A waterfall is an area where water flows over a vertical drop or a series of steep drops in the course of a stream or river. Waterfalls occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls are formed in the upper course of a river in steep mountains; because of their landscape position, many waterfalls occur over bedrock fed by little contributing area, so may be ephemeral and flow only during rainstorms or significant snowmelt. The further downstream, the more perennial a waterfall can be. Waterfalls can have a wide range of depths; when the river courses over resistant bedrock, erosion happens and is dominated by impacts of water-borne sediment on the rock, while downstream the erosion occurs more rapidly. As the watercourse increases its velocity at the edge of the waterfall, it may pluck material from the riverbed, if the bed is fractured or otherwise more erodible. Hydraulic jets and hydraulic jumps at the toe of a falls can generate large forces to erode the bed when forces are amplified by water-borne sediment.
Horseshoe-shaped falls focus the erosion to a central point enhancing riverbed change below a waterfalls. A process known as "potholing" involves local erosion of a deep hole in bedrock due to turbulent whirlpools spinning stones around on the bed, drilling it out. Sand and stones carried by the watercourse therefore increase erosion capacity; this causes the waterfall to recede upstream. Over time, the waterfall will recede back to form a canyon or gorge downstream as it recedes upstream, it will carve deeper into the ridge above it; the rate of retreat for a waterfall can be as high as one-and-a-half metres per year. The rock stratum just below the more resistant shelf will be of a softer type, meaning that undercutting due to splashback will occur here to form a shallow cave-like formation known as a rock shelter under and behind the waterfall; the outcropping, more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. These blocks of rock are broken down into smaller boulders by attrition as they collide with each other, they erode the base of the waterfall by abrasion, creating a deep plunge pool in the gorge downstream.
Streams can become wider and shallower just above waterfalls due to flowing over the rock shelf, there is a deep area just below the waterfall because of the kinetic energy of the water hitting the bottom. However, a study of waterfalls systematics reported that waterfalls can be wider or narrower above or below a falls, so anything is possible given the right geological and hydrological setting. Waterfalls form in a rocky area due to erosion. After a long period of being formed, the water falling off the ledge will retreat, causing a horizontal pit parallel to the waterfall wall; as the pit grows deeper, the waterfall collapses to be replaced by a steeply sloping stretch of river bed. In addition to gradual processes such as erosion, earth movement caused by earthquakes or landslides or volcanoes can cause a differential in land heights which interfere with the natural course of a water flow, result in waterfalls. A river sometimes flows over a large step in the rocks. Waterfalls can occur along the edge of a glacial trough, where a stream or river flowing into a glacier continues to flow into a valley after the glacier has receded or melted.
The large waterfalls in Yosemite Valley are examples of this phenomenon, referred to as a hanging valley. Another reason hanging valleys may form is where two rivers join and one is flowing faster than the other. Waterfalls can be grouped into ten broad classes based on the average volume of water present on the fall using a logarithmic scale. Class 10 waterfalls include Paulo Afonso Falls and Khone Falls. Classes of other well-known waterfalls include Kaieteur Falls. Alexander von Humboldt "Father of Modern Geography" Humboldt was marking waterfalls on maps for river navigation purposes. Oscar von Engeln Published "Geomorphology: systematic and regional", this book had a whole chapter devoted to waterfalls, is one of the earliest examples of published works on waterfalls. R. W. Young Wrote "Waterfalls: form and process" this work made waterfalls a much more serious topic for research for modern Geoscientists. Ledge waterfall: Water descends vertically over a vertical cliff, maintaining partial contact with the bedrock.
Block/Sheet: Water descends from a wide stream or river. Classical: Ledge waterfalls where fall height is nearly equal to stream width, forming a vertical square shape. Curtain: Ledge waterfalls which descend over a height larger than the width of falling water stream. Plunge: Fast-moving water descends vertically, losing complete contact with the bedrock surface; the contact is lost due to horizontal velocity of the water before it falls. It always starts from a narrow stream. Punchbowl: Water descends in a constricted form and spreads out in a wider pool. Horsetail: Descending water maintains contact with bedrock most of the time. Slide: Water glides down maintaining continuous contact. Ribbon: Water descends over a long narrow strip. Chute: A large quantity of water forced through a narrow, vertical passage. Fan: Water spreads horizontally as
Lake Tanganyika is an African Great Lake. It is the second oldest freshwater lake in the world, the second largest by volume, the second deepest, in all cases after Lake Baikal in Siberia, it is the world's longest freshwater lake. The lake is divided among four countries – Tanzania, Democratic Republic of the Congo and Zambia, with Tanzania and DRC possessing the majority of the lake; the water flows into the Congo River system and into the Atlantic Ocean. The name'Tanganyika' refers to'the great lake spreading out like a plain', or'plain-like lake'." Lake Tanganyika is situated within the Albertine Rift, the western branch of the East African Rift, is confined by the mountainous walls of the valley. It is the second largest lake by volume in the world, it is the deepest lake in Africa and holds the greatest volume of fresh water, accounting for 16% of the world's available fresh water. It extends for 676 km in averages 50 km in width; the lake covers 32,900 km2, with a shoreline of 1,828 km, a mean depth of 570 m and a maximum depth of 1,470 m.
It holds an estimated 18,900 cubic kilometres. The catchment area of the lake is 231,000 km2. Two main rivers streams. There is the Lukuga River, which empties into the Congo River drainage; the major river flowing into the lake is the Ruzizi River, formed about 10,000 years ago, which enters the north of the lake from Lake Kivu. The Malagarasi River, Tanzania's second largest river, enters the east side of Lake Tanganyika; the Malagarasi is older than Lake Tanganyika and, before the lake was formed, directly drained into the Congo River. The lake has a complex history of changing flow patterns, due to its high altitude, great depth, slow rate of refill and mountainous location in a turbulently volcanic area that has undergone climate changes, it has in the past had an outflow to the sea. It has been described as'practically endorheic' for this reason; the lake's connection to the sea is dependent on a high water level allowing water to overflow out of the lake through the Lukunga into the Congo.
Due to the lake's tropical location, it has a high rate of evaporation. Thus it depends on a high inflow through the Ruzizi out of Lake Kivu to keep the lake high enough to overflow; this outflow is not more than 12,000 years old, resulted from lava flows blocking and diverting the Kivu basin's previous outflow into Lake Edward and the Nile system, diverting it to Lake Tanganyika. Signs of ancient shorelines indicate that at times Tanganyika may have been up to 300 m lower than its present surface level, with no outlet to the sea, its current outlet is intermittent and thus may not have been operating when first visited by Western explorers in 1858. The lake may have at times had different inflows and outflows: inward flows from a higher Lake Rukwa, access to Lake Malawi and an exit route to the Nile have all been proposed to have existed at some point in the lake's history. Lake Tanganyika is an ancient lake, its three basins, which in periods with much lower water levels were separate lakes, are of different ages.
The central began to form 9 -- 12 million years ago, the northern 7 -- the southern 2 -- 4 mya. There are several islands in Lake Tanganyika; the most important of them are: Kavala Island Mamba-Kayenda Islands Milima Island Kibishie Island Mutondwe Island Kumbula Island The lake's water is alkaline with a pH of around 9 at depths of 0–100 m. Below this it is around 8.7 decreasing to 8.3—8.5 in the deepest parts of Tanganyika. A similar pattern can be seen in the electric conductivity, ranging from about 670 μS/cm in the upper part to 690 μS/cm in the deepest. Surface temperatures range from about 24 °C in the southern part of the lake in early August to 28–29 °C in the late rainy season in March—April. At depths greater than 400 m the temperature is stable at 23.1–23.4 °C. The water has warmed since the 1800s and this has accelerated with global warming since the 1950s; the lake is stratified and seasonal mixing does not extend beyond depths of 150 m. The mixing occurs as upwellings in the south and is wind-driven, but to a lesser extent there are up- and downwellings elsewhere in the lake.
As a consequence of the stratification, the deep sections contain "fossil water". This means that there is no oxygen in the deeper parts limiting fish and other aerobic organisms to the upper part. There are some geographical variations in this limit, but it is at depths of around 100 m in the northern part of the lake and 240–250 m in the south; the oxygen-devoid deepest sections contain high levels of toxic hydrogen sulphide and are lifeless, except for bacteria. Lake Tanganyika and associated wetlands are home to Nile crocodiles, Zambian hinged terrapins, serrated hinged terrapins and pan hinged terrapins; the Storm's water cobra, a threatened subspecies of banded water cobra that feeds on fish, is only found in Lake Tanganyika where it prefers rocky shores. The lake holds at least 250 species of cichlid fish and undescribe
The marabou stork is a large wading bird in the stork family Ciconiidae. It breeds in Africa south of the Sahara, in both wet and arid habitats near human habitation landfill sites, it is sometimes called the "undertaker bird" due to its shape from behind: cloak-like wings and back, skinny white legs, sometimes a large white mass of "hair". The name marabou is thought to be derived from the Arabic word murābit meaning hermit-like; the species was described in the stork genus Ciconia as Ciconia crumenifera by Lesson. The species was moved into the genus Leptoptilos and the ending was modified to crumeniferus and used by many authors until it was noted that the correct masculine ending to match the genus is crumenifer; the marabou stork is a massive bird: large specimens are thought to reach a height of 152 cm and a weight of 9 kg. A wingspan of 3.7 m was accepted by Fisher and Peterson, who ranked the species as having the largest wing-spread of any living bird. Higher measurements of up to 4.06 m have been reported, although no measurement over 3.20 m has been verified.
It is credited with the largest spread of any landbird, to rival the Andean condor. Typical weight is 4.5–8 kg, unusually as low as 4 kg, length is 120 to 130 cm. Females are smaller than males. Bill length can range from 26.4 to 35 cm. Unlike most storks, the three Leptoptilos species fly; the marabou is unmistakable due to its size, bare head and neck, black back, white underparts. It has a huge bill, a pink gular sac at its throat, a neck ruff, black legs and wings; the sexes are alike. Full maturity is not reached for up to four years. Like most storks, the marabou is a colonial breeder. In the African dry season, it builds a tree nest in which three eggs are laid, it is known to be quite ill-tempered. It resembles other storks in that it is not vocal, but indulges in bill-rattling courtship displays; the throat sac is used to make various noises at that time. The marabou stork breeds starting during the dry season; the female lays two to three of eggs in a small nest made of sticks. Their young reach sexual maturity at 4 years of age.
Lifespan is 25 years in wild. The marabou stork is a frequent scavenger, the naked head and neck are adaptations to this livelihood, as it is with the vultures with which the stork feeds. In both cases, a feathered head would become clotted with blood and other substances when the bird's head was inside a large corpse, the bare head is easier to keep clean; this large and powerful bird eats carrion and faeces but will opportunistically eat any animal matter it can swallow. It eats other birds including quelea nestlings, doves and cormorant chicks, flamingos. During the breeding season, adults scale back on carrion and take small, live prey since nestlings need this kind of food to survive. Common prey at this time may consist of fish, insects, small mammals and reptiles such as crocodile hatchlings and eggs, lizards and snakes. Though known to eat putrid and inedible foods, these storks may sometimes wash food in water to remove soil; when feeding on carrion, marabou follow vultures, which are better equipped with hooked bills for tearing through carrion meat and may wait for the vultures to cast aside a piece, steal a piece of meat directly from the vulture or wait until the vultures are done.
As with vultures, marabou storks perform an important natural function by cleaning areas via their ingestion of carrion and waste. Marabous have become dependent on human garbage and hundreds of the huge birds can be found around African dumps or waiting for a hand out in urban areas. Marabous eating human garbage have been seen to devour anything that they can swallow, including shoes and pieces of metal. Marabous conditioned to eating from human sources have been known to lash out. A number of endoparasites have been identified in wild marabous including Cheilospirura and Acuaria nematodes, Amoebotaenia sphenoides and Dicrocoelium hospes. Marabou down is used in the trimming of various items of clothing and hats, as well as fishing lures. Turkey down and similar feathers have been used as a substitute for making'marabou' trimming. Marabou Stork - The Atlas of Southern African Birds
The Oldowan is the earliest widespread stone tool archaeological industry in prehistory. These early tools were simple made with one or a few flakes chipped off with another stone. Oldowan tools were used during the Lower Paleolithic period, 2.6 million years ago up until 1.7 million years ago, by ancient Hominin across much of Africa, South Asia, the Middle East and Europe. This technological industry was followed by the more sophisticated Acheulean industry. Oldowan is pre-dated by Lomekwian tools at a single site dated to 3.3 mya. It is not clear; the term Oldowan is taken from the site of Olduvai Gorge in Tanzania, where the first Oldowan lithics were discovered by the archaeologist Louis Leakey in the 1930s. However, some contemporary archaeologists and palaeoanthropologists prefer to use the term Mode 1 tools to designate pebble tool industries, with Mode 2 designating bifacially worked tools, Mode 3 designating prepared-core tools, so forth. Classification of Oldowan tools is still somewhat contentious.
Mary Leakey was the first to create a system to classify Oldowan assemblages, built her system based on prescribed use. The system included choppers and pounders. However, more recent classifications of Oldowan assemblages have been made that focus on manufacture due to the problematic nature of assuming use from stone artefacts. An example is Isaac et al.'s tri-modal categories of "Flaked Pieces", "Detached Pieces", "Pounded Pieces" and "Unmodified Pieces". Oldowan tools are sometimes called "pebble tools", so named because the blanks chosen for their production resemble, in pebble form, the final product, it is not known for sure which hominin species used Oldowan tools. Its emergence is associated with the species Australopithecus garhi and its flourishing with early species of Homo such as H. habilis and H. ergaster. Early Homo erectus appears to inherit Oldowan technology and refines it into the Acheulean industry beginning 1.7 million years ago. The oldest known Oldowan tools have been found in Gona and are dated to about 2.6 mya.
The use of tools by apes including chimpanzees and orangutans can be used to argue in favour of tool-use as an ancestral feature of the hominin family. Tools made from bone, wood, or other organic materials were therefore in all probability used before the Oldowan. Oldowan stone tools are the oldest recognisable tools which have been preserved in the archaeological record. There is a flourishing of Oldowan tools in eastern Africa, spreading to southern Africa, between 2.4 and 1.7 mya. At 1.7 mya. the first Acheulean tools appear as Oldowan assemblages continue to be produced. Both technologies are found in the same areas, dating to the same time periods; this realisation required a rethinking of old cultural sequences in which the more "advanced" Acheulean was supposed to have succeeded the Oldowan. The different traditions may have been used by different species of hominins living in the same area, or multiple techniques may have been used by an individual species in response to different circumstances.
Sometime before 1.8 mya Homo erectus had spread outside of Africa, reaching as far east as Java by 1.8 mya and in Northern China by 1.66 mya. In these newly colonised areas, no Acheulean assemblages have been found. In China, only "Mode 1" Oldowan assemblages were produced, while in Indonesia stone tools from this age are unknown. By 1.8 mya early Homo was present in Europe, as shown by the discovery of fossil remains and Oldowan tools in Dmanisi, Georgia. Remains of their activities have been excavated in Spain at sites in the Guadix-Baza basin and near Atapuerca. Most early European sites yield "Mode 1" or Oldowan assemblages; the earliest Acheulean sites in Europe only appear around 0.5 mya. In addition, the Acheulean tradition does not seem to spread to Eastern Asia, it is unclear from the archaeological record. Other tool-making traditions seem to have supplanted Oldowan technologies by 0.25 mya. To obtain an Oldowan tool, a spherical hammerstone is struck on the edge, or striking platform, of a suitable core rock to produce a conchoidal fracture with sharp edges useful for various purposes.
The process is called lithic reduction. The chip removed by the blow is the flake. Below the point of impact on the core is a characteristic bulb with fine fissures on the fracture surface; the flake evidences ripple marks. The materials of the tools were for the most part quartz, basalt, or obsidian, flint and chert. Any rock that can hold an edge will do; the main source of these rocks is river cobbles, which provide both hammer stones and striking platforms. The earliest tools were split cobbles, it is not always clear, the flake. Tool-makers identified and reworked flakes. Complaints that artifacts could not be distinguished from fractured stone have helped spark careful studies of Oldowon techniques; these techniques have now been duplicated many times by archaeologists and other knappers, making misidentification of archaeological finds less likely. Use of bone tools by hominins producing Oldowan tools is known from Swartkrans, where a bone shaft with a polished point was discovered in Member I, dated 1.8–1.5 mya.
The Osteodontokeratic industry, the "bone-tooth-horn" industry hypothesized by Raymond Dart, is less certain. Mary Leakey classified the Oldowan tools as Heavy Duty, Light Duty, Utilized Pieces and Debitage, or waste. Heav
J. Desmond Clark
John Desmond Clark was a British archaeologist noted for his work on prehistoric Africa. Clark was born in London, but his childhood was spent in a hamlet in the Chiltern Hills of Buckinghamshire. Clark went to a preparatory boarding school in Buckinghamshire at age 6 1/2, from where he moved on to Monkton Combe School near Bath. Clark graduated with a B. A. from Christ's College, under Miles Burkitt and Grahame Clark. In 1937 Clark became the curator of Northern Rhodesia's Rhodes-Livingstone Museum. A year he married Betty Cable née Baume, who would accompany him on a number of expeditions throughout his life. Clark served in the military during World War II with the East Africa Command forces in Somalia and Ethiopia, being subsequently attached to the British Military Administration, when he managed to find time to carry out archaeological fieldwork in the Horn of Africa. Following the war, he returned to Cambridge, completing his Ph. D. in 1947. In 1948 he founded the Northern Rhodesian National Monuments Commission.
Clark returned to Northern Rhodesia to serve once more as the Museum's director. In 1953, Clark ordered an excavation at Kalambo Falls, a 235m high, single-drop waterfall at the southeast end of Lake Tanganyika, on what is now the border between Zambia and Tanzania; the site would emerge as one of the most important archaeological finds of the twentieth century, providing a record of more than two hundred and fifty thousand years of human history. To date, artifacts of Acheulean, Lupemban, Magosian and Bantu cultures have all been found at the falls. Clark undertook significant fieldwork in Ethiopia, Malawi and Niger, some of which led him to collaborate with Louis and Mary Leakey. In 1961, Clark resigned from his post as Director of the Museum, became Professor of Anthropology at the University of California, where he taught until his retirement in 1986. Under his guidance, the programme became one of the world's foremost in paleoanthropology. In 1965, he was elected a Fellow of the American Academy of Sciences.
He received the Gold Medal Award for Distinguished Archaeological Achievement in 1988 from the Archaeological Institute of America. Clark continued working until his death, including a 1991 dig in China, the first to be led in that country by foreign archaeologists in more than 40 years. Clark died of pneumonia in Oakland in 2002, having published more than twenty books and over 300 scholarly papers on paleoanthropology and African prehistory in the course of his career, his wife survived him by only two months. He is survived by his children and John. Clark was appointed OBE in 1956 and CBE in 1960, he was elected FSA in 1952 and FBA in 1961. He was a Fellow of the American Academy of Arts and Sciences, of the National Academy of Science, his Cambridge ScD was awarded in 1975 and honorary doctorates at Witwatersrand and Cape Town universities in 1985, along with the Gold Medals of the Society of Antiquaries of London and the Archaeological Institute of America. The British Academy awarded him the Grahame Clark Medal for Prehistory in 1997.
He became an American citizen in 1993. The Prehistoric Cultures of the Horn of Africa. University Press. 1954. The prehistory of Southern Africa. Penguin Books. 1959. Prehistoric Cultures of Northeast Angola and Their Significance in Tropical Africa Background to Evolution in Africa: Systematic Investigation of the African Later Tertiary and Quaternary. University of Chicago Press. 1967. With Walter W. Bishop Background to Evolution in Africa Atlas of African Prehistory Further Palaeo-Anthropological Studies in Northern Lunda Kalambo Falls Prehistoric Site The Prehistory of Africa J Desmond Clark, ed.. "From the Earliest Times to c. 500 B. C.". The Cambridge History of Africa. Vol 1. Cambridge University Press. ISBN 978-0-521-20701-0; the Acheulean and the Plio-Pleistocene Deposits of the Middle Awash Valley, Ethiopia See African Archaeological Review 5, 1987. The Pastmasters: Eleven Modern Pioneers of Archaeology. New York: Thames and Hudson. ISBN 0-500-05051-1. UC Berkeley obituary Leakey Foundation press release Journal of Anthropological Research Tribute National Academy of Sciences Biographical Memoir J. Desmond Clark Memorial Page
Homo habilis is a proposed archaic species of Homo, which lived between 2.1 and 1.5 million years ago, during the Gelasian and early Calabrian stages of the Pleistocene geological epoch. The type specimen is OH 7, discovered in 1960 at Olduvai Gorge in Tanzania, associated with the Oldowan lithic industry. In its appearance and morphology, H. habilis is intermediate between Australopithecus and the somewhat younger Homo erectus and its classification in the genus Homo has been the subject of controversial debate since its original proposal. A main argument for its classification as the first Homo species was its use of flaked stone tools. However, evidence for earlier tool use by undisputed members of Australopithecus has been found in the 1990s. In January 2019, scientists reported that Australopithecus sediba is distinct from, but shares anatomical similarities to, both the older Australopithecus africanus, the younger Homo habilis. There has been scholarly debate regarding its placement in the genus Homo rather than the genus Australopithecus.
The small size and rather primitive attributes have led some experts to propose excluding H. habilis from the genus Homo and placing them instead in Australopithecus as Australopithecus habilis. Louis Leakey, the British-Kenyan paleoanthropologist, the first to suggest the existence of H. habilis, his wife, Mary Leakey, found the first trace of H. habilis in 1955: two hominin teeth. These were classified as "milk teeth", therefore considered difficult to link to taxa, unlike permanent teeth. H. habilis had disproportionately long arms compared to modern humans. H. habilis had a cranial capacity less than half of the size of modern humans. Despite the ape-like morphology of the bodies, H. habilis remains are accompanied by primitive stone tools. Homo habilis has been thought to be the ancestor of the more gracile and sophisticated Homo ergaster, which in turn gave rise to the more human-appearing species, Homo erectus. Debates continue over whether all of the known fossils are properly attributed to the species, some paleoanthropologists regard the taxon as invalid, made up of fossil specimens of Australopithecus and Homo.
New findings in 2007 seemed to confirm the view that H. habilis and H. erectus coexisted, representing separate lineages from a common ancestor instead of H. erectus being descended from H. habilis. An alternative explanation would be that any ancestral relationship from H. habilis to H. erectus would have to have been cladogenetic rather than anagenetic. Discoveries at Dmanisi, which had diverse physical traits and differences in tooth wear, suggest to some scholars that all the contemporary groups of early Homo in Africa, including Homo ergaster, Homo habilis, Homo rudolfensis are of the same species and should be assigned to Homo erectus, with the implication that variation between these “species” represents the prolonged evolution of one lineage, rather than interspecific differences. H. habilis brain size has been shown to range from 550 cubic centimetres to 687 cubic centimetres, rather than from 363 cubic centimetres to 600 cubic centimetres as thought. A virtual reconstruction published in 2015 estimated the endocranial volume at between 729 millilitres and 824 millilitres, larger than any published value.
H. Habilis' brain capacity of around 640 cm³ was on average 50% larger than australopithecines, but smaller than the 1,350 cubic centimetres to 1,450 cubic centimetres range of modern Homo sapiens; these hominins were smaller on average standing no more than 1.3 metres. The body proportions for H. habilis are in accordance with craniodental evidence, suggesting closer association with H. erectus. Based on dental microwear-texture analysis, Homo habilis did not specialize on tough foods. Microwear-texture complexity is, on average, somewhere between that of tough-food feeders and leaf feeders These measurements are analyses of the percentages of tooth surface structure containing "pits", it is a used, henceforth accepted as reliable, measure of wear that a species, on average, endures from eating certain food. These measurements point to an generalized, omnivorous diet in Homo habilis. Homo habilis is thought to have mastered the Lower Paleolithic Olduwan tool set, which used stone flakes. H. habilis used these stones to skin animals.
These stone flakes were more advanced than any tools used, gave H. habilis the edge it needed to prosper in hostile environments too formidable for primates. Whether H. habilis was the first hominin to master stone tool technology remains controversial, as Australopithecus garhi, dated to 2.6 million years ago, has been found along with stone tool implements. Most experts assume the intelligence and social organization of H. habilis were more sophisticated than typical australopithecines
Palynology is the "study of dust" or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposits including sediments of any age; the condition and identification of those particles and inorganic, give the palynologist clues to the life and energetic conditions that produced them. The term is sometimes narrowly used to refer to a subset of the discipline, defined as "the study of microscopic objects of macromolecular organic composition, not capable of dissolution in hydrochloric or hydrofluoric acids", it is the science that studies contemporary and fossil palynomorphs, including pollen, orbicules, acritarchs and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments. Palynology does not include diatoms, foraminiferans or other organisms with siliceous or calcareous exoskeletons. Palynology as an interdisciplinary science stands at the intersection of earth science and biological science plant science.
Stratigraphical palynology, a branch of micropalaeontology and paleobotany, studies fossil palynomorphs from the Precambrian to the Holocene. The earliest reported observations of pollen under a microscope are to have been in the 1640s by the English botanist Nehemiah Grew, who described pollen and the stamen, concluded that pollen is required for sexual reproduction in flowering plants. By the late 1870s, as optical microscopes improved and the principles of stratigraphy were worked out, Robert Kidston and P. Reinsch were able to examine the presence of fossil spores in the Devonian and Carboniferous coal seams and make comparisons between the living spores and the ancient fossil spores. Early investigators include Gideon Mantell and Henry Hopley White. Quantitative analysis of pollen began with Lennart von Post's published work. Although he published in the Swedish language, his methodology gained a wide audience through his lectures. In particular, his Kristiania lecture of 1916 was important in gaining a wider audience.
Because the early investigations were published in the Nordic languages, the field of pollen analysis was confined to those countries. The isolation ended with the German publication of Gunnar Erdtman's 1921 thesis; the methodology of pollen analysis became widespread throughout Europe and North America and revolutionized Quaternary vegetation and climate change research. Earlier pollen researchers include Früh, who enumerated many common tree pollen types, a considerable number of spores and herb pollen grains. There is a study of pollen samples taken from sediments of Swedish lakes by Trybom. Georg F. L. Sarauw studied fossil pollen of middle Pleistocene age from the harbour of Copenhagen. Lagerheim and C. A. Weber appear to be among the first to undertake'percentage frequency' calculations; the term palynology was introduced by Hyde and Williams in 1944, following correspondence with the Swedish geologist Ernst Antevs, in the pages of the Pollen Analysis Circular. Hyde and Williams chose palynology on the basis of the Greek words paluno meaning'to sprinkle' and pale meaning'dust'.
Pollen analysis in North America stemmed from Phyllis Draper, an MS student under Sears at the University of Oklahoma. During her time as a student, she developed the first pollen diagram from a sample that depicted the percentage of several species at different depths at Curtis Bog; this was the introduction of pollen analysis in North America. Pollen analysis advanced in this period due to advances in optics and computers. Much of the science was revised by Knut Fægri in their textbook on the subject. Palynomorphs are broadly defined as organic-walled microfossils between 5 and 500 micrometres in size, they are extracted from sedimentary rocks and sediment cores both physically, by ultrasonic treatment and wet sieving, chemically, by chemical digestion to remove the non-organic fraction. Palynomorphs may be composed of organic material such as chitin and sporopollenin. Palynomorphs that have a taxonomy description are sometimes referred to as palynotaxa. Palynomorphs form a geological record of importance in determining the type of prehistoric life that existed at the time the sedimentary formation was laid down.
As a result, these microfossils give important clues to the prevailing climatic conditions of the time. Their paleontological utility derives from an abundance numbering in millions of cells per gram in organic marine deposits when such deposits are not fossiliferous. Palynomorphs, however have been destroyed in metamorphic or recrystallized rocks. Palynomorphs are dinoflagellate cysts, spores, fungi, arthropod organs and microforams. Palynomorph microscopic structures that are abundant in most sediments are resistant to routine pollen extraction including stron