| Are
rocks used to date fossils or are fossils used to date
rocks?
In
the high school biology textbook Chapter 15 entitled
Evolution: Evidence and Theory contains Table 15-1 Geological
History of Earth.1 It shows the most recent
550 million years of the earth’s existence neatly
sliced into Eras, Periods and Epochs with various kinds
of flora and fauna that made their appearances in each
slice. In addition the absolute age of each slice is
given in units of “million of years ago”.
For example, the table indicates that primitive mammals
and dinosaurs arose in the Triassic Period 208 million
years ago, fishes arose in the Ordovician Period 438
million years ago, etc. The text gives a brief explanation
as to how the table was assembled indicating that the
relative ages of fossils in successive
layers of rock are determined by the law of
superposition--fossils in lower strata are
older than those in higher strata. It also states “The
fossil’s absolute age ( its age
in years ) could be estimated from the amount of sediment
deposit above the fossil.”2
Is
it really that simple? Do the positions of the millions
of fossils in the estimated 200 million cubic miles
of sediment provide irrefutable evidence of biological
evolution as the chapter claims? There is a chicken
and egg scenario lurking here. That is, did the strata
lead to evolution or did evolution via the fossils lead
to the strata? Or put another way, do rocks date the
fossils or do fossils date the rocks? Students are told
that the the former is true because they are told that
a fossil’s position in the rocks determines its
age.
Consider
the following scenario of the earth’s strata that
could produce the data on which Table 15-1 is based.
Suppose the stratigraphers find that rock formations
are remarkably similar all over the earth. That no matter
where they look, they find the same sequences of rock
layers, not only types of rock such as sandstones, shales
and limestones occurring in the same order, but also
having the same thicknesses and depths. Furthermore
the absolute ages of the layers can be determined by
radiometric means or sedimentation rates resulting in
a complete coherent model of the earth’s strata.
After the stratigraphers have completed their work,
the fossil hunters or paleontologists go to work and
find the exact succession of fossils in the strata as
shown in Table 15-1. Thus the stratigraphers and the
paleontologists working independently corroborate each
others findings, the stratigraphers telling the paleontologist
that they can be sure that the ages of fossils increases
with depth and the paleontologists assuring the stratigraphers
that their model of the earth’s strata is correct
because less complex organisms evolved first and they
indeed are in the lower strata.
This scenario is not true and while it is not presented
to the students, if it were, they could not detect its
falsity from the brief, matter-of-fact presentation
of the fossil record in Chapter 15. Nothing in the chapter
dissuades students from believing that the strata shown
in Table 15-1 can be found everywhere on earth, that
if they dig deeply enough in their back yards, they
will penetrate all the strata and find the complete
succession of fossils shown in the table. The statements
on determining relative and absolute ages tell students
that a fossil’s age is determined by its location
in the strata whereas the truth is much more complicated
than that simplistic representation.
The
fact is that not only is the geological column of strata
not found everywhere on earth but also that it is not
found anywhere on earth. The fact is that the law of
superposition is only applicable to layers in a rock
formation that are horizontal with no evidence of disruption
after their deposition. In addition its usefulness is
limited because while it says lower layers are older,
it can’t tell you how much older-----years, centuries,
millennia, millions of years? The fact is that no physical
property of the formation, such as its thickness, provides
the answer. The thickness of the layer is not much help
because deposition rates of sediment vary greatly with
ratios of rates as large as one hundred billion. Some
deposition rates are given as millimeters per 1000 years
while mud slides accompanying the eruption of Mount
St. Helens produced cliffs hundreds of feet thick in
a matter of days. So even with rocks in the same vertical
section, determining the relative ages in any quantitative
sense ( eg. 10 million years older) is problematic.
An even more daunting problem arises when stratigraphers
attempt to correlate the ages of strata in different
locations. Does the Devonian in England consist of the
same kind of rocks as the Devonian in other locations?
Does a layer of black shale in China have any relevance
to a similar layer in Pennsylvania? Obviously it does
not, since the materials available for deposition are
not the same in different regions. Therefore, lithological
( rock ) properties of strata are not useful for correlating
distant strata. In fact, there are no worldwide lithological
markers or phenomena that can be used to correlate distant
strata.
If
rocks cannot date themselves, how was the geological
column of the earth’s strata developed? The answer
is fossils. They provide a reliable worldwide marker
if it is true that characteristic organisms lived at
certain times in the past. These organisms evolved into
existence, lived for a relatively short time and either
became extinct or evolved into a more advanced species.
In other words, stratigraphers are able to date rocks
because they have adopted the all-encompassing concept
or worldview of earth’s history that life evolved
during the long lifetime of earth.
The
remains of the characteristic organisms are called index
fossils. They are the primary means for dating strata
in the same vertical section and correlating strata
at different locations. Stratigraphers believe that
all strata in which a particular index fossil is found
have the same age. For example, stratigraphers use the
leioceras genus of ammonites which are mollusks, to
mark the lower boundary of the Cretaceous period; the
planktonic foraminifer, Hantkenina, to mark the lower
boundary of the Oligocene. This use of fossils by stratigraphers
has enormous significance. It means, for example, that
the Oligocene is not first and foremost a period of
time but rather all sediment in which certain fossils
are found. It means the Cretaceous Period 70-140 million
years ago was not defined by a worldwide search for
rocks of that age but rather for the search of leioceras
ammonites. The assignment of age came after the requisite
fossils were found.
In
the mid 19th century.....” the German geologist
Albert Oppel said that geologists need to explore, on
the scale of centimeters, ‘the vertical stratigraphic
range of each separate species in the most diverse localities,
while ignoring the lithological development of beds;
by this means will be brought into prominence those
zones which, through constant and exclusive occurrence
of certain species, mark themselves off from their neighbors
as distinct horizons. In this way the ideal profile
is obtained in which layers of the same age in different
areas are characterized by the same association of species.’
Oppel named each zone after a prominent species in the
zone, and this is the way it is still done today.”3
Following
is an excerpt from an address by Edmund M. Spieker in
the early 1950’s given under the auspices of the
Distinguished Lecture Committee of the American Association
of Petroleum Geologists. It concerns the time scale
of the earth’s strata.
“And
what, essentially, is this actual time scale-- on what
criteria does it rest? When all is winnowed out, and
the grain reclaimed from the chaff, it is certain that
the grain in the product is mainly the paleontological
record and highly likely that the physical evidence
is the chaff. To repeat myself in excerpt (Spieker,
1946, p.146) `...if the question is raised as to what
the terms Cretaceous and Tertiary actually mean,...it
is evident that they have come to stand essentially
for times in the geologic past when more or less characteristic
organisms lived.` The physical evidence, even if it
should turn out eventually to warrant some of the reliance
that has been placed on it, can support no such general
statement of worth.”4
Sixty
years later the physical evidence is still secondary
to the fossil evidence as Blatt et al. report, “Even
the development of sophisticated geochemical, isotopic,
and paleomagnetic systems for dating strata has not
displaced fossils as the most important tool for stratigraphic
research, because fossils are consistently the most
usable and reliable dating tool in Phanerozoic [the
last 550 million years] sedimentary strata.”5
The
IUGS International Commission on Stratigraphy, the body
responsible for selecting the boundaries of strata,
says the following, “Fossils constitute one of
the best and most widely used means of tracing and correlating
sedimentary sequences and thus determining their relative
age. Because the orderly and progressive course of organic
evolution is irreversible with respect to geologic time
and the remains of life are widespread and distinctive,
fossils have also constituted the best means for worldwide
relative dating and approximate long-distance time correlation
throughout the Phanerozoic and have largely made possible
the development of a global Chronostratigrahpic Scale
for Phanerozoic strata.”6
More
gap than sediment?
A particular problem in correlating distant strata is
that the sedimentary sequences may be more gap than
sediment. The geological column of strata is not found
anywhere on earth and furthermore, most locations have
at most a small portion of the column. Blatt et al.
have this to say: “In this regard the standard
stratigraphic columns that we see in published stratigraphic
studies are terribly misleading. They convey the impression
of rock sections as a long record of sedimentation with
occasional gaps. A far more accurate picture of the
stratigraphic record is one of long gaps with only occasional
records of sedimentation. Interpretation of the stratigraphic
record is an excellent illustration of Mark Twain’s
aphorism about the wonder of science - one gets such
wholesale returns of conjecture from such a trifling
investment of fact.”7
Have
you ever heard of a type of gap called a paraconformity?
It is a hypothesized gap in sedimentation to accommodate
anomalies in the fossil content. As Sam Boggs, Jr. defines
it in his book Principles of Sedimentology and Stratigraphy
(2nd Ed.) “A paraconformity is an obscure
unconformity characterized by beds above and below the
unconformity contact that are parallel and in which
no erosional surface or other physical evidence of unconformity
is discernible. ...Paraconformities are not easily recognized
and must be identified on the basis of a gap in the
rock record (owing to non deposition or erosion) as
determined from paleontological evidence such as absence
of faunal zones or abrupt faunal changes.”8
In other words the physical evidence indicates a continuous
deposition of sediment with no gaps but since that is
not consistent with the fossil content, for example,
much older fossils immediately below younger fossils,
a long gap in time is assumed with its missing sediment.
The
fossil content can cause stratigraphers to assign questionable
lengths of time to the deposition of rock formations,
resulting in vastly disparate sedimentation rates. For
example, Blatt, et al., report that in the Apennines
of Italy the Late Jurassic through Early Oligocene a
period of 133 million years is represented by an apparently
unbroken stratigraphic sequence only 70 meters thick,
while the rest of Oligocene time (6 million years) is
represented by 3000 meters of sediment. They also report
that 30 ammonite zones are assigned to a 0.3 meter stratum
in Sicily, while 5000 meters represents a single zone
in Oregon.9 (How is it possible to have 30
fossil zones in only 0.3 meters of sediment? That is
an evolutionary sequence of 30 species each in a layer
with an average thickness of one centimeter. Or are
many of the species absent in Sicily because possibly
an early one, for example the third, migrated to Rome,
evolved many of the descendent species there and then
one, for example the 28th, migrated back to Sicily?
So in Sicily the 0.3m stratum spans, in a chronological
sense, 30 sequential species but only a few species
are actually present? )
How
are marine and terrestrial strata correlated?
The fossils used for correlating strata are exclusively
marine invertebrate fossils and yet the geological column
shows the periods of time when various terrestrial animals
evolved. How do you correlate layers that do not contain
common organisms, for example, layers found in near-shore
environments containing marine fossils and mid-continental
layers containing terrestrial fossils? Boggs writes
of the difficulty: “Because many organisms were
confined to biogeographic provinces in the past, however,
we cannot always correlate time-equivalent strata from
different environments because the organisms that existed
in different biogeographic provinces during the same
period of time were different. Thus, correlation between
geographic provinces is difficult, and it is commonly
not possible to make worldwide correlations.”10
Why
isn’t radiochronology supreme?
Why endure all the problems associated with using fossils
to correlate strata which only yields relative ages
when radioactive dating gives absolute ages? It would
also eliminate the need to invoke evolution and, thereby,
avoid the circular reasoning conundrum that evolution
dates the rocks whose ages are then cited as evidence
for evolution. There are two primary reasons. First
stratigraphers can never be sure that a radioactive
date is accurate because they can never be sure that
the sample remained a closed system from the time of
deposition. In addition, all methods of analysis to
minimize these problems have produced spurious results.
Hence, radioactive dates will only pass muster if they
are consistent with the fossil content. Secondly sedimentary
rock does not contain the radioactive isotopes used
for dating. However, nearby igneous or metamorphic rock
may provide a radioactive date for a sedimentary formation.
Is
the order of old and young fossils ever reversed in
sedimentary sequences?
Definitely yes. Here are three examples: 11
1)
The Heart Mountain formation in Wyoming has 200 million
year older Mississippian limestone overlying Tertiary
limestone.
2)
Along the continental divide at the British Columbia-Alberta
boundary, Precambrian dolomite lies conformably over
Cretaceous shale which is 500 million years younger.
3)
The Glarus formation in Switzerland has 200 million
year older Permian arkosic schist overlying Eocene slate.
The
truth of even one of these would be devastating to evolution.
Evolutionary stratigraphers believe that the older layers
were thrust on top of the younger layers; other stratigraphers
say that the physical evidence does not support overthrusting.
A case of circular reasoning?
The belief in evolution was pivotal in establishing
the geological column of strata, which, in turn, is
presented as evidence for evolution.
Here
are three quotes expressing the same opinion compliled
by John Morris in his book The Young Earth.
David
B. Kitts writes in Paleobiology, “...the
record of evolution, like any other historical record,
must be construed within a complex of particular and
general preconceptions, not the least of which is the
hypothesis that evolution has occurred.”12
Niles
Eldridge writes, “And this poses something of
a problem: If we date the rocks by fossils, how can
we then turn around and talk about patterns of evolutionary
change through time in the fossil record?”13
Tom
Kemp writes in the New Scientist, “A
circular argument arises: Interpret the fossil record
in the terms of a particular theory of evolution, inspect
the interpretation, and note that it confirms the theory.
Well, it would, wouldn’t it?”14
1
A. Towle, Modern Biology, ( Austin, Texas:
Holt, Rinehart and Winston, 1999), p. 280.
2
Ibid., p. 281.
3
H. Blatt, W. B. Berry, and S. Brande, Principles
of Stratigraphic Analysis, ( Boston: Blackwell
Scientific Publications, 1991 ), p. 90.
4
E. M. Spieker, “Mountain- Building Chronology
and Nature of Geologic Time Scale”, in Bulletin
of the American Association of Petroleum Geologists:
1769-1815 (Aug. 1956).
5
H. Blatt et al., op. cit. p. 145.
6
International Stratigraphic Guide, 2nd ed.,
( Copublished by The International Union of Geological
Sciences and The Geological Society of America, 1994),
p. 93.
7
H. Blatt et al., op. cit., p. 69.
8
S. Boggs Jr., Principles of Sedimentology and Stratigraphy,
2nd ed., (Upper Saddle River, New Jersey: Prentice-Hall,
Inc., 1995), p. 495.
9
H. Blatt et al. op. cit., p. 67.
10
S. Boggs Jr., op. cit., p. 613.
11
D. T. Gish, Creation Research Society Quarterly,
25(4): 161 (March, 1989).
12
D. B. Kitts, Paleobiology, 353-354, (1979).
13
N. Eldridge, Time Frames, p. 52, (1985).
14
T. Kemp, “A Fresh Look at the Fossil Record”,
New Scientist, Vol. 108, p. 67, (Dec. 5, 1985)
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