Abrahamskraal Formation

Abrahamskraal Formation
Stratigraphic range: Wordian-Capitanian ~268–259  Ma PreꞒ Ꞓ O S D C P T J K Pg N
Hill with outcropping Teekloof and Abrahamskraal Formations
Type	Geological formation
Unit of	Beaufort Group
Sub-units	Tapinocephalus Assemblage Zone, Eodicynodon Assemblage Zone
Underlies	Teekloof Formation
Overlies	Ecca Group
Thickness	up to 2,565 m (8,415 ft)
Lithology
Primary	Mudstone, sandstone
Other	Siltstone
Location
Coordinates	31°24′S23°06′E / 31.400°S 23.100°E / -31.400; 23.100
Approximate paleocoordinates	59°54′S38°54′W / 59.9°S 38.9°W / -59.9; -38.9
Region	Northern, Western & Eastern Cape
Country	South Africa
Type section
Named for	Abrahams Kraal 29 (farm), 18 km south of Leeu-Gamka
Named by	A.W. Keyser, P.J. Rossouw & Lieuwe Dirk Boonstra
Abrahamskraal Formation (South Africa)

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]}

Geology

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.

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

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

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

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

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

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

Sauropsida

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

Therapsids

Anomodonts

Chainosauria

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

Dicynodonts of the Abrahamskraal Formation
Taxa	Species	Locality	Assemblage Zone	Material	Notes	Images
Brachyprosopus	B. broomi	Beukesplaas	Tapinocephalus A-Z	A skull.	A dicynodont.	Brachyprosopus broomi Diictodon Feliceps Emydops Arctatus Eodicynodon oosthuizeni Eosimops newtoni Nyaphulia oelofseni Robertia broomiana
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

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

Anteosauridae

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 anteosaur.
Australosyodon	A. nyaphuli	Prince Albert and Tuinkraal	Eodicynodon A-Z.	A skull and mandible with a preserved left side.	A dinocephalian.

Styracocephalidae

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.

Tapinocephalidae

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.
Keratocephalus	K. moloch	Prince Albert, Leeu Gamka, and Buffelsvlei.	Tapinocephalus A-Z.	Variable skulls and postcrania.	A tapinocephalian.
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.

Titanosuchidae

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

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.	Aelurosaurus Eriphostoma
	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

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

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 longiceps
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.

Paleoflora

Plants of the Abrahamskraal Formation
Taxa	Species	Locality	Assemblage Zone	Material	Notes	Images
Dadoxylon	D. sp	Onder Karoo locality
Dictyopteridium [57]	D. sp			Cast fossil specimens	A Glossopteridaceae morphotaxon
Equisetum	E. modderdriftensis
Glossopteris [57]	G. sp			Cast fossil specimens	A Glossopteris morphotaxon
Lidgettonia [57]	L. sp			Cast fossil specimens	A Lidgettoniaceae morphotaxon
Schizoneura	S. africana
Ottokaria [57]	O. sp			Cast fossil specimens	A Glossopteris morphotaxon

Correlation

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, ^{[58] [59]} the Madumabisa Mudstone Formation of Zambia, ^[60] the Ocher and Isheevo faunas of Russia, ^[61] 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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