Gebruik van Paleontologie in Litostratigrafiese korrelasie in die Beaufort Groep, Karoo opeenvolging van Suid-Afrika [The use of palaeontology in the correlation of lithostratigraphic units in the Beaufort Group, Karoo sequence of South Africa]
Date
1990
Authors
Groenewald, Gideon H
Journal Title
Journal ISSN
Volume Title
Publisher
Bernard Price Institute for Palaeontological Research
Abstract
In die Noordoos-Vrystaat is die Beaufort Groep litostratigrafies onderverdeel in 'n onderste Norrnandien Forrnasie en boonste Tarkastad Subgroep waarin twee forrnasies onderskei is. Van onder na bo is die Frankfort (sandsteen), Rooinek (sandsteen), Schoondraai (sandsteen) en Harrismith (moddersteen) Lede in die Norrnandien Forrnasie onderskei, terwyl die Verkykerskop (sandsteen) en Driekoppen (moddersteen) Forrnasies in die Tarkastad Subgroep erken is. Biostratigrafie korreleer goed met litostratigrafie en word as volg opgesom: Schoondraai Lid en onderliggende moddersteen (Dicynodon lacerticeps-Whaitsia Versamelsone); Harrismith Lid (Lystrosaurus-Thrinaxodon Versamelsone). Die Verkykerskop en Driekoppen Forrnasies het nog geen fossiele in die studiegebied opgelewer nie. Nuwe fossielvondse ( 127 eksemplare) van Dicynodon lacerticeps, Whaitsia platyceps, Prorubidgea maccabei, Lystrosaurus murrayi, Lydekkerina sp. en Rhachiocephalus magnus, in die NoordoosVrystaat, is gebruik vir die korrelasie en kartering van die Schoondraai en Harrismith Lede van die Beaufort Groep. Die Dicynodon lacerticeps-Whaitsia Versamelsone word met modderige en sanderige kronkelstrome geassosieerterwyl dieLystrosaurus-Thrinaxodon Versamelsone met droe kronkelstroom afsettings geassosieer word. . Die voorkoms van fossiele is gebruik om te bewys dat die litostratigrafiese indelings van die Beaufort Groep in die Noordoos-Vrystaat met die in die Oos-Kaap, korreleerbaar is.
[In the North Eastern Orange Free State the Beaufort Group can be divided lithostratigraphically into a lower Normandien Formation and an upper Tarkastad Subgroup. Four lithostratigraphic units were recognized within the Normandien Formation, namely the Frankfort (sandstone), Rooinek (sandstone), Schoondraai (sandstone) and Harrismith (mudstone) members. The Tarkastad Subgroup is subdivided into a lower Verkykerskop Formation (sandstone) and upper Driekoppen Formation (mudstone). Biostratigraphy was found to correlate well with lithostratigraphy in the following way: Schoondraai Member and underlying mudstone (Dicynodon-Lacerticeps-Whaitsia Assemblage-zone); Harrismith Member ( Lystrosaurus-Thrinaxodon Assemblage-zone); Verkykerskop and Driekoppen Formations (barren). New discoveries (127 specimens) of Dicynodon lacerticeps, Whaitsia platyceps, Proruhidgea maccahei, Lystrosaurus murrayi, Lydekkerina sp. and Rhachiocephalus magnus , in the northeastern Orange Free State, South Africa, were used in correlating and mapping the Schoondraai and Harrismith Members of the Beaufort Group, Karoo Sequence in South Africa. Dicynodon lacerticeps-Whaitsia Assemblage-zone is associated with muddy and sandy meandering rivers while the Lystrosaurus-Thrinaxodon Assemblage-zone is associated with dry meandering river deposits. The fossil occurrences are used as proof for the correlation of the lithostratigraphic subdivisions of the Beaufort Group in the north-eastern Orange Free State with those in the Eastern Cape Province of South Africa.]
ENGLISH SUMMARY
Mapping of the map area 2729 (North Eastern Orange Free State, South Africa) showed that the relationship of the sedimentary history and the occurrence of vertebrate fossils within the different palaeosedimentary environments, were useful in facilitating an improved lithostratigraphic subdivision and correlation. Using 127 newly discovered vertebrate fossils for purposes of correlation, the following conclusions were arrived at: (i) Dicynodon lacerticeps and Lystrosaurus murrayi were found not to occur together, Lystrosaurus murrayi always occurring stratigraphically higher than Dicynodon lacerticeps. (ii)Rhachiocephalus mag nus is more widely distributed than was previously thought, and it is consequently eliminated as a possible marker fossil. (iii) The association of Whaitsia platyceps with Dicynodon /acerticeps indicates that the Dicynodon lacerticeps-Whaitsia Assemblage-zone extends to the northern part of the Karoo Basin. (iv) The absence of Thrinaxodon sp. fossils in this northern part of the Basin still needs to be explained. (v) The association of specific fossils with specific palaeosedimentary environments is well documented, which could be of use in correlation reasoning within the study area. (vi) Palaeontology is as much part of the sedimentary history of an area as is the smallest sedimentary structure found in mudstone or sandstone, and knowledge of, or at least interest in, palaeontology is essential in the mapping, correlation and understanding of Beaufort Group sediments.
Description
In Afrikaans, extended English abstract available at bottom of document.