Radiocarbon Dating and Fossils

Radiocarbon Dating

THOMAS CASSIDY
Originally posted by Blade:
Yes, the older something gets, the less accurate carbon dating is. However, the "mistakes" that these "young earth" defenders point to are generally in the order of millions of years, not thousands. Carbon dating has shown animals (i.e., mammoths that were preserved in ice) to have been around for at least 20,000 years by carbon dating.
As a scientist, I have no reason to doubt this dating. It has been replicated and no error has been found.

As a former scientist specializing in the Nuclear Sciences, I find the major short-coming of Radiocarbon dating to be the assumption that carbon-14 production has been a constant throughout the period of time being tested for. Carbon-14 is continually formed in nature by the interaction of neutrons with nitrogen-14 in the Earth's atmosphere; the neutrons required for this reaction are produced by cosmic rays interacting with the atmosphere. If the nature of the atmosphere has changed sometime in the past, then the production rate of carbon-14 may also have changed. If the atmosphere were at one time thicker, for example, less carbon-14 would have been produced and migrated to the lower level of the atmosphere, giving the appearence of greater age due to a lesser amount of carbon-14 present in the test subject. Those who postulate a steady-state of radiocarbon production would see the lesser amount of c-14 as an indication of radiometric decay thus indicating an older specimen.
However, if the rate of c-14 production had been lower in the past, the age of the specimen would be much younger than the steady-state theorist's hypothesis.

There are many Christians who postulate a pre-flood atmosphere which was thicker than present, often including a "vapor canopy" in their theory which could account for the lower levels of c-14 in those animals who lived prior to the postulated flood which marked the collapse of said vapor canopy.

Radiocarbon dating is, at best, an educated guess dependent on the foundational assumptions of the testing method. If those assumptions are flawed, the results will be equally flawed.

Or we can go with this report on the problems associated with radiocarbon dating: http://www.esd.ornl.gov/projects/qen/nerc14C.html


JOHN2001
A partial chronology of the development of the method.

Here is a partial chronology of the development of the calibration of 14C, which includes consideration of sources of fluctuations in the background level of 14C.

Much of creationist commentary on the possible errors in 14C is intended to portray the scientific community as being either incompetent or dishonest regarding such issues as the consideration of potential errors in radiometric dating methods. Creationists never discuss the fact that given these analyses, scientists have found ways of identifying and mitigating the effects of these potential sources of error.

What follows is a summary from chapter 14.1.3, p.364-366 of Dickin [1995]:

1941 Thellier proposed that Earth's magnetic field experiences secular variations.
1949 Arnold and Libby publish radiocarbon dates of items of known age.
1952 Libby publishes first book on radiocarbon dating.
1954 Forbush observed that the 11-year cycle of sunspot activity was inversely correlated with cosmic-ray intensity.
1955 Suess proposed dilution due to the burning of fossil fuels for the 2% depletion of 14C activity seen in 20th century wood compared to 19th century wood.
1956 Elasser, et al. predicted variations in the cosmic ray flux due to secular variations in Earth's magnetic field.
1958 de Vries found that 17-th century wood had a 2% higher activitythan 19th century wood.
1961 Stuiver used historical records of sunspot activity to calculate cosmic ray intensity, and hence 14C production for the past 1500 years, and suggesting that the observations of de Vries, correlated with a sunspot minima.
1965 Stuiver used more detailed records to confirm the correlation of a sunspot minimum with de Vries observations.
1967 Bucha and Neustupny provided paleomagnetic intensity measurments that supported the existence of secular variations in the Earth's magnetic field first proposed by Thellier. They were able to model the variations of 14C production, and almost exactly match the deviations between the tree-ring and radiocarbon time scales.

By 1969, it became apparent that calibration of the 14C dating method was both possible, and required, to make radiocarbon dates useful for the determination of calendar dates. Indeed, it is often material from prior to 1969 that creationists use as ammunition against the 14C dating method. One useful method of calibrating 14C is dendrochronology, or age dating by counting tree rings. The basic idea of calibration is simple. Plot the true date determined from counting tree rings versus the radiocarbon date. The result is a plot that can be used to both determine the actual original 14C/12C ratios (useful for studies in paleoclimatology) and can be used to convert radiocarbon dates of other samples into calendar dates.

The first use of dendrochronlogy to calibrate 14C was made by

1970 Furgeson used dendrochronology of bristlcode pines to calibrate radiocarbon dating back to 7484- years b.p. (before the present).

Through comparison with tree ring dates, the 14C method has been calibrated back to more than 13,000 years before the present,

1991 Becker, et al publish a stable dendrochronological calibration of 14C back to 11,000 years before the present using tree rings. The chronology consists of a 9,928-year absolutely dated dendrochronological record of Holocene oak (Quercus robur, Quercus petraea) and a 1,604-year floating Late Glacial and Early Holocene chronology of pine (Pinus sylvestris) from subfossil tree remains deposited in alluvial terraces of central European rivers.

In addition, 14C dating has also been calibrated back to more than 30,000 years before the present using uranium-thorium (isochron) dating of corals [Bard, et al, 1990] and [Edwards, et al, 1993].
While it is unlikely that 14C will be useful for objects older than 50,000 years, owing to the problems of background contamination
[Dickin, 1995] and [Lowe, 1991], there is a recent paper by [Kitagawa, H., and van der Plicht, J., 1998] discusses calibration of 14C dating back to 45,000 b.p. using U-Th dates of glacial lake varve sediments (periodic sedimentary layers).

References:
--Arnold, J. R. and Libby, W. F. (1949) Age determinations by radiocarbon content: Checks of samples with known age. Science 110, 678-680.
--Bard, E., Hamelin, B., Fairbanks, R.G., and Zinder, A., (1990), Calibration of the 14C timescale over the past 30,000 years using mass spectrometric U-Th ages from Barbados corals, Nature, 345, 405-410.
--Becker, B., Kromer, B., and Trimborn P., 1991, A stable-isotope tree-ring timescale of the Late Glacial/Holocene boundary: Nature, vol. 353 (17 Oct 1991), 647-649.
--Dickin, A. P. (1995), Radiogenic Isotope Geology, Cambridge University Press.
--Dalrymple, G. Brent, (1991), The Age of the Earth. California: Stanford University Press, ISBN 0-8047-1569-6.
--Edwards, R. L., Beck, J. W., Burr, G. S., Donahue, D. J., Chappell, J. M. A., Bloom, E. R. M., Druffel, E. R. M., Taylor, F. W., 1993, A large drop in atmospheric 14-C/12-C and reduced melting in the Younger Dryas*, documented with 230-Th ages in corals: Science, vol. 260 (14 May 1993), 962-967
--Furgeson, C. W. (1970), Dendrochronology of bristlecone pines, Pinus aristata. Establishment of a 7484-year chronology in the White Mountains of eastern-central California, USA. In: I. U. Olsson (Ed.), Radiocarbon Variations and Absolute Chronology, Proc. 12th Nobel Symp. Wiley, pp. 629-40.
--Kitagawa, H., and van der Plicht, J., (1998), Atmospheric radiocarbon calibration to 45,000 yr B.P>: Late glacial fluctuations and cosmogenic isotope production, Science, v. 279, 20 Feb 1998.
--Libby, W. F. (1952) Radiocarbon dating, University of Chicago Press.
--Libby, W. F. (1970) Ruminations on radiocarbon dating In: I. U. Olsson (Ed.), Radiocarbon Variations and Absolute Chronology, Proc. 12th Nobel Symp. Wiley, pp. 629-40.
--Lowe, J. John, ed. (1991) Radiocarbon Dating: Recent Applications and Future Potential, Quaternary Proceedings, Number 1, 1991, Published for the Quaternary Research Association, Wiley.

* * * * *

[Administrater: the following is from a different, related thread]

HELEN
[In response to the protest that there is no circularity in fossil dating/rock strata dating]

Rocks that contain fossils are much easier to interpret chronologically than rocks
without fossils. http://www.cce.umn.edu/dis/courses/GEO1002_4503_03.www/


DATING INDIVIDUAL FOSSILS
Paleontologists use many ways of dating individual fossils in geologic time.

1.The oldest method is stratigraphy, studying how deeply a fossil is buried. Dinosaur fossils are usually found in sedimentary rock. Sedimentary rock layers (strata) are formed episodically as earth is deposited horizontally over time. Newer layers are formed on top of older layers, pressurizing them into rocks. Paleontologists can estimate the amount of time that has passed since the stratum containing the fossil was formed. Generally, deeper rocks and fossils are older than those found above them. http://www.zoomdinosaurs.com/subjects/dinosaurs/dinofossils/Fossildating.html

http://www.rael.org/int/english/evidence/evidence/body_evolution2.html
M.C. van Oosterwyck-Gastruche
CHALLENGING THE DATING OF GEOLOGIC AREAS
The isotopic measurements, "dating" geologic eras,
have no chronological meaning.
But the conclusions of the manuals are, as we know,
diametrically opposed. I started informing myself by
asking my fellow geologists. Above all I wanted to know
the chronological points of reference which had been used
to validate the millions of years of evolution and allowed
the selection of geochronological data in order to keep
only the good results ("best values"). They confessed they
did not know about them but they advised me to consult
the Holmes' manual "Physical Geology" (1965), because
"everything was in it."

The geological
time measured by the decay of a radioactive isotope was
essentially the work of Arthur Holmes (1890-1963), who
shared Lyell's "creed". In fact, he confirmed Lyell's thesis
by giving the oldest ages (from 3000 to 600 millions of
years) to Archean or Precambrian formations, where
elaborate life signs had not yet been discovered.
Moreover, his "Phanerozoic time scale", from 600 million
years ago to our era, confirmed evolution observed in
Lyell's stratigraphical scale, proving the "emergence of
life" and officially dating the main recorded "events" within
the geological eras.

In spite of his apparently convincing palaeontological
documentation and his impressive mathematical formality,
Holmes' geological scale appears to be very confused. The
dates of his "Phanerozoic scale" are among the most
doubtful, as was noticed on several occasions, the first of
which during a meeting which took place the very year of
his death. They reproached him at that time for leaning on
a too limited number of mostly questionable data
(Harland, Smith and Wilcook ed., 1964). Later, York and
Farquhar (1972), disconcerted by the profusion of
abnormal ages and asking for more data, ironically wrote
about Holmes' scale, "These two necessary
presuppositions, precise stratigraphical localisation and
reliable radiometric dating, seem to exclude one another:
we almost end up at a geological uncertainty principle".

The worrying point is the following: these isotopic
determinations which provide the millions of years which
are so well recieved, (and so controversial for specialists)
which proved "the Emergence of Life," were never applied
to any fossil or to any strata in which these fossils are
buried; sedimentary rocks not lending themselves to
radio-dating. The material dated is generally a lava flow
covering these fossiliferous layers, the lava flow
supposedly intimately linked to the evolution process as
designed in the "actualist" framework which inspired
Holmes' scale, all without a shadow of proof.

Another disconcerting fact: the "correct" ages which
appear are the result of a selection (Holmes, 1965), the
author having only accepted the "best values" (those
confirming Lyell's stratigraphical scale), rejecting the
others as "anomalous."

The hypothetical character of such a construction, valid if
Lyell's theory is exact, is underlined by geochronologists
themselves, beginning with the authors of the
Potassium-Argon dating method, Dalrymple and Lanphere
(1979). Fitch, Hooker and Miller (1978), confronted by field
problems, debated in "Geological Background to Fossil
Man" on the capacity of radioactive decay techniques to
provide real ages for principal "events" of the African
Oriental Rift (East Rift Valley) linked to the "emergence
process." They note that the phenomenon of radioactive
decay gives dates for "events" taking place in the rocks
but on the basis of temperature changes and/or of the
arrival of solutions. They emphasize, "It is important to
realise that exactitude of ages obtained from this means
depends on the integrity and condition of preservation of
isotopic recording of rocks (since they change with the
above factors and with the alteration of mineral
constituents) and it also depends on our interpretation of
radio-isotopic experiments." This is essentially based "on
our interpretation of data related to fossil fauna" (what is
unsaid is that the interepretation is by proponents of the
the actualist and Evolution theory framework), since
"combination of stratigraphy of rocks and stratigraphical
palaeontology gives us the geological time scale."
Unfortunately, they note that the results obtained in the
Oriental Rift, far from confirming the actualist hypothesis,
remain particularly strange. Furthermore, these authors
conclude: "The two principal tools of geochronology being
equally fallible, the best is to use them jointly and not to
oppose them".

Therefore the principle tool is not geochronology, but
Lyell's scale, and the sledgehammer argument, which
seems to lack any sense, remains the "characteristic
fossil," the isotopic results being filtered according to its
theoretical age.


------------ http://www.emporia.edu/earthsci/student/nang/treering.htm
Limitation of Dendrochronology

Although growth rings are useful for tracing the past, not all tree-rings are suitable for dating. Specific limiting factors, both external and internal, affect the plant growth rings. External factors are water, temperature, light, CO2, Oxygen, and soil minerals. Internal factors are growth regulators, enzymes, and water. These factors can be the result of external factors as well. Each ring is the result of both factors within a single year. Growth begins in spring, and ends in summer or early autumn. When one or more factors are limiting, distinct growth rings, or layers are formed. It is possible that no growth rings are formed under favorable conditions, or, one or more growth rings can be formed during an unfavorable year.

Therefore, there are many species in different geographic areas thart are not suitable for applying dendrochronology, because their growth rings are inconsistent. For example, Cupressus arizonia, several species of Juniperus, and most of the subtropical and tropical trees are not suitable for dendrochronology (Fritts, 1976). However, recent study shows that tree-rings study can be applied at the tropical areas where there is a seasonal rainfall. Growth rings of teak (Tectona grandis) and pines (Pinus spp.) from Indonesia and Thailand are significantly related to the variation of rainfall and ENSO (El Nino/Southern Oscillation). Geographical areas where suitable trees are available, are shown in the map.

Problems and Difficulties

Tree-rings can estimate the minimum-limiting age. However, there are some difficulties in defining the age of the tree.

Determination the ecesis: the estimation of the length of time between land surface stablization and seedling establishment
Determination the year between seedling and the stage at which tree-rings samples can be taken
Determination of the oldest tree inthe area
False rings
Missing rings: years of extreme environmental condition

 

DAVID PLAISTED

From what I have heard, there are some problems with Ferguson's tree ring chronology. A standard statistical procedure called "whitening" was never applied to it. Typically there are many ways of matching tree ring sequences, and the matches that Ferguson chose may have been influenced by radiocarbon dating. Whitening tends to greatly reduce the possible numbers of choices. I also got an email from someone who had intimite knowledge of Ferguson's data and expressed strong skepticism about it. But anyway, it would be good if Ferguson's data were made public (if this has not yet been done) and independent analysis could be done on it.

David Plaisted

 

EARL DETRA
"Someone" expressed skepticism? Ferguson "might have been influenced?" I can't think of more devastating arguments, David. Have you read Ferguson's paper? What data does he show? Usually in peer-reviewed literature some data must be presented to make the author's case. What more would you want to see? What is whitening? When is it used? Perhaps Ferguson didn't feel it was necessary. Maybe the interpretations were clear to him and no reduction of alternatives was necessary.

 

DAVID PLAISTED

Here is the email about tree ring dating; it was sent to me on February 11, 1998:

As one who has taught dendrochronnology, I have a few opinions on this particular subject. Also, one of my graduate students went to work for Ferguson in his lab at U of A, and in fact was the curator of his work after his death, and is presently probably the only one who knows anything about how he [Ferguson] produced the bristlecone chronology. Another of my graduate students gave a seminar to the lab on dendrochronology of fossil trees and had ample opportunity to analyze the procedures there, and to work with Ferguson for a while. I can say on pretty firm grounds that the Bristlecone chronology before 4000bp is fraught with problems and unanswered questions. While Ferguson was alive, he never allowed anyone to analyze his original data or the bases for the many suppositions that went into the establishment of the chronology. Thus the chronology was not subjected to the normal rigors of science. This is regrettable, because I believe he was a careful and sincere scientist. Of course one could always excuse Ferguson for not revealing the bases of his decisions (for example, the most important rings in any chronology are the "missing rings" which have to be added by the investigator). But suffice to say the chronology before 4000bp is entirely dependent on C14 dates of the wood, and is thus tautologous. This does not mean it is meaningless or necessarily wrong, just that I wouldn't base too much on it.


A good web link about tree ring dating and possible problems with Ferguson's chronology:
http://www.grisda.org/origins/22047.htm

It also mentions "whitening."

Dave Plaisted

[ January 29, 2002: Message edited by: Administrator ]

 

PATRICK PARSON

The Barbarian says:
The questions about C-14 calibration are put to rest by the work done on
varves in a Japanese lake:
http://abcnews.go.com/sections/science/DailyNews/carbon0220.html


Unless someone can show that many years had more than one summer and more
than one winter each, there's no way to explain away the evidence.

 

RADIOCHEMIST

The creationists talk as if carbon-14 is the major support for
believing that the world is very old. There are many other dating methods that
agree on the age of the earth as being approximately 4.5 billion years.

The important thing to remember about any dating method is that
they are not perfect. All have potential problems but that does
not mean that they are useless - far from it. It reminds me
of a conversation that A. Lincoln had with someone about horses.
He said that all horses have faults. Back in the days when
horses were the only form of transportation, almost everyone
had them. And yet as Lincoln noted, all horses have faults. That
did not make them useless. People learned to use them in spite
of their faults. Some horses were lazy, some did not obey
certain commands and had various other problems. But the fact
there are flaws in dating methods does not make them useless.
Scientists learn to understand the potential sources of error
and to correct for them. In the case of carbon-14, it is true
that it depends on certain assumptions. But those assumptions
can be checked and if necessary corrections can be made if the
assumptions are not quite right. And that has been done in the
case of carbon-14 to the extent that it is a highly useful dating
methods.

Corrections have been and are
being made with regard to this method.

RADIOCHEMIST

 

RADIOCHEMIST

I will quote part of Thomas Cassidy's post and then comment on it
below.
<BLOCKQUOTE>quote:</font><HR>THOMAS CASSIDY: There are many Christians who postulate a pre-flood
atmosphere which was thicker than present, often including a "vapor
canopy" in their theory which could account for the lower levels of
c-14 in those animals who lived prior to the postulated flood which
marked the collapse of said vapor canopy.

Radiocarbon dating is, at best, an educated guess dependent on the
foundational assumptions of the testing method. If those assumptions
are flawed, the results will be equally flawed.

Or we can go with this report on the problems associated with
radiocarbon dating: http://www.esd.ornl.gov/projects/qen/nerc14C.html"
<HR></BLOCKQUOTE>

Thomas Cassidy talks favorably of a vapor canopy and
unfavorably of C-14 methods. The fact is that there is zero scientific
evidence for a vapor canopy and an abundance of evidence for the
general usefulness of the C-14 method. How then is he able to point
to a scientific site that discusses some weaknesses of the method?

In order for the weaknesses of the C-14 method to be of any use to
creationists in their ideological battle, the method must be grossly
and wildly inaccurate without any hope of improvement. In other words
a date of 40,000 years by C-14 would need to be in error by several
hundred percent so that, for example, the true age is actually 6,000
rather than 40,000. But the creationists are out of luck on that sort
of wild error. What is being discussed in scientific circles, when
they talk about the the weaknesses of C-14, are errors that do not
give the creationists much comfort. For example, to historians who
study ancient things, the C-14 method can have an error of plus or
minus 10 or maybe even 20 percent. For an object 20,000 years old,
this limits the amount of useful information, since the C-14 age
might be anywhere in the range of 16,000 to 24,000 years. It is
the effort to reduce these uncertainties that occupy much of the
time of the workers in this field. Obviously it would be more useful
to know if an object is a certain age to within 100 years, rather
than to an uncertainty of 3 or 4 thousand years. So great attention
is given to the possibility of errors and attempts are made to
reduce the uncertainty as much as possible. These methods and
discussions are misrepresented by creationists as meaning that
the method is totally unreliable. Nothing could be further from
the truth. I suspect that more than 90 percent of the alleged
weaknesses in the C-14 method do nothing at all to lend support
to the creationist cause. Rather, these weaknesses involve very
fine points of the method and are not related to any fundamental
problem with the method. A close reading of the web site referred
to by Thomas Cassidy supports this view.

Thomas Cassidy says that the C-14 method is an educated guess. That
is a gross misrepresentation. He also fails to mention
that the fundamental assumptions have been tested many times and
that the C-14 method has been calibrated to adjust for errors
in the underlying assumptions. An important factor in determining
the usefulness of the method is the nature of the question to be
answered by the method. The C-14 method was entirely adequate to
determine whether the Shroud of Turin was the burial shroud of
Christ (it was not) but it is not good enough to determine the
precise year in which the shroud was made. It is this type of
fine point which is of interest to science and underlies most of
the discussion of the weaknesses of the method. I think it can be
said without fear of contradiction, that the C-14 method is
easily good enough to disprove the theory that the earth is
less than 10,000 years old. It is a robust method for that
purpose.

RADIOCHEMIST