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Thure E. Cerling
|Known for||Modern animal diet and physiology|
Geological record of ecological change
|Awards||Fellow, National Academy of Sciences (2001)|
|Fields|| Geology |
Thure E. Cerling (b. 1949)is a Distinguished Professor of Geology and Geophysics and a Distinguished Professor of Biology at the University of Utah. Cerling is a leading expert in the evolution of modern landscapes including modern mammals and their associated grassland ecologies and stable isotope analyses of the atmosphere. Cerling lives in Salt Lake City, Utah.
Cerling's research interests are primarily focused on Earth surface geochemistry processes and on the geological record of ecological change.Particularly, working on conservation biology, Cerling has analyzed the modern animal diet and physiology by using stable isotopes as natural tracers as well as studying dietary changes of different mammalian lineages extending over millions of years.
Emphasizing continental ecologies of lakes and modern soils and ecosystems, Cerling has written extensievely about the evolution of ecosystems, the inception and strengthening of monsoons, and the atmosphere over geological time scales through evidence gathered about the fractionation of stable istopes in these systems.
Current research work includes a focus on the development of landforms in semi-arid regions, the geology of Old World paleo-anthropologic sites and on contaminant migration in surface and ground waters, including the use of tritium and helium as hydrological tracers.
Thure E. Cerling received his Bachelor of Science degree in geology and chemistry from Iowa State University, in Ames, Iowa, in 1972, and, in 1973, his Master of Science in geology from Iowa State. In 1977 he was awarded a Ph.D. in geology from the University of California at Berkeley. From 1977 to 1979 he worked as a research scientist at Oak Ridge National Laboratory and, from 1979 he has been a member of the University of Utah's faculty.
With the publication of "Expansion of C4 ecosystems as an indicator of global ecological change in the late Miocene" in 1993, Cerling, helped by Yang Wang and Jay Quade, made relevant studies relatively to carbon isotopes. Thanks to a deep analysis of palaeovegetation from palaeosols and palaeodiet measured in fossil tooth enamel, was demonstrated a global increase in the biomass of plants using C4 photosynthesis between 7 and 5 million years ago. The decrease of atmospheric CO2 concentrations over the history below a threshold that favored the C3-photosynthesizing plants was considered as a valid reason for the global expansion of C4 biomass. The publication "Global vegetation change through the Miocene/Pliocene boundary" in 1997 confirmed these results, demonstrating even how at lower latitudes the change appeared to occur earlier because of the threshold for C3 photosynthesis is higher at warmer temperatures.
Thure Cerling and James Ehleringer, a biology professor at the University of Utah, founded Isoforensics in 2003, a company with the aim of interpreting the stable isotope composition of various biological and synthetic materials. This was the first step for the discovery they made which was first published on February 25, 2008, by the "Proceedings of the National Academy of Sciences" with the title "Hydrogen and oxygen isotope ratios in human hair are related to geography". To know where people have been and where they lived for a while are information that became available by analyzing the stable isotope composition of their scalp hair. Cerling discovered that a strand of hair could provide valuable clues about a person's travels by studying the variation of hydrogen-2 (δ2H) and oxygen-18 (δ18O) isotopes and comparing them to the ones in the drinking water. The extent of the information that can be deduced depends on the length of the hair: the longer is the hair, the greater is the extraction of information. The variation with geography of isotope concentrations is linked with precipitations, cloud temperatures and with the amount of water that evaporates from soil and plants. When clouds move off the ocean towards inland the ratios of oxygen-18 to oxygen-16 and hydrogen-2 to hydrogen-1 tend to decrease because of the rain water with oxygen-18 and hydrogen-2, being heavier, tends to fall first. Samples of tap water were collected from more than 600 cities across the United States as well as hair samples from the barbershops in 65 cities in 20 states. The comparison showed that both hair and drinking water samples had the same isotopic variations. In order to display these information, the scientists produced color-coded maps based on the correlation of the isotopes in hair to those in drinking water. This maps show how ratios of hydrogen and oxygen isotopes in scalp hair vary in different areas of the United States. It was so proved that the water drank by a human being leaves in the hair an evidence which contain oxygen and hydrogen isotopes equal to the ones in the tap water. This technique would have been a new tool for policemen, anthropologists, archaeologists and doctors.
Professor Cerling, helped by James Ehleringer and Christopher Remien (two University of Utah colleagues), George Wittemyer of Colorado State University and member of "Save the Elephants" in Nairobi, and Iain Douglas-Hamilton, who founded the association "Save the Elephants", conducted a research around the Samburu and Buffalo Springs national reserves in northern Kenya analyzing carbon and other stable isotopes in elephant tail hair to discover where and what Victoria, Anastasia and Cleopatra, three daughters of a mother elephant named Queen Elizabeth, usually eat over a six-years period (2000–2006). In order to monitor their life, the elephants were equipped with a Global Positioning System that recorded their positions every hour for the whole research period. For getting the sample of tail hair, elephants were immobilized with drug-filled dart guns when necessary. Considering that the hair grows about an inch per month, a single hair contained isotopic information to diet during an 18-month period.
The analysis of ratios of carbon-13 to carbon-12 along the length of a single elephant hair led Cerling and his crew to understand the elephants' diet. During the wet season, after the grass had grown long enough for elephants to grab with their trunks, their tail hair showed the presence of different form of carbon, indicating a high amount of high-protein grass. On the other hand, during the dry season, the results obtained by the analysis of the hair pointed out how elephants had switched over to shrubs and trees.
For what concern the Samburu-Buffalo Springs, five weeks after the rainy season had started, the grass became rich in nutrients and the females were most likely to conceive, giving birth 22 months later, just in time for another rainy season to provide nutrients to the grass they would have eaten: the cycle could restart. The research also pointed out how developed is the competition between elephants and cattle: during the typical wet season diet of elephants, the overgrazing by cattle caused the grass to be very short, resulting in a limited access to it for elephants, out-competing them. This situation could have influenced the elephants' ability to bulk up for pregnancy.
All these analyses pointed out even that there are some elephant families friendlier than others and showed how there are dominant families that settle down in the best places, where there is plenty of food and water.
The Permian–Triassic extinction event, also known as the P–Tr extinction, the P–T extinction, the End-Permian Extinction, and colloquially as the Great Dying, formed the boundary between the Permian and Triassic geologic periods, as well as between the Paleozoic and Mesozoic eras, approximately 252 million years ago. It is the Earth's most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. It was the largest known mass extinction of insects. Some 57% of all biological families and 83% of all genera became extinct.
Isotope analysis is the identification of isotopic signature, the abundance of certain stable isotopes and chemical elements within organic and inorganic compounds. Isotopic analysis can be used to understand the flow of energy through a food web, to reconstruct past environmental and climatic conditions, to investigate human and animal diets in the past, for food authentification, and a variety of other physical, geological, palaeontological and chemical processes. Stable isotope ratios are measured using mass spectrometry, which separates the different isotopes of an element on the basis of their mass-to-charge ratio.
Carbon fixation or сarbon assimilation is the conversion process of inorganic carbon to organic compounds by living organisms. The most prominent example is photosynthesis, although chemosynthesis is another form of carbon fixation that can take place in the absence of sunlight. Organisms that grow by fixing carbon are called autotrophs. Autotrophs include photoautotrophs, and lithoautotrophs. Heterotrophs are organisms that grow using the carbon fixed by autotrophs. The organic compounds are used by heterotrophs to produce energy and to build body structures. "Fixed carbon", "reduced carbon", and "organic carbon" are equivalent terms for various organic compounds.
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope ratio mass spectrometry, and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them.
Vienna Standard Mean Ocean Water (VSMOW) is an isotopic standard for water. Despite the name, VSMOW is pure water with no salt or other chemicals found in the oceans. The VSMOW standard was promulgated by the International Atomic Energy Agency in 1968, and since 1993 continues to be evaluated and studied by the IAEA along with the European Institute for Reference Materials and Measurements and the American National Institute of Standards and Technology. The standard includes both the established values of stable isotopes found in waters and calibration materials provided for standardization and interlaboratory comparisons of instruments used to measure these values in experimental materials.
The sulfur cycle is the collection of processes by which sulfur moves between rocks, waterways and living systems. Such biogeochemical cycles are important in geology because they affect many minerals. Biochemical cycles are also important for life because sulfur is an essential element, being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes.
An isotopic signature is a ratio of non-radiogenic 'stable isotopes', stable radiogenic isotopes, or unstable radioactive isotopes of particular elements in an investigated material. The ratios of isotopes in a sample material are measured by isotope-ratio mass spectrometry against an isotopic reference material. This process is called isotope analysis.
Oxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances, such as polar ice or calcite in ocean core samples, measured with the isotope fractionation. The ratio is linked to water temperature of ancient oceans, which in turn reflects ancient climates. Cycles in the ratio mirror climate changes in geologic history.
The Great Oxidation Event (GOE), sometimes also called the Great Oxygenation Event, Oxygen Catastrophe, Oxygen Crisis, Oxygen Holocaust, or Oxygen Revolution, was a time period when the Earth's atmosphere and the shallow ocean experienced a rise in oxygen, approximately 2.4 billion years ago (2.4 Ga) to 2.1–2.0 Ga during the Paleoproterozoic era. Geological, isotopic, and chemical evidence suggests that biologically produced molecular oxygen (dioxygen, O2) started to accumulate in Earth's atmosphere and changed Earth's atmosphere from a weakly reducing atmosphere to an oxidizing atmosphere, causing many existing species on earth to die out. The cyanobacteria producing the oxygen caused the event which enabled the subsequent development of multicellular forms.
Cholestane is a saturated tetracyclictriterpene. This carbon-27 biomarker is produced by diagenesis of cholesterol and is one of the most abundant biomarkers in the rock record. Presence of cholestane in environmental samples are commonly interpreted as an indicator of animal life and/or traces of O2, as animals are known for exclusively producing cholesterol, and thus has been used to draw evolutionary relationships between ancient organisms of unknown phylogenetic origin and modern metazoan taxa. Cholestane is made in low abundance by other organisms (e.g., rhodophytes), but because these other organisms produce a variety of sterols it cannot be used as a conclusive indicator of any one taxa. It is often found in analysis of organic compounds in petroleum.
The term Middle Miocene disruption, alternatively the Middle Miocene extinction or Middle Miocene extinction peak, refers to a wave of extinctions of terrestrial and aquatic life forms that occurred around the middle of the Miocene, roughly 14 million years ago, during the Langhian stage of the Miocene. This era of extinction is believed to have been caused by a relatively steady period of cooling that resulted in the growth of ice sheet volumes globally, and the reestablishment of the ice of the East Antarctic Ice Sheet (EAIS). Cooling that led to the Middle Miocene disruption is primarily attributed to orbitally paced changes in oceanic and atmospheric circulation due to continental drift. These may have been amplified by CO2 being pulled out of the Earth's atmosphere by organic material before becoming caught in different locations like the Monterey Formation. This period was preceded by the Miocene Climatic Optimum, a period of relative warmth from 18 to 14 Ma.
Ardipithecus ramidus is a species of australopithecine from the Afar region of Early Pliocene Ethiopia 4.4 million years ago (mya). A. ramidus, unlike modern hominids, has adaptations for both walking on two legs (bipedality) and life in the trees (arboreality). However, it would not have been as efficient at bipedality as humans, nor at arboreality as non-human great apes. Its discovery, along with Miocene apes, has reworked academic understanding of the chimpanzee-human last common ancestor from appearing much like modern day chimps, orangutans, and gorillas to being a creature without a modern anatomical cognate.
The Cretaceous Thermal Maximum (CTM), also known as Cretaceous Thermal Optimum, was a period of climatic warming that reached its peak approximately 90 million years ago during the Turonian age of the Late Cretaceous epoch. The CTM is notable for its dramatic increase in global temperatures characterized by high carbon dioxide levels.
The greater Turkana Basin in East Africa determines a large endorheic basin, a drainage basin with no outflow centered around the north-southwards directed Gregory Rift system in Kenya and southern Ethiopia. The deepest point of the basin is the endorheic Lake Turkana, a brackish Soda lake with a very high ecological productivity in the Gregory Rift.
Zachary D. Sharp is an American stable isotope geochemist. He is credited with the development of laser-based technology for measuring oxygen isotopes in silicates and oxides. His contributions include laser analyses of meteorites, paleoclimate reconstruction by oxygen and hydrogen isotope ratios, and analysis of isotopic composition of volcanoes, fossils, and forensic samples.
The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally, yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, used in radiometric dating. However, the expression stable-isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by isotope fractionation in nature. This field is termed stable isotope geochemistry.
The evolution of photosynthesis refers to the origin and subsequent evolution of photosynthesis, the process by which light energy synthesizes sugars from carbon dioxide and water, releasing oxygen as a waste product. The process of photosynthesis was discovered by Jan Ingenhousz, a Dutch-born British physician and scientist, first publishing about it in 1779.
Hydrogen isotope biogeochemistry is the scientific study of biological, geological, and chemical processes in the environment using the distribution and relative abundance of hydrogen isotopes. There are two stable isotopes of hydrogen, protium 1H and deuterium 2H, which vary in relative abundance on the order of hundreds of permil. The ratio between these two species can be considered the hydrogen isotopic fingerprint of a substance. Understanding isotopic fingerprints and the sources of fractionation that lead to variation between them can be applied to address a diverse array of questions ranging from ecology and hydrology to geochemistry and paleoclimate reconstructions. Since specialized techniques are required to measure natural hydrogen isotope abundance ratios, the field of hydrogen isotope biogeochemistry provides uniquely specialized tools to more traditional fields like ecology and geochemistry.
Marilyn Fogel is an American geo-ecologist, currently working as a Professor of Geo-ecology at UC Riverside in Riverside, California. She is known for her work with stable isotope geochemistry, studying ancient climate, animal behavior, ecology, and astrobiology. Fogel has also served in many leadership roles, including Program Director at the National Science Foundation in geobiology and low-temperature geochemistry.
Pliopapio is an extinct genus of Old World monkey known from the latest part of the Miocene to the early Pliocene Epochs from the Afar Region of Ethiopia. It was first described based on a very large series of fossils from the site of Aramis in the Middle Awash, which has been dated by 40Ar/39Ar to 4.4 million years old. It has since been found from similarly aged sediments at Gona, approximately 75 km to the North. Additional fossils from the Middle Awash extend its known time range back to at least 5.3 million years ago. There is only one known species, Pliopapio alemui.