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Δ18O
In geochemistry, paleoclimatology and paleoceanography ''δ''18O or delta-O-18 is a measure of the ratio of stable isotopes oxygen-18 (18O) and oxygen-16 (16O). It is commonly used as a measure of the temperature of precipitation, as a measure of groundwater/mineral interactions, and as an indicator of processes that show isotopic fractionation, like methanogenesis. In paleosciences, 18O:16O data from corals, foraminifera and ice cores are used as a proxy for temperature. The definition is, in "per mil" (‰, parts per thousand): :\delta \ce = \left( \frac - 1 \right) \times 1000 ‰ where the standard has a known isotopic composition, such as Vienna Standard Mean Ocean Water (VSMOW). The fractionation can arise from kinetic, equilibrium, or mass-independent fractionation. Mechanism Foraminifera shells are composed of calcium carbonate (CaCO3) and are found in many common geological environments. The ratio of 18O to 16O in the shell is used to indirectly determine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton. A coral "group" is a colony of very many genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. A set of tentacles surround a central mouth opening. Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously overnight, often around a full moon. Fertilized eggs form planulae, a mobile early form of the coral polyp which, when matu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleoceanography
Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment models and different proxies enable the scientific community to assess the role of the oceanic processes in the global climate by the re-construction of past climate at various intervals. Paleoceanographic research is also intimately tied to paleoclimatology. Source and methods of information Paleoceanography makes use of so-called proxy methods as a way to infer information about the past state and evolution of the world's oceans. Several geochemical proxy tools include long-chain organic molecules (e.g. alkenones), stable and radioactive isotopes, and trace metals. Additionally, sediment cores can also be useful; the field of paleoceanography is closely related to sedimentology and paleontology. Sea-surface temperature Sea-surface temp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen-18
Oxygen-18 (, Ω) is a natural, stable isotope of oxygen and one of the environmental isotopes. is an important precursor for the production of fluorodeoxyglucose (FDG) used in positron emission tomography (PET). Generally, in the radiopharmaceutical industry, enriched water () is bombarded with hydrogen ions in either a cyclotron or linear accelerator, creating fluorine-18. This is then synthesized into FDG and injected into a patient. It can also be used to make an extremely heavy version of water when combined with tritium (hydrogen-3): or . This compound has a density almost 30% greater than that of natural water. The accurate measurements of rely on proper procedures of analysis, sample preparation and storage. Paleoclimatology In ice cores, mainly Arctic and Antarctic, the ratio of to (known as δ) can be used to determine the temperature of precipitation through time. Assuming that atmospheric circulation and elevation has not changed significantly over the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lorraine Lisiecki
Lorraine Lisiecki is an American paleoclimatologist. She is a professor in the Department of Earth Sciences at the University of California, Santa Barbara. She has proposed a new analysis of the 100,000-year problem in the Milankovitch theory of climate change. She also created the analytical software behind the LR04, a "standard representation of the climate history of the last five million years". Education Lisiecki graduated in 1995 from the South Carolina Governor’s School for Science and Mathematics. Lisiecki received her B.Sc. in Earth, Atmospheric, and Planetary Science in 1999 and also obtained an M.Sc. in Geosystems in 2000 from the Massachusetts Institute of Technology. She earned a M.Sc. and Ph.D. in Geological Sciences, both from Brown University in 2003 and 2005. Lisiecki's Ph.D. thesis was titled “''Paleoclimate time series: New alignment and compositing techniques, a 5.3-Myr benthic δ18O stack, and analysis of Pliocene-Pleistocene climate transitions''”. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maureen Raymo
Maureen E. "Mo" Raymo (born 1959) is an American paleoclimatologist and marine geologist. She is the Co-Founding Dean of the Columbia Climate School, Director of the Lamont–Doherty Earth Observatory of Columbia University, the G. Unger Vetlesen Professor of Earth & Environmental Sciences, and Director of the Lamont–Doherty Core Repository at the Lamont–Doherty Earth Observatory of Columbia University. She is the first female climate scientist and first female scientist to head the institution. Raymo has done pioneering work on ice ages, the geologic temperature record, and climate, examining and theorizing about global cooling and warming and transitions in ice age cycles. Her work underlies fundamental ideas in paleoceanography including the uplift weathering hypothesis, the "41,000-year problem", the Pliocene sea-level paradox, and the Lisiecki-Raymo δ18O stack. Among other awards and honors, Raymo became in 2014 the first woman to win the Wollaston Medal for geolog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geochemistry
Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the entire Solar System, and has made important contributions to the understanding of a number of processes including mantle convection, the formation of planets and the origins of granite and basalt. It is an integrated field of chemistry and geology. History The term ''geochemistry'' was first used by the Swiss-German chemist Christian Friedrich Schönbein in 1838: "a comparative geochemistry ought to be launched, before geognosy can become geology, and before the mystery of the genesis of our planets and their inorganic matter may be revealed." However, for the rest of the century the more common term was "chemical geology", and there was little contact between geologists and chemists. Geochemistry emerged as a separate discipline af ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass Spectrometry
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures. A mass spectrum is a type of plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical identity or structure of molecules and other chemical compounds. In a typical MS procedure, a sample, which may be solid, liquid, or gaseous, is ionized, for example by bombarding it with a beam of electrons. This may cause some of the sample's molecules to break up into positively charged fragments or simply become positively charged without fragmenting. These ions (fragments) are then separated acco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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