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Geochronology is the science of determining the absolute age of rocks, fossils, and sediments, within a certain degree of uncertainty inherent within the method used. Science (from the Latin scientia, meaning " Knowledge " or "knowing" is the effort to discover, and increase human understanding In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of A variety of dating methods are used by geologists to achieve this.

Geochronology is different in application from biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloguing and comparing fossil floral and faunal assemblages. Biostratigraphy is the branch of Stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the Fossil assemblages contained Biostratigraphy does not directly provide an absolute age determination of a rock, merely places it within an interval of time at which that fossil assemblage is known to have coexisted.

For instance, with reference to the Geologic time scale, the Upper Permian (Lopingian) lasted from 270. The geologic time scale is a chronologic schema (or idealized Model) relating Stratigraphy to time that is used by Geologists and other The Permian is a geologic period and system that extends from 299 6 +/- 0. 7 Ma until somewhere between 250. 1 +/- 0. 4 Ma (oldest known Triassic) and 260. The Triassic is a geologic period and system that extends from about 251 to 199 Ma (million years ago 4 +/- 0. 7 Ma (youngest known Lopingian) - a gap in known, dated fossil assemblages of nearly 10 Ma. While the biostratigraphic age of an Upper Permian bed may be shown to be Lopingian, the true date of the bed could be anywhere from 270 to 251 Ma.

On the other hand, a granite which is dated at 259. 5 +/- 0. 5 Ma can reasonably safely be called "Permian", or most properly, to have intruded in the Permian.

The science of geochronology is the prime tool used in the discipline of chronostratigraphy, which attempts to derive absolute age dates for all fossil assemblages and determine the geologic history of the Earth and extraterrestrial bodies. Chronostratigraphy is the branch of Stratigraphy that studies the age of rock strata in relation to Time.

Contents

Geochronologic units[1]

Dating methods

Radiometric dating

By measuring the amount of radiocative decay of a radioactive isotope with a known half-life, geologists can establish the absolute age of the parent material. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. A radionuclide is an Atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created Half-Life (computer-game page here It's already listed in the disambiguation page A number of radioactive isotopes are used for this purpose, and depending on the rate of decay, are used for dating different geological periods.

Other radiogenic dating techniques include:

Luminescence Dating

Luminescence dating techiques observe 'light' emitted from materials such as quartz, diamond, feldspar, and calcite. Fission track dating is a Radiometric dating technique based on analyses of the damage trails or tracks left by fission fragments in certain Uranium bearing The rubidium-strontium dating method is a Radiometric dating technique that geologists use to determine the age of rocks. Samarium-neodymium dating is useful for determining the age relationships of rocks and meteorites based on decay of a long-lived Sm isotope to a Radiogenic Nd isotope Rhenium-Osmium dating is a form of Radiometric dating based on the Beta decay of the Isotope 187 Re which usually has a Half life Paleomagnetism is the study of the record of the Earth's magnetic field preserved in various Magnetic Minerals through time Thermoluminescence (TL dating is the determination by means of measuring the accumulated Radiation dose of the time elapsed since material containing Many types of luminescence techniques are utilized in geology, including optically stimulated luminescence (OSL), cathodoluminescence (CL), and thermoluminescence (TL). In Physics Optically stimulated luminescence or (OSL is a method for measuring doses from Ionizing radiation (commonly known as Radioactive radiation) Cathodoluminescence is an optical and electrical Phenomenon whereby a beam of Electrons is generated by an Electron gun (e Some mineral substances such as Fluorite store energy when exposed to Ultraviolet or other Ionising radiation. Thermoluminescence and [optically stimulated luminescence]] are used in archaeology to date 'fired' objects such as pottery or cooking stones, and can be used to observe sand migration. Some mineral substances such as Fluorite store energy when exposed to Ultraviolet or other Ionising radiation.

Incremental dating

Incremental dating techniques allow the construction of year-by-year annual chronologies, which can be fixed (i. Incremental dating techniques allow the construction of year-by-year annual chronologies which can be temporally fixed ( i e. linked to the present day and thus calendar or sidereal time) or floating. The word Calendar consist of two words 1 Cal ( in Pashto means Year in Hindi and Persian is Sal- also means Year

Source of error

The geochronologic and chronostratigraphic units can be mixed up[2]. Dendrochronology (from Greek grc δένδρον dendron, "tree" grc χρόνος khronos, "time" and grc -λογία An ice core is a Core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods In Archeology and Paleontology, lichenometry is the study of dating a surface using Lichens as age markers lichens increase in size radially as they grow A varve is an annual layer of Sediment or Sedimentary rock. The word 'varve' is derived from the Swedish word varv whose

References

  1. ^ According to "Glossary of Geology, 4th. edition, American Geological Institute publications 1997, ISBN 0-922152-34-9": Geochronological units are divisions of time based on chronostratigraphic units. It is time spans corresponding to the chronostratigraphic material units. Geochronological units in order of decreasing rank are eon, era, period, epoch and age. Names of periods and units of lower rank are the same as those of the corresponding chronostratigraphic units; the names of some eras and eons are independently formed.
  2. ^ David Weishampel:The Evolution and Extinction of the Dinosaurs, 1996, Cambridge Press, ISBN 0-521-44496-9

See also

Modern geologists and Geophysicists consider the age of Earth to be around 4 Arthur Holmes ( January 14 1890 &ndash September 20 1965) was a British Geologist. Friedrich Georg "Fritz" Houtermans ( January 22, 1903 &ndash March 1, 1966) was an atomic and nuclear Alfred Otto Carl Nier ( May 28, 1911 - May 16, 1994) was an American Physicist who pioneered the development of Mass Thomas Edvard "Tom" Krogh, FRSC (1936 &ndash April 29, 2008) was a geochronologist and a former Curator for

Dictionary

geochronology

-noun

  1. (uncountable) The science of dating samples of rock or sediment.
  2. (countable) Any one of the methods by which the age of different samples of rock can be determined.
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