Micropaleontology is the branch of palaeontology that studies microfossils, or fossils that require the use of a microscope to see the organism, its morphology and its characteristics details. Microfossils are fossils that are generally between 0. 001mm and 1 mm in size, the study of which requires the use of light or electron microscopy. Fossils which can be studied with the eye or low-powered magnification. For example, some organisms, such as Bryozoa have relatively large colonies. In another example, many genera of Foraminifera, which are protists are known from shells that were as big as coins. Microfossils are a feature of the geological record, from the Precambrian to the Holocene. They are most common in deposits of marine environments, but occur in water, fresh water. This division reflects differences in the mineralogical and chemical composition of microfossil remains rather than any strict taxonomic or ecological distinctions, most researchers in this field, known as micropaleontologists, are typically specialists in one or more taxonomic groups.
Calcareous microfossils include coccoliths, calcareous dinoflagellate cysts, phosphatic microfossils include conodonts, some scolecodonts, Shark spines and teeth, and other Fish remains. Siliceous microfossils include diatoms, silicoflagellates, phytoliths, some scolecodonts, the study of organic microfossils is called palynology. Organic microfossils include pollen, chitinozoans, acritarchs, dinoflagellate cysts, the resulting concentrated sample of microfossils is mounted on a slide for analysis, usually by light microscope. Taxa are identified and counted, the enormous numbers of microfossils that a small sediment sample can often yield allows the collection of statistically robust datasets which can be subjected to multivariate analysis. A typical microfossil study will involve identification of a few hundred specimens from each sample, Microfossils are especially noteworthy for their importance in biostratigraphy. Since microfossils are often abundant and quick to appear and disappear from the stratigraphic record.
Microfossils, particularly from deep-sea sediments, some of the most important records of global environmental change on long. Across vast areas of the floor, the shells of planktonic micro-organisms sinking from surface waters provide the dominant source of sediment. Study of changes in assemblages of microfossils and changes in their shell chemistry are fundamental to research on change in the geological past. Micropaleontology is a tool of geoarchaeology used in the reconstruction of human habitation sites
Plankton are organisms drifting in oceans and bodies of fresh water. The word zooplankton is derived from the Greek zoon, meaning animal, individual zooplankton are usually microscopic, but some are larger and visible with the naked eye. Zooplankton is a categorization spanning a range of organism sizes including small protozoans, although zooplankton are primarily transported by ambient water currents, many have locomotion, used to avoid predators or to increase prey encounter rate. Ecologically important protozoan zooplankton groups include the foraminiferans and dinoflagellates and this wide phylogenetic range includes a similarly wide range in feeding behavior, filter feeding and symbiosis with autotrophic phytoplankton as seen in corals. Zooplankton feed on bacterioplankton, other zooplankton, detritus, as a result, zooplankton are primarily found in surface waters where food resources are abundant. Just as any species can be limited within a geographical region, species of zooplankton are not dispersed uniformly or randomly within a region of the ocean.
As with phytoplankton, ‘patches’ of zooplankton species exist throughout the ocean, zooplankton patchiness can be influenced by biological factors, as well as other physical factors. Biological factors include breeding, concentration of phytoplankton, the physical factor that influences zooplankton distribution the most is mixing of the water column that affects nutrient availability and, in turn, phytoplankton production. Since they are small, zooplankton can respond rapidly to increases in phytoplankton abundance, for instance. Zooplankton can act as a disease reservoir, crustacean zooplankton have been found to house the bacterium Vibrio cholerae, which causes cholera, by allowing the cholera vibrios to attach to their chitinous exoskeletons. This symbiotic relationship enhances the ability to survive in an aquatic environment, as the exoskeleton provides the bacterium with carbon. A global coverage database of zooplankton biomass and abundance data
A micrometeoroid is a tiny meteoroid, a small particle of rock in space, usually weighing less than a gram. A micrometeorite is such a particle that survives passage through the Earths atmosphere, micrometeoroids are very small pieces of rock or metal broken off from larger chunks of rock and debris often dating back to the birth of the Solar System. Micrometeoroids are extremely common in space, tiny particles are a major contributor to space weathering processes. When they hit the surface of the Moon, or any airless body, in order to understand the micrometeoroid population better, a number of spacecraft have carried micrometeoroid detectors. In 1957 Hans Peterson conducted one of the first direct measurements of the fall of space dust on the Earth, if this were true, the Moon would be covered to a very great depth as there are limited forms of erosion to remove this material. In 1961 Arthur C. Clarke popularized this possibility in his novel A Fall of Moondust and this was cause for some concern among the groups attempting to land on the Moon, so a series of new studies followed to better characterize the issue.
This included the launch of spacecraft designed to directly measure the micrometeorite flux or directly measure the dust on the surface of the Moon. These showed that the flux was much lower than earlier estimates, around 10,000 to 20,000 tons per year, most lunar samples returned during the Apollo Program have micrometeorite impacts marks, typically called zap pits, on their upper surfaces. Micrometeoroids have less stable orbits than meteoroids, due to their surface area to mass ratio. Micrometeoroids that fall to Earth can provide information on millimeter scale heating events in the solar nebula and micrometeorites can only be collected in areas where there is no terrestrial sedimentation, typically polar regions. Ice is collected and melted and filtered so the micrometeorites can be extracted under a microscope, sufficiently small micrometeoroids avoid significant heating on entry into the Earths atmosphere. Micrometeoroids pose a significant threat to space exploration, the average velocity of micrometeoroids relative to a spacecraft in orbit is 10 kilometers per second.
Resistance to micrometeoroid impact is a significant design challenge for spacecraft, while the tiny sizes of most micrometeoroids limits the damage incurred, the high velocity impacts will constantly degrade the outer casing of spacecraft in a manner analogous to sandblasting. Long term exposure can threaten the functionality of spacecraft systems, impacts by small objects with extremely high velocity are a current area of research in terminal ballistics. The risk is high for objects in space for long periods of time. They pose major engineering challenges in theoretical low-cost lift systems such as rotovators, space elevators, and orbital airships
Limonite is an iron ore consisting of a mixture of hydrated iron oxide-hydroxides in varying composition. The generic formula is written as FeO·nH2O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the two principal iron ores, the other being hematite, and has been mined for the production of iron since at least 2500 BCE. Limonite is named from the Greek word for meadow, in allusion to its occurrence as bog ore in meadows. In its brown form it is called brown hematite or brown iron ore. In its bright yellow form it is sometimes called lemon rock or yellow iron ore, limonite is relatively dense with a specific gravity varying from 2.7 to 4.3. It varies in colour from a bright yellow to a drab greyish brown. The streak of limonite on a porcelain plate is always brownish. The hardness is variable, but generally in the 4 -5.5 range, although originally defined as a single mineral, limonite is now recognized as a mixture of related hydrated iron oxide minerals, among them goethite, akaganeite and jarosite.
Because of its amorphous nature, and occurrence in hydrated areas limonite often presents as a clay or mudstone, there are limonite pseudomorphs after other minerals such as pyrite. This means that chemical weathering transforms the crystals of pyrite into limonite by hydrating the molecules, limonite pseudomorphs have been formed from other iron oxides and magnetite, from the carbonate siderite and from iron rich silicates such as almandine garnets. It is often the major component in lateritic soils. It is often deposited in run-off streams from mining operations, one of the first uses was as a pigment. The yellow form produced yellow ochre for which Cyprus was famous, roasting the limonite changed it partially to hematite, producing red ochres, burnt umbers and siennas. Bog iron ore and limonite mudstones are mined as a source of iron, Iron caps or gossans of siliceous iron oxide typically form as the result of intensive oxidation of sulfide ore deposits. These gossans were used by prospectors as guides to buried ore, in addition the oxidation of those sulfide deposits which contained gold, often resulted in the concentration of gold in the iron oxide and quartz of the gossans.
Goldbearing limonite gossans were mined in the Shasta County, California mining district. Similar deposits were mined near Rio Tinto in Spain and Mount Morgan in Australia, in the Dahlonega gold belt in Lumpkin County, Georgia gold was mined from limonite-rich lateritic or saprolite soil
Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay minerals form in the presence of water and have been important to life and they are important constituents of soils, and have been useful to humans since ancient times in agriculture and manufacturing. Clays form flat hexagonal sheets similar to the micas, Clay minerals are common weathering products and low-temperature hydrothermal alteration products. Clay minerals are common in soils, in fine-grained sedimentary rocks such as shale, mudstone. Clay minerals are usually ultrafine-grained and so may require special techniques for their identification. These methods can be augmented by polarized light microscopy, a traditional technique establishing fundamental occurrences or petrologic relationships. Given the requirement of water, clay minerals are rare in the Solar System, though they occur extensively on Earth where water has interacted with other minerals.
Clay minerals have been detected at several locations on Mars including Echus Chasma and Mawrth Vallis and the Memnonia quadrangle, spectrography has confirmed their presence on asteroids including the dwarf planet Ceres and Tempel 1 as well as Jupiters moon Europa. A1,1 clay would consist of one sheet and one octahedral sheet. A2,1 clay consists of an octahedral sheet sandwiched between two sheets, and examples are talc and montmorillonite. Smectite group which includes dioctahedral smectites such as montmorillonite and beidellite, in 2013, analytical tests by the Curiosity rover found results consistent with the presence of smectite clay minerals on the planet Mars. Illite group which includes the clay-micas, illite is the only common mineral. Chlorite group includes a variety of similar minerals with considerable chemical variation. Other 2,1 clay types exist such as sepiolite or attapulgite, mixed layer clay variations exist for most of the above groups. Ordering is described as random or regular ordering, and is described by the term reichweite.
Literature articles will refer to a R1 ordered illite-smectite, for example and this type would be ordered in an ISISIS fashion. R0 on the other hand describes random ordering, and other advanced ordering types are found, mixed layer clay minerals which are perfect R1 types often get their own names. R1 ordered chlorite-smectite is known as corrensite, R1 illite-smectite is rectorite, knowledge of the nature of clay became better understood in the 1930s with advancements in x-ray diffraction technology necessary to analyze the molecular nature of clay particles
Phytoplankton /ˌfaɪtoʊˈplæŋktən/ are the autotrophic components of the plankton community and a key part of oceans and freshwater basin ecosystems. The name comes from the Greek words φυτόν, meaning plant, most phytoplankton are too small to be individually seen with the unaided eye. Phytoplankton are photosynthesizing microscopic organisms that inhabit the upper layer of almost all oceans. They are agents for primary production, the creation of organic compounds from carbon dioxide dissolved in the water, Phytoplankton obtain energy through the process of photosynthesis and must therefore live in the well-lit surface layer of an ocean, lake, or other body of water. Phytoplankton account for half of all activity on Earth. Their cumulative energy fixation in carbon compounds is the basis for the vast majority of oceanic, the effects of anthropogenic warming on the global population of phytoplankton is an area of active research. Additionally, changes in the mortality of phytoplankton due to rates of zooplankton grazing may be significant, as a side note, one of the more remarkable food chains in the ocean – remarkable because of the small number of links – is that of phytoplankton-feeding krill feeding baleen whales.
Phytoplankton are dependent on minerals. However, across large regions of the World Ocean such as the Southern Ocean and this has led to some scientists advocating iron fertilization as a means to counteract the accumulation of human-produced carbon dioxide in the atmosphere. Large-scale experiments have added iron to the oceans to promote phytoplankton growth, controversy about manipulating the ecosystem and the efficiency of iron fertilization has slowed such experiments. Phytoplankton depend on other substances to survive as well, in particular, Vitamin B is crucial. Areas in the ocean have been identified as having a lack of Vitamin B. While almost all species are obligate photoautotrophs, there are some that are mixotrophic and other. Of these, the best known are dinoflagellate genera such as Noctiluca and Dinophysis, the term phytoplankton encompasses all photoautotrophic microorganisms in aquatic food webs. Phytoplankton serve as the base of the food web, providing an essential ecological function for all aquatic life.
However, unlike terrestrial communities, where most autotrophs are plants, phytoplankton are a group, incorporating protistan eukaryotes. There are about 5,000 known species of marine phytoplankton, how such diversity evolved despite scarce resources is unclear. In terms of numbers, the most important groups of phytoplankton include the diatoms and dinoflagellates, one group, the coccolithophorids, is responsible for the release of significant amounts of dimethyl sulfide into the atmosphere
Plankton are the diverse collection of organisms that live in the water column of large bodies of water and are unable to swim against a current. They provide a source of food to many large aquatic organisms, such as fish. These organisms include bacteria, algae and drifting or floating animals that inhabit, for example, plankton are defined by their ecological niche rather than any phylogenetic or taxonomic classification. Though many planktonic species are microscopic in size, plankton includes organisms covering a range of sizes. The name plankton is derived from the Greek adjective πλαγκτός, meaning errant and it was coined by Victor Hensen. Plankton typically flow with ocean currents, while some forms are capable of independent movement and can swim hundreds of meters vertically in a single day, their horizontal position is primarily determined by the surrounding currents. This is in contrast to nekton organisms that can swim against the ambient flow, within the plankton, holoplankton spend their entire life cycle as plankton.
By contrast, meroplankton are only planktic for part of their lives, examples of meroplankton include the larvae of sea urchins, crustaceans, marine worms, and most fish. Plankton abundance and distribution are strongly dependent on such as ambient nutrient concentrations, the physical state of the water column. The study of plankton is termed planktology and an individual is referred to as a plankter. The adjective planktonic is widely used in both the scientific and popular literature, and is an accepted term. However, from the standpoint of prescriptive grammar the less commonly used planktic is more strictly the correct adjective, when deriving English words from their Greek or Latin roots the gender specific ending is normally dropped, using only the root of the word in the derivation. Among the more important groups are the diatoms, cyanobacteria and coccolithophores, small protozoans or metazoans that feed on other plankton and telonemia. Some of the eggs and larvae of larger animals, such as fish, bacterioplankton and archaea, which play an important role in remineralising organic material down the water column.
Mycoplankton and fungus-like organisms, which are significant in nutrient cycling and this scheme divides the plankton community into broad producer and recycler groups. However, determining the level of some plankton is not straightforward. For example, although most dinoflagellates are either photosynthetic producers or heterotrophic consumers, Plankton are often described in terms of size. Usually the following divisions are used, some of terms may be used with very different boundaries
Tektites are gravel-size bodies composed of black, brown or gray natural glass formed from terrestrial debris ejected during meteorite impacts. They generally range in size from millimeters to centimeters, millimeters-size tektites are known as microtektites. First, they are completely glassy and lack any microlites or phenocrysts, tektites contain virtually no water, unlike terrestrial volcanic glasses. Fourth, the flow-banding within tektites often contains particles and bands of lechatelierite, finally, a few tektites contain partly melted inclusions of shocked and unshocked mineral grains, i. e. quartz and zircon, as well as coesite. The difference in water content can be used to distinguish tektites from terrestrial volcanic glasses, when heated to their melting point, terrestrial volcanic glasses will turn into a foamy glass because of their content of water and other volatiles. Unlike terrestrial volcanic glass, a tektite will produce only a few bubbles at most when heated to its melting point, on the basis of morphology and physical characteristics, tektites have traditionally been divided into four groups.
The tektites which have found on land have traditionally been subdivided into three groups, splash-form tektites, aerodynamically shaped tektites, and Muong Nong-type tektites. Splash-form and aerodynamically shaped tektites are only differentiated on the basis of their appearance, splash-form tektites are centimeter-sized tektites that are shaped like spheres, teardrops and other forms characteristic of isolated molten bodies. They are regarded as having formed from the solidification of rotating liquids, aerodynamically shaped tektites, which are mainly part of the Australasian strewn field, are splash-form tektites which display a secondary ring or flange. The secondary ring or flange is argued as having been produced during the high-speed reentry, Muong Nong tektites are typically larger, greater than 10 cm in size and 24 kg in weight and layered tektites. Microtektites, the group of tektites, are tektites that are less than 1 mm in size. They exhibit a variety of shapes ranging from spherical to dumbbell, oval, the color of microtektites ranges from colorless and transparent to yellowish and pale brown.
They frequently contain bubbles and lechatelierite inclusions, microtektites are typically found in deep-sea sediments that are of the same ages as those of the four known strewn fields. As summarized by Koeberl, the tektites within each strewn field are related to each other with respect to the criteria of petrological, physical, in addition, three of the four strewn fields have been clearly linked with impact craters using those same criteria. Recognized types of tektites, grouped according to their known strewn fields, their associated craters and others have proposed the existence of an additional tektite strewn field, the Central American strewn field. Evidence for this reported tektite strewn field consists of tektites recovered from western Belize in the area of the villages of Bullet Tree Falls, Santa Familia and Billy White. This area lies about 55 km east-southeast of Tikal where 13 tektites, a limited amount of evidence is interpreted as indicating that the proposed Central American strewn field likely covers Belize, Guatemala and possibly parts of southern Mexico.
It is speculated that the hypothesized Pantasma Impact Crater in northern Nicaragua might be the source of these tektites, the ages of tektites from the four strewnfields have been determined using radiometric dating methods
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a variety of scientific disciplines. The term applies to the calcium carbonate tests of often more or less microscopic Foraminifera, note that not all tests are calcareous and radiolaria have siliceous tests. The molluscs are calcareous, as are calcareous sponges, that have spicules which are made of calcium carbonate, calcareous grassland is a form of grassland characteristic of soils containing much calcium carbonate from underlying chalk or limestone rock. Species of algae such as the green-segmented genus Halimeda are calcareous, the term is used in pathology, for example in calcareous conjunctivitis, and when referring to calcareous metastasis or calcareous deposits, which may both be removed surgically. The term calcareous can be applied to a sediment, sedimentary rock, or soil type which is formed from, or contains a proportion of. Calcareous sediments are deposited in shallow water near land, since the carbonate is precipitated by marine organisms that need land-derived nutrients.
Generally speaking, the farther from land sediments fall, the less calcareous they are, some areas can have interbedded calcareous sediments due to storms, or changes in ocean currents. Calcareous ooze is a form of calcium derived from planktonic organisms that accumulates on the sea floor. This can only occur if the ocean is shallower than the carbonate compensation depth, below this depth, calcium carbonate begins to dissolve in the ocean, and only non-calcareous sediments are stable, such as siliceous ooze or pelagic red clay. Calcareous soils are alkaline, in other words they have a high pH. This is because of the very weak acidity of carbonic acid, note that this is not the only reason for a high soil pH
Radiolarite is a siliceous, comparatively hard, fine-grained, chert-like, and homogeneous sedimentary rock that is composed predominantly of the microscopic remains of radiolarians. This term is used for indurated radiolarian oozes and sometimes as a synonym of radiolarian earth. However, radiolarian earth is regarded by Earth scientists to be the unconsolidated equivalent of a radiolarite. A radiolarian chert is well-bedded, microcrystalline radiolarite that has a well-developed siliceous cement or groundmass, radiolarites are biogenic, finely layered sedimentary rocks. The layers reveal an interchange of clastic mica grains, radiolarian tests, clay minerals are usually not abundant. Radiolarites deposited in shallow depths can interleave with carbonate layers. Yet most often radiolarites are pelagic, deep water sediments, radiolarites are very brittle rocks and hard to split. They break conchoidally with sharp edges, during weathering they decompose into small, rectangular pieces. The colors range from light to dark via red, radiolarites are composed mainly of radiolarian tests and their fragments.
The skeletal material consists of amorphous silica, radiolarians are marine, planktonic protists with an inner skeleton. Their sizes range from 0.1 to 0.5 millimeters, amongst their major orders albaillellaria, the spherical spumellaria and the hood-shaped nassellaria can be distinguished. According to Takahashi radiolarians stay for 2 to 6 weeks in the zone before they start sinking. Their descent through 5000 meters of water can take from two weeks to as long as 14 months. As soon as the protist dies and starts decaying silica dissolution affects the skeleton, the dissolution of silica in the oceans parallels the temperature/depth curve and is most effective in the uppermost 750 meters of the water column, farther below it rapidly diminishes. Upon reaching the interface the dissolution drastically increases again. Several centimeters below this interface the dissolution continues within the sediment and it is in fact astonishing that any radiolarian tests survive at all. It is estimated that only as little as one percent of the skeletal material is preserved in radiolarian oozes.
The organic wrappings act as a protection for the tests and spare them from dissolution, after deposition diagenetic processes start affecting the freshly laid down sediment
Bay mud manifests low shear strength, high compressibility and low permeability, making it hazardous to build upon in seismically active regions like the San Francisco Bay Area. Typical bulk density of bay mud is approximately 1.3 grams per cubic centimetre, Bay mud has its own official geological abbreviation. The designation for Quaternary older bay mud is Qobm and the acronym for Quaternary younger bay mud is Qybm, an alluvial layer is often found overlying the older bay mud. In relation to shipping channels, it is necessary to dredge bay bottoms. It is not uncommon to dredge the same channel repeatedly since further settling sediments are prone to redeposit on an open valley floor. Bay muds originate from two generalized sources, first alluvial deposits of clays and sand occur from streams tributary to a given bay. The extent of these unconsolidated interglacial deposits typically ranges throughout a given bay to the extent of the historical perimeter marshlands, second, in periods of high glaciation, deposits of silts and organic plus inorganic detritus may form a separate distinct layer.
Thus bay muds are important time records of activity and streamflow throughout the Quaternary period. Some depositional formation is quite recent, such as in the case of Florida Bay, where much of the bay mud has accumulated since 2000 BC, and consists of primarily decayed organic material. In the case of the Bristol Channel in the United Kingdom bay, mud formation has been occurring at least since the Eemian Stage, in other cases such as with San Francisco Bay, deposition has been interrupted by sea-level changes, and strata of vastly different vintages are found. In the San Francisco Bay Area, these are called Young bay mud, human activities can affect deposition, close to half of the Young Bay Mud in San Francisco Bay was placed in the period 1855–1865, as a result of placer mining in the Sierra Nevada foothills. Construction on bay mud sites is difficult because of the low strength. A number of buildings have been constructed over bay muds, typically employing special mitigation designs to withstand seismic risks.
Complicating design issues, fill is sometimes deposited on the surface level. For example, the Dakin Building in Brisbane, California was designed in 1985 to sit on piles 150 feet deep, anchoring to the Franciscan formation, below the bay muds and through an upper fill layer. Furthermore, the entrance ramp has been set on a giant hinge to allow the surrounding land to settle, while the building absolute height remains constant. The Crowne Plaza high-rise hotel in Burlingame, California was designed to sit over bay muds, as was the Westin Hotel in Millbrae, indeed, Bostons entire Back Bay district is named for the tidal bay that it now covers. Logan International Airport and the San Francisco International Airport are constructed over bay mud, when the mud layer is exposed at the tidal fringe, mudflats result affording a unique ecotone that affords numerous shorebird species a safe feeding and resting habitat