoptera) nests: evidence from the Clarens Formation in the Tuli Basin, southern Africa. Palaios, 19(1), pp.68-78.
^Sues, H.D., Reisz, R.R., Hinic, S. and Raath, M.A., 2004. On the skull of Massospondylus carinatus Owen, 1854 (Dinosauria: Sauropodomorpha) from the Elliot and Clarens formations (Lower Jurassic) of South Africa. Annals of Carnegie Museum, 73(4), pp.239-257.
^Kitching, J.W., 1979. Preliminary report on a clutch of six dinosaurian eggs from the Upper Triassic Elliot Formation, Northern Orange Free State.
^Knoll, Fabien (2005-01-01). "The tetrapod fauna of the Upper Elliot and Clarens formations in the main Karoo Basin (South Africa and Lesotho)". Bulletin de la Société Géologique de France. 176 (1): 81–91.
doi:
10.2113/176.1.81.
ISSN0037-9409.
^Bordy, E. M., Catuneanu, O. (2002-08-01). "Sedimentology and palaeontology of upper Karoo aeolian strata (Early Jurassic) in the Tuli Basin, South Africa". Journal of African Earth Sciences. 35 (2): 301–314.
Bibcode:
2002JAfES..35..301B.
doi:
10.1016/S0899-5362(02)00103-3.
ISSN1464-343X.{{
cite journal}}: CS1 maint: multiple names: authors list (
link)