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92-714: The Bouri Formation stretches down much of the length and breadth of the Bouri "peninsula", which projects across the dry bed of the Afar Depression. The Formation is sufficiently eroded to expose three geological members or layers: the Hatayae, the Dakanihylo, and the Herto. Human remains with signs of having been prepared for burial have been found in the Upper Herto layers. The Bouri "peninsula"

184-575: A 15–20 m thick main sequence found in the southwestern part of the Bouri peninsula. The division between the Lower and Upper Herto layers is characterized by an erosion surface filled with rounded pebbles. This layer presents lignite , veins of pink carbonate, and silty clays (of predominantly lake origin) containing gastropod and bivalve fossils; it is dated to 260 thousands of years ago (kya). Late Acheulean tools are found associated with hominin remains as yet unclassified. Humans in this habitat lived next to

276-505: A deep cladogenesis between African and Asian H. erectus ..."; and 2) "..that geographic subdivision of early H. erectus into separate species lineages is biologically misleading, artificially inflating early Pleistocene species diversity." Further, they suggest that "..by 1 Myr the taxon had colonized much of the Old World without speciating. A finding of considerable biogeographic and behavioural significance". The Herto layers consist of

368-414: A different shape. The horns of female bovids are believed to have evolved for defence against predators or to express territoriality, as nonterritorial females, which are able to use crypsis for predator defence, often do not have horns. Females possess horns only in half of the bovid genera, and females in these genera are heavier than those in the rest. Females use horns mainly for stabbing. In bovids,

460-405: A fault as oblique requires both dip and strike components to be measurable and significant. Some oblique faults occur within transtensional and transpressional regimes, and others occur where the direction of extension or shortening changes during the deformation but the earlier formed faults remain active. The hade angle is defined as the complement of the dip angle; it is the angle between

552-574: A fault hosting valuable porphyry copper deposits is northern Chile's Domeyko Fault with deposits at Chuquicamata , Collahuasi , El Abra , El Salvador , La Escondida and Potrerillos . Further south in Chile Los Bronces and El Teniente porphyry copper deposit lie each at the intersection of two fault systems. Faults may not always act as conduits to surface. It has been proposed that deep-seated "misoriented" faults may instead be zones where magmas forming porphyry copper stagnate achieving

644-489: A fault plane, where it becomes locked, are called asperities . Stress builds up when a fault is locked, and when it reaches a level that exceeds the strength threshold, the fault ruptures and the accumulated strain energy is released in part as seismic waves , forming an earthquake . Strain occurs accumulatively or instantaneously, depending on the liquid state of the rock; the ductile lower crust and mantle accumulate deformation gradually via shearing , whereas

736-408: A fault's age by studying soil features seen in shallow excavations and geomorphology seen in aerial photographs. Subsurface clues include shears and their relationships to carbonate nodules , eroded clay, and iron oxide mineralization, in the case of older soil, and lack of such signs in the case of younger soil. Radiocarbon dating of organic material buried next to or over a fault shear

828-667: A few such as the buffalo, bushbuck, reedbuck, and grysbok are exceptions. Social activity and feeding usually peak during dawn and dusk. The bovids usually rest before dawn, during midday, and after dark. Grooming is usually by licking with the tongue. Rarely do antelopes roll in mud or dust. Wildebeest and buffalo usually wallow in mud, whereas the hartebeest and topi rub their heads and horns in mud and then smear it over their bodies. Bovids use different forms of vocal, olfactory, and tangible communication. These involve varied postures of neck, head, horns, hair, legs, and ears to convey sexual excitement, emotional state, or alarm. One such expression

920-456: A freshwater lake and killed large mammals such as hippopotamids . The Upper Herto member changes to yellow sandstone (from the fluvial and lake-margin deposits of the lower layer), and dates to between 160 and 154 kya. Immediately above the erosion surface separating the two layers is a sequence of volcanic sandstone and gravel deposits of variable thicknesses. It shows cross-bedded sedimentation containing pumice rocks and has produced all

1012-427: A hanging wall or foot wall where a thrust fault formed along a relatively weak bedding plane is known as a flat and a section where the thrust fault cut upward through the stratigraphic sequence is known as a ramp . Typically, thrust faults move within formations by forming flats and climbing up sections with ramps. This results in the hanging wall flat (or a portion thereof) lying atop the foot wall ramp as shown in

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1104-509: A level muzzle. Fighting techniques differ amongst the bovid families and also depend on their build. While the hartebeest fight on knees, others usually fight on all fours. Gazelles of various sizes use different methods of combat. Gazelles usually box, and in serious fights may clash and fence, consisting of hard blows from short range. Ibex, goat and sheep males stand upright and clash into each other downwards. Wildebeest use powerful head butting in aggressive clashes. If horns become entangled,

1196-472: A major fault. Synthetic faults dip in the same direction as the major fault while the antithetic faults dip in the opposite direction. These faults may be accompanied by rollover anticlines (e.g. the Niger Delta Structural Style). All faults have a measurable thickness, made up of deformed rock characteristic of the level in the crust where the faulting happened, of the rock types affected by

1288-400: A manner that creates multiple listric faults. The fault panes of listric faults can further flatten and evolve into a horizontal or near-horizontal plane, where slip progresses horizontally along a decollement . Extensional decollements can grow to great dimensions and form detachment faults , which are low-angle normal faults with regional tectonic significance. Due to the curvature of

1380-421: A non-vertical fault are known as the hanging wall and footwall . The hanging wall occurs above the fault plane and the footwall occurs below it. This terminology comes from mining: when working a tabular ore body, the miner stood with the footwall under his feet and with the hanging wall above him. These terms are important for distinguishing different dip-slip fault types: reverse faults and normal faults. In

1472-465: A pale white (as in the Arabian oryx ) to black (as in the black wildebeest ). However, only the intermediate shades, such as brown and reddish brown (as in the reedbuck ), are commonly observed. In several species, females and juveniles exhibit a light-coloured coat, while those of males darken with age. As in the wildebeest , the coat may be marked with prominent or faint stripes. In some species such as

1564-825: A permanent sheath of keratin. Although horns occur in a single pair on almost all bovid species, there are exceptions such as the four-horned antelope and the Jacob sheep . The unique horn structure is the only unambiguous morphological feature of bovids that distinguishes them from other pecorans . A high correlation exists between horn morphology and fighting behaviour of the individual. For instance, long horns are intended for wrestling and fencing, whereas curved horns are used in ramming. Males with horns directed inwards are monogamous and solitary, while those with horns directed outwards tend to be polygynous . These results were independent of body size. Male horn development has been linked to sexual selection , Horns are small spikes in

1656-460: A reverse fault, the hanging wall displaces upward, while in a normal fault the hanging wall displaces downward. Distinguishing between these two fault types is important for determining the stress regime of the fault movement. Faults are mainly classified in terms of the angle that the fault plane makes with the Earth's surface, known as the dip , and the direction of slip along the fault plane. Based on

1748-513: A tribe of Caprinae, in Africa date back to the late Miocene. The earliest Hippotragine fossils date back to the late Miocene, and were excavated from sites such as Lothagam and Awash Valley . The first African fossils of Reduncinae date back to 6-7 Mya. Reduncinae and Peleinae probably diverged in the mid-Miocene. All bovids have the similar basic form - a snout with a blunt end, one or more pairs of horns (generally present on males) immediately after

1840-447: A volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth 's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as the megathrust faults of subduction zones or transform faults . Energy release associated with rapid movement on active faults is

1932-422: Is a horst . A sequence of grabens and horsts on the surface of the Earth produces a characteristic basin and range topography . Normal faults can evolve into listric faults, with their plane dip being steeper near the surface, then shallower with increased depth, with the fault plane curving into the Earth. They can also form where the hanging wall is absent (such as on a cliff), where the footwall may slump in

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2024-659: Is a geological fault -raised horst that diverts the Awash River , forming a partial dam and creating Lake Yardi ; and it contains the Bouri Formation. The peninsula is about 4 km wide by 10 km long, and lies in a NNW-SSE direction in the Quaternary -period rift zone in the southern part of the Afar Depression ( Afar Triangle ). The Bouri Formation is a sediment area some 80 m thick that stretches down much of

2116-423: Is a zone of folding close to a fault that likely arises from frictional resistance to movement on the fault. The direction and magnitude of heave and throw can be measured only by finding common intersection points on either side of the fault (called a piercing point ). In practice, it is usually only possible to find the slip direction of faults, and an approximation of the heave and throw vector. The two sides of

2208-427: Is almost never present in hominid [hominin] or nonhuman faunal remains processed for consumption, and is therefore unlikely to represent evidence of utilitarian or economic behaviour." On one skull, "..this defleshing manipulation must have occurred after removal of the mandible. The intentional and deliberate removal of soft tissues such as basicranial vessels, nerves and muscles is therefore indicated. The specimen lacks

2300-577: Is believed to have come into being in the Pliocene, but became extinct in the middle Pleistocene . Several genera of Hippotraginae are known since the Pliocene and Pleistocene. This subfamily appears to have diverged from the Alcelaphinae in the latter part of early Miocene. The Bovinae are believed to have diverged from the rest of the Bovidae in the early Miocene . The Boselaphini became extinct in Africa in

2392-449: Is called a bovid . With 143 extant species and 300 known extinct species , the family Bovidae consists of 11 (or two) major subfamilies and thirteen major tribes. The family evolved 20 million years ago, in the early Miocene . The bovids show great variation in size and pelage colouration. Except some domesticated forms , all male bovids have two or more horns , and in many species, females possess horns, too. The size and shape of

2484-530: Is defined by the direction of movement of the ground as would be seen by an observer on the opposite side of the fault. A special class of strike-slip fault is the transform fault when it forms a plate boundary. This class is related to an offset in a spreading center , such as a mid-ocean ridge , or, less common, within continental lithosphere , such as the Dead Sea Transform in the Middle East or

2576-708: Is disputed, with suggestions of as many as ten and as few as two subfamilies. However, molecular, morphological and fossil evidence indicates the existence of eight distinct subfamilies: Aepycerotinae (consisting of just the impala), Alcelaphinae (bontebok, hartebeest, wildebeest and relatives), Antilopinae (several antelopes, gazelles, and relatives), Bovinae (cattle, buffaloes, bison and other antelopes), Caprinae (goats, sheep, ibex, serows and relatives), Cephalophinae (duikers), Hippotraginae (addax, oryx and relatives) and Reduncinae (reedbuck and kob antelopes). In addition, three extinct subfamilies are known: Hypsodontinae (mid- Miocene ), Oiocerinae ( Turolian ) and

2668-487: Is in the savannas of Eastern Africa . Other bovid species also occur in Europe, Asia, and North America. Bovidae includes a number of domesticated species, including three whose use has spread worldwide, namely cattle , sheep , and goats . Dairy products , such as milk , butter , and cheese , are manufactured largely from domestic cattle. Bovids are also raised for their leather , meat , and wool . The name "Bovidae"

2760-407: Is likely due to the lack of streams strong enough to carry hand-sized pebbles and the absence of nearby outcrops of basalt. In spite of rarity, some isolated and widely scattered cores and flakes of Mode I technology have been found. The excavators (de Heinzelin, et al., 2002) report: "..our surveys and excavations have demonstrated that early hominids [hominins] were actively using stone tools on

2852-543: Is often critical in distinguishing active from inactive faults. From such relationships, paleoseismologists can estimate the sizes of past earthquakes over the past several hundred years, and develop rough projections of future fault activity. Many ore deposits lie on or are associated with faults. This is because the fractured rock associated with fault zones allow for magma ascent or the circulation of mineral-bearing fluids. Intersections of near-vertical faults are often locations of significant ore deposits. An example of

Bouri Formation - Misplaced Pages Continue

2944-492: Is particularly clear in the case of detachment faults and major thrust faults . The main types of fault rock include: In geotechnical engineering , a fault often forms a discontinuity that may have a large influence on the mechanical behavior (strength, deformation, etc.) of soil and rock masses in, for example, tunnel , foundation , or slope construction. The level of a fault's activity can be critical for (1) locating buildings, tanks, and pipelines and (2) assessing

3036-402: Is the flehmen response . Bovids usually stand motionless, with the head high and an intent stare, when they sense danger. Some like the impala, kudu, and eland can even leap to heights of a few feet. Bovids may roar or grunt to caution others and warn off predators. Bovids such as gazelles stot or pronk in response to predators, making high leaps on stiff legs, indicating honestly both that

3128-718: Is the only bovid that is both solitary and not territorial. This antelope hardly displays aggression, and tends to isolate itself or form loose herds, though in a favourable habitat, several bushbuck may be found quite close to one another. Excluding the cephalophines (duikers), tragelaphines (spiral-horned antelopes) and the neotragines, most African bovids are gregarious and territorial. Males are forced to disperse on attaining sexual maturity, and must form their own territories, while females are not required to do so. Males that do not hold territories form bachelor herds. Competition takes place among males to acquire dominance, and fights tend to be more rigorous in limited rutting seasons . With

3220-745: The Alpine Fault in New Zealand. Transform faults are also referred to as "conservative" plate boundaries since the lithosphere is neither created nor destroyed. Dip-slip faults can be either normal (" extensional ") or reverse . The terminology of "normal" and "reverse" comes from coal mining in England, where normal faults are the most common. With the passage of time, a regional reversal between tensional and compressional stresses (or vice-versa) might occur, and faults may be reactivated with their relative block movement inverted in opposite directions to

3312-1113: The Antilopinae , was later placed in its own subfamily, Pantholopinae . However, molecular and morphological analysis supports the inclusion of Pantholops in Caprinae . Below is a cladogram based on Yang et al . , 2013 and Calamari, 2021: Bovini (bison, buffalo, cattle, etc.) [REDACTED] Boselaphini (nilgai and four-horned antelope) [REDACTED] Tragelaphini (kudus, nyalas etc.) [REDACTED] Aepycerotinae (impala) [REDACTED] Nesotraginae (suni and bates's antelope) Antilopinae (gazelles, springbok, dik-dik, royal antelope, saiga, etc.) [REDACTED] Cephalophinae (duikers etc.) [REDACTED] Oreotraginae (klipspringer) Reduncinae (kobs, reedbucks, waterbucks etc.) [REDACTED] Caprinae (chamois, sheep, ibexes, goats, muskox, etc.) [REDACTED] Alcelaphinae (hartebeest, topi, wildebeest etc.) [REDACTED] Hippotraginae (sable antelopes, oryxes etc.) [REDACTED] Alternatively, all members of

3404-491: The addax , the coat colour can vary by the season. Scent glands and sebaceous glands are often present. Some species, such as the gemsbok , sable antelope , and Grant's gazelle , are camouflaged with strongly disruptive facial markings that conceal the highly recognisable eye. Many species, such as gazelles, may be made to look flat, and hence to blend into the background, by countershading . The outlines of many bovids are broken up with bold disruptive colouration,

3496-399: The dental pad , that provides a surface to grip grasses and foliage. They are hypsodont and selenodont , since the molars and premolars are low- crowned and crescent-shaped cusps . The lower incisors and canines project forward. The incisors are followed by a long toothless gap, known as the diastema . The general dental formula for bovids is 0.0.2-3.3 3.1.3.3 . Most members of

3588-645: The seismic shaking and tsunami hazard to infrastructure and people in the vicinity. In California, for example, new building construction has been prohibited directly on or near faults that have moved within the Holocene Epoch (the last 11,700 years) of the Earth's geological history. Also, faults that have shown movement during the Holocene plus Pleistocene Epochs (the last 2.6 million years) may receive consideration, especially for critical structures such as power plants, dams, hospitals, and schools. Geologists assess

3680-531: The Acheulean and the MSA. In this layer are found a large number of Hippopotamus bones: "One occurrence shows abundant remains of several hippo calves, mostly newborn to a few weeks old, scattered together with butchered adults". Of 15 of the 24 recovered fragments of humans in the Upper Herto layer have cut marks due to soft tissue removal. Clark, et al., (2003) reports that "The latter pattern of bone surface modification

3772-524: The Aegodontia, can be classified within the subfamily Antilopinae, with the individual subfamilies being tribes in this treatment. In the early Miocene, bovids began diverging from the cervids (deer) and giraffids . The earliest bovids, whose presence in Africa and Eurasia in the latter part of early Miocene (20 Mya ) has been ascertained, were small animals, somewhat similar to modern gazelles , and probably lived in woodland environments. Eotragus ,

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3864-440: The Bovidae, where for example Bos , Ovis , bontebok and gemsbok have white stockings. Again, communication is the likely function. Excepting some domesticated forms, all male bovids have horns, and in many species, females, too, possess horns. The size and shape of the horns vary greatly, but the basic structure is a pair of simple bony protrusions without branches, often having a spiral, twisted, or fluted form, each covered in

3956-552: The Bovidae-Moschidae clade 27 to 28 million years ago. The following cladogram is based on the 2003 study. Tragulidae [REDACTED] Antilocapridae [REDACTED] Giraffidae [REDACTED] Cervidae [REDACTED] Moschidae [REDACTED] Bovidae [REDACTED] Molecular studies have supported monophyly in the family Bovidae (a group of organisms comprises an ancestral species and all their descendants). The number of subfamilies in Bovidae

4048-587: The Daka member, as well as evidence of butchery processing on equid , bovid and hippo bones. Homo erectus fossils include the specimen BOU-VP-2/66 , or the Daka skull , an incomplete skull that had an endocranial capacity of 995 cm. These fossils (of H. erectus ) are important to the current debate as to whether Asian and African H. erectus were actually different human species . Asfaw, et al. (2002) reports: 1) that these fossils do not support "..the hypothesis of

4140-456: The Hatayae member have been found the remains of Australopithecus garhi , the most complete specimen of which is BOU-VP-12/130 . According to Asfaw and White, et al. (1999), that species is "..descended from Australopithecus afarensis and is a candidate ancestor for early Homo." Excavations in general have failed to disclose large numbers of stone tools . The likely explanation is the lack of raw materials on lake margins, which, in turn,

4232-640: The Herto member, Lower layer at 260 kya, and Upper layers at 160 to 154 kya—fossils of Homo sapiens idaltu were found. The area is important because active tectonics in the Afar Depression created varying habitats for early hominins across the most recent few million years known informally as the Plio-Pleistocene . These habitats, laid down in sedimentary rocks, have since been uplifted , which allowed their erosion over time and their accessibility today to paleoanthropologists . Volcanic eruptions have left volcanic tuff layers that enable accurate dating of

4324-599: The Pliocene-Hata landscape"; and: "It is not currently possible to positively identify the creators of the earliest stone tools here or at Gona, even though A. garhi is currently the only recognized hominid [hominin] taxon recovered from Hata sediments." Existence of stone tools is also evidenced by bones of large mammals—such as alcelaphinae (Wildebeest related bovids ) and Hipparion , an extinct genus of three-toed horse—that show butchery cut marks by hominins including those made in removing an animal's tongue. "These are

4416-410: The Pliocene. By the late Miocene, around 10 Mya, the bovids rapidly diversified , leading to the creation of 70 new genera. This late Miocene radiation was partly because many bovids became adapted to more open, grassland habitats. The Aepycerotinae first appeared in the late Miocene, and no significant difference in the sizes of the primitive and modern impala has been noted. Fossils of ovibovines,

4508-440: The afternoon. Temperature is regulated through sweating in cattle, whereas goats use panting for the same. The right lung , consisting of four to five lobes , is around 1.5 times larger than the left, which has three lobes. Most bovids bear 30 to 32 teeth. While the upper incisors are absent, the upper canines are either reduced or absent. Instead of the upper incisors, bovids have a thick and tough layer of tissue, called

4600-417: The beginning of the 21st century it was understood that the family Moschidae (musk deer) was sister to Cervidae . However, a 2003 phylogenetic study by Alexandre Hassanin (of National Museum of Natural History, France ) and colleagues, based on mitochondrial and nuclear analyses, revealed that Moschidae and Bovidae form a clade sister to Cervidae . According to the study, Cervidae diverged from

4692-403: The brittle upper crust reacts by fracture – instantaneous stress release – resulting in motion along the fault. A fault in ductile rocks can also release instantaneously when the strain rate is too great. Slip is defined as the relative movement of geological features present on either side of a fault plane. A fault's sense of slip is defined as the relative motion of the rock on each side of

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4784-422: The cause of most earthquakes . Faults may also displace slowly, by aseismic creep . A fault plane is the plane that represents the fracture surface of a fault. A fault trace or fault line is a place where the fault can be seen or mapped on the surface. A fault trace is also the line commonly plotted on geologic maps to represent a fault. A fault zone is a cluster of parallel faults. However,

4876-409: The complex cellulose into simpler fatty acids , which are then absorbed through the rumen wall. Bovids have a long small intestine ; the length of the small intestine in cattle is 29–49 m (95–161 ft). Body temperature fluctuates through the day; for instance, in goats the temperature can change slightly from nearly 37 °C (99 °F) in the early morning to 40 °C (104 °F) in

4968-592: The day. While small bovids forage in dense and closed habitat, larger species feed on high-fiber vegetation in open grasslands. Most bovids are polygynous . Mature bovids mate at least once a year and smaller species may even mate twice. In some species, neonate bovids remain hidden for a week to two months, regularly nursed by their mothers; in other species, neonates are followers, accompanying their dams, rather than tending to remain hidden. The greatest diversities of bovids occur in Africa . The maximum concentration of species

5060-436: The direction of slip, faults can be categorized as: In a strike-slip fault (also known as a wrench fault , tear fault or transcurrent fault ), the fault surface (plane) is usually near vertical, and the footwall moves laterally either left or right with very little vertical motion. Strike-slip faults with left-lateral motion are also known as sinistral faults and those with right-lateral motion as dextral faults. Each

5152-506: The duiker browse for a few hours during day or night. Feeding habits are related to body size; while small bovids forage in dense and closed habitat, larger species feed upon high-fiber vegetation in open grasslands. Subfamilies exhibit different feeding strategies. While Bovinae species graze extensively on fresh grass and diffused forage, Cephalophinae species (with the exception of Sylvicapra ) primarily consume fruits. Reduncinae and Hippotraginae species depend on unstable food sources, but

5244-437: The earliest documented percussion marks made by hominids [hominins], who were presumably processing these bones for contained fatty marrow"; and, "These are the earliest documented cut marks made by hominids [hominins]." As concluded by the excavators, the evidence from the site shows "..a major function of the earliest known tools was meat and marrow processing of large carcasses." This pattern of butchery processing of large prey

5336-492: The earliest known bovid, weighed 18 kg (40 lb) and was nearly the same in size as the Thomson's gazelle . Early in their evolutionary history, the bovids split into two main clades: Boodontia (of Eurasian origin) and Aegodontia (of African origin). This early split between Boodontia and Aegodontia has been attributed to the continental divide between these land masses. When these continents were later rejoined, this barrier

5428-510: The early Pliocene; their latest fossils were excavated in Langebaanweg (South Africa) and Lothagam (Kenya). The middle Miocene marked the spread of the bovids into China and the Indian subcontinent. According to Vrba, the radiation of the subfamily Alcelaphinae began in the latter part of middle Miocene. The Caprinae tribes probably diverged in the early middle Miocene. The Caprini emerged in

5520-438: The entire occipital region surrounding the foramen magnum, and the edges of this broken region are smooth and polished, as are the specimen’s unweathered parietal surfaces." Ethnographic study upon modern cultures suggests that such post-mortem manipulation could be due to "..curation of human remains as part of mortuary practices". Fault (geology) In geology , a fault is a planar fracture or discontinuity in

5612-723: The exception of migratory males, males generally hold the same territory throughout their lives. In the waterbuck, some male individuals, known as "satellite males", may be allowed into the territories of other males and have to wait till the owner grows old so they may acquire his territory. Lek mating , where males gather together and competitively display to potential mates, is known to exist among topis , kobs , and lechwes . The tragelaphines, cattle, sheep, and goats are gregarious and not territorial. In these species, males must gain absolute dominance over all other males, and fights are not confined to territories. Males, therefore, spend years in body growth. Most bovids are diurnal, although

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5704-647: The family are herbivorous , but most duikers are omnivorous . Like other ruminants, bovids have four-chambered stomachs, which allow them to digest plant material, such as grass , that cannot be used by many other animals. Ruminants (and some others like kangaroos , rabbits , and termites ) are able to use micro-organisms living in their guts to break down cellulose by fermentation . The bovids have various methods of social organisation and social behaviour, which are classified into solitary and gregarious behaviour. Further, these types may each be divided into territorial and nonterritorial behaviour. Small bovids such as

5796-456: The fault and of the presence and nature of any mineralising fluids . Fault rocks are classified by their textures and the implied mechanism of deformation. A fault that passes through different levels of the lithosphere will have many different types of fault rock developed along its surface. Continued dip-slip displacement tends to juxtapose fault rocks characteristic of different crustal levels, with varying degrees of overprinting. This effect

5888-402: The fault concerning the other side. In measuring the horizontal or vertical separation, the throw of the fault is the vertical component of the separation and the heave of the fault is the horizontal component, as in "Throw up and heave out". The vector of slip can be qualitatively assessed by studying any drag folding of strata, which may be visible on either side of the fault. Drag folding

5980-569: The fault plane and a vertical plane that strikes parallel to the fault. Ring faults , also known as caldera faults , are faults that occur within collapsed volcanic calderas and the sites of bolide strikes, such as the Chesapeake Bay impact crater . Ring faults are the result of a series of overlapping normal faults, forming a circular outline. Fractures created by ring faults may be filled by ring dikes . Synthetic and antithetic are terms used to describe minor faults associated with

6072-401: The fault plane, the horizontal extensional displacement on a listric fault implies a geometric "gap" between the hanging and footwalls of the fault forms when the slip motion occurs. To accommodate into the geometric gap, and depending on its rheology , the hanging wall might fold and slide downwards into the gap and produce rollover folding , or break into further faults and blocks which fil in

6164-427: The fault-bend fold diagram. Thrust faults form nappes and klippen in the large thrust belts. Subduction zones are a special class of thrusts that form the largest faults on Earth and give rise to the largest earthquakes. A fault which has a component of dip-slip and a component of strike-slip is termed an oblique-slip fault . Nearly all faults have some component of both dip-slip and strike-slip; hence, defining

6256-475: The gap. If faults form, imbrication fans or domino faulting may form. A reverse fault is the opposite of a normal fault—the hanging wall moves up relative to the footwall. Reverse faults indicate compressive shortening of the crust. A thrust fault has the same sense of motion as a reverse fault, but with the dip of the fault plane at less than 45°. Thrust faults typically form ramps, flats and fault-bend (hanging wall and footwall) folds. A section of

6348-501: The ground. The bovids show great variation in size: the gaur can weigh more than 1,500 kg (3,300 lb), and stand 2.2 m (87 in) high at the shoulder. The royal antelope , in sharp contrast, is only 25 cm (9.8 in) tall and weighs at most 3 kg (6.6 lb). The klipspringer , another small antelope, stands 45–60 cm (18–24 in) at the shoulder and weighs just 10–20 kg (22–44 lb). Differences occur in pelage colouration, ranging from

6440-671: The horns vary greatly, but the basic structure is always one or more pairs of simple bony protrusions without branches, often having a spiral, twisted or fluted form, each covered in a permanent sheath of keratin . Most bovids bear 30 to 32 teeth. Most bovids are diurnal . Social activity and feeding usually peak during dawn and dusk. Bovids typically rest before dawn, during midday, and after dark. They have various methods of social organisation and social behaviour , which are classified into solitary and gregarious behaviour. Bovids use different forms of vocal, olfactory, and tangible communication. Most species alternately feed and ruminate throughout

6532-679: The human fossils and tools found in the Upper layer. The Upper layer is topped by a volcanic tuff. Two volcanic layers of very fine ash occur, one just below the hominin fossils and one just above; this important feature allows accurate argon–argon dating of adjacent sedimentary layers and their fossils, as reported above. This is valuable "..because the accurate dating of faunas and artefacts of many sites of this general antiquity in Pleistocene Africa has proved notoriously difficult." In this layer have been found early Middle Stone Age (MSA) tools and

6624-482: The klipspringer, oribi , and steenbok are generally solitary and territorial. They hold small territories into which other members of the species are not allowed to enter. These antelopes form monogamous pairs. Many species such as the dik-dik use pheromone secretions from the preorbital glands and sometimes dung, as well, to mark their territories. The offspring disperse at the time of adolescence, and males must acquire territories prior to mating. The bushbuck

6716-488: The length and breath of the peninsula. The formation consists of three geological units , called members, from which fossils and artifacts of different periods of human evolution have been excavated. They are: the lowest member, named Hatayae, or the Hata, dated to 2.5 million years ago (mya)—and in which fossils of Australopithecus garhi were found; the Dakanihylo, or Daka, member, one mya—fossils of Homo erectus were found; and

6808-494: The middle Miocene, and seem to have been replaced by other bovids and cervids in Eurasia. The earliest fossils of the antilopines are from the middle Miocene, though studies show the existence of the subfamily from the early Miocene. Speciation occurred in the tribe Antilopini during the middle or upper Miocene, mainly in Eurasia. Tribe Neotragini seems to have appeared in Africa by the end of Miocene, and had become widespread by

6900-431: The monogamous duikers and other small antelopes, whereas in the polygynous, they are large and elaborately formed (for example in a spiral structure, as in the giant eland ). Thus, to some extent, horns depict the degree of competition among males in a species. However, the presence of horns in females is likely due to natural selection . The horns of females are usually smaller than those of males, and are sometimes of

6992-413: The opponent's head rather than its body. The S-shaped horns, such as those on the impala , have various sections that help in ramming, holding, and stabbing. Serious fights leading to injury are rare. Most bovids alternately feed and ruminate throughout the day. While those that feed on concentrate feed and digest in short intervals, the roughage feeders take longer intervals. Only small species such as

7084-429: The opponents move in a circular manner to unlock them. Muskoxen will ram into each other at high speeds. As a rule, only two bovids of equal build and level of defence engage in a fight, which is intended to determine the superior of the two. Individuals that are evidently inferior to others would rather flee than fight; for example, immature males do not fight with the mature bulls. Generally, bovids direct their attacks on

7176-500: The original movement (fault inversion). In such a way, a normal fault may therefore become a reverse fault and vice versa. In a normal fault, the hanging wall moves downward, relative to the footwall. The dip of most normal faults is at least 60 degrees but some normal faults dip at less than 45 degrees. A downthrown block between two normal faults dipping towards each other is a graben . A block stranded between two grabens, and therefore two normal faults dipping away from each other,

7268-442: The oval or pointed ears, a distinct neck and limbs, and a tail varying in length and bushiness among the species. Most bovids exhibit sexual dimorphism , with males usually larger as well as heavier than females. Sexual dimorphism is more prominent in medium- to large-sized bovids. All bovids have four toes on each foot – they walk on the central two (the hooves ), while the outer two (the dewclaws ) are much smaller and rarely touch

7360-498: The predator has been seen, and that the stotting individual is strong and not worth chasing. In the mating season, rutting males bellow to make their presence known to females. Muskoxen roar during male-male fights, and male saigas force air through their noses, producing a roar to deter rival males and attract females. Mothers also use vocal communication to locate their calves if they get separated. During fights over dominance, males tend to display themselves in an erect posture with

7452-477: The recognition of Peleinae and Pantholopinae , comprising the genera Pelea and Pantholops respectively, as subfamilies . In 2000, American biologist George Schaller and palaeontologist Elisabeth Vrba suggested the inclusion of Pelea in Reduncinae , though the grey rhebok, the sole species of Pelea , is highly different from kobs and reduncines in morphology. Pantholops , earlier classified in

7544-766: The remains of Homo sapiens idaltu . Most of the tools are scrapers , cleavers, and various lithic cores ; but hand axes, picks and blades are rare. Most stone tools are made of fine-grained basalt except for points and blades made from obsidian . Many are made with the Levallois technique ; these are comparable to those found in the Garba III layer at Melka Kunture . As at Herto, Garba III includes terminal Acheulean hand axes, typical Levalloisian method, and many retouched tools on flakes (side-scrapers and end-scrapers, backed knives, burins, unifacial and bifacial points). The Garba III assemblage has been considered transitional between

7636-412: The right time for—and type of— igneous differentiation . At a given time differentiated magmas would burst violently out of the fault-traps and head to shallower places in the crust where porphyry copper deposits would be formed. As faults are zones of weakness, they facilitate the interaction of water with the surrounding rock and enhance chemical weathering . The enhanced chemical weathering increases

7728-425: The sedimentary deposits via Argon–argon dating . The Hatayae layer is 40 m thick at its base and is composed of variegated silt clay and paleosols , zeolitic and bentonitic tuffs, carbonates that are pedogenic , sandstone with bivalve and gastropod shells, and mudstone . It was deposited in a floodplain alongside river delta channels and a shallow fluctuating lake dated to around 2.5 mya. In

7820-410: The size of the weathered zone and hence creates more space for groundwater . Fault zones act as aquifers and also assist groundwater transport. Bovid Alternate taxonomy: The Bovidae comprise the biological family of cloven-hoofed , ruminant mammals that includes cattle , bison , buffalo , antelopes (including goat-antelopes ), sheep and goats . A member of this family

7912-463: The strongly contrasting patterns helping to delay recognition by predators. However, all the Hippotraginae (including the gemsbok) have pale bodies and faces with conspicuous markings. The zoologist Tim Caro describes this as difficult to explain, but given that the species are diurnal, he suggests that the markings may function in communication. Strongly contrasting leg colouration is common only in

8004-709: The subfamily Tethytraginae , which contains Tethytragus (mid- Miocene ). In 1992, Alan W . Gentry of the Natural History Museum, London divided the eight major subfamilies of Bovidae into two major clades on the basis of their evolutionary history: the Boodontia, which comprised only the Bovinae, and the Aegodontia, which consisted of the rest of the subfamilies. Boodonts have somewhat primitive teeth, resembling those of oxen , whereas aegodonts have more advanced teeth like those of goats. A controversy exists about

8096-468: The term is also used for the zone of crushed rock along a single fault. Prolonged motion along closely spaced faults can blur the distinction, as the rock between the faults is converted to fault-bound lenses of rock and then progressively crushed. Due to friction and the rigidity of the constituent rocks, the two sides of a fault cannot always glide or flow past each other easily, and so occasionally all movement stops. The regions of higher friction along

8188-405: The third and fourth metapodials are combined into the cannon bone . The ulna and fibula are reduced, and fused with the radius and tibia, respectively. Long scapulae are present, whereas the clavicles are absent. Being ruminants , the stomach is composed of four chambers: the rumen (80%), the omasum , the reticulum , and the abomasum . The ciliates and bacteria of the rumen ferment

8280-493: Was given by the British zoologist John Edward Gray in 1821. The word "Bovidae" is the combination of the prefix bov- (originating from Latin bos , "ox", through Late Latin bovinus ) and the suffix -idae . The family Bovidae is placed in the order Artiodactyla (which includes the even-toed ungulates ). It includes 143 extant species, accounting for nearly 55% of the ungulates , and 300 known extinct species. Until

8372-536: Was maintained by hominins well into the Pliocene. The Dakanihylo (Daka) layer is 22 to 45 m thick and composed of pumice sandstone that is cross-bedded ; it is situated in the southern half of the Bouri horst and dated to 1 mya. Fossils found in the layer suggest open grassland—some 377 species of bovids (including three new species and two new genera); and water-margin habitats—species of Kobus antelope and abundant Hippopotamus . Early Acheulean stone tools such as hand axes and cleavers have also been found in

8464-605: Was removed, and both groups expanded into the territory of the other. The tribes Bovini and Tragelaphini diverged in the early Miocene. Bovids are known to have reached the Americas in the Pleistocene by crossing the Bering land bridge . The present genera of Alcelaphinae appeared in the Pliocene . The extinct Alcelaphine genus Paramularius , which was the same in size as the hartebeest,

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