The Cistecephalus Assemblage Zone is a tetrapod assemblage zone or biozone found in the Adelaide Subgroup of the Beaufort Group , a majorly fossiliferous and geologically important geological group of the Karoo Supergroup in South Africa . This biozone has outcrops located in the Teekloof Formation north-west of Beaufort West in the Western Cape , in the upper Middleton and lower Balfour Formations respectively from Colesberg of the Northern Cape to east of Graaff-Reinet in the Eastern Cape . The Cistecephalus Assemblage Zone is one of eight biozones found in the Beaufort Group , and is considered to be Late Permian in age.
28-509: The name of the biozone refers to Cistecephalus , a small, burrowing dicynodont therapsid . It is characterized by the presence of this species, known especially from the upper sections of this biozone , and the first appearance of the dicynodont Aulacephalodon . The first fossils to be found in the Beaufort Group rocks that encompass the current eight biozones were discovered by Andrew Geddes Bain in 1856. However, it
56-467: A far more broader stratigraphic range between the uppermost occurrence of Endothiodon and the lowermost of Lystrosaurus . Decades later, James Kitching revised the biostratigraphic ranges of the Beaufort Group . Kitching observed that Cistecephalus fossils were most abundant in a narrow band at the very top of the biozone . He named this area the " Cistecephalus acme zone" or " Cistecephalus Band". Later, researchers sought to redefine
84-413: A large retroarc foreland basin in southwestern Gondwana . The sedimentary rocks are mainly sandstone , mudrock layers containing mudstone , siltstone , and fine sandstone. The sandstones are thought to have been deposited in broad alluvial plains where low- sinuosity streams flowed, while the mudrock accumulated on the floodplains that flanked these streams. The majority of the fossils in
112-479: A small portion of fossils are preserved, a biozone does not represent the true range of that species in time. Moreover, ranges can be influenced by the Signor-Lipps effect , meaning that the last "disappearance" of a species tends to be observed further back in time than was actually the case. Alluvium Alluvium (from Latin alluvius , from alluere 'to wash against')
140-409: Is a biozone that is defined by the range in which the abundance of a particular taxon is highest. Because an abundance zone requires a statistically high proportion of a particular taxon, the only way to define them is to trace the abundance of the taxon through time. As local environmental factors influence abundance, this can be an unreliable way of defining a biozone. Abundance zones are named after
168-433: Is a biozone with the upper boundary being the appearance of one taxon, and the lower boundary the appearance of another taxon. A lineage zone, also called a consecutive range zone , are biozones which are defined by being a specific segment of an evolutionary lineage. For example, a zone can be bounded by the highest occurrence of the ancestor of a particular of a taxon and the lowest occurrence of its descendant, or between
196-706: Is arranged into lower and upper zones due to the appearance or frequency of certain fossils. The lower zones are characterized by the first appearance of the dicynodont species Aulacephalodon and Oudenodon . Other species found are the Biarmosuchian therapsid Herpetoskylax , Burnetiamorph species namely Lemurosaurus , and numerous Gorgonopsian species such as Lycaenops , Rubidgea , and Dinogorgon . In addition species of Dicynodonts such as Endothiodon and Diictodon , Therocephalians , Pareiasaurs , and rare occurrences of parareptiles such as Owenetta and Milleretta have been found in
224-401: Is called a biohorizon . Biozones can be further subdivided into subbiozones , and multiple biozones can be grouped together in a superbiozone in which the grouped biozones usually have a related characteristic. A succession of biozones is called biozonation . The length of time represented by a biostratigraphic zone is called a biochron . The concept of a biozone was first established by
252-491: Is loose clay , silt , sand , or gravel that has been deposited by running water in a stream bed, on a floodplain , in an alluvial fan or beach , or in similar settings. Alluvium is also sometimes called alluvial deposit . Alluvium is typically geologically young and is not consolidated into solid rock. Sediments deposited underwater, in seas, estuaries , lakes, or ponds, are not described as alluvium. Floodplain alluvium can be highly fertile, and supported some of
280-402: The Beaufort Group have affected the uniformity in colour and texture of the biozone rocks in areas. This includes the colour of the fossilized bones, which range from a smooth, white appearance to being nearly black depending on their proximity to the dolerite intrusions . The Cistecephalus biozone is well known for its diversity of fossil fauna , especially of therapsid species. It
308-578: The biozone again as Cistecephalus fossils are extremely rare apart from the uppermost portion. It was suggested that, due to the biozone containing the first appearance of Aulacephalodon and its fossils being found throughout, the biozone should be renamed to the Aulacephalodon Assemblage Zone. The biozone was then, for a brief time, renamed the Aulacephalodon - Cistecephalus Assemblage Zone. However, due to
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#1732779674428336-573: The 19th century paleontologist Albert Oppel , who characterized rock strata by the species of the fossilized animals found in them, which he called zone fossils. Oppel's biozonation was mainly based on Jurassic ammonites he found throughout Europe, which he used to classify the period into 33 zones (now 60). Alcide d'Orbigny would further reinforce the concept in his Prodrome de Paléontologie Stratigraphique , in which he established comparisons between geological stages and their biostratigraphy. The International Commission on Stratigraphy defines
364-645: The 19th century, the term had come to mean recent sediments deposited by rivers on top of older diluvium , which was similar in character but interpreted as sediments deposited by Noah's flood . With the rejection by geologists of the concept of a primordial universal flood, the term "diluvium" fell into disfavor and was replaced with "older alluvium". At the same time, the term "alluvium" came to mean all sediment deposits due to running water on plains. The definition gradually expanded to include deposits in estuaries, coasts, and young rock of marine and fluvial origin. Alluvium and diluvium were grouped as colluvium in
392-448: The basis of their characteristic fossil taxa , as opposed to a lithostratigraphic unit which is defined by the lithological properties of the surrounding rock. A biostratigraphic unit is defined by the zone fossils it contains. These may be a single taxon or combinations of taxa if the taxa are relatively abundant, or variations in features related to the distribution of fossils. The same strata may be zoned differently depending on
420-448: The biozone are found in these interchannel mudrock layers as animal remains that came to rest on the floodplains were quickly buried by alluvial sediments washed downstream. Articulated fossils are not commonly found. However, isolated skulls are fairly common and are usually found encased in calcareous nodules . Fossils not encased in nodules are often fragmented. In addition, Jurassic-aged dolerite sheet and dike intrusions into
448-584: The biozone first being named after Cistecephalus , the initial nomenclature of the biozone later overruled its renaming on historical grounds. The Cistecephalus Assemblage Zone is located in the lower portion of the Teekloof Formation west of 24°E, in the upper Middleton Formation and lower Balfour Formation east of 24°E. These formations all fall within the Adelaide Subgroup of the Beaufort Group , sediments of which were formed in
476-404: The diagnostic criteria or fossil group chosen, so there may be several, sometimes overlapping, biostratigraphic units in the same interval. Like lithostratigraphic units, biozones must have a type section designated as a stratotype . These stratotypes are named according to the typical taxon (or taxa) that are found in that particular biozone. The boundary of two distinct biostratigraphic units
504-608: The earliest human civilizations. The present consensus is that "alluvium" refers to loose sediments of all types deposited by running water in floodplains or in alluvial fans or related landforms . However, the meaning of the term has varied considerably since it was first defined in the French dictionary of Antoine Furetière , posthumously published in 1690. Drawing upon concepts from Roman law , Furetière defined alluvion (the French term for alluvium) as new land formed by deposition of sediments along rivers and seas. By
532-411: The following biozones (from oldest to youngest): These biozone divisions were approved by paleontologists of the time and were left largely unchanged for several decades. The Cistecephalus Assemblage Zone was first coined by Robert Broom in 1906, where Broom referred to the rock layers Cistecephalus fossils were found in as the "Kistecephalus beds". The biozone was originally assigned to
560-496: The following types of biozones: Range zones are biozones defined by the geographic and stratigraphic range of occurrence of a taxon (or taxa). There are two types of range zones: A taxon-range zone is simply the biozone defined by the first ( first appearance datum or FAD ) and last ( last appearance datum or LAD ) occurrence of a single taxon. The boundaries are defined by the lowest and highest stratigraphic occurrence of that particular taxon. Taxon-range zones are named after
588-408: The late 19th century. "Colluvium" is now generally understood as sediments produced by gravity-driven transport on steep slopes. At the same time, the definition of "alluvium" has switched back to an emphasis on sediments deposited by river action. There continues to be disagreement over what other sediment deposits should be included under the term "alluvium". Most alluvium is Quaternary in age and
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#1732779674428616-418: The lowest occurrence of a taxon and the lowest occurrence of its descendant. Lineage zones are different from most other biozones because they need that the segments its bounded by are successive segments of an evolutionary lineage. This makes them similar to chronostratigraphical units - however, lineage zones, being a biozone, are restricted by the actual spatial range of fossils. Lineage zones are named for
644-460: The specific taxon they represent. An assemblage zone is a biozone defined by three or more different taxa, which may or may not be related. The boundaries of an assemblage zone are defined by the typical, specified fossil assemblage's occurrence: this can include the appearance, but also the disappearance of certain taxa. Assemblage zones are named for the most characteristic or diagnostic fossils in its assemblage. An abundance zone, or acme zone ,
672-417: The taxon in it. A concurrent-range zone uses the overlapping range of two taxa, with low boundary defined by the appearance of one taxon and high boundary defined by the disappearance of the other taxon. Concurrent-range zones are named after both of the taxa in it. An interval zone is defined as the body of strata between two bio-horizons, which are arbitrarily chosen. For example, a highest-occurrence zone
700-586: The taxon that is the most abundant within its range. A great variety of species can be used in establishing biozonation. Graptolites and ammonites are some of the most useful as zone fossils, as they preserve well and often have relatively short biozones. Microfossils , such as dinoflagellates , foraminiferans , or plant pollen are also good candidates because they tend to be present even in very small samples and evolve relatively rapidly. Fossils of pigs and cannabis can be used for biozonation of Quaternary rocks as they were used by hominids . As only
728-559: The upper zones. The temnospondyl amphibian Rhinesuchus , and some fish and plant species have also been found. A dicynodont track way is also known in an outcrop of the biozone east of Graaff-Reinet . Cistecephalus fossils are rare until the uppermost portion of the biozone where the " Cistecephalus Band" is located. Correlations in biostratigraphy have been made with the Cistecephalus zone to geological formations outside of South Africa . An Endothiodon snout
756-985: Was discovered in the Rio do Rasto Formation in Brazil , and Cistecephalus fossils have been found in Madumabisa Mudstone in Zambia . Recently, a new cistecephalid dicynodont was discovered in the Kundaram Formation of the Pranhita-Godavari Valley in India . The zone also correlates with the Malokinelskaya and Vyazovskaya Formations of Russia. Biozone In biostratigraphy , biostratigraphic units or biozones are intervals of geological strata that are defined on
784-428: Was not until 1892 that it was observed that the geological strata of the Beaufort Group could be differentiated based on their fossil taxa . The initial undertaking was done by Harry Govier Seeley who subdivided the Beaufort Group into three biozones , which he named (from oldest to youngest): These proposed biozones Seeley named were subdivided further by Robert Broom between 1906 and 1909. Broom proposed
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