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30-539: During the period when sedimentation of the Beaufort Group rocks took place, the Ecca sea had retreated to the northeastern Karoo Basin . All sediment deposition at this time took place in a terrestrial, although in a predominantly fluvial or alluvial environment that was seasonally arid . This environment covered a vast area and deposition was influenced by a retroarc foreland basin . This foreland system

60-413: A sufficiently strong force to produce significant sedimentation. Settling is the process by which particulates move towards the bottom of a liquid and form a sediment . Particles that experience a force, either due to gravity or due to centrifugal motion will tend to move in a uniform manner in the direction exerted by that force. For gravity settling, this means that the particles will tend to fall to

90-409: 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

120-433: 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

150-484: Is called aggradation . The rate of sedimentation is the thickness of sediment accumulated per unit time. For suspended load, this can be expressed mathematically by the Exner equation . Rates of sedimentation vary from less than 3 millimeters (0.12 in) per thousand years for pelagic sediment to several meters per thousand years in portions of major river deltas . However, long-term accumulation of sediments

180-401: 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

210-461: Is determined less by rate of sedimentation than by rate of subsidence, which creates accommodation space for sediments to accumulate over geological time scales. Most sedimentation in the geologic record occurred in relative brief depositional episodes separated by long intervals of nondeposition or even erosion. In estuarine environments, settling can be influenced by the presence or absence of vegetation. Trees such as mangroves are crucial to

240-491: Is opposed by the diffusion of the particles. The distribution of sediment near the boundary comes into sedimentation equilibrium . Measurements of the distribution yields information on the nature of the particles. In geology , the term sedimentation is broadly applied to the entire range of processes that result in the formation of sedimentary rock, from initial formation of sediments by erosion of particles from rock outcrops, through sediment transport and settling, to

270-410: Is the deposition of sediments . It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the forces acting on them: these forces can be due to gravity , centrifugal acceleration , or electromagnetism . Settling is the falling of suspended particles through

300-605: The Abrahaamskraal and Teekloof Formations, west of 24°E, Middleton and Balfour Formations east of 24°E, and the Normandien and Emakwezini Formations in the northern Free-State and Kwa-Zulu Natal provinces. Composing the lower Beaufort succession, the rocks are mudstone-dominated. The mudstones in the lower Beaufort Group are mainly greenish-grey to blueish-grey and gradually change to greyish-red, reddish-brown or purple in color. The dominant presence of mudstones in

330-446: The attenuation of waves or currents, promoting the settlement of suspended particles. An undesired increased transport and sedimentation of suspended material is called siltation , and it is a major source of pollution in waterways in some parts of the world. High sedimentation rates can be a result of poor land management and a high frequency of flooding events. If not managed properly, it can be detrimental to fragile ecosystems on

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360-462: The lithification of the sediments. However, the term is more particularly applied to the deposition of sediments, and in the strictest sense, it applies only to the mechanical deposition of sediment particles from an initial suspension in air or water. Sedimentation results in the formation of depositional landforms and the rocks that constitute the sedimentary record . The building up of land surfaces by sedimentation, particularly in river valleys,

390-573: 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

420-540: The Karoo Basin. Orogenic loading was the initial subsidence mechanism acting on the Karoo Basin and flexural tectonics partitioned the Karoo Basin into the foredeep , forebulge , and backbulge flexural provinces. Orogenic loading and unloading caused changes in position of the forebulge and foredeep. This resulted in the deposition zones shifting from the proximal or distal regions of the Karoo Basin. The Beaufort Group rocks are predominantly mudstone-dominated up until

450-448: 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

480-399: The bottom of the vessel, forming sludge or slurry at the vessel base. Settling is an important operation in many applications, such as mining , wastewater and drinking water treatment, biological science, space propellant reignition, Classification of sedimentation: When particles settling from a suspension reach a hard boundary, the concentration of particles at the boundary

510-551: The central Karoo and continue north-north-eastwards to Gariep Dam, Colesberg, and up to Bloemfontein. In the extreme north and north-east, the Beaufort Group outcrops in Harrismith and northeastern KwaZulu-Natal. Adelaide Subgroup The Adelaide Subgroup is the lower subgroup of the Beaufort Group and contains all Middle to Late Permian -aged rocks. This subgroup contains six geological formations in total, however, these formations are latitude specific. These formations are

540-404: 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

570-496: 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

600-421: The liquid, whereas sedimentation is the final result of the settling process. In geology , sedimentation is the deposition of sediments which results in the formation of sedimentary rock . The term is broadly applied to the entire range of processes that result in the formation of sedimentary rock, from initial erosion through sediment transport and settling to the lithification of the sediments. However,

630-499: The lower Beaufort Group represent tranquil depositional settings such as overbank or floodplain facies associations. The formations here are listed below (from oldest to youngest): West of 24 degrees East of 24 degrees Tarkastad Subgroup There are no equivalent deposits of the Tarkastad Subgroup west of 24°E. This is either due to erosion of the lowlands west of 24°E or sediment deposition in

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660-418: 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

690-417: The receiving end, such as coral reefs. Climate change also affects siltation rates. In chemistry, sedimentation has been used to measure the size of large molecules ( macromolecule ), where the force of gravity is augmented with centrifugal force in an ultracentrifuge . Biozone In biostratigraphy , biostratigraphic units or biozones are intervals of geological strata that are defined on

720-460: 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 ,

750-417: The strict geological definition of sedimentation is the mechanical deposition of sediment particles from an initial suspension in air or water. Sedimentation may pertain to objects of various sizes, ranging from large rocks in flowing water, to suspensions of dust and pollen particles, to cellular suspensions, to solutions of single molecules such as proteins and peptides . Even small molecules supply

780-417: 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

810-586: 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

840-485: The upper sections in the lower Tarkastad Subgroup. Tuffs are also found due to concurrent volcanic activity that took place with the foreland tectonics. The geological formations of the Beaufort Group are outcrop over approximately 145 000 km, attaining a total thickness of around 6000 m thick at its thickest outcrops. In the west, the lowermost Beaufort Group rocks are found east of Laingsburg and remain continuous eastward to East London. Deposits are also found in

870-1236: The western section of the Karoo Basin ceased at the end of the Permian . In the lower sections sandstones dominate, especially in the Katberg Formation . In the upper units the sandstone to mudstone ratio steadily evens out. The Tarkastad Subgroup is composed of the following formations (from oldest to youngest): The Beaufort Group is internationally renowned for its diverse fossil fauna , in particular for its therapsid fossils. The entire expanse of this geological group has been categorized into eight fossil biozones or assemblage zones. These assemblage zones are listed below: The Beaufort Group deposits also yield numerous insect , plant , and trace fossils. The Beaufort Group rocks correlate chronologically with numerous other geological formations and groups within southern Africa and abroad. Most notably from numerous localities in Russia , China , South America , Antarctica , Madagascar , India , and Australia . Sedimentation Sedimentation

900-692: Was caused by crustal uplift ( orogenesis ) that had previously begun to take course due to the subduction of the Palaeo-pacific plate beneath the Gondwanan Plate. This resulted in the rise of the Gondwanide mountain range in what is known as the Gondwanide orogeny . The continuation of mountain-building and erosion from the growing Gondwanide mountain chain and associated subduction created accommodation space for sediment deposition in

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