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GEO AND COSMIC CHRONOLOGY

by
R. H. Brown
Geoscience Research Institute

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WHAT THIS ARTICLE IS ABOUT

This article represents an added feature to Origins. The material on geo and cosmic chronology is presented in brief outline form and is supplemented by an extensive bibliography. In the narrative portion, the author discusses the various evidences for a 4.5 billion-year-old universe and lists the different methods used to develop this date. Twenty-four different methods for dating and their conclusions are briefly listed. It is hoped that the readers of Origins will find this format useful as a reference tool for their own research. The Editors invite your suggestions to assist us in determining other areas that should be considered.

Scientific creationism that is neutral with respect to religious issues has no need to defend a particular viewpoint regarding time. Proceeding only on the basis of inductive logic, it is free to pursue any interpretation that may seem to be suggested by available data. The data related to chemical evolution probabilities, thermodynamic considerations, spontaneous origin of life, genetics, and paleontology lead naturally to the conclusion that life and the life support system are products of intelligent design and creative ability. But at present there are no data that independently suggest inductively either a 6-day creation week or placement of such an event within the last 8000 years.

In contrast with neutral scientific creationism, apologetic scientific creationism utilizes deductive logic in an effort to relate satisfactorily available scientific data to viewpoints derived from religious sources. Some individuals would insist that only neutral scientific creationism is truly "scientific." However, apologetic scientific creationism can be defended as truly "scientific" to the extent that it does not go beyond sound principles of logic, data collection, and data evaluation. Efforts to explain data concerning the natural world within the constraints of the first eleven chapters of Genesis, if carried out in a sound scientific manner, would be classified as apologetic scientific creationism.

In certain areas apologetic scientific creationism may have an advantage over neutral scientific creationism and non-theistic science in that it operates from a larger data base and may develop scientifically sound interpretive models that would not have been accessible by pure inductive logic. This advantage is illustrated by a comparison between a reconstruction of an event based on both the testimony of a reliable eyewitness and analysis of the consequences, and a reconstruction based on only analysis of the consequences. These two reconstructions may be evaluated on the basis of which one provides a better account of the available after-the-event data.

On the basis of the principle that truth is consistent, irrespective of the means by which it is apprehended, one can say that when rightly understood, natural science and authentic historical or religious source material agree, each complementing and supplementing the other. Accordingly, apologetic scientific creationism can be an instrument for arriving at a more correct understanding of specifications obtained from a religious source, as well as of data obtained from investigation in the natural sciences.

It may be appropriate to digress at this point and state my conviction that in a pluralistic society such as the United States only neutral scientific creationism is appropriate for inclusion in public school science curricula. A limited amount of apologetic scientific creationism would be appropriate in a public school sociology course that aims to acquaint the student with the various streams of thought in modern culture.

Geo and cosmic chronology are major concerns of creationist literature, usually from an apologetic viewpoint. The major purpose of this essay is to provide the reader with convenient access to the principal areas of evidence that must be taken into account by any scientific treatment of geo and cosmic chronology. For each of these areas I have endeavored to provide an introduction to the pertinent literature. Limitations of time and interest have prevented me from providing an adequate bibliography for some of the areas that are included in this outline.

Radiation Cooling of the Earth (1)

Serious attempts to determine the scale of geochronology on a scientific basis began in 1862 when William Thomson, who later became Lord Kelvin, estimated that planet Earth could have cooled from a molten state to its present temperature configuration within between 400 and 20 million years (m.y.). This constraint was an irritation to Charles Darwin who sensed that it did not provide sufficient time for his model of biologic evolution. By 1897 Lord Kelvin had narrowed the range of uncertainty in his estimate to between 40 and 20 m.y. By including the contribution of heat presumed to be available from radioactive material, the geophysicist, Arthur Holmes was able in 1947 to extend this estimate of cooling time to between 2 and 4 billion years (b.y.).

Mineral Content of Seawater (2)

The astronomer Edmund Halley suggested in 1715 that planet Earth might be "much older than many have hitherto imagined," and proposed that the salinity of the ocean might provide a basis for an estimate of its minimum age. By 1898 sufficient information on the rates at which the major rivers carry salt into the ocean became available to permit John Joly to estimate that the present salinity of the ocean could be attained within 80 to 90 m.y. In the early 1940s this estimate was reexamined and extended to between 150 and 250 m.y. on the basis of processes by which salt is now known to be recycled from the sea back to the land. By postulating slower input from rivers in the ancient past, Arthur Holmes was finally able to suggest an age of the Earth between 1 and 7 b.y. on the basis of ocean salinity.

Earth-Moon Separation (3)

As the principles of celestial mechanics were developed it became evident that tidal friction causes both Earth and Moon to slow down in their rotations until they each maintain the same face toward the other (no further tidal energy dissipation). During this process the separation between them gradually increases as required to conserve angular momentum. On the basis of his study of tides throughout the world Lord Kelvin came to the conclusion that the Earth-Moon system had been in existence less than a billion years. G. H. Darwin estimated that the present Earth-Moon separation has been achieved in 57 m.y. More recent calculations indicate that, beginning with close proximity to Earth, the Moon would reach its present separation distance in between 1 and 4 b.y.

Denudation of Igneous Rocks (4)

The previously mentioned early efforts to obtain an age estimate for planet Earth are significant only for their historical interest. They depend on highly uncertain initial assumptions concerning a molten state of the planet, a fresh-water ocean, and a tightly bound Earth-Moon system. Another interesting attempt to obtain an age for the Earth is based on the assumption that all sedimentary rocks have been produced by erosion of igneous rocks, at present rates. The uncertainties in these rates and in the volume of sediments involved lead to estimates in the range between approximately 400 million and 3 billion years.

Comet Frequency (5)

The existence of comets has been taken to indicate that the Solar System has not been in existence longer than a few million years. This conclusion comes from recognition that because of evaporation, radiation pressure, and solar wind effects very few comets survive as many as ten trips around the Sun. Since there is only speculation concerning the manner in which the Solar System has acquired cometary material, and there is absolutely no data with respect to the inventory of this material at any time, one should not expect the frequency with which comets appear to give a reliable indication of the scale for Solar System chronology.

Cosmic Dust Density (6)

There is sufficient cosmic dust in interplanetary space to produce the phenomenon known as Zodiacal Light. In the order of 10-100 thousand tons of this dust are captured by Earth each year. Since this dust is constantly swept up by the planets, driven out of the Solar System by radiation pressure, and pulled into the Sun as a result of the Poynting-Robertson effect, its present existence has been taken as evidence that the Solar System has been in existence no longer than approximately 2 b.y. It can be shown that all particles smaller than one centimeter in diameter would be removed from the space between Earth and the Sun within 10 m.y. The credibility of maximum Solar System age estimates based on the density of cosmic dust suffers from our ignorance concerning the distribution of this material in the past, and particularly from our ignorance concerning the amount of such material that may be swept up as the Solar System moves through its galaxy.

Synchronous Orbits of Satellites (7)

The Moon is in a synchronous orbit, i.e., it makes precisely one rotation on its axis for each revolution about the Earth, with the result that it always shows the same face toward Earth. Any elastic object orbiting in a force field that causes deformation will approach a synchronous orbit due to conversion of rotational energy into heat by internal friction. The synchronous orbit of the Moon may be taken as evidence that the Earth-Moon system has been in existence for many hundreds of millions of years, presuming the Moon was once rotating more rapidly than at present.

All planetary satellites that have been adequately observed (telescopic observation of Jupiter and Saturn, space probe observation of Mars, direct observation of the Moon) are in a synchronous orbit. Most of these satellites are marked by craters from meteoroid impacts that would have changed the rotation rate of these satellites. Calculations have been made of the amount of time that would be required for the Martian satellites to reach a synchronous orbit after the last significant perturbation by meteoroid impact. The greater the orbit radius the weaker the tidal forces will be, and the longer the time required to achieve a synchronous orbit. For the outermost satellite of Mars, Deimos, the estimated minimum synchronization time is 3 m.y. if the structure is compacted sand, and 100 m.y. if it is solid basalt.

Synchronous Orbits of Planets (8)

The planets experience tidal forces that reduce their motions to synchronous orbits with respect to the Sun. The motion of Venus is within -8% of perfect synchronism (retrograde spin with -243/225 spin/orbit periods in Earth days). Mercury has a commensurate orbit with a spin/orbit period ratio of 2/3 (58.6/88 in Earth days). A spin/orbit period coupling of 2/3 is a resonant state that is stable and is a special case of synchronous orbits. A mass distribution of Mercury and/or the Sun that does not have perfect spherical symmetry (dipole and higher terms in the gravitational field) could prevent a transition of the spin/orbit ratio from the 2/3 state to the 1/1 state.

More amazing is the discovery that Venus is in a synchronous relationship with respect to Earth. Venus turns the same face to Earth at each inferior conjunction. The most reasonable explanation of this relationship requires gravitational coupling between Earth and Venus over a time period in the magnitude of billions of years. The lack of a synchronous relationship of Earth with respect to Venus is explainable as the consequence of the diurnal cycle necessary for the maintenance of organic life and established at the beginning of the creation week described in the first chapter of Genesis. In summary, one can say that the observed characteristics of the inner planet orbits indicate that the Solar System has been in existence for a billion years, or more.

Extraterrestrial Erosion (9)

Rocks on the surface of the Moon are found to be highly eroded. They are pitted, have rounded edges, and are often surrounded by a sloping bank of fine material that can be described as soil, while the buried portion may have relatively smooth surfaces bounded by sharp angular edges. The factors that produce this erosion are expansion and contraction associated with rapid extreme changes in temperature, the "sandblasting" effect of micrometeoroid bombardments, and sputtering produced by the solar wind.

Fresh-looking craters with sharp edges are found superimposed on highly eroded, "old," rounded-off craters, some of which are so eroded as to be scarcely discernible. In the highland areas of the Moon craters are found in a saturation distribution (further meteoroid bombardment would not produce a major change in the crater density, obliterating previous craters as rapidly as new ones are formed). But in the mare areas the crater density is only 1 /10 to 1/50 as great. The evident interpretation is that since the mare areas were filled in by lava flow they have been exposed to meteoroid impact for a much shorter time than have the highland areas. The impact crater density on the Moon cannot be accounted for within a 5 b.y. time span unless the meteoroid impact rate is assumed to have been much greater during the early history of the Solar System than it has been during recorded Earth history.

The totality of this evidence leads to the conclusion that the Moon has been in existence as a solid object for a time in the order of at least one billion years.

Similar features of crater distribution and erosion have been revealed in the televised pictures sent from Mercury and Mars by space probes. The erosion features seen on Mercury are probably due to the same processes that have been operating on the Moon. Mars is experiencing strong aeolean erosion at the present time. It appears to have had an episode of severe fluid erosion under climatic conditions vastly different from those that can be accounted for under present circumstances.

Light-Year Scale (10)

Astronomers have good reasons for believing that they are now observing galaxies and quasars that are tens of billions of light years distant from Earth. If the current estimation of distance for these objects is correct, the universe must have been in existence for at least tens of billions of years.

Galaxy Clusters (11)

Galaxies are known to be grouped in clusters. At the present state of our knowledge concerning the mass of matter contained within galaxies, the gravitational forces that can be expected to act between members of a cluster are not sufficient to hold the cluster together. With the individual galactic motions that have been observed, the known galactic clusters can be expected to dissolve within less than 100 b.y. On the basis of this argument some galactic clusters have been considered to be no more than 2-4 b.y. old.

Spiral Galaxy Structure (12)

The Milky Way and its neighbor, Andromeda, belong to the Spiral Galaxy classification. It is thought that the spiral arm features of these galaxies would be obliterated after between one and three full rotations of the galaxy about its center of mass, since the angular velocity of revolution increases the closer a star is to the galactic center. On the basis of the rotation rates that have been observed, the lifetime of spiral galaxies has been estimated to be in the order of 300 m.y. Accordingly, our own galaxy would not be more than 300 m.y. old. It has been suggested that spiral arm galactic structure is not due to an initial star distribution, but rather is the result of gravity waves that cause the stars to bunch together in a cyclic manner as they revolve about the galactic center of gravity.

Star Clusters (13)

Many of the stars within galaxies are themselves grouped into clusters. It is expected that perturbing gravitational influences from nearby stars and star clusters will gradually pull these clusters apart. Detailed consideration leads to the estimate that star clusters are no more than 3-6 b.y. old.

Binary Stars (14)

Within our own Milky Way galaxy it is possible to observe that many of the stars are gravitationally coupled in pairs that revolve about a common center of mass. It can be expected that a high proportion of binary stars is to be found only in a relatively young galaxy, for the perturbing influences of nearby stars should slowly pull the binary stars apart. On the basis of the expected mean lifetime of a binary star system our galaxy has been estimated to be less than 10 b.y. old.

Stellar Dynamics (15)

With the knowledge of thermonuclear reactions man has acquired since World War II, and with the aid of electronic computers, it is possible to predict the detailed history of a large mass of hydrogen gas that will experience nuclear fusion under gravitational confinement — i.e., calculate the history of a star. Astronomers can observe numerous stars that have the characteristics associated with each state but one in the theoretical life history of a star. The stage for which no definite example has yet been found is the extremely rapid transition (lifetime measured in months) to the White Dwarf stage.

If the correspondence between real stars and the theoretically determined life history of a star is not merely fortuitous, one can confidently state that an average star such as our Sun has a life of approximately 10 b.y., provided it is maintained as an isolated system without replenishment of fuel (hydrogen). According to this model, the observed distribution of star types places the age of our galaxy, as well as the age of the universe, at not less than 10 b.y.

Residual Radioactivity (16)

The accidental discovery of radioactivity by Henri Bequerel in 1896 initiated a series of developments that have provided man with his most precise and most reliable tools for investigating geo and cosmic chronology. The most crucial steps in this development were the discovery of spontaneous atomic transmutation by Madame Curie in 1898, and the discovery of isotopes by Sir J. J. Thomson in 1913. Instrumentation and laboratory techniques developed since World War II have made possible spectacular advances in geo and cosmic chronology.

An infinitely old object would not be radioactive, for any radioactive isotopes it may have contained originally would have transformed to stable daughter isotopes. The presence of uranium in minerals from Earth, the Moon, and meteorites indicates that these components of the Solar System have been in existence less than 20 b.y. The present ratio of uranium-235 to uranium-238 further indicates that Earth and the Solar System have not been in existence longer than about 5 b.y.

Extinct Radioactivity (17)

Uranium-235, which is the basis of the contemporary nuclear energy technology, is present as only 0.72 atom percent of relatively rare uranium. The half-life of uranium-235, 704 m.y., is the lowest among unsupported radioactive nuclides that are known to exist in significant quantity throughout the Solar System. The next lower half-life among the nuclide possibilities is 170 m.y. (within a factor of two) niobium-92. There is 90 percent confidence that niobium-92 has been observed at (1.2 ± 0.7) × 10^-10 percent isotopic abundance in association with stable niobium-93. No evidence for natural occurrence of 100 m.y. samarium-146 has yet been found. Diligent search with the most sophisticated techniques has detected 83 m.y. plutonium-244 at approximately 10^-16 weight percent in a sample of the rare earth bastnaesite. Since plutonium is chemically similar to cerium, it is most likely to be found in a high-cerium-content mineral such as bastnaesite. Search for other unsupported radioactive nuclides with half-life less than 80 m.y. has been diligent but unfruitful.

All nuclides that are stable or have half-lives greater than 80 m.y. have been found in Earth, Moon and meteorite material. In Solar System material there is both fission-track and daughter-product isotope evidence for the prior existence of extinct 100 m.y. samarium-146, 83 m.y. plutonium-244, 15.9 m.y. iodine-129, 15.4 m.y. curium-247, 6.5 m.y. palladium-107 and 740,000 year aluminum-26. The conclusion from this evidence is that at least some components of Earth and other members of the Solar System have been in existence as solid objects for no less than 300 m.y. — the time for a 90 m.y. half-life nuclide to reach 1/10 of its initial concentration. Since there is good reason for expecting that in a creation of elementary matter plutonium-244 appears in the ratio of 0.013/1 with respect to uranium-238, the data on the present availability of natural plutonium-244 indicates that the matter from which the bulk of the Solar System is constructed has been in existence in the order of 5 b.y. Similar consideration regarding niobium-92 yields the same conclusion.

Cosmogenic Radioactivity (18)

Atomic nuclei that have been ejected from stars and acquired immense amounts of kinetic energy are known as cosmic rays. (The relatively low energy atomic particles emitted by a star are known as "solar wind"). These cosmic particles have the capability to shatter atoms which they may strike. Some of the atom fragments thus produced are unstable atoms of a simpler construction than the target atom that was shattered. (Spallation is the scientific name for this process). Unstable atoms produced in this matter are described as having cosmogenic radioactivity.

The half-lives of the principle cosmogenic radioactive products range from 5.7 day Mn⁵² to 740 thousand year Al²⁵, 1.6 m.y. Be¹⁰, and 3.7 m.y. Mn⁵³. Some 1.28 b.y. K⁴⁰ is also produced in this manner. After exposure to a constant cosmic ray flux for a time equal to about four half-lives, a cosmogenic radioactive nuclide reaches an equilibrium concentration at which the number of new atoms formed within a given period of time is equal to the number that experience radioactive decay during the same time.

The land and water surface of Earth is protected by the atmosphere from primary cosmic radiation. In meteorites and in material that has been secured from the Moon we have access to objects that contain cosmogenic radioactivity. The cosmogenic nuclides from 5.7 day Mn⁵² to 740 thousand year Al²⁶ and 3.7 m.y. Mn⁵³ found in these objects are in almost all cases in equilibrium with the present cosmic ray flux. This implies that the meteoroids and the surface of the Moon have been exposed to cosmic rays for at least 15 m.y., that the intensity of cosmic rays at present is very close to the average intensity over the past 15 m.y., and that the intensity of cosmic rays probably has not varied by more than a factor of two during this time. A short burst of radiation at some time in the recent past could adjust two cosmogenic nuclides to be in equilibrium with the present cosmic ray intensity, but it is inconceivable that as many as eleven could be simultaneously adjusted in this way.

Cosmic Ray Exposure (19)

The shattering of atoms by impact from cosmic rays produces both stable and unstable nuclides. The stable spallation products accumulate continuously as long as there is exposure to cosmic radiation. In many cases stable cosmogenic nuclides can be clearly distinguished from primordial matter. In such cases the concentration of a cosmogenic nuclide indicates the amount of exposure to cosmic radiation. The time of exposure, or cosmic ray exposure age, is readily obtained by dividing the amount of exposure by the exposure rate — the cosmic ray intensity. Within the experimental uncertainties, independent cosmic ray exposure age determinations with nuclides such as He³, Ne²¹, Ne²², and Ar³⁸ are usually in agreement.

As a primary cosmic ray particle passes through a solid it disrupts the crystalline arrangement along its track. In certain minerals it is possible with appropriate etching techniques to make these tracks visible in a microscope. The density of these cosmic ray tracks provides an independent measure of the total exposure to cosmic radiation, and the cosmic ray exposure age. If the mineral has not experienced heating or shock that erases damage patterns by realignment of crystal structure, the cosmic ray exposure age determined by track analysis may be expected to be in agreement with that determined by stable cosmogenic nuclide analysis.

Cosmic ray exposure ages for meteorite and lunar material that has been studied are scattered over a range from one million to one billion years, with strong grouping at several points over this range. The range over which these exposure ages fall has been taken to indicate that at various times portions of the lunar surface have experienced turnover due to volcanic activity and meteoroid impact; and that meteorites have been formed by the breakup of larger objects at various times in the history of the Solar System.

Radioactive Decay Sequences (20)

The possibility of using radioactive elements for determining chronology was recognized by Lord Rutherford in 1904. Substantial radiometric dating was not achieved until many years later, after techniques had been developed for quantitative analysis of isotopes. At the present time as many as ten independent techniques may be available for determining radioisotope age of a mineral specimen.

Among the various radioisotope age determination techniques there is potential capability for indicating the time at which the matter of which a specimen is composed, experienced events such as nucleogenesis, solidification, heating, remelting, shock, mixing with other material, exposure to water, and exposure to high energy radiation. Because a given sample may have experienced two or more such events all the various radiometric age determinations that may be performed on it should not be expected to be in agreement. Disagreement between independent radiometric age determinations (discordance is the technical term) may be taken as an indication that the sample has a complex history, and may provide useful insight into the chronology of events that the sample has experienced.

The many cases in which chemically and physically independent radiometric age determinations are in agreement (concordant) within limits of precision and accuracy indicate that radiometric dating procedures may yield physically significant results, regardless of whether there may not be a one-to-one correspondence between a specific radioisotope age and real time. Discordant ages generally have a rational explanation in terms of metamorphic events that the sample may have experienced.

It is well known that a radiometric age is equivalent to the corresponding real time age if the initial conditions are specified with sufficient accuracy and precision, the associated radioactive decay constant(s) has (have) not changed essentially during the time involved, and the sample has been chemically isolated during this time. The large number of cases in which essential agreement exists between diverse radiometric age determinations can hardly be fortuitous, and indicate that samples can be obtained which meet the requirements for conversion of radiometric age into real time. All the radiometric age data that have accumulated for minerals from meteorites, the Moon and planet Earth lead to the conclusion that these portions of the Solar System have been in existence and contained solid material for 4.56 b.y. The available radiometric evidence indicates that the present crust of Earth does not contain rocks older than 3.9 b.y.

Inherited Radiometric Age (21)

If a radiometric age can be satisfactorily converted into real time there often still remains a problem in determining the nature of the event that initiated the time period. Radiometric dating techniques were developed in a climate that fostered a presumption concerning vast ages for the evolutionary development of living organisms, and that stimulated search for evidence supporting such ages. This situation gave rise to a naive, oversimplified, and unjustified assumption that radiometric "clocks" are set at zero in transport of mineral by igneous processes, and also in many sedimentary processes. According to this assumption a radiometric age of mineral that has replaced organic material, that has been injected into a fossiliferous stratum, or that overlies fossils gives a minimum real-time age for the association with the fossils involved. It would be both unfair and unkind to most of the individuals who have supported this assumption to describe it as "the graveyard hoax"; yet such description emphasizes an important consideration that is generally overlooked. Radiometric ages for the mineral components of the soil in a cemetery plot are not expected to date the burials made there.

There is ample evidence that radiometric chronometer systems are often set to zero time in natural processes that transport or metamorphose minerals, as popularly assumed. It is not so well recognized that the inheritance of previously established radiometric age characteristics through metamorphic and transfer processes is also well established in the scientific literature. Situations are known in which even fission track and potassium-argon age characteristics have survived through a subaerial volcanic event. The survival may be anywhere between total and zero. A potassium-argon age of 465,000 years has been reported for volcanic material overlying trees that were buried by the eruption and have a carbon-14 age of only 225 years (McDougall et al. 1969). It has become recognized that the radioisotope characteristics of intrusive and volcanic material may be related more to the crustal material through which the magma was ejected and to the characteristics of successive zones in the magma chamber than to the time at which the transfer took place. There also is evidence that the radioisotope age characteristics of sediments may be related more to the source from which the material was derived than to the time at which sedimentation occurred. Extensive references to the literature on inherited radiometric age are appended to this paper.

Radiation Damage (22, 23)

Radioactive decay produces structural and electronic damage tracks in the host mineral. These damage tracks can be quantitatively analyzed to determine the total radiation exposure. A quantitative analysis of the amount of radioactive material available for producing the observed damage tracks readily leads to a computation of the irradiation time. The result is a radiometric age based on the evidence left by the radiogenic products, rather than on an assay of the products themselves. The evidence may be trapped excited electron states produced by alpha, beta or gamma radiation; or it may be crystal lattice dislocation produced by alpha particles, recoil of alpha-emitting parent nuclei, or fission products.

The excited electrons are detected by observing the optical radiation produced when the mineral is heated sufficiently to free the trapped electrons and allow them to return to their ground (lowest energy) state. The technique involved is known as thermoluminescence or electroluminescence dating. Since the excited electrons slowly return to the ground state at normal temperatures, this technique has a relatively short time range. Although a 300,000 year range has been claimed (Göksu et al. 1974) other authorities limit its usefulness to about 4000 years (Michels 1973). This method of dating further suffers in lack of precision (22).

The crystal lattice dislocation tracks produced by radioactive decay can be seen with a microscope after suitable etching. Where high concentrations of radioactive material have existed regions that contain alpha-particle damage tracks can be seen without resort to etching techniques, as in pleochroic halos (more correctly termed radiohalos). The density of these halos can be related to the concentration of radioactive material at their center to obtain a crude estimate of the minimum exposure time involved in producing the halo. Microprobe analysis permits relatively precise evaluation of radiogenic daughter to radioactive mother ratios in the halo nucleus. These ratios can readily be expressed in terms of a radioisotope age.

Radiometric ages obtained from tracks produced by parent nucleus recoil, alpha-particles, or fission fragments often are in agreement, or at least consistent, with ages obtained from daughter/parent ratios. Discordant but consistent situations arise when there has been total or partial annealing of radiation tracks by elevation of temperature, or migration of either parent or daughter atoms as a result of heating or contact with water.

The existence of isolated polonium radiohalos in uraniferous fossil wood (Gentry et al. 1976) indicates that radiohalos may be formed as a result of prolonged deposition of radioactive material at a halo center site, and are not always dependent on an initial concentration of radioactive material.

Chondrite Structure Features (24)

Radiation damage track investigations have turned up some remarkable evidence concerning the history and formation of meteoroids. Meteorites that have been classified as chondrites are made up of units called chondrules that are cemented together in a matrix to form the meteorite body. Some of these chondrules from inside the meteorite body have been found to be marked on their surfaces by micro-meteoroid impact pits, and to contain in a thin layer of their surface solar wind atom implants and damage tracks from the low energy cosmic radiation produced by the Sun. Identical phenomena are found on the surface of rocks obtained from the Moon. (Ablation during passage through Earth's atmosphere removes such features from the surface of meteorites). Some chondrules have sharp fracture edges. This evidence strongly indicates that chondrites have been formed from an accretion of smaller meteoroid bodies which had been in existence long enough to acquire substantial exposure to solar radiation and cosmic dust.

Summary

The picture that emerges from all the data that relate to cosmic chronology appears to be one of dynamic physical processes operating over extended periods of time, during the last 4.5 billion years of which discrete entities of the Solar System have been in existence.

Theological Issues

It would not be appropriate to conclude this presentation without some consideration of related theological issues.

Any interpretation that is made of the available inspired testimony must satisfactorily accommodate the various lines of evidence concerning geo and cosmic chronology in accord with the basic hermeneutic principle that the books of nature and the Scriptures should be consistent with each other.

It is possible to interpret the book of Genesis to require that all matter in the Solar System came into existence ex nihilo by fiat creation less than 10,000 years ago. This interpretation requires that all the features of mineral, meteoroid, planetary body, and planetary satellite age were the immediate expression of deliberate design on the part of the Creator, and have no relationship to actual age. We should recognize that God has the prerogative to produce a creation in this manner, and that doing so would be less extraordinary than producing the total complex of organic life on this planet within four 24 hour days.

It also is possible to interpret the inspired testimony concerning creation as an eyewitness-style account using language of appearance to describe creative activity that within six consecutive 24-hour days equipped this planet with the total complex of its organic life and established the physical circumstances on which this life depends. According to this interpretation our planet may now contain matter that was in existence as a consequence of creative activity prior to the Genesis Creation Week, matter that was brought into existence during Creation Week, and a relatively minute amount of matter that came into existence in connection with Christ's miracles (specifically His feeding of the multitudes).

Let everyone be persuaded in his own mind as to which interpretation he should favor, giving appropriate respect to the considerations that may lead others to choose differently.

 

REFERENCES

(1) Radiation Cooling of Earth

• Jeffreys, Harold. 1952. The earth. 3rd ed., Chapter IX Cambridge University Press.
• ter Har, D. 1953. The age of the universe. Scientific Monthly 77:173-181.

(2) Mineral Content of Seawater

• Goldberg, Edward D. 1965. Minor elements in sea water. In J. P. Riley and G. Skirrow, eds. Chemical Oceanography, Vol. 1, Chapter 5. Academic Press, London and New York.
• Jeffreys, Harold, loc. cit.
• Livington, D. 1963. The sodium cycle and the age of the ocean. Geochimica et Cosmochimica Acta 27:1055-1069,
• ter Har, D., loc. cit.

(3) Earth-Moon Separation

• Hughes, David W., 1981. Why is the moon slowing down? Nature 290:190.
• Jeffreys, Harold, op. cit., Chapter VIII.
• Kahn, Peter C. K. and Stephen M. Pompea. 1978. Nautiloid growth rhythms and dynamical evolution of the Earth-Moon system. Nature 275:606-611.
• Kaula, William M. and Alan W. Harris. 1975. Dynamics of lunar origin and orbital evolution. Reviews of Geophysics and Space Physics 13:363-371.
• Rosenberg, C. D. and S. K. Runcorn, eds. 1975. Growth rhythms and history of the earth's rotation. John Wiley & Sons, New York.
• ter Har, D., loc. cit.

(4) Denudation of Igneous Rocks

• Jeffreys, Harold, op. cit., Chapter IX.
• ter Har, D., loc. cit.

(5) Comet Frequency

• Alfvén, Hannes and Asoka Mendis. 1973. Nature and origin of comets. Nature 246:410-411.
• Bailey, M. E. 1976. Can 'invisible' bodies be observed in the solar system? Nature 259:290-291.
• Gribbin, John. 1975. Halley lecturer produces new theory of comet origins. Nature 255:196.
• Hanson, James N. 1974. Comets: the Lord's weapon and sign. Bible-Science Newsletter, January 1974.
• Lindsay, John F. and L. J. Srnka. 1975. Galactic dust lanes and lunar soil. Nature 257:776-777.
• Slusher, Harold S. 1971. Some astronomical evidences for a youthful solar system. Creation Research Society Quarterly 8:55-57.
• Wetherill, George W. 1976. Where do the meteorites come from? A reevaluation of the Earth-crossing Apollo objects as sources of chondritic meteorites. Geochimica et Cosmochimica Acta 40:1297-1317.
• Whipple, Fred L. 1976. Background of modern comet theory. Nature 263:15-19.

(6) Cosmic Dust Density

• Briggs, Robert E. 1962. Steady-state distribution of meteoric particles under the operation of the Poynting-Robertson effect. Astronomical Journal 67:711ff.
• Brownlee, D. E. 1979. Interplanetary dust. Reviews of Geophysics and Space Physics 17:1735-1743.
• Herbig, George H. 1974. Interstellar smog. American Scientist 62:200-217.
• Kerker, Milton. 1974. Movement of small particles by light. American Scientist 62:92-98.
• Levy, E. H. and J. R. Jokipii., 1976. Penetration of interstellar dust into the Solar System. Nature 264:423-424.
• Lindsay, John F. and L. J. Srnka. 1975. Galactic dust lanes and lunar soil. Nature 257:776-777.
• Misconi, N. Y. 1976. On the rotational bursting of interplanetary particles. Geophysical Research Letters 3(10):585-588.
• Paddack, Stephen J. and John W. Rhee. 1976. Rotational bursting of interplanetary dust particles. Geophysical Research Letters 2(9):365-367.
• Pettersson, H. 1960. Cosmic spherules and meteoric dust. Scientific American 202:123-133.
• Reyss, J. L., Y. Yokoyama and S. Tanaka. 1976. Aluminum-26 in deep-sea sediment. Science 193:1119-1121. Footnote 15.
• Sakamoto, Koh. 1974. Possible cosmic dust origin of terrestrial plutonium-244. Nature 248:130-132.
• Slusher, Harold S. 1971. Some astronomical evidences for a youthful solar system. Creation Research Society Quarterly 8:55-57.
• Slusher, Harold S. and Stephen J. Duursma. 1978. The age of the solar system: a study of the Poynting-Robertson Effect and extinction of interplanetary dust. Institute for Creation Research Technical Monograph No. 6.
• Wetherill, George W. 1976. Where do the meteorites come from? A reevaluation of the Earth-crossing Apollo objects as sources of chondritic meteorites. Geochimica et Cosmochimica Acta 40:1297-1317.

(7) Synchronous Orbits of Satellites

• Pollack, J. B., J. Veverka, M. Noland, C. Sagan, T.C. Duxbury, C. H. Acton, Jr., G. H. Born, W. K. Hartman and B. A. Smith. 1973. Mariner 9 television observations of Phobos and Deimos, 2. Journal of Geophysical Research 78:4313-4326.
• Jeffreys, Harold, op. cit., Chapter VIII.

(8) Synchronous Orbits of Planets

• Anderson, J. D. 1974. Geodetic and dynamical properties of planets. Transactions, American Geophysical Union 55:515-523.
• Gold, Thomas and Steven Soter. 1979. Theory of the Earth-synchronous rotation of Venus. Nature 277:280-281.
• Goldreich, P. and S. J. Peale. 1966. Spin orbit coupling in the solar system. Astronomical Journal 71:425-438.

(9) Extraterrestrial Erosion

• Bloch, M. R., H. Fechtig, W. Gentner, C. Neukum and E. Schneider. 1971. Meteorite impact craters, crater simulations, and the meteoroid flux in the early solar system. Proceedings of the Second Lunar Science Conference, Vol. 3, pp. 2639-2652. The M.I.T. Press, Cambridge.
• Hartman, William K. 1962. Martian cratering, 4, Mariner 9 initial analysis of cratering chronology. Journal of Geophysical Research 78:4096-4116.
• Hiners, N. W. 1971. The new moon: a view. Reviews of Geophysics and Space Physics 9:447-522, specifically pp. 490-503.
• Hörz, F. and J. B. Hartung. 1971. The lunar-surface orientation of some Apollo 12 rocks. Proceedings of the Second Lunar Science Conference, Vol. 3, pp. 2629-2638. The M.I.T. Press, Cambridge.

(10) Light-Year Scale

• Weinberg, Steven. 1972. Gravitation and cosmology: principles and applications of the general theory of relativity, Chapter 14. John Wiley & Sons, New York.

(11) Galaxy Clusters

• Bouw, Gerardus D. 1977. Galaxy clusters and the mass anomaly. Creation Research Society Quarterly 14:108-112.
• Editorial. 1949. American astronomers report. Sky and Telescope 8:123-126.
• Geller, Margaret J. 1978. Large-scale structure in the universe. American Scientist 66:176-184.

(12) Spiral Galaxy Structure

• Icke, Vincent and James Pringle. 1975. Structure and dynamics of spiral galaxies. Nature 253:312-313.
• Lindsay, John F. and L. J. Srnka. 1975. Galactic dust lanes and lunar soil. Nature 257:776-777.
• Mulfinger, George. 1970. Critique on stellar evolution. Creation Research Society Quarterly 7:7-24.

(13) Star Clusters

• Chandrasekhar, S. 1942. Principles of stellar dynamics, Chapter V. University of Chicago Press.

(14) Binary Stars

• ter Har, D. 1953. The age of the universe. Scientific Monthly 77:173-181.

(15) Stellar Dynamics

• Appenzeller, I., J. L. Lequeux and J. Silk. 1980. Star formation. Geneva Observatory, Sauverny, Switzerland.
• Clayton, Donald D. 1968. Principles of stellar evolution and nucleosynthesis. McGraw-Hill Book Co., New York.
• Jastrow, Robert and Malcolm H. Thompson. 1972. Astronomy, fundamentals and frontiers, Chapter 7. John Wiley & Sons, New York.

(16) Residual Radioactivity

• Cowan, George A. 1976. A natural fission reactor. Scientific American 235(1):36-47.
• Jeffreys, Harold, op. cit., Chapter IX.
• Rankma, K. 1954. Isotope geology, pp. 415-418. McGraw-Hill Book Co., New York.
• Ruffenach, J. C., J. Menes, C. Devillers, M. Lucas and R. Hagemann. 1976. Etudes chimiques et isotopiques de l'urianium, du plomb et de plusiers produits de fission clans un enchatillon de mineral du reactor naturel d'Oklo. Earth and Planetary Science Letters 30:94-108.
• ter Har, D., loc. cit.

(17) Extinct Radioactivity

• Apt, K. E., J. D. Knight, D. C. Camp and R. W. Perkins. 1974. On the observation of ⁹²Nb and ⁹⁴Nb in nature. Geochimica et Cosmochimica Acta 38:1485-1488.
• Arden, John W. 1977. Isotopic composition of uranium in chondritic meteorites. Nature 269:788-789.
• Bernatowicz, T. J., C. M. Hohenberg, B. M. Kennedy and F. A. Podosek. 1978. Excess fission xenon in Apollo 16. Proceedings of the Ninth Lunar and Planetary Science Conference, pp. 1571-1597. Pergamon Press, New York.
• Bradley, J. G., J. C. Hupeke and G. J. Wasserburg. 1978. Ion microprobe evidence for the presence of excess ²⁶Mg in an Allende anorthite crystal. Journal of Geophysical Research 83:244-254.
• Brown, R. H. 1969. Radioactive time clocks. Chapter 25 in H. G. Coffin, ed. Creation: Accident or Design? Review & Herald Publishing Association, Washington, D.C. More recent half-life determinations differ by as much as a factor of two from some of the data given in Table VII — 100 m.y. for Samarium-146, e.g.
• Carver, Eugene A. and Edward Anders. 1976. Nuclear tracks in the Angra dos Reis and Moore County meteorites. Geochimica et Cosmochimica Acta 40:935-944.
• Gray, C. M. and W. Compton. 1974. Excess ²⁶Mg in the Allende meteorite. Nature 251:495-497.
• Hennecke, E. W. and O. K. Manuel. 1975. Noble gases in an Hawaiian xenolith. Nature 257:778-780.
• Herzog, G. F. 1977. ²⁶Al in stony meteorites with gas losses. Geochimica et Cosmochimica Acta 41:1526-1529.
• Hoffman, D. C., F. O. Lawrence, J. L. Mewherter and F. M. Rourke. 1971. Detection of plutonium-244 in nature. Nature 234:132-134.
• Hohenberg, C. M., M. N. Munk and J. H. Reynolds. 1967. Spallation and fissiogenic xenon and krypton from stepwise heating of the Pasamonter achondrite; the case for extinct Plutonium-244 in meteorites; relative ages of chondrites and achondrites. Journal of Geophysical Research 72:3139-3177.
• Hutcheon, I. D., I. M. Steele, J. V. Smith and R. N. Clayton. 1978. Ion microbe, electron microprobe and cathodoluminescence data for Allende inclusions with emphasis on plagioclase chemistry. Proceedings of the Ninth Lunar and Planetary Science Conference, pp. 1345-1368. Pergamon Press, New York.
• Kaiser, T., W. R. Kelly and G. J. Wasserburg. 1980. Isotopically anomalous silver in the Santa Clara and Pinon iron meteorites. Geophysical Research Letters 7:271-274.
• Kelley, William R. and G. J. Wasserburg. 1978. Evidence for the existence of ¹⁰⁷Pd in the early Solar System. Geophysical Research Letters 5:1079-1082.
• Lee, Typhoon. 1979. New isotopic clues to solar system formation. Reviews of Geophysics and Space Physics 17:1591-1611.
• Lee, T. and D. A. Papanastassiou. 1974. ²⁶Mg isotopic anomalies in the Allende meteorite and correlation with O and Sr effects. Geophysical Research Letters 1:225.
• Lee, T., D. A. Papanastassiou and G. J. Wasserburg. 1976. ²⁶Mg excess in Allende and evidence for ²⁶Al. Geophysical Research Letters 3:109.
• Lee, T., D. A. Papanastassiou and G. J. Wasserburg. 1977. Astrophysics Journal Letters 211:1107. (Primordial ²⁶Al).
• Lewis, Roy S. 1975. Rare gases in separated whitlockite from the St. Severin chondrite: xenon and krypton from fission of extinct ²⁴⁴Pu. Geochimica et Cosmochimica Acta 39:417-432.
• Lugmair, G. W. and K. Marti. 1977. Sm-Nd-Pu timepieces in the Angra dos Reis meteorite. Earth and Planetary Science Letters 35:273-284.
• Podosek, F. A. 1970. The abundance of ²⁴⁴Pu in the early Solar System. Earth and Planetary Science Letters 8:183-187.
• Podosek, F. A. 1970. Dating of meteorites by the high-temperature release of Iodine-correlated Xe¹²⁹. Geochimica et Cosmochimica Acta 34:341-365.
• Podosek, F. A. 1972. Gas retention chronology of Petersburg and other meteorites. Geochimica et Cosmochimica Acta 36:755-772.
• Podosek, Frank A. 1979. Solar system. Geotimes, June 1979, pp. 18, 19.
• Reynolds, J. H., E. C. Alexander, Jr., P. K. Davis and B. Srinivasan. 1974. Studies of K-Ar dating and xenon from extinct radioisotopes in breccia 14318; implications for early lunar history. Geochimica et Cosmochimica Acta 38:401-417.
• Sahamoto, Koh, 1974. Possible cosmic dust origin of terrestrial plutonium-244. Nature 248:130-132.
• Scheinin, N. B., G. W. Lugmair and K. Marti. 1977. Sm-Nd systematics and evidence for extinct ¹⁴⁶Sm in an Allende inclusion (abstract). Meteoritics 11:357-368.
• Srinivasan, B., E. C. Alexander, Jr. and O. K. Manuel. 1971. Iodine-129 in terrestrial ores. Science 173:327-328.
• Stegmann, W. and F. Begemann. 1981. Al-correlated ²⁶Mg excess in a large Ca-Al-rich inclusion of the Leoville meteorite. Earth and Planetary Science Letters 55:266-272.
• Storzer, D. and P. Pellas. 1977. Angra dos Reis plutonium distribution and cooling history. Earth and Planetary Science Letters 35:285-293.

(18) Cosmogenic Radioactivity

• Bogard, D. D. and P. J. Cressy, Jr. 1973. Spallation production of ³He, ²¹Ne, and ³⁸Ar from target elements in the Bruderheim chondrite. Geochimica et Cosmochimica Acta 37:527-546.
• Cressy, Philip J., Jr. 1971. Cosmogenic nuclides in the Lost City and Ucera meteorites. Journal of Geophysical Research 76:4072-4075.
• Shedlovsky, Julian P., Philip J. Cressy, Jr, and Truman P. Kohman. 1967. Cosmogenic radioactivities in the Peace River and Harleton chondrites. Journal of Geophysical Research 72:5051-5058.
• Trivedi, B. M. P. and D. S. Goel. 1973. Nuclide production rates in stone meteorites and lunar samples by galactic cosmic radiation. Journal of Geophysical Research 78:4885-4900.

(19) Cosmic Ray Exposure

• Bhai, N. B., K. Gopalan, J. N. Goswami, M. N. Rao and T. R. Venkatesan. 1978. Solar cosmic ray produced neon and xenon isotopes and particle tracks in feldspars from lunar fines 14148 and 24087. Proceedings of the Ninth Lunar and Planetary Science Conference, pp. 1629-1645. Pergamon Press, New York.
• Bhandari, Narendra and J. T. Padia. 1974. Secular variations in the abundances of heavy nuclei in cosmic rays. Science 185:1043-1045.
• Bogard, D. D. and P. J. Cressy, Jr. 1973. Spallation production of ³He, ²¹Ne, and ³⁸Ar from target elements in the Bruderheim chondrite. Geochimica et Cosmochimica Acta 37:527-546.
• Brown, R. H. 1971. The age of meteorites. Spectrum 3:19-27 (Winter 1971).
• Eberhardt, D., J. Geiss, H. Graf, N. Grögler, U. Krähenbühl, H. Schwaller and A. Stettler. 1974. Noble gas investigation of lunar rocks 10017 and 10071. Geochimica et Cosmochimica Acta 38:97-120.
• Eugster, O., N. Grögler, M. D. Medina, P. Eberhardt and J. Geiss. 1973. Trapped solar wind noble gases and exposure age of Luna 16 lunar fines. Geochimica et Cosmochimica Acta 37:1991-2003.
• Fleischer, R. L., P. B. Price and R. M. Walker; M. Maurette; G. Morgan. 1967. Tracks of heavy cosmic rays in meteorites. Journal of Geophysical Research 72:355-366.
• Fleischer, Robert L. and Howard R. Hart, Jr. 1974. Particle track record of Apollo 16 rocks from Plumb Crater. Journal of Geophysical Research 79:766-768.
• Hampel, W. and O. A. Schaeffer. 1979. ²⁶Al in iron meteorites and the constancy of cosmic ray intensity in the past. Earth and Planetary Science Letters 42:348-358.
• Heimann, M., P. P. Parekh and W. Herr. 1974. A comparative study of ²⁶Al and ⁵³Mn in eighteen chondrites. Geochimica et Cosmochimica Acta 38:217-234.
• Herzog, G. F. 1973. Variability of the He³ and Ne^2l production rates in ordinary chondrites. Geochimica et Cosmochimica Acta 37:2125-2133.
• Hohenberg, C. M., K. Marti, F. A. Podosek, R. C. Reedy and I. R. Shirck. 1978. Comparisons between observed and predicted cosmogenic noble gases in lunar samples. Proceedings of the Ninth Lunar and Planetary Science Conference, pp. 2311-2344. Pergamon Press, New York.
• Kohl, C. P., M. T. Murrell, G. P. Russ III and J. R. Arnold. 1978. Evidence for the constancy of the solar cosmic ray flux over the past ten million years: ⁵³Mn and ²⁶Al measurements. Proceedings of the Ninth Lunar and Planetary Science Conference, pp. 2299-2310. Pergamon Press, New York.
• Rajan, R. Sundar. 1974. On the irradiation history and origin of gas-rich meteorites. Geochimica et Cosmochimica Acta 38:777-788.
• Smith, S. and E. L. Fireman. 1973. Ages of eight recently fallen meteorites. Journal of Geophysical Research 78:3249-3259.
• Trivedi, B. M. P. and D. S. Goel. 1973. Nuclide production rates in stone meteorites and lunar samples by galactic cosmic radiation. Journal of Geophysical Research 78:4885-4900.
• Voshage, H. and H. Feldmann. 1979. Investigations on cosmic-ray-produced nuclides in iron meteorites, 3. Exposure ages, meteoroid sizes and sample depths determined by mass spectrometric analyses of potassium and rare gases. Earth and Planetary Science Letters 45:293-308.
• Wilkening, Laurel L., Gerald F. Herman and Edward Anders. 1973. Aluminum-26 in meteorites — VII. Urelites, their unique radiation history. Geochimica et Cosmochimica Acta 37:1803-1810.

(20) Radioactive Decay Sequences

• Brown, R. H. 1969. Radioactive time clocks. Chapter 25 in H. G. Coffin, ed. Creation: Accident or Design? Review & Herald Publishing Association, Washington, D.C.
• Chen, J. H. and G. J. Wasserburg. 1981. The isotope composition of uranium in Allende inclusions and meteoric phosphates. Earth and Planetary Science Letters 52:1-15.
• Emery, G. T. 1972. Perturbation of nuclear decay rates. Annual Review of Nuclear Science 22:165-202.
• Hamilton, E. I. and R. M. Farquhar, eds. 1968. Radiometric dating for geologists. John Wiley & Sons, New York.
• Hiners, N. W. 1971. The new moon: a view. Reviews of Geophysics and Space Physics 9:447-522, specifically, pp. 477-490.
• Hart, S. R., G. L. Davis, R. H. Steiger and G. R. Tilton. 1968. A comparison of the isotope mineral age variations and petrologic changes induced by contact metamorphism, In E. I. Hamilton and R. M. Farquhar, op. cit., pp. 73-110.
• Shlyakhter, A. I. 1976. Direct test of the constancy of fundamental nuclear constants. Nature 264:340.
• Spector, Richard M. 1972. Pleochroic halos and the constancy of nature. Physical Review A 5(3):1323-1326.
• Wolfe, A. M., Robert L. Brown and Morton S. Roberts. 1976. Limits on the variation of fundamental atomic quantities over cosmic time scales. Physical Review Letters 37(4):179-181. See also discussion in Physics Today, September 1976, pp. 17, 18.
• York, D. and M. Farquhar. 1972. The earth's age and geochronology. Pergamon Press, New York.

(21) Inherited Radiometric Age

• Aleinikoff, John N., Cynthia Dusel-Bacon, Helen L. Foster and Kiyoto Futa. 1981. Proterozoic zircon from augen gneiss, Yukon-Tanana Upland, east-central Alaska. Geology 9:469-473.
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• Armstrong, R. L. 1975. The geochronometry of Idaho (Part 1 and 2). Isochron/West, Nos. 15 and 16.
• Armstrong, R. L., W. P. Leeman and H. E. Malde. 1975. K-Ar dating, Quaternary and Neogene volcanic rocks of the Snake River plain, Idaho. American Journal of Science 275:225-251.
• Bailey, S. W., P. M. Hurley, H. W. Fairbairn and W. H. Pinson, Jr. 1962. K-Ar dating of sedimentary illite polytypes. Geological Society of America Bulletin 73:1167-1170.
• Banks, N. G., H. R. Cornwall, M. L. Silverman, S. C. Creasy and R. F. Marvin. 1972. Geochronology of intrusion and ore deposition of Ray, Arizona, Part I, K-Ar ages. Economic Geology 67:864-878.
• Bickford, M. E. and W. R. Van Schmus. 1979. Geochronology and radiogenic isotope research. Reviews of Geophysics and Space Physics 17:824-839.
• Brewer, M. S. 1969. Excess radiogenic argon in the metamorphic micas from the Eastern Alps, Austria. Earth and Planetary Science Letters 6:321-331.
• Brooks, C., D. E. James and S. R. Hart. 1976. Ancient lithosphere: its role in young continental volcanism. Science 193:1086-1094.
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• Clarke, Roy S., Jr., John F. Wosinski, Richard F. Marvin and Irving Friedman. 1966. Potassium-argon ages of artificial tektite. glass. Transactions, American Geophysical Union 47:144.
• Condomines, M., M. Bernat and C. J. Allegre. Evidence for contamination of Recent Hawaiian lavas from ²³⁰Th-²³⁸U data. Earth and Planetary Science Letters 33:122-125.
• Dallmeyer, R. D. 1975. The Palisades sill; a Jurassic intrusion? Geology 3:243-245.
• Dalrymple, G. Brent. 1969. ⁴⁰Ar/³⁶Ar analyses of historic lava flows. Earth and Planetary Science Letters 6:47-55.
• Dalrymple, G. Brent and Marvin A. Lanphere. 1969. Potassium-argon dating, Chapter 8. W. H. Freeman & Co., San Francisco.
• Dalrymple, G. Brent and James G. Moore. 1968. Argon-40 excess in submarine pillow basalts from Kilauea volcano, Hawaii. Science 161:1132-1135.
• Damon, Paul E. 1968. Potassium-argon dating of igneous and metamorphic rocks with applications to the Basin ranges of Arizona and Sonora. In E. I. Hamilton and R. M. Farquhar, eds. Radiometric Dating for Geologists, pp. 1-71, particularly Section E, pp. 12-18. John Wiley & Sons, New York.
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• Dickinson, D. R. and I. L. Gibson. 1972. Feldspar fractionation and anomalous Sr⁸⁷/Sr⁸⁶ ratios in a suit of peralkaline silicic rocks. Geological Society of America Bulletin 83:231-240.
• Doe, Bruce R. 1970. Lead isotopes, p. 55. Springer-Verlag, New York.
• Duncan, R. A. and W. Compston. 1976. Sr-isotope evidence for an old mantle source region for French Polynesian volcanism. Geology 4:728-732.
• Dymond, Jack. 1970. Excess argon in submarine basalt pillows. Geological Society of America Bulletin 81:1229-1232.
• Faure, Gunter. 1977. Principles of isotope geology, pp. 103, 172. John Wiley & Sons, New York.
• Faure, G. and J. L. Powell. 1972. Strontium isotope geology, pp. 35, 41, 48-50, 63. Springer-Verlag, New York.
• Fisher, David E. 1969. Fission track ages of deep sea glasses. Nature 221:549-550.
• Fisher, David E. 1971. Excess rare gases in a subaerial basalt from Nigeria. Nature Physical Science 232:60-61.
• Fisher, David E. 1972. U/He ages as indicators of excess argon in deep-sea basalts. Earth and Planetary Science Letters 14:255-258.
• Funkhouser, J. G., I. L. Barnes and J. J. Naughton. 1968. The determination of a series of ages of Hawaiian volcanoes by the potassium-argon method. Pacific Science 22:369-372.
• Funkhouser, John G., D. E. Fisher and E. Bonatti. 1968. Excess argon in deep sea rocks. Earth and Planetary Science Letters 5:95-100.
• Funkhouser, John G. and John J. Naughton. 1968. Radiogenic helium and argon in ultramafic inclusions from Hawaii. Journal of Geophysical Research 73:4601-4607.
• Gentry, Robert V., Warner H. Christie, David H. Smith, J. F. Emery, S. A. Reynolds, Raymond Walker, S. S. Cristy and P. A. Gentry. 1976. Radiohalos in coalified wood: new evidence relating to the time of uranium introduction and coalification. Science 194:315-318.
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• Ghosh, Protip Kumar. 1972. Use of bentonites and glauconites in potassium-40/argon-40 dating in Gulf Coast stratigraphy. Doctoral dissertation, Rice University. University Microfilms, Ann Arbor, Michigan 72-26, 413.
• Hanson, G. N. 1975. ⁴⁰Ar/³⁹Ar spectrum ages on Logan intrusions, a Late Keweenawan flow, and mafic dikes in northeastern Minnesota-northwestern Ontario. Canadian Journal of Earth Sciences 12:821-835.
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• Hart, R. 1978. Excess ⁴⁰Ar in Precambrian cherts. Transactions, American Geophysical Union 59:1215-1216.
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• Hebeda, E. H., N. A. I. M. Boelrijik, H. N. A. Priem, E. A. Th. Verdurmen and R. H. Versuchure. 1973. Excess radiogenic argon in the Precambrian Avanavero dolerite in Western Suriname (South America). Earth and Planetary Science Letters 20:189-200.
• Hebeda, E. H., N. A. I. M. Boerlrijik, H. N. A. Priem, E. A. Th. Verdurman and R. H. Versuchure. 1980. Excess radiogenic Ar and undisturbed Rb-Sr systems in basic intrusives subjected to Alpine metamorphism in southeastern Spain. Earth and Planetary Science Letters 47:87-90.
• Hedge, Carl E. and Donald C. Noble. 1971. Upper Cenozoic basalts with high Sr⁸⁷/Sr⁸⁶ and Sr/Rb ratios, Southern Great Basin, Western United States. Geological Society of America Bulletin 82:3503-3510.
• Hennecke, E. W. and O. K. Manuel. 1975. Noble gases in lava rock from Mount Capulin, New Mexico. Nature 256:284-287.
• Hoffmann, A. W., J. W. Mahoney, Jr. and B. J. Giletti. 1974. K-Ar and Rb-Sr data on detrital and postdepositional history of Pennsylvanian clay from Ohio and Pennsylvania. Geological Society of America Bulletin 85:639-644.
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• Kaneoka, Ichiro. 1974. Investigation of excess argon in ultramafic rocks from the Kola Peninsula by the ⁴⁰Ar/³⁹Ar method. Earth and Planetary Science Letters 22:145-156.
• Kaneoka, Ichiro and Ken-Ichiro Aoki. 1978. ⁴⁰Ar/³⁹Ar analysis of phlogopite nodules and phlogopite-bearing peridotites in South African kimberlites. Earth and Planetary Science Letters 40:119-129.
• Kirsten, T. and O. Muller. 1967. Argon and potassium in mineral fractions of three ultramafic rocks from the Baltic Shield. In Radioactive Dating and Methods of Low-Level Counting, pp. 483-498. International Atomic Energy Agency, Vienna.
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• Lanphere, Marvin A. and G. Brent Dalrymple. 1971. A test of the ⁴⁰Ar/³⁹Ar age spectrum technique on some terrestrial materials. Earth and Planetary Science Letters 12:359-372; specifically, section 3.3.
• Laughlin, A. W. 1969. Excess radiogenic argon in pegmatite minerals. Ph.D. thesis, University of Arizona.
• Leventhal, J. S. 1975. An evaluation of the U-Th-He method for dating young basalts. Journal of Geophysical Research 80:1911-1914.
• Ludwig, Kenneth R. 1978. Uranium-daughter migration and U/Pb isotope apparent ages of uranium ores, Shirley Basin, Wyoming. Economic Geology 73:29-49.
• Macdougall, J. Douglas. 1976. Fission track annealing and correction procedures for oceanic basalt glasses. Earth and Planetary Science Letters 30:19-26.
• McCulloch, Malcolm T., Robert T. Gregory, G. J. Wasserburg, and Hugh P. Taylor, Jr. 1980. A neodymium, strontium, and oxygen isotope study of Cretaceous Samil ophialite and implications for petrogenesis and sea water-hydrothermal alteration of oceanic crust. Earth and Planetary Science Letters 46:201-211.
• McDougall, L and D. H. Green. 1964. Excess radiogenic argon in pyroxenes and isotopic ages on minerals from Norwegian eclogites. Norsk Geologisk Tidsskrift 44:183-196.
• McDougall, I., H. A. Polach and J. J. Stipp. 1969. Excess radiogenic argon in young subaerial basalts from Auckland volcanic field, New Zealand. Geochimica. et Cosmochimica Acta 33:1485-1520.
• Maluski, H. 1978. Behaviour of biotites, amphibolites, plagioclases and K-feldspars in response to tectonic events with the ⁴⁰Ar-³⁹Ar radiometric method. Example of Corsican granite. Geochimica et Cosmochimica Acta 42:1619-1633.
• Mellor, D. W. and A. E. Mussett. 1975. Evidence for initial ³⁶Ar in volcanic rocks, and some implications. Earth and Planetary Science Letters 26:312-318.
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• Nevins, Stuart E. 1974. Post-Flood strata of the John Day Country, northeastern Oregon. Creation Research Society Quarterly 10:191-204.
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• Noble, Donald C. and Carl E. Hedge. 1969. Sr⁸⁷/Sr⁸⁶ variations within individual ash-flow sheets. U.S. Geological Survey Professional Paper 650-C, pp. C133-Cl39.
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(22) Thermoluminescent Dating

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(23) Nuclear Radiation Track Dating

• Burnett, D., M. Monnin, M. Seitz, R. Walker and D. Yuhas. 1971, Lunar astrology — U-Th distributions and fission-track dating of lunar samples. Proceedings of the Second Lunar Science Conference, Vol. 2, pp. 1503-1519. The M.I.T. Press, Cambridge.
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(24) Chondrite Structure Features

• Brownlee, D. E. and R. S. Rajan. 1973. Micrometeorite craters discovered on chondrule-like objects from Kapaeta meteorite. Science 182:1341-1344.
• Chen, J. H. and G. R. Tilton. 1976. Isotopic lead investigations on the Allende carbonaceous chondrite. Geochimica et Cosmochimica Acta 40:635-643.
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• Hughes, David W., editorial. 1974a. Even small meteoroids are fluffy. Nature 248:99.
• Hughes, David W., editorial. 1974b. Where do meteorites come from? Nature 248:278-279.
• Hutcheon, I. D. and J. N. Goswami. 1975. Microcraters and solar flare records in C2 chondrites. Transactions, American Geophysical Union 56:1016.
• Lange, David E. and John W. Larimer. 1973. Chondrules: an origin by impacts between dust grains. Science 182:920-922.
• Lindsay, John F. and L. J. Srnka. 1975. Galactic dust lanes and lunar soil. Nature 257:776-777.
• Macdougall, J. Douglas. 1976. Extraterrestrial materials. Geotimes 21(5):25-27.
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• MacPherson, Glenn J. and Lawrence Grossman. 1981. A once-molten, coarse-grained, Ca-rich inclusion in Allende. Earth and Planetary Science Letters 52:16-24.
• Rajan, R. Sundar. 1974. On the irradiation history and origin of gas-rich meteorites. Geochimica et Cosmochimica Acta 38:777-788.
• Sabu, D. C. 1973. Solar wind xenon in some carbonaceous chondrites. Journal of Geophysical Research 78:3245-3248.
• Tatsumoto, Mitsunobu, Daniel M. Unruh and George A. Desborough. 1976. U-Th-Pb and Rb-Sr systematics of Allende and U-Th-Pb systematics of Orgueil. Geochimica et Cosmochimica Acta 40:617-634.