Radiometric dating is a method used by geochronologists to determine the age of a rock. Many rocks appear to give ages of thousands and millions of years old, but how accurate are the assumptions involved in this dating method? To begin, here is a quick overview of how radiometric dating works. Atoms from a given element will always have the same number of protons, but can have different numbers of neutrons, this is called an isotope of the element (Lutgens and Edward, 2006:39). Some isotopes decay radioactively from an unstable state to a stable state, from the unstable parent isotope to a stable daughter isotope. A half-life is the amount of time it takes for half of the parent isotope to decay into its daughter isotope. By measuring the amounts of both parent and daughter isotopes in a sample relative to each other scientists can predict how long ago the parent isotope was formed. Five radioactive isotopes are commonly used in radiometric dating. Uranium-238 decays into Lead-206 with a half-life of 4.5 billion years, Uranium-235 decays into Lead-207 with a half-life of 712 million years, Thorium-232 decays into Lead-208 with a half-life of 14.1 billion years, Rubidium-87 decays into Strontium-87 with a half-life of 47 billion years, and Potassium-40 decays into Argon-40 with a half-life of 1.3 billion years (Lutgens and Edward, 2006:430). Radiometric dating works best for igneous rocks, because sedimentary rocks consist of grains from multiple rocks of different ages (Lutgens and Edward, 2006:433). Therefore sedimentary layers are dated relative to the igneous rocks nearby (Lutgens and Edward, 2006:435). Radiometric dating involves very precise measurements of the different isotopes, but there are many unprovable assumptions involved in dating rocks whose origin was not witnessed. We will examine some of these assumptions, take a look at some “unexpected” radiometric dates, see some examples of discordant dates, and explore some of the specific challenges of individual methods.
Radiometric dating assumptions
The first assumption in radiometric dating is that the radioactive decay rates of elements are constant, but some research suggests that this may not be the case, “Not only have radioactive decay rates been slightly altered in the laboratory but several researchers believe they have found evidence in pleochroic halos that decay rates have changed through geological time.” (Johannsen, 1980:5).
The second assumption is that no daughter atoms were originally present in the sample, this is something that simply cannot be guaranteed since it was not witnessed.
The third assumption is that the sample remained a “closed system” from the time of formation. This means that no parent or daughter atoms were added or removed. “Unfortunately, geological materials and environments do not often meet this requirement” (Durrance, E.M. 1986. Radioactivity in Geology. Chichester, England: Ellis Horwood Ltd., 441, p.287) (Woodmorappe, 1999:28). For example, an iron meteorite lost 80% of its potassium content when distilled water ran over it for 4.5 hours (Bowden, 1981:65). Argon has a tendency to diffuse from areas of high pressure to areas of lower pressure, so it will move from the bottom of a rock to the top making the top look older (Bowden, 1981:65). “Unfortunately, the U-Pb and Th-Pb systems rarely stay closed in silicate rocks, due to the mobility of Pb, Th, and especially U, under conditions of low-grade metamorphism and superficial weathering” (Dickin, A.P. 1997. Radiogenic Isotope Geology (updated paper-back edition). U.K., New York: Cambridge University Press, p.105) (Woodmorappe, 1999:33). To avoid issues of weathering or leaching, “one simple safeguard is to use only fresh, unweathered material and not samples that may have been chemically altered” (Lutgens and Edward, 2006:430). In practice this is not always easy. For example, regarding carbon-14 dating, “It is self-evident that a contaminated sample will give an erroneous date, but it is frequently very difficult to ascertain the extent to which a sample has been contaminated” (Bradley, 1999:54). A very revealing discovery showed that different layers of a given mollusk shell contained different uranium concentrations, showing that uranium is mobile in biogenic carbonates (Schroeder, 1970:869).
Geochronologists know about these challenges and assumptions, but some of their solutions should be critically questioned, “It is common geochronological practice to regard the oldest age obtained from a suite of geologically contemporaneous rocks as a best estimate of the true age, radiogenic Ar loss implicitly being assumed to be the only perturbing mechanism” (Mitchell, 1989:56). But more disturbing is the fact that, “radiocarbon dates are often ignored or dismissed as a “bad date” if they do not fit an a priori hypothesis” (Thompson, T. A., G. S. Fraser, and G. Olyphant. 1988. Establishing the altitude and age of past lake levels in the Great Lakes. Geological Society of American Abstracts with Programs 20(5):392) (Woodmorappe, 1999:41). If this is the level of subjectivity involved in radiometric dating, can we be certain about the data that does get published?
Dates older than expected
Now we will take a look at some radiometric dates that are older than expected by evolutionists. The reason for these examples is to show that this does occur and therefore radiometric dates can not and should not be treated as “scientific facts”.
According to evolutionists the earth is approximately 4.5 billion years old. Here are some examples of radiometric dates for rocks on the earth that appear to be older than the earth itself!
Rb-Sr isochrons gave dates up to 8.75 billion years (Holland, 1995:504) and K-Ar datings on biotites gave dates of 4.9 billion years (Pankhurst, 1973:163).
A supposed Tertiary basalt isochron yielded an age of 10 billion years (Mark, R.K., Lee-Hu C., Bowman, R.E., and E.H. McKee. 1974. Recently (-109y) Depleted Radiogenic (87/86 Sr=0.706) Mantle Source of Ocean Ridge-Like Thoileitte, Northern Great Basin. Geological Society of America Abstracts with Programs 6:456) (Woodmorappe, 1979:122).
The K-Ar age of chlorites yielded 7-15 billion years (Gerling, E.K., Morozova, I.M., and V.D. Sprintsson. 1968. On the Nature of the Excess Argon in Some Minerals. Geochemistry International 9(6):1090) (Woodmorappe, 1979:122).
Here are some examples of radiometric ages that were unexpectedly older than anticipated by evolutionists.
Sandstone in Yenisei, USSR from the Tertiary period, expected to be 1 million years old was dated to be 81 million years by K-Ar dating (Firsov L.V. and S.S. Sukhorukova. 1968. “Quaternary” Glauconite of Cretaceous Age from the Lower Yenisei. Doklady: Earth Science Sections(translation from Russian) 183:101-2) (Woodmorappe, 1979:103).
A Nogales Formation tuff in Arizona from the Tertiary period, expected to be 10 million years was dated to be 153±10 million years by K-Ar dating (Marvin, R.F., Stern, T.W., Creasey, S.C., and H.H. Mehnert. 1973. Radiometric Ages of Igneous Rocks From Pima, Santa Cruz, and Cochise Counties, Southeastern Arizona. United States Geological Survey Professional Paper Bulletin 1379:18) (Woodmorappe, 1979:103).
Uranium ores in Wyoming from the Tertiary period, expected to be 55 million years were dated to be 200-280 million years using Pb207/Pb206 dating (Ludwig, K.R. 1978. Uranium-Daughter Migration and U/Pb Isotope Apparent Ages of Uranium Ores, Shirley Basin, Wyoming. Economic Geology 73:31) (Woodmorappe, 1979:103).
Basalts in Patagonia, Argentina from the Tertiary period, expected to be less than 70 million years were dated to be 500 million years using Rb-Sr dating (Hawkesworth, C.J., Norry, M.J., Roddick, S.C., and P.E. Baker. 1979. 143Nd/144Nd, 87Sr/86Sr, and Incompatible Element Variations in Cale Alkaline andesites and Plateau Lavas From South America. Earth and Planetary Science Letters 42:46, 48) (Woodmorappe, 1979:103).
Shale in Great Basin, Australia from the Jurassic period, expected to be around 140 million years was dated to be 435-780 million years by Rb-Sr dating (Faure, G., Kaplan, G., and G. Kulbicki. 1966. Interpretation des mesures d’ages fournies par l’analyse de mineraux argileux d’une se’rie sedimentarie d’Australie. Colloques Internationaux du Centre National de la Recherche Scientifique No. 151, p.572) (Woodmorappe, 1979:104).
The Rose Dome Granite in Kansas from the Permian period, expected to be less than 270 million years was dated to be 1180±60 million years using Rb-Sr dating (Bickford, M.E. and D.G. Mose. 1969. Age of the Rose Dome Granite, Woodson County, Kansas. Geological Society of America Abstracts with Programs-1969, part 2, p.2) (Woodmorappe, 1979:107).
Dates younger than expected
Aside from radiometric dates that appear to be older than expected, there are also examples of dates that appear to be younger than expected by evolutionists. Here are some examples, again, to show the subjectivity involved.
Granite porphyry in New Mexico from the Pre-Cambrian period, expected to be greater than 600 million years was dated to be 34 million years using K-Ar dating (Hoggatt, W.C., Silberman, M.L., and V.R. Todd. 1977. K-Ar Ages of Intrusive Rocks of the Central Peloncillo Mountains, Hidalgo County, New Mexico. Isochron/West: A Bulletin for Isotope Geochronology 19:4) (Woodmorappe, 1979:112).
Bentonite in Tennessee from the Ordovician period, expected to be 475 million years was dated to be 44 million years using Rb-Sr dating (Adams, J.A.S., Edwards, G., Henle, W., and K. Osmond. 1958. Absolute Dating of Bentonites by Strontium-Rubidium Isotopes. Geological Society of America Bulletin 69:1527) (Woodmorappe, 1979:111).
Tuffs in Andscollo, Argentina from the Carboniferous period, expected to be around 300 million years turned out to be 85 million years according to K-Ar dating (Valencio, D.A. 1977. The paleomagnetism and K-Ar age of Upper Carboniferous Rocks from Andscollo Province of Neuquen, Argentina. Transactions American Geophysical Union 58:744) (Woodmorappe, 1979:107).
Ponta Grossa Formation shale in Brazil from the Devonian period, expected to be around 370 million years ended up being 173±16 million years using Rb-Sr dating (Cordani, U.G., Kawashita, K., and A.T., Filho. 1978. Applicability of the Rubidium-Strontium Method to Shales and Related Rocks. Contributions to the Geologic Time Scale (American Association of Petroleum Geologists Studies in Geology No.6) p.106) (Woodmorappe, 1979:109).
Rhyolite tuff in Florida from the Silurian period, expected to be 400 million years was dated to be 173±4 million years according to K-Ar dating (Lowry, W.D., 1974. North American Geosynclines-Test of Continental-Drift Theory. American Association of Petroleum Geologists Bulletin 58:591-2) (Woodmorappe, 1979:109).
Mt. St. Elias pluton in Alaska from the Triassic period, expected to be about 190 million years turned out to be 80 million years according to K-Ar dating (Hudson, T., Plfaker, G., and M.A. Lanphere. 1977. Intrusive Rocks of the Yakutat-St. Elias Area, South Central Alaska. Journal of Research of the United States Geological Survey 6:161, 164) (Woodmorappe, 1979:106).
An ore from Wittichen, West Germany from the Permian period, expected to be greater than 230 million years was dated to be 97 million years using Pb207/U235 dating (Davidson, C.F. 1960. (a). Rejuvenation of Pitchblende in Hercynian Ore Deposits. Economic Geology 55:384) (Woodmorappe, 1979:106).
Discordant dates
One way geochronologists check a radiometric date is to use one or more different methods and compare the results. If the dates are similar they are called “concordant”, if they are are different they are called “discordant”. Discordant dates are a common occurrence, and causes include errors in measurements, errors in decay constants, unknown original isotopic compositions, and unknown migration of parent or daughter products (Stern, 1981:5). Here are a few examples of discordant dates.
“If a mineral has taken on no new uranium, thorium, and lead since it was formed, and if the original lead isotopic composition is known, 206Pb/238U, 207Pb/235U, 207Pb/206Pb, and 208Pb/232Th will agree, provided that there are no geologic complications such as xenocrystic material in the sample. However, rarely do all the calculated ages agree” (Stern, 1981:5).
“When determined by several methods (K-Ar, Rb-Sr and fission track), radiometric ages for coexisting minerals in a metamorphic or igneous rock generally differ because of different closure temperatures for retention of daughter products or tracks” (Itaya, 1988:281).
“It is well documented that Rb-Sr whole-rock dates tend to be younger than U-Pb zircon dates from the same rock” (Beakhouse, 1988:346).
“Detailed dating studies using pre-Tertiary whole rock basalt and dolerite specimens have been made…and limited optimism for the method appears justified. In spite of collection of unweathered samples and precautions taken to discard samples with evident alteration, it is usual to obtain a spectrum of discordant dates and to select the concentration of highest values as the correct ‘age’” (Armstrong, R.L. and J. Besancon. 1970. A Triassic Time Scale Dilemma: K-Ar Dating of Upper Triassic Mafic Igneous Rocks, Eastern USA and Canada, and Post-Upper Triassic Plutons, Western Idaho, USA. Eclogae Geologicae Helvetiae 63:19) (Woodmorappe, 1979:117).
“In general, dates in the “correct ball park” are assumed to be correct and are published, but those in disagreement with other data are seldom published nor are discrepancies fully explained” (Mauger, 1977:37). This is hardly an objective way of conducting scientific research.
Carbon-14 dating
How does carbon-14 dating work? “Carbon-14 is continuously produced in the upper atmosphere as a consequence of cosmic-ray bombardment. Cosmic rays, which are high-energy particles, shatter the nuclei of gas atoms, releasing neutrons. Some of the neutrons are absorbed by nitrogen atoms (atomic number 7), causing their nuclei to emit a proton. As a result, the atomic number decreases by 1 (to 6), and a different element, carbon-14, is created…” (Lutgens and Edward, 2006:430). Plants absorb carbon-14 during photosynthesis, and humans and animals consume plants, so they end up with carbon-14 as well. When plants, animals, and humans die, carbon-14 starts to decay into nitrogen-14. “Since no one was there to measure the amount of 14C when a creature died, scientists need to find a method to determine how much 14C has decayed. To do this, scientists use the main isotope of carbon, called carbon-12 (12C)” (Riddle, 2007). The half-life of carbon-14 is 5,730 years, so by measuring the ratio of carbon-14 relative to carbon-12 and comparing it to the ratio in living organisms, geochronologists can come up with an age for the organism. Since carbon-14 is only taken in by living organisms, carbon-14 dating is only useful in dating organic materials like wood, charcoal, bones, flesh and cotton cloth” (Lutgens and Edward, 2006:431). The principle behind carbon-14 dating is fine, but there are many unprovable assumptions involved that can skew the results. We will examine these assumptions individually.
One assumption of carbon-14 dating is that the level of carbon-14 in the atmosphere has remained constant throughout history. “However, even in the early days of radiocarbon dating, comparisons between archeologically established Egyptian chronologies and 14C dates suggested that the assumption of temporal constancy in 14C levels might not be correct. It is now abundantly clear that 14C levels have varied over time, though fortunately the magnitude of these variations can be assessed, at least since the Late Glacial” (Bradley, 1999:62).
Another assumption is that the level of carbon-14 is constant throughout the atmosphere. “However, the [C14] level is not constant as the ground level activity of 1.63 is still rising to a generation rate in the upper atmosphere of 2.5, i.e. the amount of C14 is not yet in equilibrium…. This method is quite unreliable for ages over 3,000 years, despite datings up to 40,000 years being quoted” [brackets added] (Bowden, 1982:200).
A related assumption is that the rate of carbon-14 formation has remained fairly constant in history. But the rate of carbon-14 formation depends on the intensity of cosmic rays, which in turn depends on the strength of the earth’s magnetic field and solar activity. “The strength of the earth’s magnetic field affects the amount of cosmic rays entering the atmosphere. A stronger magnetic field deflects more cosmic rays away from the earth. Overall, the energy of the earth’s magnetic field has been decreasing, (K.L. McDonald and R.H. Gunst, “An Analysis of the Earth’s Magnetic Field from 1835 to 1965,” ESSA Technical Report IER 46-IES, 1965, U.S. Government Printing Office, Washington, D.C., p. 14) so more 14C is being produced now than in the past. This will make old things look older than they really are” (Batten, 1990:78). “The strength of the magnetic field apparently accounts for a thousand year difference in dates at approximately 5,000 B.C. (Renfrew, 1973; Bucha, 1970). Solar (sunspot) activity seems to be less important, possibly accounting for a 15% variation in radiocarbon formation (Stuiver, 1961; Venkatavaradan, 1965; and Eddy, 1977)” (Johannsen, 1980:4). Therefore fluctuations in the strength of the magnetic field and solar activity in the past could cause inaccurate dates. “If the production rate of 14C in the atmosphere was less in the past, dates given using the carbon-14 method would incorrectly assume that more 14C had decayed out of a specimen than what has actually occurred. This would result in giving older dates than the true age” (Riddle, 2007).
An additional assumption is that the carbon-14 to carbon-12 ratio is a constant. “Several other geochronologists have also suggested that the C14/C12 ratio changes with altitude (Berger, 1970), while many other researchers have found discrepancies in the C14/C12 ratio in trees from Australia and Europe (MacKie, et. at. [sic], 1971; Jansen, 1970)” (Johannsen, 1980:4).
One vital assumption about carbon-14 dating is that the rate of production and decay of carbon-14 is in equilibrium. “Long-age chronologists have assumed that the rate of formation of C14 equals the rate of decay of C14. This assumption seems very reasonable to long-age chronologists because they know that the earth is billions of years old and yet it would take only 30,000-70,000 years to obtain equilibrium between the rate of production and the rate of decay of C14.
However, if the earth is only a few thousand years old, equilibrium can not be assumed and we should find observational evidence that the rate of production is greater than the rate of decay” (Johannsen, 1980:5). Even Willard Libby, who developed carbon-14 dating, found that the rate of production and decay were different. “Libby tried to estimate the production and decay rates and obtained a value of 18.8 atoms/gm-minute for the present production rate and between 14.5 and 16.3 atoms/gm-min for the present decay rate. He found that the rate of production exceeded the rate of decay by about 20% (Libby, 1955)” (Johannsen, 1980:5). “Subsequent researchers, however, have failed to show that the rate of production is in equilibrium with the rate of decay. For example, Hess, et. al. (1961) calculated the rate of formation to be 21.2 atoms/gm-min, and Lingenfelter (1963) obtained a value of 18.4. On the other hand, Suess (1965) has revised Libby’s original estimate on the decay rate down to 13.3 atoms/gm-min” (Johannsen, 1980:5). Since the rate of production exceeds the rate of decay, any assumptions about equilibrium would be invalid and the dates obtained would be skewed.
Yet another unprovable assumption in carbon-14 dating is that the level of carbon-14 and carbon-12 in the earth’s atmosphere has remained fairly consistent throughout history, and natural disasters have had little influence on these levels. But how would a global catastrophic flood, denied by uniformitarianism, influence these levels? “The amount of fossil fuels indicates there must have been a vastly larger quantity of vegetation in existence prior to the Flood than exists today. This means that the biosphere just prior to the Flood might have had 500 times more carbon in living organisms than today. This would further dilute the amount of 14C and cause the 14C/12C ratio to be much smaller than today” (Riddle, 2007). So dating any materials before the flood under the assumption that the carbon-14 to carbon-12 ratio was the same in the past would result in giving dates perhaps ten times older than is true (Riddle, 2007). “The flood buried a huge amount of carbon, which became coal, oil, etc., lowering the total 12C in the biosphere (including the atmosphere – plants regrowing after the flood absorb CO2 which is not replaced by the decay of the buried vegetation). Total 14C is also proportionately lowered at this time, but whereas no terrestrial process generates any more 12C, 14C is continually being produced, and at a rate which does not depend on carbon levels (it comes from nitrogen). Therefore, the 14C level relative to 12C increases after the flood” [emphasis in original] (Batten, 1990:78). The flood was also accompanied by immense volcanic activity, and volcanoes released a lot of CO2 depleted in carbon-14 causing post-flood fossils to give older ages (Batten, 1990:79).
Contamination is also a factor that can lead to inaccurate dates. “More abstruse problems arise when dating materials that contain carbonates (e.g., shell, coral, bone). These materials are particularly susceptible to contamination by modern carbon because they readily participate in chemical reactions with rainwater and/or groundwater” (Bradley, 1999:54-55). Contamination plays a big role in dating materials with carbonates, so how do geochronologists deal with this problem? “Contamination of samples by either modern or ancient carbon can often be clearly discerned if the result of a measurement deviates considerably from the expected value” (Neustupný, 1970:25). Who defines the expected value? Geochronologists who have a pre-conceived notion of what they think the age of the material should be. Therefore geochronologists with differing views and “expected” values would give differing opinions on the levels of contamination of a material and the accuracy of a calculated age.
Now we will look at a few “unexpected” results. “For example, Reed (1959) reported that C14 dates gave a spread of 6,000 years for Jarmo, a prehistoric village in northern Iraq. On the basis of all the archaeological evidence, however, analysts concluded that the village was occupied no more than 500 years before it was finally abandoned” (Johannsen, 1980:5). “Laboratories that measure 14C would like a source of organic material with zero 14C to use as a blank to check that their lab procedures do not add 14C. Coal is an obvious candidate because the youngest coal is supposed to be millions of years old, and most of it is supposed to be tens or hundreds of millions of years old. Such old coal should be devoid of 14C. It isn’t. No source of coal has been found that completely lacks 14C” [emphasis in original] (Batten, 1990:85).
The assumptions involved in carbon-14 dating are many and cannot be upheld by the observational evidence. The process of carbon-14 dating involves many areas of subjectivity and estimates that are based on “expected” values. One final quote to conclude this section, “C14 dating was being discussed at a symposium on the prehistory of the Nile Valley. A famous American colleague, Professor Brew, briefly summarized a common attitude among archaeologists towards it, as follows: “If a C14 date supports our theories, we put it in the main text. If it does not entirely contradict them, we put it in a foot-note. And if it is completely ‘out of date’, we just drop it”” (Säve-Söderbergh, 1970:35). There is no need for commentary on such practices, the level of subjectivity and bias is unacceptable.
Potassium-argon (K-Ar) dating
How does potassium-argon dating work? “Although potassium (K) has three natural isotopes – K39, K40, and K41 – only K40 is radioactive. When K40 decays, it does so in two ways. About 11 percent changes to argon-40 (Ar40) by means of electron capture… The remaining 89 percent of K40 decays to calcium-40 (Ca40) by beta emission… The decay of K40 to Ca40, however, is not useful for radiometric dating, because the Ca40 produced by radioactive disintegration cannot be distinguished from calcium that may have been present when the rock formed” (Lutgens and Edward, 2006:428). When minerals with potassium crystallize from magma or form inside a metamorphic rock, the potassium-argon clock begins. “At this point the new minerals will contain K40 but will be free of Ar40, because this element is an inert gas that does not chemically combine with other elements” (Lutgens and Edward, 2006:428-429). Potassium-argon dating has several difficulties which will be examined below.
One requirement to obtaining an accurate radiometric age is that the sample must remain a closed system with neither parent nor daughter atoms being added or removed. This poses great difficulty to the potassium-argon dating method since argon is a gas, and high temperatures can cause it to escape the sample (Lutgens and Edward, 2006:429). The other side of the equation is that a sample can be contaminated with extra argon, which skews the results. “The excess argon problem arose at the same time as the K-Ar method became widely used because anomalously high ages were obtained for some rocks and minerals. At first, excess argon was found only in materials that are exotic for K-Ar dating such as beryl, cordierite, chlorite, and pyrite, whereas subsequently excess argon was observed in minerals and rocks traditionally used for dating purposes” (Rublev, A. G. 1985. The possibility of correcting for excess argon in K-Ar dating. Geochemistry International 22(4):73) (Woodmorappe, 1999:30). Concerning xenocrysts (crystals foreign to the igneous rock),“Mixing calculations indicate that only 1% – 4% contamination may be required to increase K-Ar ages by 10-15 Ma for xenocrysts outgassed as much as 75%” (Nelson, 1992:1547). How would a global catastrophic flood affect potassium-argon dating? During a global flood a lot of magma would be produced and much argon would be trapped producing dates much higher than is accurate (Austin, S. A. 1996. Excess argon within mineral concentrates from the new dacite lava dome at Mt. St. Helens Volcano. Creation Ex Nihilo Technical Journal 10(3):335-343, and Snelling, A. A. 1998. The cause of anomalous potassium-argon “ages” for recent andesite flows at Mt. Ngauruhoe, New Zealand, and the implications for potassium-argon “dating.” Proceedings of the Fourth International Conference on Creationism, pp.503-525) (Woodmorappe, 1999:18).
The minuscule amounts of potassium and argon that must be accurately measured to give a date allow much room for error and disagreeing dates. For example, one laboratory dated an ash layer as being 1.8 million years old, while another laboratory dated it as being 2.9 million years old (Fix, 1984:9). Another interesting study found that there were more discordances in dates obtained from fresh samples of igneous rocks than from samples that clearly appeared to be weathered (Zartman, R.E. 1964. A Geochronological Study of the Lone Grove Pluton from the Llano Uplift, Texas. Journal of Petrology 5(3):399) (Woodmorappe, 1979:115). To make matters worse, “In two cases altered and fresh samples of the same granite body were analyzed and in both excellent agreement was obtained” (Armstrong, R.L. 1970. Geochronology of Tertiary igneous rocks, eastern Basin and Range Province, eastern Nevada and vicinity, USA. Geochimica et Cosmochimica Acta 34:222) (Woodmorappe, 1979:115). These kind of findings cast shadows of skepticism on the accuracy of the potassium-argon dating method.
Rubidium-strontium (Rb-Sr) dating
How does rubidium-strontium dating work? 87Rb decays into 87Sr, and these values are compared to the ratio of radiogenic 87Sr to naturally occurring 86Sr to derive a date for a sample. Several challenges of this method are described below.
“The validity of Rb-Sr isochron dates is based on the assumptions that all samples had, at some time in the past, uniform Sr isotopic compositions and have remained closed systems with respect to Rb and Sr since that time” (Beakhouse, 1988:346). This, however, is often not the case. “In particular, because of variable and possibly repetitive repartitioning of both 87Sr and Rb in an open system, and because there is no certainty that any sample has remained closed since the time of its formation, the true age and subsequent history of these gneisses cannot be determined with any confidence. That Fig. 7 does typify open systems is seen from the apparent primary ages of the samples represented on the diagram, which fall in the range 8750 Ma (sample 3310) to 2130 Ma (sample 3292)” (Holland, 1995:504). Hydrothermal, diagenetic, and metamorphic processes can easily reset rubidium-strontium systems (Toulkeridis, T., 1998. Sm-Nd, Rb-Sr, and Pb-Pb dating of silicic carbonates from the early Archaean Barberton Greenstone Belt, South Africa. Precambrian Research 92:138) (Woodmorappe, 1999:28). Geochronologists are aware of these issues and therefore do not solely rely on rubidium-strontium dating to obtain an accurate result. “Unfortunately, the parent radionuclide, 87Rb, is a volatile and mobile alkali element, characteristics which lead to open-system behaviour and anomalous ages. The current practice is not to rely on the Rb-Sr system to give the only absolute age information on the crystallization age of a suite of rocks but to use it in concert with other decay schemes” (Shirey, S.B. 1991. The Rb-Sr, Sm-Nd, and Re-Os isotopic systems (pp.103-166), in Heaman and Ludden, eds., (Heaman, L., and J. N. Ludden. 1991. Applications of Radiogenic Isotope Systems to Problems in Geology. Short Course Handbook, vol.19, 498) p.11) (Woodmorappe, 1999:33).
Discordant dates are widely present, “Although the problems of loss of daughter product are far less severe in the 87Rb-87Sr method than in 40K-40Ar dating, they do, as shown, still exist. Even in igneous rocks, discordant mineral dates are more often encountered than concordant dates” (Durrance, E.M. 1986. Radioactivity in Geology. Chichester, England: Ellis Horwood Ltd., 441, p.296) (Woodmorappe, 1999:29). “It is well documented that Rb-Sr whole-rock dates tend to be younger than U-Pb zircon dates for the same rock (see, e.g., Bickford and Mose, 1975; Van Schmus et al., 1975; Page, 1978; Pasteels et al., 1979; Kalsbeek and Pidgeon, 1980)” (Beakhouse, 1988:346).
The wording of quotes similar to the following one is very suspicious, “An anomalously low Rb-Sr age…was found for the biotites. Although no effects of metamorphism or alteration are visible in the syenite, some such process undoubtedly disturbed this…radiometric system” (Zartman, R.E., Brock, M.R., Heyl, A.V., and H.H. Thomas. 1967. K-Ar and Rb-Sr Ages of some Alkalic Intrusive Rocks from Central and Eastern United States. American Journal of Science 265:861) (Woodmorappe, 1979:115). Using the word “undoubtedly” to describe a process that left no visible evidence in order to explain an unexpected result is not good science. It is also not good science to rely on unprovable assumptions about the initial amounts of the daughter product present in a sample, in this case strontium. “There is no really valid way of determining what the initial amounts of Sr87 in rocks were. There is much juggling of numbers and equations to get results in agreement with the U-Th-Pb “clocks.” In all these radioactive clocks, all methods are made to give values that fit the evolutionist’s belief as to the age of the earth and the ages of the various geological events. The reason that the various dating methods give similar ages after “analysis” is that they are made to do so. In the case of the initial Sr87/Sr86 ratios, these values can be adjusted so that any age desired is obtainable” (Slusher H.S. 1973. Critique of radiometric dating. ICR Technical Monograph 2, p.32) (Woodmorappe, 1978:195). The assumptions involved in radiometric dating and methods used in publishing data are highly questionable, and the discordant data cannot be ignored. Perhaps radiometric dating is far too subjective to give us accurate dates?
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