Chronological dating

Last updated

Chronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously established chronology. This usually requires what is commonly known as a "dating method". Several dating methods exist, depending on different criteria and techniques, and some very well known examples of disciplines using such techniques are, for example, history, archaeology, geology, paleontology, astronomy and even forensic science, since in the latter it is sometimes necessary to investigate the moment in the past in which the death of a cadaver occurred.

Contents

Dating methods

Dating methods are most commonly classified following two criteria: relative dating and absolute dating.

Relative dating

Relative dating methods are unable to determine the absolute age of an object or event, but can determine the impossibility of a particular event happening before or after another event of which the absolute date is well known. In this relative dating method, Latin terms ante quem and post quem are usually used to indicate both the most recent and the oldest possible moments when an event occurred or an artifact was left in a stratum, respectively. But this method is also useful in many other disciplines. Historians, for example, know that Shakespeare's play Henry V was not written before 1587 because Shakespeare's primary source for writing his play was the second edition of Raphael Holinshed's Chronicles, not published until 1587. [1] Thus, 1587 is the post quem dating of Shakespeare's play Henry V. That means that the play was without fail written after (in Latin, post) 1587.

The same inductive mechanism is applied in archaeology, geology and paleontology, by many ways. For example, in a stratum presenting difficulties or ambiguities to absolute dating, paleopalynology can be used as a relative referent by means of the study of the pollens found in the stratum. This is admitted because of the simple reason that some botanical species, whether extinct or not, are well known as belonging to a determined position in the scale of time.

For a non-exhaustive list of relative dating methods and relative dating applications used in geology, paleontology or archaeology, see the following:

Absolute dating

Absolute dating methods, by using absolute referent criteria, mainly include the radiometric dating methods. [4] Some examples of both radiometric and non-radiometric absolute dating methods are the following:

Dating methods in archaeology

Same as geologists or paleontologists, archaeologists are also brought to determine the age of ancient materials, but in their case, the areas of their studies are restricted to the history of both ancient and recent humans. Thus, to be considered as archaeological, the remains, objects or artifacts to be dated must be related to human activity. It is commonly assumed that if the remains or elements to be dated are older than the human species, the disciplines which study them are sciences such geology or paleontology, among some others.

Nevertheless, the range of time within archaeological dating can be enormous compared to the average lifespan of a singular human being. As an example Pinnacle Point's caves, in the southern coast of South Africa, provided evidence that marine resources (shellfish) have been regularly exploited by humans as of 170,000 years ago.[ citation needed ] On the other hand, remains as recent as a hundred years old can also be the target of archaeological dating methods. It was the case of an 18th-century sloop whose excavation was led in South Carolina (United States) in 1992. [11] Thus, from the oldest to the youngest, all archaeological sites are likely to be dated by an appropriate method.

Dating material drawn from the archaeological record can be made by a direct study of an artifact, or may be deduced by association with materials found in the context the item is drawn from or inferred by its point of discovery in the sequence relative to datable contexts. Dating is carried out mainly post excavation, but to support good practice, some preliminary dating work called "spot dating" is usually run in tandem with excavation. Dating is very important in archaeology for constructing models of the past, as it relies on the integrity of dateable objects and samples. Many disciplines of archaeological science are concerned with dating evidence, but in practice several different dating techniques must be applied in some circumstances, thus dating evidence for much of an archaeological sequence recorded during excavation requires matching information from known absolute or some associated steps, with a careful study of stratigraphic relationships.

In addition, because of its particular relation with past human presence or past human activity, archaeology uses almost all the dating methods that it shares with the other sciences, but with some particular variations, like the following:

Written markers

Seriation

Seriation is a relative dating method (see, above, the list of relative dating methods). An example of a practical application of seriation, is the comparison of the known style of artifacts such as stone tools or pottery.

Age-equivalent stratigraphic markers

Stratigraphic relationships

The stratigraphy of an archaeological site can be used to date, or refine the date, of particular activities ("contexts") on that site. For example, if a context is sealed between two other contexts of known date, it can be inferred that the middle context must date to between those dates.

See also

Related Research Articles

Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of the Earth itself, and can also be used to date a wide range of natural and man-made materials.

The rubidium-strontium dating method is a radiometric dating technique used by scientists to determine the age of rocks and minerals from the quantities they contain of specific isotopes of rubidium (87Rb) and strontium.

Stratigraphy The study of rock layers and their formation

Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has two related subfields: lithostratigraphy and biostratigraphy.

Geochronology Science of determining the age of rocks, sediments and fossils

Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is provided by tools such as palaeomagnetism and stable isotope ratios. By combining multiple geochronological indicators the precision of the recovered age can be improved.

Artifact (archaeology) Something made by humans and of archaeological interest

An artifact, or artefact, is something made or given shape by humans, such as a tool or a work of art, especially an object of archaeological interest.

Oscar Montelius Swedish archaeologist

Gustav Oscar August Montelius, known as Oscar Montelius was a Swedish archaeologist who refined the concept of seriation, a relative chronological dating method.

Kalambo Falls waterfall

The Kalambo Falls on the Kalambo River is a 772-foot (235 m) single-drop waterfall on the border of Zambia and Tanzania at the southeast end of Lake Tanganyika. The falls are some of the tallest uninterrupted falls in Africa. Downstream of the falls is the Kalambo Gorge, which has a width of about 1 km and a depth of up to 300 m, running for about 5 km before opening out into the Lake Tanganyika rift valley.

Archaeological science, also known as archaeometry, consists of the application of scientific techniques to the analysis of archaeological materials, to assist in dating the materials. It is related to methodologies of archaeology. Martinón-Torres and Killick distinguish ‘scientific archaeology’ from ‘archaeological science’. Martinón-Torres and Killick claim that ‘archaeological science’ has promoted the development of high-level theory in archaeology. However, Smith rejects both concepts of archaeological science because neither emphasize falsification or a search for causality.

Stratigraphy (archaeology) field of archeology

Stratigraphy is a key concept to modern archaeological theory and practice. Modern excavation techniques are based on stratigraphic principles. The concept derives from the geological use of the idea that sedimentation takes place according to uniform principles. When archaeological finds are below the surface of the ground, the identification of the context of each find is vital in enabling the archaeologist to draw conclusions about the site and about the nature and date of its occupation. It is the archaeologist's role to attempt to discover what contexts exist and how they came to be created. Archaeological stratification or sequence is the dynamic superimposition of single units of stratigraphy, or contexts.

Absolute dating is the process of determining an age on a specified chronology in archaeology and geology. Some scientists prefer the terms chronometric or calendar dating, as use of the word "absolute" implies an unwarranted certainty of accuracy. Absolute dating provides a numerical age or range in contrast with relative dating which places events in order without any measure of the age between events.

The following outline is provided as an overview of and topical guide to archaeology:

In archaeology, seriation is a relative dating method in which assemblages or artifacts from numerous sites, in the same culture, are placed in chronological order. Where absolute dating methods, such as carbon dating, cannot be applied, archaeologists have to use relative dating methods to date archaeological finds and features. Seriation is a standard method of dating in archaeology. It can be used to date stone tools, pottery fragments, and other artifacts. In Europe, it has been used frequently to reconstruct the chronological sequence of graves in a cemetery.

Dating is an activity by two humans who are exploring or are in a romantic relationship.

Luminescence dating refers to a group of methods of determining how long ago mineral grains were last exposed to sunlight or sufficient heating. It is useful to geologists and archaeologists who want to know when such an event occurred. It uses various methods to stimulate and measure luminescence.

Sequence dating, a relative dating method, allows assemblages to be arranged in a rough serial order, which is then taken to indicate time. Sequence dating is a method of seriation developed by the Egyptologist Sir William Matthew Flinders Petrie. By linking styles of pottery with different time periods, he was able to establish the relative chronology of the site.

Amino acid dating is a dating technique used to estimate the age of a specimen in paleobiology, molecular paleontology, archaeology, forensic science, taphonomy, sedimentary geology and other fields. This technique relates changes in amino acid molecules to the time elapsed since they were formed.

Geochronometry is a branch of stratigraphy aimed at the quantitative measurement of geologic time. It is considered a branch of geochronology.

Arizona Accelerator Mass Spectrometry Laboratory focuses on the study of cosmogenic isotopes, and in particular the study of radiocarbon, or Carbon-14. As a laboratory, part of its aim is to function as a research center, training center, and general community resource. Its stated mission is conducting original research in cosmogenic isotopes. The AMS laboratory was established in 1981 at the University of Arizona.

George Francis Carter was an American professor of geography who taught at Johns Hopkins University and later Texas A&M University. Carter had a background in anthropology and conducted archaeological excavations in Southern California. He is best known for supporting the theories of trans-cultural diffusion and early human settlement of the Americas.

This page is a glossary of archaeology, the study of the human past from material remains.

References

  1. Greer, Clayton A. (June 1954). "Shakespeare's Use of The Famous Victories of Henry V". Notes and Queries : 238–41. doi:10.1093/nq/199.jun.238.
  2. Chemistry Professor Shimon Reich, a specialist in superconductivity, has demonstrated a method for dating artifacts based on the magnetic properties of lead, a material widely used in Israel and elsewhere in antiquity. Reich and coworkers found that at cryogenic temperatures, lead becomes a superconductor, but the corrosion products formed from centuries of exposure to air and water (lead oxide and lead carbonate) do not superconduct. On the basis of magnetic measurements and comparison with artifacts that were known (using other techniques) to be up to 2500 years old, the group showed that the mass of lead corrosion products is directly proportional to an object's age (New Journal of Physics, 2003, 5, 99)
  3. Jacoby, M. (5 March 2007). "Chemistry in the Holy Land". Chemical & Engineering News. American Chemical Society. p. 20.
  4. IUPAC , Compendium of Chemical Terminology , 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006) " radioactive dating ". doi : 10.1351/goldbook.R05082
  5. J L Bada (1985). "Amino Acid Racemization Dating of Fossil Bones". Annual Review of Earth and Planetary Sciences. 13: 241–268. Bibcode:1985AREPS..13..241B. doi:10.1146/annurev.ea.13.050185.001325.
  6. Laureano Canoira; Maria-Jess Garca-Martnez; Juan F. Llamas; Jos E. Ortz; Trinidad De Torres (2003). "Kinetics of amino acid racemization (epimerization) in the dentine of fossil and modern bear teeth". International Journal of Chemical Kinetics. 35 (11): 576–591. doi:10.1002/kin.10153.
  7. B. J. Johnson; G. H. Miller (1997). "Archaeological Applications Of Amino Acid Racemization". Archaeometry. 39 (2): 265–287. doi:10.1111/j.1475-4754.1997.tb00806.x.
  8. "Quantifying Time-Averaging In 4th-Order Depositional Sequences: Radiocarbon-Calibrated Amino-Acid Racemization Dating of Late Quaternary Mollusk Shells from Po Plain, Italy". 2008. The results provide a compelling case for applicability of amino acid racemization methods as a tool for evaluating changes in depositional dynamics, sedimentation rates, time-averaging, temporal resolution of the fossil record, and taphonomic overprints across sequence stratigraphic cycles.Cite journal requires |journal= (help)
  9. Eighmy, Jeffery; Sternberg, Robert, eds. (1990). Archaeomagnetic Dating. Tucson: The University of Arizona Press. ISBN   9780816511327.
  10. "Fire And Water Reveal New Archaeological Dating Method". Science Daily. May 25, 2009. Retrieved 2009-05-26. A team from the University of Manchester and the University of Edinburgh has discovered a new technique which they call 'rehydroxylation dating' that can be used on fired clay ceramics like bricks, tile and pottery.
  11. "Clydesdale Plantation 18th-Century Sloop Excavation", Institute of Nautical Archaeology, Texas, USA