The following text was posted to the talk.origins newsgroup on December 28, 1998. It consists of David Plaisted's response to Kevin Henke's original critique, with additional comments in response from Henke. All contents are © 1998,1999 by Dr. Kevin R. Henke. The text has been reformatted into HTML, with live links in place of text URLs where appropriate. I have not altered the content in any substantial way.
Dr. Henke is currently a post doctoral fellow in the Department of Chemistry at the University of Kentucky. Dr. David Plaisted earned his PhD in computer science from Stanford University in 1976, and is currently Professor of Computer Science at the University of North Carolina, Chapel Hill.
Text was provided by Dr. Kevin Henke, HTML formatting by Tim Thompson.
For the readers of Talk.origins and others:
In early December, 1998, I commented on David A. Plaisted's anti-radiometric dating article "The Radiometric Dating Game". David kindly replied to my critique on December 15, 1998. Below I reply further to David's comments of December 15, 1998. My original critique, from early December 1998, is in Part 1.
DAP = comment by David A. Plaisted, creationist.
KRH = comment by Kevin R. Henke, geologist and advocate of radiometric dating.
DAP: I was not aware that many of my arguments originated from Slusher. I appreciate this clarification.
KRH: You're welcome. However, I don't think that Mr. Slusher would appreciate how one of your anonymous email friends misused his 1981 book. There were no quotation marks around the word for word statements in your report on pages 4-5, 10-11 in The Radiometric Dating Game and Slusher (1981, p. 38-40) was never credited. Because it is difficult to check the reliability of anonymous emails, I don't think that it's a good idea to use them in reports. Anonymous sources are of questionable quality and they cannot be checked or verified by your readers. Certainly, you wouldn't want to be associated with anonymous contacts that possibly plagiarize the works of their fellow creationists.
DAP: Dr. Henke criticizes my stand on the age of the earth. My main concern is not with the age of the earth, but with the strata of the Cambrian period and later.
DAP: I appreciate the technical clarifications about lava and magma and about mica, but these do not affect the main argument.
DAP: Dr. Henke is right that my discussion of a change in decay rates is speculation. But a tremendously large number of neutrinos might not have much of an effect on most elements, except to cause radiactive elements to decay faster, since neutrinos interact principally (but very weakly) with nucleii.
KRH: If a large number of neutrinos affected radioactive decay, why wouldn't they also disrupt the nuclei of stable isotopes? If neutrinos disrupted atomic nuclei, what effect would that have had on terrestrial life forms? Again, we have NO evidence that radioactive decays rates have been significantly affected by neutrinos, neutrons or anything else. Arguments about changes in radioactive decay rates have no scientific support and are just wishful thinking by creationists.
DAP: I realize that neutrons would not have been responsible, rather neutrinos. Another proposal by some creationists is that the physical constants have changed, allowing for a more rapid decay rate in the past. But if the decay rates have not changed, it would not bother me.
KRH: Creationist Setterfield has argued that the speed of light has decayed since the "creation a few thousand years ago." If the speed of light has changed, then radioactive decay rates and other physical constants would also be changed. Setterfield's arguments are so flawed that even some of his follow creationists tore them apart in a couple of 1988 issues of the "Creation Research Society Quarterly." See:
Aardsma, Gerald E., 1988, "Has the Speed of Light Decayed Recently?"
Creation Research Society Quarterly, vol. 25, #1, June, 1988, p. 36f.
Humphreys, D. Russell, "Has the Speed of Light Decayed Recently? - Paper 2"
Creation Research Society Quarterly, vol. 25, #1, June, 1988, p. 40-45.
KRH: There are also other comments and articles from Setterfield's creationist critics in the September 1988 issue of the "Creation Research Society Quarterly". Also see Impact #179, Has the Speed of Light Decayed?, by Aardsma.
DAP: The problem with decay rates and branching factors is discussed nicely in a recent issue of Science (December 4, 1998, p. 1840). The problem is not that better values are not always known, but that even when they are known, they are not always used. But still, I appreciate the clarifications and updates provided by Dr. Henke.
KRH: Nothing in Renne et al. (1998a) gives any comfort to creationists. The article is dealing with errors of about 3% and less.
DAP: Dr. Henke states that the argon retention abilities of minerals are well known. There are many variables involved in a supposed millions of years history, and the analysis is done under the assumption that such a history of life is correct. Without knowing the ages of the rocks, it is hard to see how one can correctly account for all of these variables. The same applies to the effects of water.
KRH: A rock with a long history has not necessarily experienced a lot of events or "variables." It's history may have been very quiet and boring. Some Precambrian rocks, like those in the subsurface of central North America, have no chemical or mineralogical evidence to indicate that they have been heated or otherwise altered in 2.5 billion years. This is especially true if they're dense and unfractured plutonic rocks that have never been exposed to oxidizing conditions. Yes, as surprising as it sounds, nothing significant may happen to rocks for millions or even billions of years. Many of these ancient rocks are located in the center of continents far away from subduction zones and other active boundaries of tectonic plates.
KRH: How do analytical chemists that measure Pb, Sr, Rb, etc. allow their results to be determined by any assumptions about the "history of life"? The chemists would need to make sure that the zircons, feldspars, biotites or whatever minerals that they're analyzing are unaltered. They would then need to properly analyze the samples. But they don't need to know if the samples came from the Precambrian Canadian Shield of western Ontario or a Tertiary granite from New Zealand. The chemists might ask the geologist if they should expect a lot of daughter product or not. Having a rough idea of what to expect may be important in the detection efforts or to speed up their work. However, I would think that to keep biases out of the analysis that the geologist would tell the chemists as little about the samples and their origins as possible. I know that with the recent controversy about "life" in a Martian meteorite, the geologists did not tell many of their subcontracting analytical chemists that the samples supposedly came from Mars.
KRH: Again, if water has greatly disrupted the isotopic chemistry of a rock sample, in all probability, the water would also noticeably change the mineralogy of the sample. Altered rocks are usually easy to identify.
DAP: Along this line, it is interesting that I received e-mail from an author of a book on radiometric dating from an evolutionary viewpoint. He stated that K/Ar dating and Rb/Sr dating are no longer considered accurate, but that dating based on zircons is now emphasized.
KRH: This is another anonymous email. Instead of using anonymous emails, we should be looking at any peer-reviewed documents from your anonymous contact that summarize his/her skepticism of radiometric dating methods. Again, why should we trust any source that we can't verify? Your "evolutionary" author's statement sounds like something that Alan P. Dickin might say. Dickin (1995, p. 53), interestingly, has been very critical of Rb/Sr isochron dating.
DAP: Dr. Henke admits that xenoliths can be hard to see. This is therefore another possible problem with radiometric dating.
KRH: Xenoliths can be hard to see in the field, but they're often not a problem if you use thin sections and some other laboratory work. As creationist Austin states in "Excess Argon within Mineral Concentrates from the New Dacite Lava Dome at Mount St. Helens Volcano", a number of different xenolith lithologies have been found at his Mt. St. Helen's field site. However, except for gabbro xenoliths, Austin's report gives no indication that he avoided other, less noticeable, xenoliths. Furthermore, it is clear from his Figure 4 that he improperly sampled and dated zoned feldspars, which may partially explain his old dates. So, the real question is: why does Austin make sampling mistakes that most other geologists would know enough to avoid?
DAP: Dr. Henke gives some examples where different methods agree. But what is needed is a comprehensive double-blind study, not a few examples.
KRH: I cited Harland et al. (1989), Faul (1966) and Dalrymple (1991), which contain MORE than just "a few examples." Before you claim that they only contain a "few examples," you should look at the page after page of data tables in these references. If Harland et al. (1989) doesn't contain enough examples for the Phanerozoic, try these references:
Odin, Gilles S., 1982, "Numerical Dating in Stratigraphy," parts 1 & 2, John Wiley & Sons, Chichester, 1040p. This two volume set contains numerous examples of reliable Phanerozoic radiometric dates.
Tucker et al., 1998, "New U-Pb zircon ages and the duration and division of Devonian time," Earth and Planetary Science Letters, 1998, v. 158, p. 175-186. Tucker et al. (1998) compare U/Pb dates to fossil data and other calibrations of the Devonian time period from the literature.
KRH: The following references report on interlaboratory studies of numerous K/Ar and 40Ar/39Ar mineral standards:
Samson and Alexander, 1987, "Calibration of the Interlaboratory 40Ar-39Ar Dating Standard, Mmhb-1," Chemical Geology (Isotope Geoscience Section), v. 66, p. 27-34. This article discusses the calibration of a hornblende in a syenite from southern Colorado. The age of the hornblende is about 520.4 ± 1.7 million years and is based on 58 potassium and 54 40Ar* analyses from more than 18 different laboratories.
Sudo et al., 1998, "SORI93 biotite: A New Mineral Standard for K-Ar Dating," Geochemical Journal, v. 32, p. 49-58. Sudo et al. (1998) describe the development of a new K/Ar standard from a 92.6 ± 0.6 million year old Japanese granodiorite.
Renne et al., 1998b, "Intercalibration of Standards, Absolute Ages and Uncertainties in 40Ar/39Ar Dating," Chemical Geology, v. 145, p. 117-152. This article discusses numerous analyses on several different mineral standards. For example, the Fish Canyon sanidine, alone, was analyzed 380 times.
Other K/Ar and 40Ar/39Ar mineral standards include: P-207 (Dalrymple and Lanphere, 1969); Bern4M and Bern4B (Jaeger et al., 1963 and Flisch, 1982); Hb3gr (Turner et al., 1971); and LP-6 (Ingamells and Engels, 1976; Odin et al., 1982).
DAP: It is, I agree, possible to correct for atmospheric argon in K/Ar dating. But this does not apply to the argon diffusing up in the earth's crust, which has a different isotopic composition.
KRH: Why not determine the initial Ar isotopes with K/Ar isochron methods? Also see Mussett and McCormack (1978) on using a three dimensional plot to distinguish initial and excess argon in K/Ar dating.
DAP: Dr. Henke's treatment of argon contamination in the crust is speculative, even though he cites some sources. How can we know for sure what is going on down there?
KRH: There have been NUMEROUS field and modeling studies of Ar in the Earth's interior (as examples, I found these studies just looking through a few recent journals: Albarede, 1998; Kamijo et al., 1998; Tolstikhin and Marty, 1998; Winckler et al., 1997; Marty and Humbert, 1997; and Morgan, 1998). Also see Dickin (1995, p. 287-293); Chamorro-Perez et al. (1996), Trieloff et al. (1997), Jackson (1998, p. 169-171) and Faure (1986, p. 79-80)). You can read this literature to get an idea of what we know about the movement of argon in the upper mantle over time. Contrary to creationist claims, scientists know quite a lot about argon in the Earth's interior. In addition, K/Ar isochron dating is often helpful in overcoming difficulties with determining irregular initial Ar isotope values. Examples from the literature, such as Harland et al. (1990) and Dalrymple (1991), show that K/Ar dates are often consistent with U/Pb and Rb/Sr dates.
DAP: He admits that some rocks (hornblendes) can be affected in this manner and give too old dates. How do we know this is not a more general problem?
KRH: First of all, hornblende is a mineral and not a rock. We know that it's not a more widespread problem because we understand the crystalline structures of hornblende, micas, and other minerals that are commonly used in K/Ar dating. Scientists have been studying the interactions between argon and different minerals for decades and they know where the argon can hide in the crystalline structures of these minerals. You can read the literature to find out how argon interacts with the minerals that are commonly used in radiometric dating. Begin by looking at the table of closure temperatures in Harland et al. (1990, p. 74) and their references. The references should provide information on how argon interacts with different crystalline structures. McDougall and Harrison (1988, chapter 5) provide laboratory results and detailed mathematical explanations of argon diffusion through various minerals, including biotite, hornblende, muscovite and feldspars.
DAP: Again, Dr. Henke brings up the age of the earth question, which is not my concern here. But I appreciate his information about the amount of argon in the earth.
DAP: Much of Dr. Henke's criticism is directed at John Woodmorappe and not at me. I do not wish to comment on this, except to express appreciation for the explanation of the 34 billion year isochron. But I would like to hear John Woodmorappe's side of the story.
KRH: In disputes between authors, it's always a good idea to look up all of the original references that are at the center of the dispute. That is, look up the references in Woodmorappe and compare what they say with what Dalrymple (1984) and Woodmorappe (1979, 1985) CLAIM that they say.
DAP: Dr. Henke admits that chlorites and devitrified glasses can produce inaccurate K/Ar dates. Why is this believed?
KRH: Again, we understand the chemical and structural changes that occur as glass devitrifies or as biotite or other minerals convert to chlorite. We recognize that these structural changes may result in the release of argon or its absorption. Look at Deer et al. (1972-1977) or another mineralogy book. You can see where the argon could be located in hornblende, biotite or chlorite crystals and how these locations could be disrupted or formed as biotite converts to chlorite. Volcanic glass is full of random bubbles that may contain argon. As the glass devitrifies (breaks down) these bubbles would be opened and their contents released. This is not difficult to understand. For further discussions, see McDougall and Harrison (1988, p. 33) and their references.
DAP: The dates do not agree with the expected values, so some explanation is found.
KRH: So, what's wrong with looking for an explanation for any observation? Sometimes, scientists think that they have an explanation for an observation, but investigations show that they are wrong. Geologists always try to explain their results, whether their results are expected or a complete surprise.
DAP: To me, it is reasonable to assume that all of the old dates for fossil-bearing rock are unreliable.
KRH: You can call them "unreliable," but that doesn't answer the question: why are they unreliable? Why is it "reasonable" to call all Phanerozoic radiometric dates unreliable? Do you call all clocks unreliable, just because a few of them don't keep good time? How do you explain the consistent results in Harland et al. (1990), Hirschmann et al. (1997) and the other references that I mention in this reply? If a K/Ar analysis of a chlorite gives a date of 17 billion years, both creationists and geochronologists would be skeptical of this result. The scientist would try to find out why the date is bad. Geochronologists would look at the crystalline structure of the chlorite. Chemical comparisons may be made between the chlorite and any surrounding minerals. Laboratory studies would look at how temperature and fluids may affect the movement of argon in and out of the chlorite. Field investigations may also reveal important information about the history of the chlorite and its host rock, such as metamorphic events, faulting, or pronounced weathering. However, is the creationist going to do any science or will the creationist just quote Genesis, walk away, and solve nothing?
DAP: I would like a clearer explanation of why Dr. Henke feels that chlorites and devitrified glasses can produce too young K/Ar dates, and if this is so, why they were dated in the first place.
KRH: Again, as I just discussed above, the gain or loss of argon has to do with changes in the chemistry and amorphous structure of glass as it devitrifies and as chlorite develops from biotite or other minerals. Often scientists date materials to determine how they retain or release argon. Not all radiometric dates are taken literally, that is, not all radiometric dates are used to determine the chronological history of their host rocks. Sometime the dates have other geochemical applications. For example, Dalrymple and Moore (1968) dated the rims and centers of submarine pillow basalts to understand the retention of Ar as a function of the lava's cooling rate. They didn't intend on deriving actual radiometric dates for the basalts. In another study, Hart (1964) obtained K/Ar and Rb/Sr dates on minerals surrounding the Eldora stock in Colorado. The purpose of the study was to understand how the injection of the pluton affected the retention of daughter products in the minerals of the surrounding rock as a function of distance from the pluton.
DAP: On reading Dr. Henke's reply, one sees that even he acknowledges a large number of problems with radiometric dating.
KRH: Yes, scientists admit that there can be problems, but they are not as hopelessly numerous or complex as creationists claim. Some rocks, especially sedimentary rocks, cannot even be dated with radiometric methods. Fortunately, radiometric methods often work so that geologists have put together a reasonable history for the Earth.
DAP: I would like to ask him what method is always reliable. I would like him to provide a list of methods that are always reliable, and together give conventional dates for the majority of the geologic column.
KRH: There is no such thing as "always" in science. No scientific method works for all samples and under all conditions. Science just doesn't work that way. Again, Harland et al. (1990) lists numerous dates that have been used to calibrate the Phanerozoic geologic time scale. I have already cited Hyndman (1985, p. 675-676), which provides a list of largely reliable radiometric methods and which minerals or other materials are most effective with those methods. Faure (1986) and Dickin (1995) provide further details on which materials in which rocks are useful for dating igneous crystallization and metamorphic events.
DAP: My impression is that even methods that are considered reliable can be explained away if the dates do not fit.
KRH: Again, no method is perfect in all situations. The real issue is not to explain away anything. Science DEMANDS that you explain EVERYTHING, whether the methods give you the results that you expect or not. Even when things seem to work, explaining the process helps scientists to understand what's going on, which in turn allows us to expand on the methods and possibly find new applications.
DAP: The problem is complicated by the fact that if the date is too young, one can invoke a later event, and if the date is too old, one can say it was inherited from before.
KRH: You can't rationally invoke anything unless you have field or laboratory evidence to back it up. People can cry "god did it" or "the argon just leaked out," but peer-reviewed journals would demand at least some reasonable ideas and field/laboratory evidence to explain an unexpected event. If a date is too old when compared with other dates, magnetic or fossil data, the scientist must explain why. If the date is too young, again the scientist must explain why and provide the field/laboratory evidence to back it up. For example, the mineralogy of the rock, minerals textures, or field structures may indicate the presence of one or more metamorphic events. If scientists don't explain anomalous results, the peer-reviewers might suspect that the geologist messed up the sample collection or the laboratory messed up the analysis. Furthermore, even when the dates seem reasonable, peer-reviewers would still want some references or evidence to back up the results. All results should be justified and verified.
DAP: But this does call these dating methods into question, since many dates could have been inherited form earlier events before the appearance of life.
KRH: Certainly, igneous rocks may have experienced a number of metamorphic, weathering or other alteration events after crystallization. Some radiometric methods, such as K/Ar, may date the last metamorphic event. Other methods, such as Rb/Sr whole rock analyses, may date the initial crystallization event. Discordant U/Pb dating may provide ages for both dates. I don't know what the appearance of life has to do with radiometric dates.
DAP: Dr. Henke discusses a few cases of double blind studies or comparisons of different methods that show agreements. But what is needed is a general study, not just isolated cases.
KRH: What do you mean by a "general study"? I really don't know what you're asking for that hasn't already been done. You just need to review the literature before calling for a "general study"and stating that the literature only has "isolated cases." The literature is full of formations and mineral samples that have been dated countless times. The results are consistent, abundant and not "isolated." Again, Harland et al. (1990) and Odin (1982) list numerous examples of radiometric dates that are used to support the geologic time scale from Cambrian to Recent. Numerous meteorites and world famous formations have been dated many times with many different methods. Dalrymple (1991, p. 140), for example, lists 56 Rb/Sr, Pb/Pb, and U/Pb analyses for the Qorqut Granite of Greenland from Moorbath et al. (1981), Pankhurst et al. (1973), and Baadsgaard (1976). The results ranged from 2.52 to 2.58 billion years. These results are very consistent and undermine creationism. The 55 million year old Skaergaard Intrusive of Greenland has been consistently dated by 40Ar/39Ar dating (Hirschmann et al., 1997); fission track methods (Brooks and Gleadow, 1977); fossils and magnetic data in associated rocks (Soper et al., 1976; Faller, 1975; Tarling, 1967; Tarling et al., 1988; Schwarz et al., 1979); and other radiometric methods (Hirschmann et al., 1997, p. 647-648). Again, interlaboratory studies of minerals from Phanerozoic outcrops fill the literature. I found several of them just looking through a few volumes of the 1998 literature and they're listed above.
DAP: I do not comment on whether haloes give evidence for altered decay rates or not.
DAP: It is true that mixings of two sources in isochrons can be detected. But mixings of three sources cannot. This is discussed in great detail in the article "More Bad News for Radiometric Dating", along with other aspects of isochron methods.
KRH: I don't know how you can claim that mixing of three sources cannot be detected. As an example, Dickin (1995, p. 180-182) shows that 87Sr/86Sr vs 1/Sr graphs have been used by Moorbath and Thompson (1980) to decipher the complex mixing history of the Tertiary Isle of Skye volcanics in northwest Scotland. Dickin (1995, p. 180-199) mentions a number of other isotopic techniques that are used to detect mixing between multiple sources. In particular, Dickin (1995, p. 192-194) discusses Carlson and Hart (1988) in some detail, where various Nd, Pb, and Sr isotope plots indicate THREE distinctive mantle sources for basalts from the northwestern United States. Simonetti et al. (1998) used Sr, Nd and Pb isotopes to demonstrate that THREE distinct mantle components mixed to form Deccan alkaline complexes in India.
KRH: Your hypothetical example in "More Bad News for Radiometric Dating" is often hard to follow, but it is clearly invalid. You attempt to show how three magmas with different concentrations of a radioactive parent isotope (P), the daughter isotope (D) of the parent, and a non-radioactive isotope (N) of the daughter would go undetected by isochron methods. You state that for the first source (#1), N1 = 0. For the second source, the parent is absent, so P2 = 0. You state that the third source has no D, N, or P, so D3 = 0, P3 = 0, and N3 = 0. To make things more realistic, let's use Rb/Sr dating, so P = 87Rb, D = 87Sr and N = 86Sr. When we apply your analogy to a real world system, we can immediately see that your assumptions are invalid. Terrestrial magmas and rocks, water, meteorites and moon rocks have initial 87Sr/86Sr (D/N) values near 0.7. However, your first source ignores nature and has D1 > N1 and N1 = 0 or an undefined 87Sr/86Sr. This is unrealistic. You can't set the Sr and 87Rb values for your hypothetical three magmas to any values you want. Nature restrains your selection of values and voids your hypothetical argument. Because nature restrains and controls the chemistry of Rb and Sr, Rb/Sr dating works.
DAP: Dr. Henke does not respond to my criticism of the isochron based on meteorites from which the 4.5 billion year age of the earth is obtained.
KRH: I did respond. I simply cited Dalrymple (1991). I did not extensively summarize or comment on Dalrymple (1991, chapter 6) because I thought that you could read it for yourself and that the reference would answer your questions better than I could.
DAP: This involves only a small number of meteorites. What happens when more meteorites are added?
KRH: Dalrymple (1991) lists more than just a "small number of meteorites." For example, tables in Dalrymple (1991, p. 287-289, 291) list numerous results. Specifically, Figure 6.9 on p. 286 contains the results of 94 radiometric ages of 69 meteorites. Table 6.3 on p. 287-289 contains the results of 240 radiometric dates on 42 meteorites. None of these results are only a few thousand years old. For further details, see Dalrymple (1991, chapter 6).
DAP: But in any case, my main concern is with the age of life, not the age of meteorites.
I encourage readers to consult the articles "More Bad News for Radiometric Dating" and "Magma Opus Tells a Tale on Radiometric Dating" for additional information. I also encourage them to re-read my article "The Radiometric Dating Game", where a number of Dr. Henke's points are well discussed.
DAP: In general, I believe that practicing geologists are well aware of the weaknesses and assumptions of radiometric dating.
KRH: Yes, we admit our weaknesses and limitations. Despite the problems, radiometric dating usually works as the literature indicates. At the same time, I wish that creationists would admit the weaknesses, limitations and questionable assumptions associated with taking Genesis literally.
DAP: I close by re-citing a quotation from an evolutionary source, cited in a creationist web site ( Science and the Bible - Part 2, The Scientific Evidences for Creation):
"It is obvious that radiometric techniques may not be the absolute dating methods that they claimed to be. Age estimates on a given geological stratum by different radiometric methods are often quite different (sometimes by hundreds of millions of years). There is no absolutely reliable long-term radiological "clock". The uncertainties inherent in radiometric dating are disturbing to geologists and evolutionists... ."
KRH: You should really look up the original reference instead of just quoting it from another creationist web site. As the web site indicates, this invalid quotation is from Stansfield, William D., 1977, "The Science of Evolution," MacMillian, p. 84. Stansfield is a biologist and not a geochronologist. So, why should I accept a 20 year old opinion on radiometric dating from a biologist? Would you want your dentist to give you advice on your eye sight? Besides, did you ever wonder why your creationist allies left off the last part of this quotation? Notice the three periods at the end of the quote. Here is the full quotation with the missing part in capital letters.
"It is obvious that radiometric techniques may not be the absolute dating methods that they claimed to be. Age estimates on a given geological stratum by different radiometric methods are often quite different (sometimes by hundreds of millions of years). There is no absolutely reliable long-term radiological "clock". The uncertainties inherent in radiometric dating are disturbing to geologists and evolutionists, BUT THEIR OVERALL INTERPRETATION SUPPORTS THE CONCEPT OF A LONG HISTORY OF GEOLOGICAL EVOLUTION."
KRH: This 20 year old quotation from a biologist is hardly a death sentence for radiometric dating.
KRH: Again, David, thanks for your time. Please read the references that I cite. They would answer most, if not all, of your concerns and questions. If not, my colleagues and I can give you dozens and dozens of other references. There's no need to be so distrustful of radiometric dating.
Aardsma, Gerald E., 1988
"Has the Speed of Light Decayed?"
Institute for Creation Research, El Cajon, CA.
Albarede, F., 1998,
"Time-dependent Models of U-Th-He and K-Ar Evolution and the Layering of Mantle Convection,"
Chemical Geology, v. 145, p. 413-429.
Baadsgaard, H., 1976,
"Further U-Pb Dates on Zircons from the Early Precambrian Rocks of the Godthaabsfjord Area, West Greenland,"
Earth and Planetary Science Letters, v. 33, p. 261-267.
Brooks, C.K. and A.J.W. Gleadow, 1977,
"A Fission Track Age for the Skaergaard Intrusion and the Age of the East Greenland Basalts,"
Geology, v. 5, p. 539-540.
Carlson, R.W. and W.K. Hart, 1988,
"Flood Basalt Volcanism in the Northwestern United States,"
in "Continental Flood Basalts," J.D. MacDougall, ed., Kluwer, p. 35-62.
Chamorro-Perez, E.; P. Gillet and A. Jambon, 1996,
"Argon Solubility in Silicate Melts at very High Pressures. Experimental Set-up and Preliminary Results for Silica and Anorthite Melts,"
Earth and Planetary Science Letters, v. 145, p. 97-107.
Dalrymple, G. B., 1984,
"How Old is the Earth?: A Reply to `Scientific' Creationism," in "Proceedings of the 63rd Annual Meeting of the Pacific Division, American Association for the Advancement of Science,"
vol. 1, pt. 3, Frank Awbrey and William Thwaites (Eds).
Dalrymple, G.B., 1991,
"The Age of the Earth," Stanford University Press, Stanford, CA.
Dalrymple, G.B. and Lanphere, M.A., 1969,
"Potassium-Argon Dating, Freeman, San Francisco.
Dalrymple, G.B. and J.G. Moore, 1968,
"Argon 40: Excess in Submarine Pillow Basalts from Kilauea Volcano, Hawaii,"
Science, v. 161, p. 1132-1135.
Deer, W.A.; R.A. Howie; and J. Zussman, 1972-1977,
"Rock Forming Minerals," 5 vols., Longman, London.
"Radiogenic Isotope Geology," Cambridge University Press.
Faller, A.M., 1975,
"Paleomagnetism of the Oldest Tertiary Basalts in the Kangerdlugssuaq Area of East Greenland,"
Bull. Soc. Soc. Denmark, 24, p. 173-178.
Faul, H., 1966,
Ages of Rocks, Planets, and Stars, McGraw- Hill, New York.
Faure, G., 1986,
"Principles of Isotope Geology," 2nd ed., John Wiley & Sons, New York.
"Potassium-Argon Analysis" in "Numerical Dating in Stratigraphy,"
(G.S. Odin, ed.), Wiley and Sons, Chichester, p. 151-158.
Harland, W.B.; R.L. Armstrong; A.V. Cox; L.E. Craig; A.G. Smith; and D.G. Smith, 1990,
"A Geologic Time Scale 1989," Cambridge University Press, Cambridge.
Hart, S.R., 1964,
"The Petrology and Isotopic-Mineral Age Relations of a Contact Zone in the Front Range, Colorado,"
Journal of Geology, v. 72, p. 493-525.
Hirschmann, M.M.; P.R. Renne; and A.R. McBirney, 1997,
"40Ar/39Ar Dating of the Skaergaard Intrusion,"
Earth and Planetary Science Letters, v. 146, p. 645-658.
Hyndman, Donald W., 1985,
"Petrology of Igneous and Metamorphic Rocks,"
2nd ed., McGraw-Hill Book Company, New York.
Ingamells, C.O. and J.C. Engels, 1976,
"Preparation, Analysis and Sampling Constants for a Biotite,"
Nat. Bur. Stand., Spec. Publ., 422, p. 401-419.
Jackson, I. (Ed.), 1998,
"The Earth's Mantle: Composition, Structure, and Evolution,"
Cambridge University Press.
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