Geochronology kata John Woodmorappe
by Steven H. SchimmrichCopyright © 1997-2003
[Text last updated: February 12,
1998]
[Links updated: November 30, 2003]
[Links updated: November 30, 2003]
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his is a critique of the paper
"Radiometric Dating Reappraised" by John Woodmorappe which
originally appeared in the Creation Research Society
Quarterly (Volume 16, September 1979).
I came across this paper when I was referred to the book Studies in Flood Geology: A Compilation of Research Studies Supporting Creation and the Flood by John Woodmorappe. This book is a compilation of seven Creation Research Society Quarterly reprints (published by the Creation Research Society), two reprints from the Proceedings of the International Conference on Creationism, and one reprint of an Institute for Creation Research Impact pamphlet. All of the papers were written by Woodmorappe and each address various topics relating to the young-earth creationist belief in a geologically-recent global deluge (Noah's Flood).
The book has no publisher's information page but it seems clear from the Forward, written by the well-known young-earth creationist Henry Morris, that it was published by the Institute for Creation Research in 1993.
On the cover of the book, John Woodmorappe is credited with possessing an M.S. in geology and a B.A. in biology. The Impact reprint in the book states that:
John Woodmorappe has a Bachelor's and a Master's Degree in Geology and a Bachelor's Degree in Biology. He is a science teacher and is also a research fellow at a university.
I found it odd that nowhere in the book was it indicated where Woodmorappe earned his degrees or his current professional affiliation (Where does he teach science? At which University is he a research fellow?). The reprints from the Creation Research Society Quarterly appear unusual in this respect since mainstream scientific journals routinely print the author's professional affiliation and a contact address.
I believe that it's reasonable, when evaluating what purports to be a scientific paper, to inquire as to the author's expertise to write about the subject -- especially when the relevant information given is so vague. A little research disclosed that "John Woodmorappe" is a nom de plume and a bit more research disclosed his true identity (confirmed by two separate sources). He evidently does have a legitimate M.S. degree in geology from a secular university with which he's still affiliated and has published a couple of papers in mainstream geologic journals under his real name. In the papers he's published under his real name, he affiliates himself with the geology department at that university, yet the 1996 American Geological Institute Directory of Geoscience Departments does not list him as a faculty member so I haven't been able to find any evidence that he currently teaches science or is a research fellow at any university.
To fairly represent Woodmorappe's thesis in this paper, I would like to reproduce his abstract in full (p. 102):
The use of radiometric dating in Geology involves a very selective acceptance of data. Discrepant dates, attributed to open systems, may instead be evidence against the validity of radiometric dating.In this paper, Woodmorappe seeks to discredit radiometric dating and the geologic time scale since (p. 102):
A systematic and critical review of dating applications is presented; emphasis being placed on the geologic column. Over 300 serious discrepancies are tabulated. It is, however, demonstrated that most discrepant results are not published. Discrepant dates capriciously relate to petrography and regional geology.
Neither internal consistencies, mineral-pair concordances, nor agreements between differing dating methods necessarily validate radiometric dating.
The large spread of values for igneous and metamorphic rocks (especially of the Precambrian) may indicate artificial imposition of time-values upon these rocks.
Once divested of all the time claims imposed upon it, the fossiliferous rock testifies to the Noahchian Deluge, and all life (fossil and extant) is then mutally contemporaneous as is demanded by a literal six (24 hr.) day Creation.
While I would strongly disagree that discrediting radiometric dating would in any way support the occurrence of a geologically-recent global flood, I will restrict myself to addressing Woodmorappe's main thesis which he summarizes as follows (p. 102):
This work, by contrast, seeks critically to evaluate the claims of radiometric dating via a geological approach; the author believing that dating is best understood in its geologic context.
Here I agree with the author, radiometric dating techniques are best understood in their geologic context. Unfortunately, I will provide evidence that Woodmorappe presents most of his examples devoid of any meaningful geologic context.
Following a short introduction, Woodmorappe's paper is divided into two main sections. In the first section he discusses Phanerozoic geochronology and in the second section he discusses Precambrian geochronology.
The Phanerozoic section is subdivided into Woodmorappe's claims regarding the selective publication of dating results, the dating of sedimentary rocks, supposed rationalizations for discrepant igneous dates from petrographic and regional geologic evidence, and what he considers to be problematic results from the radiometric dating of biostratigraphically-bracketed igneous rocks.
The Precambrian section is subdivided into claims regarding the consistency and concordance of radiometric dates, the alleged violations of superposition and cross-cutting relationships from radiometric age data, and supposedly problematic age values for igneous and metamorphic terranes.
Also included in Woodmorappe's paper is a single massive data table (Table 1, p. 103-113) containing over 350 of what are alleged to be anomalous radiometric dates with references to the primary literature.
I would like to first briefly mention three minor criticisms and one major criticism I have regarding Woodmorappe's paper as a whole.
The first criticism is in regard to the format of this paper, which may be more the fault of the Creation Science Research Quarterly than John Woodmorappe, is that the references are all referred to by a number and are listed by these numbers rather than alphabetically. Since there are 445 references, all listed in small typeface with nonstandard journal abbreviations, I found it very difficult to refer back and forth between the text and the reference list and to quickly locate references by author names. Also annoying was the frequent use of the abbreviation Op. cit. throughout the reference list necessitating a lengthy search through several pages of references for the original citation.
Secondly, throughout the paper, Woodmorappe rhetorically refers to young-earth creationists as Creationist-Diluvalists and, one assumes, anyone who disagrees as either evolutionist-uniformitarians or simply uniformitarians -- terms I believe most geologists would take issue with given the common misrepresentations by young-earth creationists of the term "uniformitarianism" first popularized by James Hutton in his 1788 Theory of the Earth (Shea, 1982).
My third criticism is Woodmorappe's use of rhetoric in general. This purports to be a scientific paper, and the Creation Research Society Quarterly considers itself to be a scientific journal, yet much of the language used by Woodmorappe to describe the work of other geologists is highly inflammatory rhetoric not normally seen in the scientific literature. For example, Woodmorappe claims that age data is routinely "explained away" (p. 102) or "rationalized away" (p. 113), that some age values are "arbitrarily" accepted or rejected as true (p. 113), that anomalous dates are not reported in the scientific literature (p. 114), that some geologists have "fudged" Rb-Sr isochrons (p. 118 & 120), and that geologists "cover-up the basic failure of the paradigm" (p. 123) of radiometric dating. The general tone throughout the paper is that geologists who use radiometric dating are often intentionally dishonest in their handling of the data.
Finally, a major general criticism of this paper is its sheer magnitude and its superficial treatment of data. Table 1 in the paper lists over 350 different radiometric dates from all geologic ages, there over 400 references in the reference list, and each paragraph in Woodmorappe's paper literally makes completely different claims against the validity of radiometric dating. Such a large volume of material means that Woodmorappe spends no more than a sentence or two (if even that) explaining each claim which results in an extremely superficial treatment of what, in many cases, are very complex, detailed studies. Quantity does not equal quality and only serves to overwhelm anyone attempting to deal with this paper in a critical manner. In my opinion, Woodmorappe would have had a much stronger paper if he simply confined himself to a detailed discussion of what he believed to be the dozen or so strongest examples discrediting a specific technique of radiometric dating as it's applied to a specific rock type or geologic environment.
Therefore, since it's practically impossible for anyone, such as myself, to properly evaluate all of the hundreds of claims made in this paper in any systematic manner, I decided to only evaluate a randomly-selected subset of claims and show why I believe they're invalid. While demonstrating that a subset of Woodmorappe's claims are invalid doesn't invalidate all of his claims, it does show that the quality of this work is highly suspect.
I would like to provide several specific examples of how Woodmorappe mishandles quotations from the geologic literature, relies on some clearly obsolete data to make his case against the reliability of radiometric dating, and cites data out of context thus giving a false impression of its validity.
Woodmorappe stated (p. 119):
There are many instances of dates with good internal consistency being rejected as not giving the correct age of a rock because they conflict with accepted values. In a Precambrian situation, K-Ar dates were much younger than the (presumed correct) Rb-Sr dates, and about the K-Ar dates McKee and Noble commented: "Continuous partial argon loss may have occurred. If this is the case, the consistency of these apparent ages is fortuitous."
In the example above, Woodmorappe misquoted McKee and Noble (reference 268) by omitting part of a sentence, without indicating this by ellipses, and by not completing their thought. What they actually wrote was (McKee & Noble, 1976, p. 1190):
Continuous partial argon loss may have occurred as a result of weathering or heating from deep burial, although neither phenomenon is apparent from field or petrographic studies. If this is the case, the consistency of these apparent ages is fortuitous. The consistency of the three K-Ar ages reported here suggests that the lower radiometric ages obtained by the K-Ar method may reflect an episode of heating about 800 m.y. ago.
This is a deliberate misquotation of McKee and Noble and this example alone would be enough to prevent publication of this paper in any reputable scientific journal.
I would also like to make a couple of other points about Woodmorappe's spin on this paper. He stated that the K-Ar dates were much younger than the (presumed correct) Rb-Sr dates which is true but may be misleading to non-geologists. The Rb-Sr method dated the basalts at 1,090,000,000 years old and the K-Ar method dated the basalts at 800,000,000 years old -- a large difference of 290,000,000 years but both dates are still well within the Proterozoic (late Precambrian). We're not talking about a possibility of the lava being 6,000 years old as young-earth creationists might like you to believe.
Well, what about that difference of 290,000,000 years? It's not a trivial discrepancy. Before I address that, I'd like to refer you to the abstract for McKee and Noble's paper:
Six whole-rock specimens of basalt from the Cardenas Lavas of the younger Precambrian Unkar Group yield a Rb-Sr isochron of 1.09 +/- 0.07 b.y. This age is believed to approximate the time of extrusion of the lava. Potassium-argon age determinations of the lava are considerably younger and may reflect either diffusive loss of 40-Ar or a period of heating about 800 m.y. ago.
By the way, it doesn't look like McKee and Noble are doing what Woodmorappe slanderously says that geologists do (p. 120):
The number of cases of concordances are no doubt exaggerated by the selective publication of dating results. In a discordancy, the results of the method most considered correct will be published, and the results of another method ignored.
McKee and Noble hardly ignored the K-Ar data, it's listed for all to see!
Read the abstract and then read the entire quotation as it should have been reported by Woodmorappe. Since he reports only a part of the quotation, it seems as if the only explanation is "fortuitous" diffusive argon loss. McKee and Noble do, however, go on to hypothesize another reason, an episode of heating around 800 Ma. Why didn't Woodmorappe discuss Elston and McKee's (1982) paper giving evidence for ...the occurrence of a thermal resetting event at 825 Ma related to uplift and erosion associated with a mild orogenic event in the Grand Canyon region (Larson, et al., 1994, p. 266)?
Why does Woodmorappe ignore this paper, and many others, which clearly have a bearing on the case he's trying to make?
A better explanation for argon loss, however, was proposed in a more recent study from Larson, et al. (1994). They reported on their detailed study of the Cardenas Basalt and their Rb-Sr age of 1125 +/- 174 Ma is a date which is statistically identical to that derived by McKee and Noble 20 years earlier. By the way, check out the isochron diagrams for Rb-Sr reported by McKee and Noble (1976) and Larson, et al. (1994). They both have beautiful correlations from different suites of samples. Anyway, Larson, et al. (1994, p. 266-267) found a correlation between the K-Ar dates and weight percent K2O in the samples. Samples with anomalously high K2O values are associated with younger dates so they proposed a perfectly reasonable (and testable!) explanation for the bad K-Ar dates from the Cardenas Basalt:
The explanation that seems most consistent with the data is that the progressive decrease in the dates is the result of increased loss of Ar associated with preferential burial alteration of those flows containing the higher contents of K2O. The more felsic the flow, the greater its viscosity, and the greater the content of mesostasis material containing large quantities of K2O and, therefore, the greater the likelihood of Ar loss during burial metamorphism.
Therefore it's clear that Woodmorappe misquoted McKee and Noble and was very selective in the presentation of data to support his claims. A full examination of the data shows the reliability of the Rb-Sr method for dating the Cardenas Basalt and a testable explanation for the argon loss and unsuitability of the Cardenas for K-Ar dating methods. This is a beautiful example of how science works in the real world.
Woodmorappe stated (p. 120):
Still other agreements between different dating methods are considered to have no meaning whatsoever. In commenting on a K-Ar/Rb-Sr agreement on biotite, Wasserburg and Lanphere said that it "... is a case of accidental concordance. That is, the time calculated does not have any meaning in terms of an event."
To begin, let's complete Wasserburg and Lanphere's (1965, p. 745) thought by quoting the entire relevant statement, as Woodmorappe, once again, should have done:
In every case, the strontium appears to have a retentivity greater than, or equal to, argon in each mineral species, and the relative order of the mineral retentivities for strontium is potassium feldspar > muscovite > biotite. It should be noted that the biotite (N-11) gives argon and strontium ages of 1390 and 1353 m.y., which is a case of accidental concordance. That is, the time calculated does not have any meaning in terms of an event. This suggests that both radiogenic argon and strontium may be lost in equal proportions from biotite during certain metamorphic events, and hence that ages based on concordant results from this mineral must be considered with caution.
Woodmorappe wants to imply that a correlation between K-Ar and Rb-Sr dating results have no meaning. He does this because correlations between different techniques are commonly taken to be evidence for the validity of the dates obtained as demonstrated by this passage from Dalrymple (1991, p. 124):
The use of different decay schemes on the same rock is an excellent way to check the accuracy of age results. If two or more radiometric clocks running at different rates give the same age, this is powerful evidence that the ages are correct.
Is Dalrymple wrong given what Wasserburg and Lanphere found? No, since this is a special case of a single date from a biotite mica. It's well known (Dalrymple and Lanphere, 1969, p. 200) that:
...strontium and argon can be lost from biotite at nearly the same rate, and the potassium-argon and rubidium-strontium ages would be concordant but incorrect.
This sample is from a pegmatite, and it was shown to have lost both Sr and Ar due to contact metamorphism from the intrusion of younger granitic rocks into an older metamorphic terrane. We have to therefore keep in mind the following advice (Dalrymple, 1991, p. 123-124):
Another method is to make age measurements of several samples (minerals or rocks) from the same rock unit. This technique helps to identify postformation geological disturbances because different mineral species usually respond differently to heating and chemical changes.
Other minerals (muscovite and microcline) from the same area were analyzed which had no such accidental concordance (Wasserburg & Lanphere, 1965, p. 745). Woodmorappe's quotation of Wasserburg and Lanphere's work was incomplete and misleading.
In Table 1 (p. 111), Woodmorappe has an entry which reads:
475 44 Rb-Sr b *bentonite/Tennessee, USA 366
This denotes an example of a biostratigraphically-bracketed bentonite (an altered ancient volcanic ash fall) in Tennessee which yielded an Rb-Sr radiometric date from biotites (the b following Rb-Sr) of 44 million years old when it should have been 475 million years old according to Woodmorappe's reference number 366 (Adams, et al., 1958).
Since the Adams, et al., (1958) reference refers to a short abstract, submitted for a Geological Society of America meeting, I would like to reproduce it in full below (including the data table) so we can see exactly what it does say:
Preliminary attempts to obtains absolute ages of bentonites have been made by isotopic Sr/Rb analysis of mica separated from the bentonites. Of the four mica samples listed below, one gives an impossibly low apparent age (44 m.y.) for the host bentonite; the other three apparent ages are somewhat systematic in indicating ages that are higher than the best estimates for the host bentonites. It is interesting to note that the maximum of 80 m.y. for the time between the Middle Ordovician and Late Devonian is in satisfactory agreement with the best estimates. Further refinements in technique should yield more accurate ages.
=============================================================== . Probably Age . Sr/Rb Age of Stratigraphic Age of Bentonites . of Bentonites . Mica Separate . (m.y.) . (m.y.) =============================================================== GH-25 Dowelltown member of the . 270 +/- 30 . 410 +/- 40 Chattenooga shale; Upper . . 417 +/- 40 Devonian . . GH-14 Chicamauga limestone, . 390 +/- 40 . 44 Middle Ordovician . . GH-27 Carters limestone, Stone . 390 +/- 40 . 496 +/- 50 Rivers Group, Middle . . Ordovician . . GH-31 Egglestone limestone, . 390 +/- 40 . 451 +/- 50 Middle Ordovician . . 479 +/- 50 ---------------------------------------------------------------The use of shorter-lived natural radioactivities e.g., K-40 on the mica - and the use of Th-U-Pb methods on the fine euhedral zircons also present in the bentonites may also lead to more accurate dates for these stratigraphic marker beds.
Anyone seeing this reference should immediately be wary given that it was published in 1958. A search on GeoRef (a large geologic bibliographic database) on the keywords "((Rubidium and Strontium) or (Rb and Sr))" reveals that one of the earliest geological papers on Rb-Sr dating was published by Hahn in 1944 and that there were only a total of 26 papers published on this subject before 1958. For comparison, GeoRef lists 1,826 papers with these keywords since 1990.
While there were some geologists working in 1958 on the application of Rb-Sr dating to geology, this was a brand new field and they were severely constrained by the limitations of their analytical equipment, particularly the mass spectrometer. Woodmorappe should be discussing the state of Rb-Sr dating today, not the state of Rb-Sr dating 40 years ago!
A short digression... Some may question if this is a fair criticism since Woodmorappe first published this paper in 1979. I believe it is for several reasons:
A more damaging indictment of this reference cited by Woodmorappe, however, is clearly explained in the following quotation from Dicken (1995, p. 40-41):
When the Rb-Sr method was first used in geochronology, the poor precision attainable in mass spectrometry limited the technique to the dating of Rb-rich minerals such as lepidolite. These minerals develop such high 87Sr/86Sr ratios over geologic time that a uniform initial 87Sr/86Sr ratio of 0.712 could be assumed in all dating studies without introducing significant errors. Such determinations are called 'model ages' because the initial ratio is predicted by a model rather than measured directly.
Subsequently, the Rb-Sr method was extended to less exotic rock-forming minerals such as biotite, muscovite and K-feldspar, with lower Rb/Sr ratios. However, discordant dates were often generated, by assuming an initial ratio of 0.712 when the real initial ratio was higher. This problem was first recognized by Compston and Jeffery (1959), and overcome by the invention of the isochron diagram (Nicolaysen, 1961).
So, we have Woodmorappe citing a 1958 paper as evidence against radiometric dating because an anomalous age was reported, yet Woodmorappe ignores the fact that such problems were recognized to be due to the invalid assumption of an initial 87Sr/86Sr ratio of 0.712 by 1959 (an assumption that needed to be made at the time because of the limitations of mass spectrometry in the 1950s) and by 1961 an entirely new technique was devised, and is still used today, which totally eliminates the problem!
Therefore, this data point does not, in any way, support Woodmorappe's thesis that present-day techniques of radiometric dating are unreliable. This example only calls into question Woodmorappe's judgement for including it.
In Table 1 (p. 104-111), Woodmorappe has at least 5 entries spread among five separate pages which, placed together here, are:
118 88 K-Ar g sediment/Esciagnelles, France 37
~260 165 K-Ar g sediment/Vestspitsbergen, Norway 92
334 250-78 K-Ar g shale/Texas, USA 123
390 303 +/- 18 Rb/Sr g Carlisle Center Fm./New York, USA 144
510 411-50 K-Ar g Franconia Fm./Wisconsin-Minnesota, USA 185
413-33 Rb-Sr g
The first column denotes the biostratigraphically expected ages for the sediments or sedimentary rocks in millions of years, the second column gives the radiometrically determined age using the mineral glauconite (denoted by the g), K-Ar or Rb-Sr is the dating method, the type and locations of the samples are given, and the last column refers to Woodmorappe's reference list. Despite the different reference numbers Woodmorappe gives, all of this data is found in a single paper by Hurley, et al. (1960).
Since Woodmorappe provides no other information, let's see what Hurley, et al. (1960, p. 1793) say about their study:
In this study an attempt has been made to discover if the mineral glauconite can be used for the measurement of the absolute age of sediments. The investigation has included the measurement of K-Ar and Rb-Sr ratios in well dated glauconite materials and also an intensive examination of the material itself to see if there is any correlation of observed age variations with the physical nature, geological history, or environment of the samples.
This paper, published in 1960, is one of the first studies of the suitability of the mineral glauconite for radiometric dating. What did they conclude (p. 1808)?
In summary, it is concluded that there is some consistent mechanism acting to lower the age of glauconites by 10-20 per cent. It appears that this mechanism may be related to modifications in the structure of the glauconitic material in diagenesis and that this process continues with time.
Doesn't it look like they've found that glauconite isn't all that suitable for radiometric dating since it's consistently giving younger-than-expected ages? In 1961, Evernden, et al. (p. 78) wrote:
Data accumulating from various geochronology laboratories appear to indicate that glauconite is of dubious usefulness for the purpose of obtaining accurate dates of sedimentary strata by the potassium-argon method.
All this shows is that the mineral glauconite may be unsuitable for radiometric dating because it loses argon. It hardly shows that radiometric dating, in general, is fundamentally flawed. Woodmorappe's inclusion of this data, from a preliminary study attempting to evaluate glauconite's usefulness, is hardly fair. Especially when the data is scattered throughout a several page data table without comment.
But is this the whole story? Listen to what Odin (1982, p. 402) says about the radiometric dating of glauconite (now referred to as glaucony):
The recent data obtained on glaucony, thanks to improved geochemical research methods together with a better understanding of the stage of genesis of this authigenic marine facies, permit the design of a specific method of sampling.
The preliminary studies done on these samples will help to presume greater reliability for the selected chronometers. This method alone will establish the numerical age of a stratigraphic horizon in the absence of preconceived ideas. The proposed method will allow a priori assessment of the reliability of data and tends to eliminate the often used procedures which deduce after the analysis the geochemical history of glaucony according to whether the obtained age 'appears correct' or not. We do not imply that it can be known with certainty beforehand that an apparent age will be that of deposition or not, but we know better today how to increase the probability of measuring glaucony ages which do accurately reflect depositional ages.
Woodmorappe quoted from what is now an obsolete source. Our knowledge of how to more accurately assess radiometric ages from glauconite has increased greatly since 1960 and the paper by Hurley, et al. is now only of historical interest. The data points used by Woodmorappe should never have been included in the data table because they're from a study which, while important in 1960, is now obsolete.
In Table 1 (p. 111), Woodmorappe has an entry which reads:
260 259-315 K-Ar b *Oslo Series (subvolcanics)/Norway 93
216 Th232/Pb208
Reference 93 refers to a paper by Neumann (1960). Let's examine exactly what Neumann (p. 173-174) says about this data:
Some of the apparent ages given in table 1 are now of historical interest only, and some of them should for different reason be disregarded. U/Pb and Th/Pb ages or a combination of them, without isotope determinations may in some cases be misleading, and should therefore be discarded because of their unreliability. Lead-alpha ages of zircons will give a first approximation only, and are too crude to merit any further discussion. The same applies to some extent to K-Ar ages of feldspars as the cause of a later leakage of already built up Ar in this mineral are not at present sufficiently well understood to permit any safe conclusions concerning the history of formation of the feldspars in question on the basis of their apparent K/Ar ages.
This paper is a compilation of earlier studies performed in the 1950s when these techniques were first being developed. According to the author, much of the data was out of date already by 1960. Once again, Woodmorappe slips clearly obsolete data into his data table and presents it as evidence against the reliability of radiometric dating.
In Table 1 (p. 103-105), Woodmorappe has 5 entries spread among three separate pages which, placed together here, are:
42 18-36 K-Ar g sediment/California, USA 10 65 46 K-Ar g sediment/California, USA 16 115 31 K-Ar g sediment/Salzgitter, W. Germany 36 152 26 K-Ar g sediment/Braunschweig, W. Germany 49 165 21 K-Ar g sediment/Coston Del Vette, Italy 54
The first column denotes the biostratigraphically expected ages for the sediments in millions of years, the second column gives the radiometrically determined age of the sediments, K-Ar is the dating method, the letter g denotes that the mineral dated was glauconite, the locations of the sediments are given, and the last column refers to Woodmorappe's reference list. Despite the different reference numbers Woodmorappe gives, all of this data comes from a single paper by Evernden, et al. (1961). Since Woodmorappe does not place the data into any sort of context, let's examine this paper and see what's going on here.
The abstract for the paper by Evernden, et al. (1961, p. 78) states that:
Potassium-argon dates of stratigraphically known biotite-bearing tuffs, lava flows, and intrusions when used as controls show that illite and glauconite sample selected carefully with regard to geologic history and prepared properly are suitable for obtaining dates almost as accurate as those from igneous biotite.
The authors want to show that illite and glauconite can be used for the K-Ar dating of sediments. They clearly admit there are some difficulties with using glauconite (p. 78):
Data accumulating from various geochronology laboratories appear to indicate that glauconite is of dubious usefulness for the purpose of obtaining accurate dates of sedimentary strata by the potassium-argon method.
But they go on to argue that it can be used if the samples are collected carefully with regard to their geologic history and spend some time discussing the factors which are detrimental to the accuracy of K-Ar dates from glauconites. One important thing to keep in mind is the date (1961) of this paper. A search of GeoRef using the keywords "(glauconite and (ar or argon))" shows that geologists only started applying K-Ar dating to glauconites in 1958 and that this was a new field of study (11 papers on the subject, half of them in Russian, before 1962). Geologists at that period of time were attempting to evaluate the applicability of K-Ar dating to glauconite. So, even before we start examining this claim, we see that Woodmorappe is reporting on the state of the art 35 years ago which may or may not have any relevance to today.
One of the major difficulties in using glauconite for K-Ar dating is the well-known fact that argon is lost from glauconites during heating. Dalrymple and Lanphere (1969, p. 172), for example, state that:
Glauconite loses argon more easily than other micas, perhaps because of its extremely small grain size. A temperature of about 150 C is sufficient to cause argon loss if the temperature is prolonged.
and (p. 173):
In summary, glauconite is a very useful mineral for potassium-argon dating and is about the only mineral that can be used to date sedimentary rocks directly. The post-depositional history of the sample is critical, however, for burial of only a few thousand feet or the slightest thermal event may cause argon loss.
As a matter of fact, Dalrymple and Lanphere use the data from Evernden, et al. (1961) to create a figure, reproduced below, illustrating this very fact:
All of these samples were collected from a single glauconite-bearing formation, the Kreyenhagen in California, and one can see the correlation of decreasing K-Ar radiometric age with depth (the subsurface material was sampled from drill holes). This correlation is due to argon loss as the material is heated with increasing burial. The age of the sample found at the surface, however, was in excellent agreement with the expected age (within 5%). The other samples clearly illustrate the well-known fact that argon is lost from glauconite with heating and will yield lowered ages. What does Woodmorappe say about this data? He only has the following entry in his Table 1 (p. 103):
42 18-36 K-Ar g sediment/California, USA 10
This is most emphatically not an example of errors in radiometric dating! As a matter of fact, the K-Ar method worked exactly as expected (argon is lost from glauconites with increasing depth of burial) and this data poses absolutely no problems for geologists.
Let's also look at a few more of Woodmorappe's examples illustrating this same effect of lowered ages for buried glauconite do to heating and argon loss (p. 103-105):
115 31 K-Ar g sediment/Salzgitter, W. Germany 36
Sample KA 311 of Evernden, et al. (1961). This sample was collected from a drill hole (no depth given).
65 46 K-Ar g sediment/California, USA 16
Sample KA 178 of Evernden, et al. (1961). This sample was collected from 8,100 feet down a drill hole.
152 26 K-Ar g sediment/Braunschweig, W. Germany 49
Sample KA 272 of Evernden, et al. (1961). This sample was collected from 1,170 meters (3,800 feet) down a drill hole.
Another reason, besides simple burial, for argon loss in glauconites, is heating due to tectonic activity. For example:
165 21 K-Ar g sediment/Coston Del Vette, Italy 54
This is sample KA 308 from Evernden, et al. (1961). What do they say about this sample and why does it date so young (p. 83)?
KA 308 is an interesting confirmation of the influence of post-depositional processes on argon retention. This is a sample of Upper Lias (Lower Jurassic) glauconitic sandstone from the Feltrine Alps of northern Italy. This area was deformed during the Alpine orogeny. The indicated potassium-argon age (21 million years) appears to date that orogeny rather than the time of deposition of the glauconite.
Once again, there are absolutely no problems here for geologists. These are not errors in radiometric ages, simply cases where the technique, in an early attempt to evaluate its applicability to dating glauconite in sediments, yielded lowered ages for buried and heated sediments as it's expected to do! Why didn't Woodmorappe discuss the 40 glauconite dates listed in the data table of this paper that were well within 10% of the expected geologic age?
Woodmorappe's citation of this data, out of its geologic context, is misleading and a cursory examination of the cited source clearly shows that this information in no way supports Woodmorappe's thesis that radiometric dating, in general, is unreliable. At most it shows that one should be careful when dating buried glauconites with the K-Ar method which is something that geologists already know (and is thoroughly discussed in the scientific literature).
Woodmorappe (p. 118) makes a serious charge when he discusses the work of Lyons & Livingston (1977):
An outright case of fudging the Rb-Sr isochron is evident in the following description of the Kinsman pluton (ref. 140) by authors Lyons and Livingston: "The Kinsman Quartz Monzonite for all six isochron points also yields an unsatisfactory isochron of 605 +/- 83 m.y. The isochron shown... however, has been drawn by eliminating sample MK 37-73... the resulting isochron of 411 +/- 19... embraces what we consider to be an accurate determination of the age of emplacement of the Kinsman."
Let's look at Figure 4, which I reproduced using the original data, from Lyons & Livingston (1977):
Note that the best-fit line does not include the data point in the lower-left region of the graph (MK 37-73). Woodmorappe states that they fudged this isochron, by omitting that data point, presumably because they liked the age of 411 million years better than the age of 605 million years. Personally, I think that if they were truly attempting to "fudge" the data, they wouldn't even have reported MK 37-73 and no one would have been the wiser.
So why did they eliminate this data point from the isochron? Reading the paper shows that this is simply another example of Woodmorappe citing an example yet not discussing its geologic context thus giving a false impression of its reliability.
What reason do the authors give for omitting MK 37-73 (p. 1809)?
Sample Mk37-73 is a sheared and boudinaged dike of aplitic texture which intrudes the Kinsman Quartz Monzonite and has been deformed along with it. Mineralogically, it is leucocratic biotite tonalite, with an extraordinarily low Rb/Sr ratio, and a sufficiently low Sr87/Sr86 ratio (0.7042) to imply mantle derivation. Sample S11-73 (Table 1) is a very similar aplitic rock cutting the Bethlehem Gneiss, probably with a similar petrogenetic history. Geochemically, both these rocks have Rb, Sr, and Sr87/Sr86 contents similar to those of basalts (Kistler and Peterman, 1973). These data imply, to us, that the anatexis responsible for the initial development of the Kinsman (and Bethlehem) magmas occurred near the crust-mantle interface. Major melting occurred in the lower crust, giving rise to granite magmas with initial Sr87/Sr86 ratios of approximately 0.710. Infrequently, however, residual melts of mantle derivation were vented upward along the same conduits that were previously used by Kinsman or Bethlehem magmas - hence the injection of minor amounts of mantle-derived material into rocks of predominantly crustal derivation.
Woodmorappe claims, about this and other examples, that (p. 118):
Any discrepant Rb-Sr isochron can be explained away by claiming that some points on it don't "belong" on that isochron because they allegedly came from different crustal sources and had different initial Sr87/Sr86 ratios.
The basic question is: Is there any basis for the omission of the MK 37-73 data point from the isochron or is it just done to "fudge" the data to obtain a more favorable result?
What do the authors claim about the data point?
Woodmorappe may very well disagree with this interpretation, but if he accuses the authors of "fudging" data he has a responsibility to at least discuss it and to explain why he disagrees. It's not enough to simply dismiss it all with a sneer. By presenting the data the way he did, isolated from the geologic context, he creates a false impression regarding the data's validity.
Woodmorappe says the following about the Baraboo sequence in Wisconsin (p. 122):
Dott and Dalziel wrote: "Lithic correlation of the Baraboo metasedimentary sequence with Animikie rocks in northern Michigan and northern Wisconsin has seemed compelling, for each succession has pure quartzite overlain by a carbonate and iron-bearing interval, which is in turn succeeded by thick slates." The Baraboo rocks have yielded a "meaningless" date near 750 m.y. and a spread of K-Ar and Rb-Sr dates from 1.1 to 1.6 b.y. By contrast, Animikie rocks have given U-Pb and Rb-Sr dates from 1.9 to 2.1 b.y., with an even older correlative of 2.1-2.4 b.y. dates. Are rocks of such similar composition and lithostratigraphy really separated by hundreds of millions of years of time, or is radiometric dating a delusion?
Once again, let's look at a more complete quotation from Dott and Dalziel (1972, p. 553-554):
Lithic correlation of the Baraboo metasedimentary sequence with Animikie rocks in northern Michigan and northern Wisconsin has seemed compelling, for each succession has pure quartzite overlain by a carbonate and iron-bearing interval, which is in turn succeeded by thick slates. While we had no evidence for doubting this age assignment, the many past errors in Wenerian lithic correlations and the isolated geographic position of the Baraboo rocks led us to test the hypothesis by isotopic dating of rocks associated with the Baraboo Quartzite and from published isotopic dates at Waterloo, Wisconsin.
Fair enough, they simply decided to test, using radiometric dating, the commonly held assumption that the two sequences were correlative since similar assumptions in the past had been incorrect.
Let's now look at Woodmorappe's comment about a "meaningless" date near 750 Ma. Dott and Dalziel say (p. 558):
In an attempt to define a younger age limit for the Precambrian sequence at Baraboo, K-Ar dating was attempted for two deformed phyllitic rocks from a zone in the upper part of the Baraboo Quartzite (Dalziel and Dott, 1970). The phyllosilicates of the first of these (sample US-12, table 3) proved to be mostly pyrophyllite [Al2Si4O10(OH)2]. The sample had very little K the resulting date of 760 +/- 50 m.y. is meaningless. The second specimen, however (sample 68-2, table 3), contained more K and yielded a calculated date of 1,109 +/- 40 m.y., which seems more meaningful even though it is clearly a minimum date.
Is there any justification for considering the date meaningless? One only needs to look at Table 3 (p. 557) where it's reported that sample US-12 had only 0.091% K and 0.00603 ppm Ar40* while sample 68-2 had 1.635% K and 0.1903 ppm Ar40*. That low a concentration of potassium for sample US-12 would mean that the analyses were done to the limits of the method's sensitivity and would therefore be unreliable. There were clearly defined reasons for considering the age to be problematic.
What about the spread of K-Ar and Rb-Sr dates from 1.1 to 1.6 b.y? The authors wrote (p. 556):
In spite of possible effects of metamorphism on the Rb-Sr ratios, whole-rock dating was performed in an attempt to establish at least the minimum age of the rhyolites, and with the hope at the same time of constraining the older age limit of the overlying Baraboo Quartzite.
In other words, they went into this knowing that the low-grade metamorphism (identified petrographically) might affect the Rb-Sr age dates. The dates they would obtain however, would constrain the minimum ages of the igneous rocks and therefore be of some use. The volcanic rocks yielded an isochron of 1,640 +/- 40 Ma with the following caution (p. 556):
The age of 1,640 m.y. is interpreted as a minimum value representing the time of most recent isotopic homogenization and closure of the Rb-Sr system of the analyzed material, whether that be the actual time of extrusion or the time of some later possible loss of radiogenic Sr87.
Yes, the dating yielded a range of values, but a range of values was expected since the rocks had been subjected to metamorphism. From this data, however, we can at least constrain the minimum age of closure of the isotopic system and this is of some use in interpreting the regional geology of the area.
Now let's look at Woodmorappe's rhetorical question Are rocks of such similar composition and lithostratigraphy really separated by hundreds of millions of years of time, or is radiometric dating a delusion?
I believe that Dott and Dalziel (1972) have made a compelling case for the Baraboo sequence being younger than the Animikie sequence and correlative with other quartzites which are younger than the Animikie (which is what half of the paper actually discussed). While more work needs to be done on these rocks, Woodmorappe has little basis for simply ignoring the data and dismissing their work with a sarcastic comment.
Woodmorappe wrote (p. 120):
Certain concordances are dissolved after further studies. In one situation described by Higgins, U-Pb and Rb-Sr isochron dates agreed at 425 m.y. for three igneous bodies. One of the igneous bodies was reinterpreted as being much later and its 425 m.y. Rb-Sr mineral isochron dissolved and considered a meaningless result.
Let's examine this claim. Higgins (1973, p. 186) states the following (for the complete references given in this quotation, refer to the original article):
I previously accepted (Higgins, 1972) Wetherill and others' (1966) radiometric ages (Rb-Sr) on pegmatites that Hopson (1964) had interpreted as postorogenic (also see Fisher, 1970, p. 313) as indicating that deformation had largely ended in the central Appalachian Piedmont by Early Silurian time and that the peak of metamorphism was past by about 425 m.y. ago. I now believe that interpretation was in error. Wetherill and others' (1966) isochrons for minerals from many different pegmatites (their figures 3-6 and 9-10) clearly indicate ages of 340 to 350 m.y. for the pegmatites. Only one of their isochrons (their fig. 2) could be interpreted as indicating an age of 425 m.y., and the initial 87Sr/86Sr ratio of 0.725 for that isochron clearly indicates an anatectic source (Baltimore Gneiss). Thus, the problems with the isochron, besides the fact that the points on which it is based have considerable scatter, probably involve differing initial ratios, a heterogeneous source region, reequilibrium (rehomogenization), and lack of a closed system (see Dalrymple, Lanphere, and Peterman, 1970). In contrast, the remarkable repetition of isochrons close to 345 m.y. from many different source pegmatites must indicate a real event. Wetherill and others (1966, p, 2151) noted various ways in which the apparently older age (they called it 'presumably older', 1966, p. 2147) might have been raised.
The next paragraph (which I won't bother quoting in full since it's about as long as the previous one) begins:
Further evidence against the 425-m.y. interpretation comes from...
And the next long paragraph (which I'll also spare you) begins:
Metamorphism after 425 m.y. ago is still further collaborated by...
Higgins concludes this long section by saying that all of the evidence he presented:
... constitute strong evidence that the end of strong regional metamorphism in the central Appalachians occurred close to 350 m.y. ago.
This paints quite a different picture than that presented by Woodmorappe. Higgins gave a lot of extremely good reasons to dispute the older interpretation of 425 m.y. in favor of a 350 m.y. age. Woodmorappe's reference to the paper by Higgins is totally misleading by stating that an isochron was "dissolved" and considered "meaningless" yet neglecting the entire geologic context in which this decision was made. The large amount of evidence carefully discussed and referenced by Higgins was totally ignored as if it never existed. A more fair characterization of this data would be to say that the validity of a marginal isochron was reevaluated by Higgins (1973) in light of more recent geologic fieldwork. This interpretation, however, wouldn't support Woodmorappe's insinuations that geologists arbitrarily toss out radiometric age data.
Woodmorappe wrote (p. 114):
There is a tendency to leave unpublished the results which conflict with those of other investigators or which disagree with accepted values. Thus, a certain reluctance to provide a non-fitting date seems to be the case in this report by Forman: "The remarkable congruent date obtained for the Tiburon Penninsula eclogite with that ... for the Cazadero tectonic blocks is very pleasing (147 m.y. versus 135 to 150 m.y.). Thus it is a little untidy to report 106 m.y. for the age of the amphibolite on Catalina Island."
Let's ignore, for now, the geologic context of Forman's (1970) study and instead simply look at what Woodmorappe is saying.
First, Woodmorappe directly implies that Forman was reluctant to provide a certain date yet Forman only states that the date was "a little untidy". I fail to see how Woodmorappe can ascribe that motive to Forman given the text of the above quotation. Secondly, Woodmorappe draws from this example, the grand conclusion that there is a tendency among researchers not to publish discrepant results. Not only doesn't this follow from the example provided, Woodmorappe is not here providing evidence for that asssertion and totally ignored is that fact that all of Woodmorappe's data comes from the published scientific literature! If it wasn't for geologists reporting all of their data, even if it isn't tidy, Woodmorappe would have had nothing to write about.
The following are what I consider to be some serious problems with the examples provided by Woodmorappe in the support of his thesis.
Several of the examples I provide above (e.g. Example 1) show that Woodmorappe was very selective in his use of quotations from the primary literature. In science, and other academic disciplines, quoting people out of context to make your point is generally frowned upon as being dishonest.
I believe that I've shown, through my examples above, that Woodmorappe presents virtually all of his examples totally devoid of any geological context. By doing so, he often presents a false picture of the validity of the radiometric age data. One cannot properly evaluate a claim, such as the example below, without referring to the original paper (p. 111):
540 340 K-Ar g sediment/ng 149
This example presents a sediment, origin not given (ng), which dated by the K-Ar method on glauconites at 340 million years when it should have been 540 million years according to reference 149. Would you perhaps be interested in seeing the paper, by Thompson and Hower (1973), if I told you it's title was "An explanation for low radiometric ages from glauconite"? Doesn't Woodmorappe believe it's relevant to discuss the study from which this data was derived?
It's a well-known fact that not all rocks and minerals are suitable for radiometric dating and that not all radiometric dating methods are suitable for all geologic samples.
An analogy I like to use is that of a wooden yardstick and a flexible tape measure. Wooden yardsticks are great for measuring tabletops yet aren't very good for measuring the circumference of trees. Flexible tape measures, on the other hand, work quite well for measuring the circumference of trees. Similarly, there are some geologic samples for which the K-Ar method doesn't work very well (because they've lost argon due to heating) yet the Rb-Sr method works perfectly well. How did geologists discover this and quantify it? By carefully testing and comparing the various analytical techniques and coupling their observations with laboratory experiments and theoretical models of things like argon diffusion in biotites.
Woodmorappe, throughout his paper, lists examples of these early tests and claims that the discordant dates reported are examples of why radiometric dating is invalid. They are nothing of the sort. They are instead examples of how geologists refine and test their analytical techniques and actually show why we should trust radiometric dating (because it's been so thoroughly evaluated for all different types of samples from all different types of geologic environments).
Woodmorappe's strategy in this paper was to present a very large number of examples of what he believed to be problems with K-Ar, Rb-Sr, U-Pb, and Ar-Ar methods of radiometric dating from the Precambrian to the Cenozoic using a multitude of minerals and rock types yet discussing each of these examples in only a superficial way, if at all. This type of quantity over quality approach is very unconvincing since it seems to indiscriminantly mix data without differentiating between any of the examples he used in support of his thesis. I would compare this approach to that of using a shotgun in the hope that one of your pellets will bring down your prey.
Woodmorappe cited some of the earliest studies of radiometric dating in geology to support his claims. Throughout this paper, studies from the 1950s, 1960s, and 1970s were all thrown together as if they had equal validity. There have been great improvements in the technology used for radiometric dating since the 1950s (analytical equipment in the 1950s had vacuum tubes and computers were a novelty) and the following data, taken from a search on GeoRef, shows the explosive growth in the number of scientific papers published on four radiometric dating techniques for each decade between 1950 and 1990 (this graph also indicates the growth in our knowledge of these radiometric dating techniques).
At first glance, Woodmorappe's paper looks quite impressive with over 350 entries in his data table of allegedly anomalous dates and over 400 references to the primary literature. Even if all 400 or so of Woodmorappe's examples, however, came from separate studies (which they don't), and even if all of Woodmorappe's examples are problematic (which I think I've shown is false), we can compare that against more than 10,000 papers published on four popular radiometric dating techniques alone up to 1980 (and some techniques, such as 40Ar/39Ar dating, aren't even included on this graph). In other words, Woodmorappe has only referenced, as a rough approximation, less than 4% of the studies and, on this basis, concludes that all radiometric dating is invalid.
As I've said before, Woodmorappe's paper would have been more interesting if he simply confined himself to discussing a specific problem, with examples, of only one radiometric dating technique. By attempting to demonstrate that all of radiometric dating is false, he spreads himself, and his examples, far too thin and weakens his case considerably.
The biggest problems I see with these claims is that organizations like the Institute for Creation Research (which published Woodmorappe's book) aim their literature at laypersons. Most non-geologists simply wouldn't be able to evaluate the claims made in this book so it's left to people like me, who seem to enjoy wasting time, to visit an academic library (luckily right down the hall from my office) and dig out these 20-30 year-old references. Most people simply wouldn't bother and if they did, wouldn't understand most of the papers anyway since many of them are highly technical.
Why doesn't Woodmorappe publish in refereed scientific journals if he has valid criticisms of radiometric dating? He needs to convince geologists of these problems, not the average person in the church pew. I think this strategy is adopted simply because his claims don't stand up to detailed scrutiny by people who are familiar with the relevant geologic literature.
To summarize, I believe that Woodmorappe's claims about the validity of radiometric dating and geochronology are not supported by a careful examination of the evidence he presents in this paper.
Does that mean I am arguing that radiometric dating works perfectly all of the time or that there are no anomalous dates or problematic results in geochronology? No, and I'm sure Woodmorappe even listed some real problems for radiometric dating along with his non-problematic examples (although I would argue that they represent a very small minority of results). The real world is a very complicated place and all scientific investigations of real-world problems uncover difficulties with our theories and methodologies. Our attempts to understand and resolve these difficulties, however, are what increase our knowledge of the natural world (which is why we understand radiometric dating far better now than we did 40 years ago!).
The impetus for reviewing this paper was favorable mention of it by someone on the Science & Christianity mailing list which I moderate. I would also like to make it clear that I am a structural geologist, not an expert on radiometric dating, and that I have not used radiometric dating in my research to date. I have no vested interest in the methodology used by my fellow geologists.
As a geologist and an evangelical Christian, I am very concerned about the popularity of young-earth creationism within the Christian community. I too believe in Genesis 1:1, but there is simply no credible evidence that the earth is less than 10,000 years old (and a lot of credible evidence that it's around 4,600,000,000 years old) or that there was a geologically-recent global flood. My experience with young-earth creationists is that their arguments are almost always based on obsolete data, a misrepresentation of the facts, and a willful ignorance of contrary data. My experience has also taught me, and many others, that virtually all of the claims made by young-earth creationists simply crumble when investigated in any detail.
Truth is important. I strongly believe that the young-earth creationism movement, with it's foundation built on the historicity of Genesis rather than the historicity of the Gospels, has harmed the cause of Christ by making Christians appear foolish and by making it very difficult for scientists and those who value reason and truth to accept Christianity. Those who teach young-earth creationism to Christians should keep in mind the warning given in James 3:1 and remember what our Lord said about those who lead His sheep astray in Matthew 18:6. Christians should have a reputation for being scrupulously honest, not a reputation for playing fast and loose with the truth.
While John Woodmorappe certainly doesn't represent the worst in young-earth creationists (people like Carl Baugh and Ron Wyatt come to mind), this paper does demonstrate a willingness to be less than completely honest in discussing the evidence for and against radiometric dating. While some young-earth creationists have hailed John Woodmorappe as a meticulous researcher and claim that his arguments are well reasoned, persuasive, and thoroughly documented, I would only recommend this paper as a typical example of pseudoscience likely to convince only those unwilling or unable to evaluate Woodmorappe's arguments by comparing his claims with what's really published in the scientific literature.
The following are some resources on the world-wide web for learning about various topics in geology which were discussed in this review:
The following books are highly recommended for learning about radiometric dating in general:
Adams, J.A.S., Edwards, G., Henle, W., & Osmond, K. 1958. Absolute dating of bentonites by strontium-rubidium isotopes. Geological Society of America Bulletin 69, 1527.
Compston, W. & Jeffery, P.M. 1959. Anomalous common strontium in granite. Nature 184, 1792-1793.
Dalrymple, G.B. & Lanphere, M.A. 1969. Potassium-Argon Dating. W.H. Freeman.
Dalrymple, G.B. 1991. The Age of the Earth. Stanford University Press.
Dickin, A.P. 1995. Radiogenic Isotope Geology. Cambridge University Press.
Dott, R.H. & Dalziel, I.W.D. 1972. Age and correlation of the Precambrian Baraboo Quartzite of Wisconsin. Journal of Geology 80, 552-568.
Elston, D.P & McKee, E.H. 1982. Age and correlation of the late Proterozoic Grand Canyon Disturbance, Northern Arizona. Geological Society of America Bulletin 93, 681-699.
Evernden, J.F., Curtis, G.H., Obradovich, J., & Kistler, R. 1961. On the evaluation of glauconite and illite for dating sedimentary rocks by the potassium-argon method. Geochimica et Cosmochimica Acta 23, 78-99.
Forman, J.A. 1970. Age of the Catalina Island Pluton, California. In: Bandy, O.L. Radiometric Dating and Paleontologic Zonation: Geological Society of America Special Paper 124, 37-45.
Hahn, O. 1944. Geologische altersbestimmungen nach der 'Strontiummethode'. Geologiska Foreningens i Stockholm Forhandlingar 66, 90-97.
Higgins, M.W. 1973. Superimposition of folding in the northeastern Maryland Piedmont and its bearing on the history and tectonics of the central Appalachians. American Journal of Science 273-A, 150-195.
Hurley, P.M., Cormier, R.F., Hower, J., Fairbairn, H.W., & Pinson, W.H., Jr. 1960. Reliability of glauconite for age measurement by K-Ar and Rb-Sr methods. American Association of Petroleum Geologists Bulletin 44, 1793-1808.
Larson, E.E., Patterson, P.E., & Mutschler, F.E. 1994. Lithology, chemistry, age, and origin of the Proterozoic Cardenas Basalt, Grand Canyon, Arizona. Precambrian Research 65, 255-276.
Lyons, J.B. & Livingston, D.E. 1977. Rb-Sr age of the New Hampshire plutonic series. Geological Society of America Bulletin 88, 1808-1812.
McKee, E.H. & Noble, D.C. 1976. Age of the Cardena Lavas, Grand Canyon, Arizona. Geological Society of America Bulletin 87, 1188-1190.
Morris, J.D. 1994. The Young Earth. Master Books.
Neumann, H. 1960. Apparent ages of Norwegian minerals and rocks. Norsk Geoloigisk Tidsskrift 40, 174-191.
Nicolaysen, L.O. 1961. Graphic interpretation of discordant age measurements on metamorphic rocks. Annals of the New York Academy of the Sciences 91, 198-206.
Odin, G.S. 1982. How to measure glaucony ages. In: Odin, G.S. Numerical Dating in Stratigraphy: Part I. John Wiley & Sons, 387-403.
Shea, J.H. 1982. Twelve fallacies of uniformitarianism. Geology 10, 455-460.
Thompson, G.R. & Hower, J. 1973. An explanation for low radiometric ages from glauconite. Geochimica et Cosmochimica Acta 37, 1473-1491.
Wasserburg, G.J. & Lanphere, M.A. 1965. Age determinations in the Precambrian of Arizona and Nevada. Geological Society of America Bulletin 76, 735-758.
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