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Abrahamskraal Formation

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The Abrahamskraal Formation is a geological formation and is found in numerous localities in the Northern Cape, Western Cape, and the Eastern Cape of South Africa. It is the lowermost formation of the Adelaide Subgroup of the Beaufort Group, a major geological group that forms part of the greater Karoo Supergroup. It represents the first fully terrestrial geological deposits of the Karoo Basin. Outcrops of the Abrahamskraal Formation are found from the small town Middelpos in its westernmost localities, then around Sutherland, the Moordenaarskaroo north of Laingsburg, Williston, Fraserburg, Leeu-Gamka, Loxton, and Victoria West in the Western Cape and Northern Cape. In the Eastern Cape outcrops are known from Rietbron, north of Klipplaat and Grahamstown, and also southwest of East London.[1][2]

Abrahamskraal Formation
Stratigraphic range: Wordian-Capitanian
~268–259 Ma
Hill with outcropping Teekloof and Abrahamskraal Formations
TypeGeological formation
Unit ofBeaufort Group
Sub-unitsTapinocephalus Assemblage Zone, Eodicynodon Assemblage Zone
UnderliesTeekloof Formation
OverliesEcca Group
Thicknessup to 2,565 m (8,415 ft)
Lithology
PrimaryMudstone, sandstone
OtherSiltstone
Location
Coordinates31°24′S 23°06′E / 31.400°S 23.100°E / -31.400; 23.100
Approximate paleocoordinates59°54′S 38°54′W / 59.9°S 38.9°W / -59.9; -38.9
RegionNorthern, Western & Eastern Cape
Country South Africa
Type section
Named forAbrahams Kraal 29 (farm), 18 km south of Leeu-Gamka
Named byA.W. Keyser, P.J. Rossouw & Lieuwe Dirk Boonstra

A simplified geological map of the outcrops of Karoo Supergroup rocks in Southern Africa. The Beaufort Group is represented by the yellow key on the map.

Geology

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The Abrahamskraal Formation comprises the majority of the Middle Permian Beaufort sequence, and are thought to range between 268 - 259 million years in age. The lowermost deposits of the Abrahamskraal Formation found in the Eastern Cape until recently were named the Koonap Formation, but these outcrops have been amalgamated into the Abrahamskraal Formation due to recent stratigraphic and biostratigraphic research.[3] The Abrahamskraal Formation incorporates the entire Tapinocephalus Assemblage Zone in its upper sections and the entire Eodicynodon Assemblage Zone its lowermost southern deposits. In the west and northerly deposits the Abrahamskraal Formation overlies the Waterford Formation and the Middleton Formation in the south, both formations containing the uppermost deposits of the Ecca Group.

The rocks of the Abrahamskraal Formation comprise mainly greenish-grey to blueish-grey mudstone coupled with rarer instances of greyish-red, reddish-brown or purple mudstones. These include subordinate greenish-grey, fine-grained sandstones which are normally observed in fining upward cycles. The sandstones vary in thickness from several metres to several tens of metres in some localities. Siltstones are also found interbedded with the mudstone beds. The presence of these rocks reveal much about the past environment that they were deposited in. They were formed by sedimentary material being deposited in the Karoo Basin - a retro-arc foreland basin - by vast, low-energy alluvial plains flowing northwards from the south. The lowermost deposits are considered to be deltaic and grade laterally into the underlying Ecca Group deposits in its southern localities. Deposits grade steadily younger in the northeast where the sedimentary facies turn fully terrestrial. The greenish-grey mudstones are usually associated with the deltaic sedimentary facies while the redder mudstones with the terrestrial.[4][5][6][7]

All sedimentary rocks of the Karoo Basin were transported downhill from the south in the shadow of the rising Gondwanide mountain range. The Gondwanides were the result of tectonic uplift that had previously begun to take course due to subduction of the Palaeo-pacific plate beneath the Gondwanan Plate. Orogenic pulses from the growing Gondwanides mountain chain and associated subduction created accommodation space for sedimentation in the Karoo Basin where the deposits of the Abrahamskraal Formation and all succeeding deposits of the Karoo Basin were deposited over millions of years.[8][9][10][11][12][13][14]

Paleontological significance

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The Abrahamskraal Formation is highly fossiliferous and well known for its biozone assemblages of therapsid fossils.[15][16][17][18] The Eodicynodon and Tapinocephalus Assemblage Zones to which this geological formation incorporates preserve the first appearance of the earliest dicynodonts, dinocephalians, biarmosuchians, therocephalians, gorgonopsians,[19][20] and pareiasaurian parareptiles.[21][22][23][24][25][26][27][28][29][30][31][32] The upper sections of this formation document the rise of and diversification of the dinocephalians.[33][34][35][36][37] The dinocephalians subsequently went extinct at the contact of the Abrahamskraal Formation with the overlying Teekloof Formation.[38][39][40] The basal pelycosaur synapsid species, Elliotsmithia longiceps, has also been found in the deposits of this formation.[41][42][43] The presence of this basal synapsid is indicative of this geological formations significance. For decades, paleontologists have puzzled over what has been termed Olsen’s Gap, which is used to describe the evolutionary gap in the tetrapod fossil record between the appearance of the more derived therapsids and their ancestors, the pelycosaurs. The rocks of the Abrahamskraal Formation and its geological correlates abroad hold the promise of that fossil gap being bridged through future research endeavors in the years to come. More notable fossil species include the dicynodont Diictodon feliceps which first appears in the upper sections of this formation, remaining ubiquitous until the Permian-Triassic boundary.[44][45][46] Finally, fossils of temnospondyl amphibians such as of Rhinesuchus, the fish Namaichthys, invertebrate fossils of molluscs, invertebrate trackways and burrows, vertebrate footprints of therapsids, and a variety of plant fossils such as Dadoxylon, Equisetum modderdriftensis, Schizoneura africana, and several different species of Glossopteris have been recovered.[47][48]

Among the species found in the Abrahamskraal Formation is Moschops Capensis [49]

Paleobiota

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Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Amphibians

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Amphibians of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Rhinesuchus[50] R. tenuceps Farm Stinkfontein, Prince Albert District Tapinocephalus A-Z. A skull associated with a partial left mandibular ramus. A temnospondyl amphibian.  
R. whaitsi Leeu-Gamka, Prince Albert District A basicranium, seven fragments of the middle portion of the left hemi-mandible, and multiple skull fragments.

Fish

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Actinopterygian
Actinopterygians of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Bethesdaichthys B. kitchingi Blourug farm, Victoria West. Tapinocephalus A-Z A preserved skull. An actinopterygian fish.
Blourugia[51] B. seeleyi Blourug farm, Victoria West. Tapinocephalus A-Z A partial skeleton. An actinopterygian fish.
Westlepis W. kempeni Blourug farm, Victoria West Tapinocephalus A-Z An actinopterygian fish.

Reptiles

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Sauropsida

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Sauropsids of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Australothyris A. smithi Beukesplaas farm Upper part of Tapinocephalus A-Z A skull and portions of the rest of the skeleton A parareptile.
Bradysaurus B. baini Prince Albert, Leeu Gamka, Hottentotsrivier Farm, Leeurivier, Mynhardtskraal, Groot Kruidfortein, Zwarts Siding, Sutherland, and Knoffelfortein. Tapinocephalus A-Z A complete skull and separate lower jaw with a complete postcranial skeleton consisting of a complete shoulder girdle and pelvis, a complete vertebral column with few missing at the end of the caudal vertebrae. The right fore and hind limbs are complete. The left humerus, radius, ulna, femur, tibia, and fibula are partially preserved. A pareiasaur.  
B. seeleyi A partial skeleton consists of a complete skull, lower jaw, partial vertebral column, some ribs, osteoderms, and parts of girdles.  
Embrithosaurus E. schwarzi Hoogeveld farm. Tapinocephalus A-Z Distorted skull with the occluded lower jaw, vertebrae 1 to 27 with articulated osteoderms, two small articulated caudal vertebrae, partial left scapulocoracoid, cleithrum, left and right clavicle, and interclavicle, complete right humerus, partial left humerus, complete right radius, partial left radius, both ulnae complete, both femora complete, both tibia complete, right fibula, partial left fibula, complete pelvis, two digits of the forelimb and two digits of the hindlimb A pareiasaur.
Eunotosaurus E. africanus De bad farm, Prince Albert, Boesmanrivier and Rietfortien Upper Tapinocephalus A-Z and parts of Pristerognathus A-Z. Fossilized ribbones. An early relative of reptile.  

Synapsids

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Therapsids

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Anomodonts
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Chainosauria
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Chainosaurs of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Galechirus G. scholtzl Victoria West Tapinocephalus A-Z. A partial skeleton An insectivorous anomodont.
 
Patranomodon P. nyaphulii Prince Albert Eodicynodon A-Z A fossilized skull A rare genus of anomodont.
 
Dicynodontia
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Dicynodonts of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Brachyprosopus B. broomi Beukesplaas Tapinocephalus A-Z A skull. A dicynodont.
 
Colobodectes [52] C. cluveri Keerom farm, Kruidfontein farm, Bastardsfontein farm, and Altringham farm. Eodicynodon and Tapinocephalus A-Z A skull lacking zygomatic arches and postorbital bars A dicynodont.
Diictodon D. feliceps Prince Albert. Tapinocephalus A-Z Several skeletal specimens. A pylaecephalid dicynodont.
 
Emydops E. arctatus Beaufort West and Prince Albert. Either Tapinocephalus A-Z or Pristerognathus A-Z. A partial skull A dicynodont.
 
Eodicynodon[53] E. oosthuizeni Tuinkraal and Zwartskraal farm, Prince Albert district Tapinocephalus A-Z Postcranial skeleton. A dicynodont.
 
Eosimops E. newtoni Victoria West. Tapinocephalus A-Z. several skull specimens and one complete skeleton. A pylaecephalid dicynodont.
 
Nyaphulia[53] N. oelofseni Botterkraal farm Eodicynodon A-Z. Partial skull, jaws, and teeth. A dicynodont, formally named E. oelofseni.  
Robertia R. broomiana Klein Koedoeskop, Beaufort West. Lower part of the Tapinocephalus A-Z. Partial skull and postcranial skeleton. A small herbivorous dicynodont.
 
Biarmosuchia
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Biarmosuchians of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Hipposaurus H. boonstrai Beaufort west and Riet Fontein Tapinocephalus A-Z A single skull. A hipposaurid therapsid.
 
H. brinki A preserved skull.
Impumlophantsi [54] I. boonstrai Palmietfontein portion (plot 57) of Kruidfontein farm, Prince Albert District Tapinocephalus A-Z The preorbital region of the skull and articulated lower jaw and a partial vertebral column and pelvis A Biarmosuchian.
 
Nierkoppia N. brucei Farm Stellenboschvlei Tapinocephalus A-Z. A relatively well-preserved fragment of skull roof, preserving the interorbital and inter-temporal regions and dorso-medial portion of the occiput. A proburnetiine burnetiamorph.
Dinocephalian
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Anteosauridae
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Anteosaurs of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Anteosaurus A. magnificus Beaufort West, Prince Albert, and Laingsburg Tapinocephalus A-Z. Several complete skulls, dentition, and partial postcranial skeleton. A large carnivorous dinocephalian.  
Australosyodon A. nyaphuli Prince Albert and Tuinkraal Eodicynodon A-Z. A skull and mandible with a preserved left side. A dinocephalian.
 
Tapinocephalidae
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Tapinocephalians of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Criocephalosaurus C. vanderbyli Prince Albert Lower and Middle Tapinocephalus A-Z. A skull cap consists of the frontals, parietals, postfrontals, and one pre-frontal. A tapinocephalian therapsid.  
Keratocephalus K. moloch Prince Albert, Leeu Gamka, and Buffelsvlei. Tapinocephalus A-Z. Variable skulls and postcrania. A tapinocephalian therapsid.  
Mormosaurus M. seeleyi Gouph tract Tapinocephalus A-Z. A partial skull. A Tapinocephalian.  
Moschops M. capensis De Cypher Farm and Hottentotsrivier. Tapinocephalus A-Z. Several skeletal specimens consist of skulls and postcranial skeletons. A subaquatic tapinocephalian.  
M. koupensis
M. romeri
Phocosaurus P. megischion Boesmansrivier and Vers Fontein/Jan Willem Fontein. Tapinocephalus A-Z. A partial skull. A Tapinocephalian.
 
Tapinocaninus T. pamelae Modderdrift farm Eodicynodon A-Z. Paratypes consist of several skulls with few post-cranial skeletons. A Tapinocephalian.
 
Tapinocephalus T. atherstonei Boesmanshoek and Prince Albert Lower, Middle, and Upper part of the Tapinocephalus A-Z. A skull and postcranial elements. A giant herbivorous Tapinocephalian.  
Struthiocephalus S. whaitsi Prince Albert Lower to Middle Tapinocephalus A-Z. A partial skull. A Tapinocephalian.  
Styracocephalidae
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Styracocephalids of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Styracocephalus S. platyrhynchus Rietfontein, Prince Albert, and Boesmansrivier Tapinocephalus A-Z. Complete skull consists of jaws, palate, and dentition. A dinocephalian therapsid.
 
Titanosuchidae
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Titanosuchids of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Jonkeria J. boonstai Farm Uitkyk, Leeu-Gamka, Groot kruidfontein, Prince Albert, and Vers Fontein. Tapinocephalus A-Z. A skull and humerus. An omnivorous titanosuchid dinocephalian.  
J. ingens A complete skull.
J. haughtoni A crushed skull.
J. koupensis A complete pelvis bone.
J. parva A femur, radius, small humerus, and tarsal.
J. rossouwi The holotype consists of postcranial skeletons.
J. truculenta A skull and partial skeleton.
J. vanderbyli A complete skull.
Titanosuchus[55] T. ferox Beaufort West, Prince Albert, Mynhardskraal, Veldmansrivier, and Lammerskraal. Tapinocephalus A-Z Fragmentary jaws and post-crania that include two left humeri, femur, and two phalanges. A carnivorous titanosuchid dinocephalian.
 
Gorgonopsia
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Gorgonopsians of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Aelurosaurus A. felinus Beaufort west. Tapinocephalus A-Z. A holotype preserved skull. A gorgonopsian.  
A. whaitsi A holotype preserved skull.
Cerdodon C. tenuidens Beaufort west. Tapinocephalus A-Z. A holotype consists of a crushed skull. A gorgonopsid.
Eriphostoma E. microdon Prince Albert, Hottentotsrivier farm, and Mynhardtskraal. Tapinocephalus A-Z. Partial skull remains. A gorgonopsid formally named Galesuchus gracilis.  
Phorcys P. dubei Delportsrivier Eodicynodon and Tapinocephalus A-Z. A partial skull from the occiput (the back face of the skull) up to the orbits, including the basicranium (the floor of the skull beneath the braincase), an eroded upper surface preserving the intact pre parietal and portions of the surrounding frontals and parietal bones, with a broken left zygomatic arch and a left palatine displaced into the left orbit, A gorgonopsid.
Therocephalia
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Therocephalians of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Alopecodon A. priscus Zeekoegat, Prince Albert. Tapinocephalus A-Z A crushed partial skull and lower jaws. A therocephalian.
Alopecognathus A. megalops Beaufort West and Prince Albert. Tapinocephalus A-Z. Skull specimens. A therocephalian.  
Eutheriodon E. vandenheeveri Modderdrift, Prince Albert. Eodicynodon A-Z. A partial snout and lower jaws. A scylacosaurid therocephalian.
Glanosuchus G. macrops Gioflok’s Fontein, near Van der Byl’s Iird in the Gouph Eodicynodon A-Z. A holotype consists of a partial skull. A scylacosaurid therocephalian.
 
Hyaenasuchus H. whaitsi Rietfontein Tapinocephalus A-Z. A weathered skull. A therocephalian.
 
Ictidosaurus I. angusticeps Beaufort West Eodicynodon and Tapinocephalus A-Z. A holotype preserved skull. A scylacosaurid therocephalian.
Pardosuchus P. whaitsi Prince Albert Tapinocephalus A-Z. Holotypes consist of preserved skulls. A pristerognathinae therocephalian formally named Lycedops scholtzi.
 
Specimens of Pardosuchus
Pristerognathus P. minor Beaufort West and Prince Albert. Pristerognathus A-Z. Multiple skull specimens. A therocephalian.
P. parvus
P. vanderbyli
P. vanwyki
Scymnosaurus S. ferox Prince Albert and Vers Fontein/Jan Willem Fortein Tapinocephalus A-Z. Partial skull consists of snout tip, dentition, and palate. A therocephalian therapsids.
Tamboeria T. maraisi Prince Albert and Tamboers Fontein. Tapinocephalus A-Z. A middle-sized carnivorous therocephalian
Trochosuchus T. acutus Rietfontein and Prince Albert. Tapinocephalus A-Z. A fossilized skull. A Lycosuchid therocephalian.
T. intermedius
T. major

Varanopidae

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Varanopids of the Abrahamskraal Formation
Taxa Species Locality Assemblage Zone Material Notes Images
Anningia [56] A. megalops Prince Albert The Middle of the Tapinocephalus A-Z. A partial skull. A varanopid synapsid.
Elliotsmithia E. longiceps Prince Albert Tapinocephalus A-Z. A holotype consists of a skull. A small varanopid synapsid.
 
Heleosaurus H. scholtzi Victoria West. Tapinocephalus A-Z. A preserved skeleton. A varanopid synapsid.
Microvaranops M. parentis Beukesplaas farm Tapinocephalus A-Z. A skeletal aggregation containing one grown and four immature individuals. A varanopid synapsid.

Correlation

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The Abrahamskraal Formation corresponds with numerous localities abroad. Currently it is considered to correlate chronostratigraphically with the Rio do Rasto Formation from the Paraná Basin in Brazil,[57][58] the Madumabisa Mudstone Formation of Zambia,[59] the Ocher and Isheevo faunas of Russia,[60] and to the Dashankou fauna from the Xidagou Formation of China. However, correlative dating between the Xidagou Formation and the Abrahamskraal Formation remains inconsistent and needs further study.

References

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