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Dating Methods in Science
Strata, Fossils and Age of the Earth

Is Dating Really Important?
Index For This Page

I wish this page was unnecessary.

Because of the distortions and lies spread by fundamentalists about scientific dating there is a need for a centralized source of information on the topic. A few examples of such lies are presented at the very bottom of this page.

For each dating or chronological method there is a link in the box at right to take you to that section of this page. There, you will find a brief description of the method, plus links to take you to other webpages with more extensive information.

Dating is not necessary to demonstrate that evolution is a fact. Chronological sequence is all that is really required. However, human beings love to see factual precision, and we want to know how old something is.

Please remember that all dating methods, even those termed "absolute," are subject to margins of error. We say the Earth is 4.56 ± 0.02 billion years old. That is a very small amount of possible error range. There are 20 methods shown here. Modern studies almost always use two or more methods to confirm dating work and to build confidence in the results obtained.

Overview of Methods
Superposition
Stratigraphy
Dendrochronology
Radiocarbon C14
Radiometric Dating Methods
Obsidian Hydration Dating
Paleomagnetic/Archaeomagnetic
Luminescence Dating Methods
Amino Acid Racemization
Fission-track Dating
Ice Cores
Varves
Pollens
Corals
Cation Ratio
Fluorine Dating
Patination
Oxidizable Carbon Ratio
Electron Spin Resonance
Cosmic-ray Exposure Dating
Overview of Scientific Dating Methods

Dating the Past : This is an excellent overview of dating methodologies, and is a chapter in a textbook on Archaeology. You may find it useful for the clear definitions, and for excellent links on a variety of topic. Many of these links also appear where appropriate below.

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Superposition

Steno's Law - The Law of Superposition : A bit of history about Nicolas Steno, who formulated the Law of Superposition.

Geologic Time: Relative Time Scale : James Hutton and William Smith advanced the concept of geologic time and strengthened the belief in an ancient world. Hutton, a Scottish geologist, first proposed formally the fundamental principle used to classify rocks according to their relative ages. He concluded, after studying rocks at many outcrops, that each layer represented a specific interval of geologic time. Further, he proposed that wherever uncontorted layers were exposed, the bottom layer was deposited first and was, therefore, the oldest layer exposed; each succeeding layer, up to the topmost one, was progressively younger. The Major Divisions of Geologic Time are shown here, arranged in chronological order with the oldest division at the bottom, the youngest at the top.

Relative Time, Superposition and Cross-cutting Relationships : Geologic intrusions, faults and unconformities are explained and pictured.

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Stratigraphy

Stratigraphy and Cross-Dating/Biostratigraphy : Stratigraphy is the study of strata, or layers. Specifically, stratigraphy refers to the application of the Law of Superposition to soil and geological strata containing archaeological materials in order to determine the relative ages of layers. Cross-dating is a technique used to take advantage of consistencies in stratigraphy between parts of a site or different sites, and objects or strata with a known relative chronology. A specialized form of cross-dating, using animal and plant fossils, is known as biostratigraphy.

Correlation by Fossils : Correlation means matching the order of geologic events in one place with the order of geologic events in another place. By far, the most widespread method of correlation uses fossils

Geologic Time: Index Fossils : Keyed to the relative time scale are examples of index fossils, the forms of life which existed during limited periods of geologic time and thus are used as guides to the age of the rocks in which they are preserved.

William "Strata" Smith, a civil engineer and surveyor, was well acquainted with areas in southern England where "limestone and shales are layered like slices of bread and butter." His hobby of collecting and cataloging fossil shells from these rocks led to the discovery that certain layers contained fossils unlike those in other layers. Using these key or index fossils as markers, Smith could identify a particular layer of rock wherever it was exposed. Because fossils actually record the slow but progressive development of life, scientists use them to identify rocks of the same age throughout the world. See more information about "Strata" Smith and his original geologic map of England. Information about Simon Winchester's delightful biography of Smith, The Map That Changed the World is available at amazon.com. Click on the map to see a larger version.

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Dendrochronology

The Principles of Dendochronology.

Dendrochronology -- Tree Rings : Tree-Ring dating is based on the principle that the growth rings on certain species of trees reflect variations in seasonal and annual rainfall. Trees from the same species, growing in the same area or environment will be exposed to the same conditions, and hence their growth rings will match at the point where their lifecycles overlap.

Bristlecone Pine Dendrochronology : Earth's oldest living inhabitant "Methuselah" at 4,767 years, has lived more than a millennium longer than any other tree. [ While this may be true, a shrub in Tasmania could be 40,000 years old. See Oldest Living Organism.]

Sheffield Research Dendrochronology : The Sheffield Laboratory now has a continuous master sequence for England going back to about 5000BC. This is made up of numerous regional tree-ring chronologies, particularly in the medieval and post-medieval periods, for which the laboratory now has more than 200 reference chronologies from many areas.

The Ultimate Tree-ring Pages : This really must be the ultimate web resource for this topic. You will find information about tree-rings, current research, and examples of practical applications of this science.

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Radiocarbon C14

Radiocarbon: The C14 Method : There are over 130 radiocarbon dating laboratories around the world producing radiocarbon assays for the scientific community. The Carbon14 technique has been and continues to be applied and used in many, many different fields including hydrology, atmospheric science, oceanography, geology, palaeoclimatology, archaeology and biomedicine.

Radiocarbon Dating : An excellent series of short movies take students through a course of explanation and demonstration of C14 methods.

Oxford Radiocarbon Accelerator Unit. About research in radiocarbon methodology. Includes many protocols for adjusting results to account for fluctuations in atmospheric C14.

C14 Resources : For learning more about radiocarbon methods, laboratories and databases.

Carbon Dating: An excellent article about the process and its limitations, written without scientific jargon.

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Radiometric Dating Methods

Radiometric Dating -- A Christian Perspective : by Dr. Roger C. Wiens, Los Alamos National Laboratory. Also discusses other dating methodologies. This article should be a "must read" for any person interested in factualy accurate information on dating methods.

Radiometric Dating Film Clips : By comparing the proportion of K-40 to Ar-40 in a sample of volcanic rock, and knowing the decay rate of K-40, the date that the rock formed can be determined. A series of movie clips walks you through the process.

Radiometric Dating Basics : Gives the simple principles of how the process works. Provides a table showing six parent/daughter isotopes and their half-lives.

Geologic Time: Radiometric Time Scale : More on the basics from the United States Geological Service. Discussed six isoptopes commonly used to date very ancient rocks.

Reliability of Radiometric Dating. : Similar to this webpage, it presents many links to articles about radiometric dating and the age of the earth, some of which I do not list here for want of space.

Isochron Radiometric Dating : Isochron methods avoid the problems which can potentially result during radiometric testing. Be sure to see An Animated Isochron Diagram, or, Watching a Rock Age on an Isochron Diagram. These are very nice pages from www.talkorigins.org.

Age of the Earth : Radiometric Dating from The Evolution Evidence Page. The most compelling argument for an age of the earth of 4.5 billion years are the large number of independent tests that have been used to confirm this date. These tests have been performed on what are thought to be the earth's oldest surviving rocks, meteorites, and moon rocks. These tests have consistently given the same ages for each of these objects. Examples of a number of consistent dates derived from different methods are given.

Isotopes, Radiometric Dating and the Geologic Time Scale : A short but clear explanation about radioactive isotopes commonly used for determining ages of rocks (with graphics) and putting numbers on the geologic time scale, extending it back before the occurance of abundant index fossils.

Thermion Mass Spectrometry : This is a relatively new method intended to to improve the precision of uranium and thorium istopy methods. It excludes contamination and weathering of travertines and makes possible more precise dating of thin deposits of secondary carbonates. No web-based resource for this method is available.

New Electron Microprobe Determines Ages of Rocks: A team of University of Massachusetts geologists is exploring a new way to determine the ages of ancient rocks, and refining our understanding of the timing and rates of the geologic events that have shaped the planet. The new method offers greater efficiency, and access to a much more detailed geologic record than current dating methods.

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Obsidian Hydration Dating

Obsidian Hydration Dating: Obsidian hydration dating is based on the fact that a fresh surface is created on a piece of obsidian in the tool manufacturing, or flintknapping, process. Obsidian contains about 0.2 percent water. When a piece of obsidian is fractured, atmospheric water is attracted to the surface and begins to diffuse into the glass. This results in the formation of a water rich hydration rind that increases in depth with time. The hydration process continues until the fresh obsidian surface contains about 3.5 percent water. This is the saturation point. The thickness of the hydration rind can be identified in petrographic thin sections cut normal to the surface and observed under a microscope. A distinct diffusion front can be recognized by an abrupt change in refractive index at the inner edge of the hydration rind. These fronts or rinds of hydration are more dense than the unhydrated inside, and the unhydrated zone has different optical properties. Friedman and Smith reasoned that the degree of hydration observed on an obsidian artifact could tell archaeologists how long it had been since that surface was created by a flintknapper.

Introduction to Obsidian Hydration Dating : When a new surface of obsidian is exposed to the atmosphere, such as during the manufacture of glass tools, water begins to slowly diffuse from the surface into the interior of the specimen. When this hydrated layer or rind reaches a thickness of about 0.5 microns, it becomes recognizable as a birefringent rim when observed as a thin section under a microscope. Hydration rims formed on artifacts can vary in width from less than one micron for items from the early historic period to nearly 30 microns for early sites in Africa.

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Paleomagnetic Dating Methods

Paleomagnetic and Archaeomagnetic Dating

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Luminescence Dating Methods
    Includes:
    • Thermoluminescence (TL, stimulated by heat)
    • Optical stimulated luminescence (OSL, stimulated by visible light)
    • Infrared stimulated luminescence (IRSL, stimulated by infrared light)
    • Radioluminescence (RL, stimulated by ionizing radiation)

Thermoluminescence : It can be applied to date a large variety of volcanic materials such as rhyolitic lava flows, tephras and other pyroclastic deposits. It can also date meteorite impact craters, earthquake-generated fault gouge material, contact heating and metamorphism of sediments baked by lava overflows, and anthropogenically heated materials such as ceramics, cooking hearths,and deliberately fire-treated rocks such as flints used by prehistoric people for toolmaking. Also see Quaternary TL Surveys - A Guide to Thermoluminescence Date Measurement. Additional information is available at Luminescence Dating.

Luminescence Dating : Scientists in North America first developed thermoluminescence dating of rock minerals in the 1950s and 1960s, and the University of Oxford, England first developed the thermoluminescence dating of fired ceramics in the 1960s and 1970s.During the 1970s and 1980s scientists at Simon Frasier University, Canada, developed standard thermoluminescence dating procedures used to date sediments. In 1985, they also developed optically stimulated luminescence dating techniques, which use laser light, to date sediments.

Luminescence Dating -- Thermo/Optical

OSL -- Optically Stimulated Luminescence Dating

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Amino Acid Racemization

Amino Acid Geochronology : This is a relative, and sometimes absolute, dating method that relates the diagenesis of fossil protein preserved in carbonate materials with time (geologic age of the sample) and temperature (long term chemical temperature of the enclosing sediment). Stratigraphic applications of the method have been demonstrated from both marine and non-marine sequences all over the world using a variety of carbonate fossil materials including mollusks, foraminifera, bone, ostrich egg shells, ostracodes, and tooth enamel. A brief explanation is given at Bear Lake Methods: Amino Acid Dating.

Amino Acid Racemization : Provides a frank discussion of possible problems encountered when using this method, and the need for cross-checking results against other methods.

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Fission-track Dating

eMuseum -- Fission-track Dating : Fission-track dating is one type of radioactive dating method used by archaeologists to determine the thermal age of artifacts containing uranium-bearing minerals. Fission tracks are created at a constant rate throughout time so that from the number of tracks present it is possible to determine the amount of time that has past since the track accumulation began. Dates from anywhere between twenty to one thousand million years ago can be determined with this particular technique.

Fission Track Dating : A brief description of the method.

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Ice Cores

Are We Right About Icecap Dating? : Scientists think that they have counted ice layers accurately. And, they think that one layer almost always means one year. The GISP2 workers believe that they were very careful, and that they are off by less than 5% at 50,000 years before present. But are they right?

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Varves

Varve Chronology : Varves form two or more distinctive layers at different seasons of the year. Gives a nice description about overcoming problems in the use of this method.

Counting Sediment Layers in Rock : The basic reason for varves is that rivers run faster in the spring. A flooding river carries coarse material. During the rest of the year, the river is slower, and carries finer material. The result is that lake bottom deposits tend to alternate, coarse/fine/coarse/fine.

The North American Varve Project : Tufts University website describing the research being done in establishing a North American varve chronology.

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Pollens

Pollen Analysis : Pollen analysis, study of vegetation history using the microfossils (pollen grain and spores of size 15-50 um), can give us useful information about the target area's condition in the present and past. Since the outside of the pollen grain wall is made of highly resistant material, the pollen spores from 400 million years ago can be found today. Each pollen grain and spore is different in structure and shape, thus, the morphology is the key to understanding the kinds of vegetation that existed and their evolutionary development. Nice graphic of pollen history at this site.
Pollen analysis is a method for reconstructing the past vegetation history in a particular area or context. As we know that vegetation cover in particular areas has altered over time, the technique used to be used as a generalized dating method. However the development of more precise dating methods, such as radiocarbon-dating and dendrochronology, has meant that that aspect of pollen analysis has faded away.

Stratigraphic Palynology : Palynology is the branch of science dealing with microscopic, decay-resistant remains of certain plants and animals. It has many applications including archaeological palynology, Quaternary palynology , and stratigraphic palynology.

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Corals

Coral Slide Set from NOAA : Corals exhibit seasonal growth bands very much like those in trees. Sometimes these bands are visible to the naked eye; usually, however, they are more visible in an x-ray like the one shown at right. When paleoclimatologists drill a coral core, they can count the growth bands and date samples exactly. Long cores can cover several hundred years; this portion of a core from Urvina Bay in the Galápagos Islands covers the period from 1716 to 1735 A. D.

Tidal Slowdown, Coral Growth, and the Age of the Earth : In certain modern corals we find growth-bands that indicate yearly, monthly, and even daily growth. There are about thirty daily bands per month and about 365 daily bands per year for modern corals and shellfish. But careful analysis of the growth-bands of fossil corals and shellfish from the Devonian and Pennsylvanian has confirmed that years in these periods contained more days than years do now (about 400).

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Cation Ratio

Cation Ratio Dating : Rocks are covered by a kind of varnish, a chemically-changed layer that builds up over time due to calcium and potassium seeping out of the rock. The cation ratio is determined by scraping the varnish from the carved or petroglyph surface back to the original rock surface and making a comparison of the two using a positively charged ion. This paper is an early example of the method applied to dating Australian petroglyphs.

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Flourine Dating

eMuseum -- Flourine Dating : Fluorine dating is chiefly of value in determining whether bone implements or human skeletal remains found in association with other bones were buried at the same time. It was fluorine dating that was instrumental in the debunking of Piltdown Man.

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Patination Dating

Patination Dating : Although it is not an actual dating technique, patination is used when multiple artifacts of the same type are found in the same area and under the same conditions. The use of this technique is to determine the age of the artifacts, relative to the others, by comparing the thickness of the patina on them. There are many variables that have to be calculated, and this makes dating lithics from patina formations a relative dating technique.

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Oxidizable Carbon Ratio Dating

Oxidizable Carbon Ratio : Even though OCR has the potential to provide archaeologists and geologists with a method of finding accurate and precise age estimates from organic carbon within soil, it is still new and in the experimental stage. Scientists question both the methods of the procedure and the accuracy of the results, which is common and needed when any new scientific theory arises. Federal and State organizations, museums, Cultural Resource Management companies, archaeologists, pedologists, and geomorphologists are all currently conducting field studies for OCR dating at hundreds of sites in Northeastern North America and in parts of Europe.

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Electron Spin Resonance

Electron Spin Resonance : Also called electron paramagnetic resonance, ESR dating also relies on the changes in electron orbits and spins caused by radioactivity over time. However, ESR dating can be used over longer time periods, up to two million years, and works best on carbonates, such as in coral reefs and cave deposits. It has also seen extensive use in dating tooth enamel.

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Cosmic-ray Exposure Dating

Cosmic-ray Exposure Dating : This dating method relies on measuring certain isotopes produced by cosmic ray impacts on exposed rock surfaces. Because cosmic rays constantly bombard meteorites flying through space, this method has long been used to date the "flight time" of meteorites--that is the time from when they were chipped off a larger body (like an asteroid) to the time they land on Earth.

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Examples of Fundamentalist Lies about Dating

Can We Really Believe the Dating Systems? : Dr. Roger C. Wiens addresses specifically the claims, misrepresentations and distortions of fundamentalists who lie about dating reliability in their attempt to prove evolution wrong.

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datingmethods.htm Last Updated April 22, 2011     Links verified April 22, 2011