Collection of Articles on Fossils and Petrification

 

Re: How long does it take for something to petrify?

 

Area: Earth Sciences

Posted By: John W. Bebout, Ph.D., Sr. Technical Specialist, Oil and Gas, Fluid Minerals Group, Bureau of Land Management (310)

Date: Tue Jul 22 19:00:03 1997

Area of science: Earth Sciences

ID: 868346572.Es

 

Message:

 

Dear Danny,

 

Petrification occurs by the replacement, recrystallization or

permineralization of the original plant or animal parts. (Permineralization

just means that mineral material fills the voids in the fossil-to-be rather

than replacing or recrystallizing the original materials).  In almost every

case, ground water is the agent that causes petrification and silica and

calcite are the main replacing minerals.

 

How long it takes for petrification to occur depends on a lot of factors

like pH and temperature, but all things being equal, groundwater saturated

with calcium carbonate(calcite)acts the fastest because calcite is more

soluble than silica or other petrifying minerals.  In the parking garage

where I work, which is only 3 years old, 4 inch stalactites have already

formed from rainwater leaching calcium carbonate out of the concrete

floors.

 

So if we accept the fact that petrification occurs as a continuum (in other

words, a gradual process from partial to complete

replacement/recrystallization/permineralization), and we assume the

replacement material is calcite under ideal chemical conditions,

petrification can certainly occur just a few hundred years or even less.

 

I hope this answers your question!  Please let me know if you would like

any clarification or additional information.

 

John Bebout

 

 

Fossilization

by
Chris Nedin

Two claims commonly made by literalist fundamentalist creationists about the fossil record are (1) that if there have been animals on Earth for hundreds of millions of years, then the fossil record should contain millions and millions of fossils, many of which should be transitional forms, so that there should be numerous examples of transitional fossils. (2) Uniformitarian sedimentation rates are too slow to preserve organisms.

Ignoring the contradiction inherent in these two statements, are they correct? To answer this we must have an understanding of the fossilization process (taphonomy) from

life -> death -> preservation -> survival -> discovery.

While it would appear that the fossilization process must start with the death of the organism, it actually starts in life (as the upper echelons of academia occasionally shows).

Life

By life I mean that the life strategy of the organism, which will have a profound impact into its fossilization potential (FP - the likelihood of being found as a fossil). For an organism even to begin considering a career as a fossil it must be buried, any life strategy which enhances the likelihood of burial will increase its FP. Consequently, organisms which live on land have a much lower FP than organisms which live in shallow, near-shore marine environments. For example, the FP of your average marine Lesser Spotted Leaping Clam has a higher FP than your average Lesser Spotted Leaping Mountain Goat, due to the periodic, rapid sedimentation events experienced in near-shore environments. Also, organisms which do not possess hard parts or whose hard parts are fragile will have a low FP since they are unlikely to survive the burial process intact.

The position of the organism in the food chain is important since those lower down tend (for excellent ecological reasons) to be more abundant than those towards the top, so that organisms which occur in large populations, due to their sheer numbers, have a higher FP than those that occur in smaller populations. Having a lifestyle which incorporates living within the sediment provides added bonus points to the organisms FP since it is already buried. So:

High chance of burial + low in the food chain = high FP (with bonuses for already buried).

Low chance of burial + high in the food chain = low FP (it can be argued that the Lesser Spotted Leaping Mountain Goat has a good chance of being buried by the occasional landslide, living as it does in the mountains, but see Survival below.)

Death

How an organism dies also affects its FP. Shuffling off this mortal coil out in the open is not good since there tends to be a large number of organisms around to take advantage of such events to reduce your remains and FP quite rapidly. Even if you are already buried, something higher in the food chain digging you out and crushing you into a thousand small bits has something of a disastrous effect on your FP. Similarly your FP can be badly affected if you are rolled around by storms. Rapid smothering is still the best way of increasing your FP. This cuts down the possibility of further contributing to the food chain and in certain instances provides an environment suitable for preservation. So we have:

smothering by storm or flood sedimentation = high FP
being eaten or rolled around = low FP

 

Preservation

This covers the survival of the organism's remains after death and its transition into a fossil. Burial is the premier method of ensuring passage into the preservation stage. Rapid burial is a common process which occurs on a regular basis. Floods, storms, landslides, and volcanic ash eruptions lay down sediments over a period of hours to days. In some cases several meters of sediment can be dumped in near-shore environments by severe storms. Sedimentation does not have to occur on a slow, steady, incremental basis. Rapid sedimentation is part and parcel of current geological theories and is an important causal constituent of the rock record. However, not all environments are preserved equally in the rock record, leading to a heavy bias towards shallow, near-shore marine environments. Also, all periods of geological history are not preserved equally. Far more is preserved of recent Earth history than of more ancient times.

Burial protects the organism from higher food chain organisms with bad intentions and from the general environment - against mechanical (abrasion and break-up) and chemical processes (decay and disintegration). In the vast majority of cases decay is inevitable. Therefore organisms which possess some robust hard parts (shell, bone) have a much higher FP than soft-bodied organisms which have no hard parts, or possess fragile hard parts. Only under exceptional circumstances are soft-bodied organisms, or non-mineralized tissues, preserved. This usually occurs when the environment surrounding the organism either is low or is lacking in oxygen. Such environments are not needed to produce all fossils. The vast, vast, vast majority of organisms were fossilized in environments with normal oxygen levels, although these organisms are only represented by their hard parts with no soft parts remaining. Fossils containing preserved soft parts are therefore exceedingly rare compared with fossils composed of hard parts.

There are a number of possible preservation pathways once burial is complete. Some result in chemical alteration of the remains. Most result in the continued destruction of soft tissues. So:

Rapid burial =

High FP

 

Hard parts =

High FP

 

Slow burial =

Low FP

 

No hard parts =

Low FP

 

Survival

Once an organism has been successfully buried and preserved the fossil must survive. If the sediments containing the fossil erode away the fossil will be lost. If the sediments are buried too deeply the resultant increase in temperature can destroy the fossil.

Loss by erosion is especially likely if the organism was buried above sea level. Sediments above sea level are far more likely to be eroded than sediments buried in basins which are sinking. Sinking basins can accommodate more sediments (e.g. in the near-shore marine environment) allowing more sediment to be deposited, protecting the sediments beneath. Our Lesser Spotted Leaping Mountain Goat (or any other non-marine animal) may well have become a fossil but its fossil is much more likely to be eroded and destroyed than that of a fossilized clam which is buried below sea level. So:

High FP

burial below sea level
burial in sinking basin
shallow burial

Low FP

burial above sea level
deep burial

 

 

Discovery

This encompasses the chance of the fossil being discovered. A fossil cannot be discovered unless the sedimentary rock containing it is exposed at the Earth's surface. At any one time only a tiny fraction of the fossil bearing sedimentary rocks are exposed and available for being searched. Of all the time that current fossil-bearing rocks have been exposed at the Earth's surface only for the last few hundred years have they been searched. Of all the fossil-bearing rocks that have ever been exposed at the Earth's surface only the ones exposed now have been searched. Rocks in past times have been eroded away leaving little, if any, trace of their fossil content. Thus the fossil-bearing rocks we have searched are only a tiny fraction of the total fossil-bearing rocks.

The fossil record we have reflects these influences on fossilization. The vast majority of fossils are of organisms with hard parts which lived in environments conducive to rapid burial, i.e., in basins that were below sea level and were sinking. In other words the vast (up to 90%) majority of all fossils are of near-shore marine organisms with hard parts. Organisms which lived on land represent a tiny fraction of the fossils record. This is understandable given what we know about the fossilization process but is hard to explain if all the fossils were laid down during one event.

Conclusion

In reply to the claims mentioned at the start:

(1) We cannot expect that all or even most of the organisms that have lived on Earth will be represented in the fossil record. On the contrary, only a few, living in favored environments and possessing hard parts, will have any likelihood of being preserved (a large number of known phyla have no members which possess hard parts, and most phyla have members which possess no hard parts). On top of this, the vast majority of fossils have not been discovered since they have either eroded away previously or remain buried and out of reach. So the fossil record is not a comprehensive record of all life that has existed on Earth. Nor is the rock record a comprehensive record of all environments that have existed. Further, with regard to transitional fossils, is has become apparent in recent years that evolution does not necessarily proceed in a constant, gradual manner over geological time, but can operate rapidly, in isolated populations. Such evolution results in small populations of intermediates separated by very short periods of geological time. such scenarios are unlikely to make it into the fossil record to begin with, let alone survive to be found. Thus preservation of any fossil from a transitional series will be rare.

(2) The rate of sedimentation is not too slow to preserve organisms. The vast majority are preserved by rapid sedimentation entirely in accordance with modern geological theories.

 

Supplemental Lecture (97/04/05 update) by Stephen T. Abedon (abedon.1@osu.edu)

  1. Chapter title: Fossilization
    1. A list of vocabulary words is found toward the end of this document
    2. The fossil record is imperfect. The fossil record is also our best window on the history of life on this planet. What happens when your best is less than ideal? You have to work that much harder to derive useful information. Consequently, paleontology, as with just about everything else associated with the sciences of evolutionary biology, is not easy to do.
    3. There are a number of basic principles which go a long way toward understanding interpretation of the fossil record. One is to understand just how fossilization occurs. Another is to be familiar with the various strategies for dating fossils. Of course, it also helps if you are an expert on the anatomy of those parts of organisms which tend to fossilize. Obviously you will not be held responsible here for this latter consideration. The object of this lecture is to familiarize you with the concepts of fossils and fossilization.
    4. To understand how it is that the history of life is thought to be understood, you have to understand fossils. In this lecture we will introduce the concept of fossilization, the dating of fossils, and dwell upon why it is that the fossil record is not perfect.
  2. Paleontology
    1. Paleontology is the study of the past through the study of fossils.
  3. Fossil
    1. Mineralized dead organisms:
      1. What is a fossil? A fossil is some remain of a dead organism preserved in rock.
      2. This remain either represents part of the organism itself or some imprintation made by the organism's body.
      3. Often the remains of preserved organisms are not of the organism itself but instead of minerals deposited where, especially, hard parts of the organism previously existed. Thus, a fossil femur (a kind of bone) is a three dimensional "depiction" of a bone but consisting all or in part of not bone-like material.
    2. Mineralized hard parts, usually:
      1. Soft parts tend not to fossilize because they usually decay prior to mineralization.
      2. However, soft parts, under the right conditions, can also make impressions.
      3. Included among such imprints are those made during the act of locomotion such as fossil foot prints or various invertebrate trails.
  4. Biases in the fossil record
    1. Convoluted series of events:
      1. The occurrence of a fossil depends on the occurrence of a sufficiently convoluted series of events that the likelihood of fossilization per dead individual is low.
      2. Fortunately for paleontologists, the many billions of years of earth's history has seen a vast accumulation of dead organisms.
    2. Bias toward numerous hard parts:
      1. A large fraction of organisms show a very low likelihood of fossilization due to a lack of sufficient hard parts such as bones or shells.
      2. Thus, the fossil record is biased toward organism's displaying hard parts.
      3. The fossil record is also biased, on a per individual basis, toward those individuals which display particularly robust hard parts (a large dinosaur, say, relative to a canary).
      4. Thus, the likelihood of fossilization is large when compared with the likelihood of fossilization of a given soft, small thing. The latter, however, tend to be more numerous among living populations, thus balancing things out somewhat.
    3. Time/location biases:
      1. The mechanism of fossilization tend to occur non-randomly about the landscape.
      2. Fossilization in one area (or time) may be more likely than in other areas or at different times.
      3. Fossilization thus is biased towards individuals who live in environments in which fossilization is more likely (e.g., not in tropical rain forests).
    4. The fossil record itself tends to show severe gaps as groups moved into and out of areas, or as populations wax and wane within areas in which fossilization was more or less likely.
  5. Fossilization
    1. Starts with burying:
      1. The key first step in the process of fossilization is the burying or otherwise entombing of an organism prior to that organism's complete decomposition.
      2. Often this entombment occurs as a corpse is buried under sediment at the bottom of a lake, stream, river, or sea. This may happen, for example, if an organism is swept away in a flood.
      3. Alternatively, organisms can be buried:
        1. under sand during storms
        2. under ash during volcanic eruptions
        3. in amber (polymerized tree sap)
        4. etc.
    2. Followed by mineralization
      1. In time, with water seepage, the atoms associated with the once living organism are replaced by minerals which precipitate out of the water within the structures of the organism before these structures are lost.
      2. Additionally, the buried sediments containing the buried organism gradually turn to stone, thus entombing the fossil in stone as well as converting imprints to stone.
  6. Fossils are rarely perfect
    1. Decomposition/predation:
      1. Often burying occurs after decomposition or following predation.
      2. Consequently, only a section of an organism may have been buried, or sections may have been buried in an orientation different from that seen in the living organism (consider what a fossilized Thanksgiving turkey might look like if buried prior to Thanksgiving dinner versus following Thanksgiving dinner).
    2. Geologic distortion:
      1. A buried fossil may also be subject to distorting forces from the rock around it.
      2. These distortions can lead to reconstruction problems, i.e., ambiguities can exist with regard to spatial relationships.
    3. Weathering:
      1. Fossils are very often found at the surface during the course of weathering.
      2. An exposed fossil likely has been subject to some degree of weathering and erosion.
      3. Weathering results in a loss of parts of the fossil even given their successful and complete preservation up to the point of exposure.
    4. Removal from rock:
      1. Fossils very often have to be removed from the strata in which they are found.
      2. Much skill and patience is often necessary to successfully and wholly extract a complex fossil and properly preserve and interpret all of the information, including positional information, plus various things often found associated with a given fossil.
  7. Relative dating
    1. Sediment positional information:
      1. Key to untangling the history of life is the dating of fossils.
      2. The earliest means of dating fossils, still a quite powerful one, is by determining relative positions in layers of sediment.
    2. Crucial assumptions:
      1. Two basic assumptions are made in determining the relative age of strata:
        1. older strata is buried beneath younger strata (unless the rock itself has been flipped by geologic forces)
        2. fossils are found within the strata that formed contemporaneously with the death of the fossilized organism (an assumption which is obviously not necessarily true for organisms which tend to burrow in sediment)
    3. Biostratography:
      1. Early geologists also assumed that sediments containing similar fossils were of similar ages, regardless of where on the surface of the earth the sediments were found (a technique known as biostratography).
      2. Thus, quite accurate relative ages and durations of many geologic periods were determined from fossil information long before methods of direct dating were developed.
      3. Indeed, many geologic periods were defined specifically in terms of the fossils present in strata.
    4. Today used along with direct dating:
      1. Relative dating is still commonly employed in paleontology today, usually in conjunction with direct dating.
      2. Ideally a fossil is buried in a directly datable layer.
      3. However, if a layer close above and another close below a fossil may be dated, it is possible to say that the layer in which the fossil was found is no older than the age of the layer below it and no younger than the age of the layer above it.
  8. Direct dating
    1. Isotope determination:
      1. Determination of the date of fossils and/or the stratum in which they are found today relies extensively on direct age determination.
      2. This, more often than not, involves some kind of isotope determination.
    2. Radioisotope clocks:
      1. The idea is that isotopes of elements that are radioactive (radioisatopes) undergo radioactive decay at both a known rate and at rate which are independent of environmental conditions.
      2. Furthermore, some of these radioisotopes are instantaneously (at least in geologic terms) incorporated into certain types of rocks and/or may have the elements into which they decay instantaneously purged.
      3. Examples of methods of direct dating employing radioisotopes include:
        1. 14C dating
        2. the 40K-40Ar clock
        3. etc.
    3. Non-radioisotope methods:
      1. Other methods of direct dating include:
        1. tree ring comparisons
        2. magnetic alignment with the earth's magnetic pole (which tends to switch from North to South from time to time; known as paleomagnitism)
        3. etc.
  9. Carbon dating
    1. Input via cosmic ray bombardment:
      1. Carbon dating is possible because radioactive carbon, 14C ("carbon-14"), is produced as a consequence of bombardment of atmospheric carbon with cosmic rays.
      2. 14C decays at a constant rate (exponential decline). Consequently, 14C is available to organisms in a fixed ratio to 12C (the stable and most common carbon isotope).
    2. The clock:
      1. The ratio of 14C to 12C is fixed at death because not more carbon is taken up by the organisms after this point.
      2. Thereafter, the ratio of 14C to 12C declines as 14C decays (with the half-life of 14C equal to 5730 years). By measuring the ratio of 14C to 12C, one can infer the relative age of the remains of an organism.
    3. Because of the relatively short 14C half-life, carbon dating is usable to date objects no older than about 50,000 years old.
  10. Potassium-argon dating
    1. Longer half-lives for older objects:
      1. Radioisotopes other with significantly longer half-lives than that of 14C are useful for dating older specimens.
      2. The half-life of 40K ("potassium-40"), for example, is equal to 1.28 x 109 years (1.3 billion).
      3. 40K decays into the radioactively stable 40Ar ("argon-40").
    2. Volcanic start of clock:
      1. Since argon is a gas, a rock upon melting is purged of all 40Ar.
      2. This sets the 40K-40Ar clock to zero.
      3. Rock melting occurs in the context of volcanic eruption.
      4. Thus a paleontologist often considers it lucky indeed if a fossil is located in strata near strata consisting of volcanic ash (i.e., a melted and resolidified product of volcanic eruption, one which is typically carried on the wind significant distances from the actual eruption).
  11. Vocabulary
    1. Absolute dating
    2. Biases in the fossil record
    3. Chronometric dating
    4. Direct age determination
    5. Direct dating
    6. Fossil
    7. Fossilization
    8. Fossilization problems
    9. Paleontology
    10. Relative dating
  12. Practice questions
    1. Discuss fossil dating. [PEEK]
    2. Give two reasons for why fossils are rarely "perfect." [PEEK]
  13. Practice question answers
    1. Details for which points may be awarded (not necessarily a complete list): "relative dating", only method available prior to invention direct dating methods, older strata found beneath newer, fossil as old as strata found in, strata with similar fossils considered same age, "direct dating", "radioisotopes" or equivalent, decay occurs at constant rates, "biostratography", 14C, 14C decays to 12C, ratio constant during life, dates only organic matter, death of organism fixes ratio (sets clock), half life 5730 years, 50,000 year maximum, 40K, 40K decays to 40Ar, clock set by purging of Ar (such as by melting rock), volcanic ash particularly good to find around fossil, half life 1.3 billion years, much longer than 50,000 year maximum, other types of direct dating.
    2. (i) the organism may be imperfect due to events occurring after death but prior to burial, (ii) in most cases soft body parts do not fossilize well, (iii) distorting forces from the rock surrounding the fossil can distort the fossil, (iv) upon exposure, fossils are subject to weathering, (v) the extraction of a fossil from rock can require great skill and perseverance.
  14. References
    1. Raven, P.H., Johnson, G.B. (1995). Biology (updated version). Third Edition. Wm. C. Brown publishers, Dubuque, Iowa. pp. 423-427.

Chapter 1: Fossilization and Preservation

Introduction

Ordinarily, only the hard parts of organisms are preserved (for example, only the shells of invertebrates, and only the bones and teeth of vertebrates). In most instances we must make inferences about fossil organisms using only these hard parts. Despite this challenge, we must try to understand the soft-part anatomy of fossil organisms so that we can better appreciate them as organisms that were once alive, that consumed food, breathed oxygen, interacted with their physical and biological environments, etc. Taphonomy is the science that studies the information that is lost between the death of an individual and its final discovery, and will be covered in the next lab.

This lab is designed to introduce you to some of the methods that paleontologists use to reconstruct fossil biology and ecology, and at the same time to acquaint you with some of the problems that are encountered after fossilization.

The following text should be studied, and referred to while examining the displays.

1.1.1 What is a fossil?

What is a fossil and what processes are required for their preservation? A fossil is any evidence of a once-living organism. This includes body fossils, casts, molds, footprints, track ways and feeding traces. This evidence of previous living organisms can then be used to study changes in life forms through time. This includes their evolution, ecology, functional morphology, growth and form, as well as their geographic distribution. Fossils provide us with our best link to the history of life.

1.1.2 How do we get fossils?

One of the keys to preservation is resistance. Either the conditions are mild enough (calm water, little oxygen) not to destroy much of the organism, or those parts that do get preserved are the most resistant to chemical and physical damage. Good examples of this are the shells of clams and the teeth of mammals. Both of these examples demonstrate that there is a preservational bias for hard parts compared to soft parts.

The nature of preservation is dependent upon the interaction of several factors. The composition of the organism and its structure play vital roles in how the body will react to the physical and chemical activities that normally break down or damage dead organisms. Intimately related to this is the sedimentary environment in which the organism lived. It will determine the type and intensity of the physical and chemical processes. These all contribute to the post-depositional changes (such as replacement, recrystallization, carbonization, the formation of casts, etc.) that take place during fossilization. And finally, numerical abundance will affect the nature of preservation by increasing or decreasing the chances of something being preserved, simply because of the sheer numbers or lack of certain organisms (this does make sense, if you think about it for awhile).

As mentioned above, the bias of hard parts over soft parts can provide considerable problems for paleontologists. Often, as is the case with most mollusks for example, much of the diagnostic information is in the soft part morphology, making it difficult to say certain specific things about organisms whose only record is in the hard parts. It is then necessary to draw upon recent analogues and extrapolate that information back to the fossil record. This can be dangerous if the past was not entirely like the present in environmental or ecological conditions. We call this the "pull of the Recent analogue" and it can be a serious problem if not recognized at the outset.

1.1.3 Types of fossils

There are many ways in which a record of an organisms can be preserved. Body fossils can occur in many ways, including: unaltered preservation, recrystallization, replacement, permineralization, carbonization, impressions, casts and internal molds.

Unaltered preservation implies the preservation of the original composition such as aragonite, calcite, chitin, cellulose, and calcium phosphate. Recrystallization means that the less stable hard part mineralogies are transformed through void time, temperature and pressure to more stable minerals. This is usually a destructive process, where much of the fine morphological detail (e.g. ribs on a clam shell) is lost. The most common form of recrystallization in the invertebrate record is the change from aragonite and/or Mg calcite to the more stable calcite form of CaCO3. In contrast to recrystallization, which is a rearrangement of the crystal lattice in which the chemical composition remains the same, replacement is an atom for atom substitution of a mineral's components with the elements composing the replacing mineral. Thus, pyritization, phosphotisation, silicification and dolomitization are all good examples of the replacement process. One should also note that contrary to recrystallization, replacement is usually NOT destructive; that is, you can see many of the original morphological details.

Permineralization is yet another mode of preservation, where pore-space is infilled by percolating fluids. The pore-space is usually the xylem and phloem (transport tissues) of woody tissue. Another name for this process is petrification.

Carbonization is often indicated by the shiny black texture of what appears to be an impression of an organism, often a plant leaf or crushed arthropod. This process is due to distillation. An organic film is formed as water is driven off. You can recognize carbonization easily by the shiny black or dark brown color.

The next three modes (impression, cast and internal mold) are often confused, but they are distinct both in pattern and process. Impressions or external molds are nothing more that what is produced when something is pressed into soft sediment and that "impression" remains. You can recognize external molds because they show only external detail, and they are negative in relief. A cast on the other hand, is the sediment infilling of an external mold. It will also show only external features, but will be positive in relief, not negative like an external mold. Lastly, internal molds form when sediment infills a shell or skeleton, hardens, and the shell is worn away. What is left is a mold showing internal features and will most likely have positive relief.

1.2 Exercises
1.2.1 Skeletal mineralogies

Before determining how a particular fossil has been preserved, its important to know the organism's original skeletal mineralogy and mineralogy present in the fossil. This, for example, enables you to distinguish between recrystallization and replacement. The following display is designed to familiarize you with different types of mineralogies commonly found in fossils.

1.2.2 Other types of fossils

1.2.3 Modes of preservation


More about preservation

Chapter 1: Questions
Table of Contents

 

 

Taphonomy


Taphonomy is the study of the post-mortem history of organic remains and the formation of fossil deposits in the rock record. Taphonomic studies focus on both the "negative" aspects of post-mortem processes (e.g. bias introduces by differential preservation), and "positive" aspects (e.g. determining diagenetic history from taphomy). In many way, taphonomy is the most multidisciplinary of the paleontological studies - requiring a good understanding of not only paleontological and sedimentological processes, but also occasionally a working knowledge or engineering, physics, and geochemistry (peruse the reference list for examples).


Common Substances in Sedimentary Environments

Substance

Formula

Produced

Susceptibilities

aragonite

CaCO3

organically (mollusks, scleractinial corals, algae, some bryozoan, etc., etc.) and inorganically in a large number of environments

acid

calcite

CaCO3

organically (mollusks, brachiopods, echinoderms, tabulate and rugosan corals, etc., etc.) and inorganically in a large number of environments

acid

dolomite

(CaMg)(CO3)2

inorganically, rarely primary - usually produced during diagenesis

acid

apatite

Ca5(PO4)3(OH, F)

organically (chordates, conodonts, brachiopods) and inorganically

acid

opalline silica

SiO2*nH20

organically (some sponges, diatoms, radiolarians, silicoflagellates, etc.) and inorganically

basic conditions

pyrite

FeS2

inorganically, reducing environments with available sulfer and iron

oxidizing conditions

iron oxides and hydroxides

FeO(OH), Fe2O3, other "rusts", etc.

inorganically, oxidizing environments with available oxygen and iron

reducing conditions

gypsum

CaSO4

inorganically, evaporitic environments

can dissolve in water

chitin

polysaccharide carbohydrate

organically (arthropod cuticle)

oxidizing conditions, heat

collagen

protein polymer

organically (chordate bone and skin, periderm)

oxidizing conditions, heat

sporopollenin

oxidative polymer of carotenoid esters

organically (plant spores and pollen, acritarchs, dinoflagellate cysts)

oxidizing conditions, heat

cellulose

polysaccharide carbohydrate

organically (plant cell walls and wood)

oxidizing conditions, heat

lignin

polyaromatic

organically (wood)

oxidizing conditions, heat

melanin

polyaromatic

organically (dye in cephalopod ink)

oxidizing conditions, heat

 

 

 

 


Modes of Preservation

Unaltered Material

Preservation of unaltered material is relatively common in younger deposits, but less common in more ancient deposits. Naturally substances that are stable at earth surface conditions (e.g. some types of apatite, lo-Mg calcite, etc.) are more likely to be preserved unaltered than less stable sustances (e.g. organic material, hi-Mg calcite, aragonite).


Carbonization/Distillation

Carbonization occurs when the volatile elements of organic matter (basically water and nitrogen) are boiled away, leaving behind a carbon film. This type of preservation is most common under anoxic and/or acidic conditions (e.g. deep oceanic basins, stagnant marshes, etc.).


Permineralization

Permineralization occurs when mineral matter fills in the void and pore spaces within the original organic structure. The mineral that fills in the pores is sometimes the same as the biomineral, although not always. Infilling by calcite, aragonite, iron oxide, silica, and other common inorganic cements are usual, although deposition of other, more unusual minerals is also known.


Recrystallization

Recrystallization is the solid state transformation of a mineral to a new crystal form (not always the same mineral). The new crystals usually obscure the original fine structural detail. The bulk elemental composition does not change in this transformation.


Replacement

Preservation by replacement involves the substitution of an inorganic mineral for the original biomineral or tissue. While fine scale preservation is possible, replacement usually obliterates very fine structures. The final mineralogy of the fossil may or may not differ in bulk composition from the original.


Molds and Casts

A mold is an impression of an object. A bump on the object is a dent on the mold. An internal mold is the impression of the inside of an object. An external mold is the impression of the outside of an object. A cast is an infilling of a mold. It is frequently useful to make a cast of a mold fossil in order to study the original morphology.


Related Websites


Reference


Allison, P.A. 1988. Konservat-Lagerstatten: causes and classification. Paleobiology 14: 331-344.
Allison, P.A. and Briggs, E.G. 1991. Taphonomy: releasing the data locked in the fossil record. Plenum Publ., New York, 560 pp.
Baird, R.F., and Rowley, M.J. 1990. Preservation of avian collagen in Australian Quaternary cave deposits. Palaeontology 33: 447-451.
Baumiller, T.K., et al 1995. Taphonomy of isocrinid stalks: Influence of decay and autonomy. Palaios 10: 87-95.
Behrensmeyer, A.K., et al 1979. New perspectives in vertebrate paleoecology from a recent bone assemblage. Paleobiology 5: 12-21.
Behrensmeyer, A.K., et al 1986. Trampling as a cause of bone surface damage and pseudo-cutmarks. Nature 319: 768-771.
Brett, C.E. and Baird G.C., 1988. Comparative taphonomy: a key to paleoenvironmental interpretation based on fossil preservation. Palaios.
Cadee, G.C., 1988. The use of size frequency distributions in paleoecology. Lethaia 21: 289-290.
Cadee, G.C. 1989. Size-selective transport of shells by birds and its paleoecological implications. Palaeontology 32: 429-437.
Cattaneo, C., Gelsthorpe, K., Phillips, P., and Sokol, R.J. 1990. Blood in ancient human bone. Nature 347: 339.
Davies, D.J., Powell, E.N., and Stanton, R.J., Jr. 1989. Taphonomic influence as a function of environmental process: shells and shell beds in a hurricane-influenced inlet on the Texas coast. Palaeogeog., Palaeoclim., Palaeoecol. 72: 317-356.
Driscoll, E.G. 1970. Selective bivalve destruction in marine environments, a field study. J. Sediment. Petrol. 40: 898-905.
Durham, J.W., 1967. The incompleteness of our knowledge of the fossil record. Journal of Paleontology 41: 559-569.
Emig, C.C. 1990. Examples of post-mortality alteration in Recent brachiopod shells and (paleo)ecological consequences. Mar. Biol. 233-238.
Gurley, L.R., et al 1991. Proteins in the fossil bone of the dinosaur Seismosaurus. J. Protein. Chem. 10: 75-90.
Hughes, Nigel C. 1995. Trilobite taphonomy and taxonomy: A problem and some implications. Palaios 10: 283-285.
Jorgensen, B.B. 1982. Mineralization of organic matter in the sea bed - the role of sulfate reduction. Nature 296: 643-645.
Kidwell, S.M. and Baumiller, T. 1990. Experimental disintegration of regular echinoids: roles of temperature. oxygen, and decay thresholds. Paleobiology 16: 247-271.
Kidwell, S.M. 1986. Taphonomic feedback in Miocene assemblages: testing the role of dead hardparts in benthic communities. Palaios 1: 239-255.
Klinkhammer, G.P., and Lambert, C.E. 1989. Preservation of organics during salinity excursions. Nature 339: 271-274.
Lescinsky, H.L. and Benninger, L. 1994. Pseudo-borings and predator traces: Artifacts of pressure-dissolution in fossiliferous shales. Palaios 9: 599-604.
Meldahl, K.H. and Flessa, K.W. 1990. Taphonomic pathways and comparative biofacies and taphofacies in a Recent intertidal/shallow environment. Lethaia 23: 599-604.
Miller, A.I., 1988. Spatial resolution of subfossil molluscan remains: implications for paleobiological analysis. Paleobiology 14: 91-103.
Miller, A.I., et al, 1990. The effect of Hurricane Hugo on molluscan skeletal distributions, Salt River Bay, St. Croix, U.S. Virgin Islands. Geol. Soc. Abst. 22: 330A.
Pip, E. , 1988. Differential attrition of molluscan shells in freshwater sediments. Can J. Earth Sci. 25: 68-73.
Schafer, W. 1972. Ecology and paleoecology of marine environments. University of Chicago Press, 568 pp.
Seilacher, A., Reif, W.E., Westpahl, F. 1985. Sedimentological, ecological, and temporal patterns of fossil Lagerstatten. Phil. Trans. R. Soc. London. B 311: 5-23.
Teichert, C. and Severtenty, D.L. 1947. Deposits of shells transported by birds. Am. J. Sci. 245: 322-328.

 

 

 

Fossils

Window to the past


Fossils pages in this web site introduce the common readers to types of fossils, conditions leading to fossilization, and the information contained in fossils. Last updated 8th Dec '96.Your feed back is welcome.


What is a fossil ?

There is a misconception that fossils are just a bunch of bones that make up an old dinosaur model, but there are many other aspects to be considered when defining a fossil. The most general definition of fossils refers to the remains of an ancient organism or the traces of activity of such an organism. There are two types of fossils- the body fossils and the trace fossils. Body fossils include preserved remains of an organism (i.e. freezing, drying, petrification, permineralization, bacteria and algea). Whereas trace fossils are the indirect signs of life that give evidence of the organism's presence (i.e. footprints, burrows, trails & other evidence of life processes).

Ages covered by fossils

Life began in the sea. The earliest evidence of life on earth is of marine animals, during the Precambrian era. But there is only sparse evidence of life before the Cambrian era. The oldest known Precambrian rocks, found in Africa and Australia, are believed to be more than three billion years old, and the fossils among them the oldest known organism on earth. The fossils found in rocks dating so far back are usually microfossils, such as elongated bacteria, Eobacterium and other water environment fossils. There have also been well defined remains of algae and bacteria found from nearly two billion years ago. Bacteria represents the first stage of recognizable organized life. The most common fossils are found in sedimentary rock. Sedimentation is the process of the accumulation of particles originating from the break up of pre-existing rock. Sedimentary layers act as evidence of the changing climate or movement of the continents during the passage of time. The Law of Superposition or Steno's law states that in a pile of undisturbed sedimentary rock, the oldest bed will lie at the bottom and the youngest on top. Layers of strata in different locations may have the same composition but carry fossils of a different time period, therefore a technique of zoning or an index fossil is used. The index fossils are specific animals or plants that had a broad geographical distribution but existed for relatively short periods of time. These fossils allow geologists to establish a parallel between layers using the presence of similar index fossils. Some excellent guide fossils are ammonites, whose evolution was such that each species lived for relatively short periods of time but had such a broad geographical distribution that they can be found today in stratigraphic rock layers often separated by great distances. The appearance of the same ammonite in different layers in different localities, gives evidence that those layers were deposited at the same time. Each time period is marked by an abundant radiation of many new life forms or the mass extinction of past life forms.

Types of fossils

Fossils undergo a variety of different fossilization processes, depending on the characteristics of the particular organism. There are various levels of fossil preservation, each containing its own clues pertaining to the organism. Fossilization at the cellular level varies in all organic compounds since not all cellular types are equally resistant to decay and decomposition. The same hold at the tissue level, where some tissue types are more susceptible to fossilization. The other two kinds include the organ level and organism level which provide information in the field of morphology and biology of the ancient organism. These levels are preserved by different processes that will be explored individually by this web site. Although there are an endless number of categories, we will focus on the broader mode of classification.

How fossils are found ?

There are certain techniques that paleontologists might exercise to find fossils, but mostly finding a fossil has to do with chance and luck. However, all paleontologists need a place to start. No person would ever go on any kind of a hunt without having at least some clues about the general locations of the object that they are looking for. For florissanstumps.gifpaleontologists, this is where an extensive knowledge of the stromatolites, the different eras, the knowledge of which era(s) certain organisms dominated the earth, and which environment was most suitable for certain organisms. With these informations, the collector can eliminate certain localities depending on what kind of fossils they are searching for. For example, if a collector was interested in finding fossils of animals of ancient rocky shores, he/she would eliminate formations and beds in which remains are likely to be rare and poor. Paleontologists can also follow leads that other paleontologists or collectors have left behind in published reports. Soon every collector realizes that fossils of certain types are found in particular kinds of rocks. For example, marsh plants are most abundant in shales and sandstones between beds of coal, and coals are found in limy shales and massive limestones, many of which are the remains of ancient reefs. Using these techniques, process of elimination, and perhaps some luck, paleontologists have retrieved all sorts of fossils and animal remains from all sorts of geological areas.

Conditions that lead to fossilization

There are many conditions that contribute to the formation of fossils. However, the most common conditions include the possession of hard parts, a skeleton or shell, and a rapid burial after death. Besides being tough and hard, the organism must come to rest in a place where it stands a good chance of being buried before it decays or disintegrates. If the organism is not buried deeply and quickly, aerobic bacteria will reduce it to rubble; or water given enough time, will dissolve it. For this reason, fossils of some kinds of organisms are rarer than others. As for the skeletons, the skeletons that contain a high percentage of mineral matter are most readily preserved, and in contrast the soft tissue that is not intimately connected with skeletal parts is least likely to be preserved. Other conditions that lead to fossils include an environment that was biologically inert, areas that are receiving a large, steady supply of sediment, such as deltas of major rivers, and parts of the earth below sea level compared to those above the sea level. The ideal place to become a fossil is at the bottom of a quiet sea or lake where the prospective fossil is safe from damage and where it is covered rapidly with sediment. For this purpose, clay is an excellent option. The sediment protects the tissues and helps to exclude predators and solvent water.

What do fossils tell us?

The realm of which this question can be answered is very broad. The answers depend upon the fossils found in particular places, and upon the questioner. Nevertheless, there are certain general ideas that can be drawn from different fossils accordingly. Different fossils depending upon how they were preserved tells us different things. For example, fossils that are preserved in amber can tell us an extraordinary amount of information about the anatomy of that organism; since the organisms that are preserved in amber, mostly insects, are preserved as a whole usually without any disintegration of organs, muscles, and its coloring. Even bones devoid of flesh may tell a great deal about the soft anatomy. For instance, the area where the muscle attaches to the bone leaves marks that indicate sizes, shapes, and functions of these varied organs. Also, the cavities and the the channels in skulls give us an idea of their intelligence, behavior, and their principle features. Certain parts of certain fossils can also tell us about their growth, injury, disease, form, function, activities, and instincts. Fossils also record the successive evolutionary diversification of living things, the successive colonization of habitats, and the development of increasingly complex organic communities. Fossils also tell a great deal about their surroundings and the conditions under which they lived. Finally, fossils also contribute greatly to the study of evolution. They are the only direct record of what has in fact occurred in sequences of reproducing populations and in the course of the time on an evolutionary scale.


Index

Amber || Casts & Molds || Compactions || Compressions || Coprolites & Gastroliths

Drying & Dessication || Freezing || Impressions || Molecular Fossils || Permineralization

Reference || Trace Fossils || Wax & Asphalt

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Fossils

Window to the past


Permineralization


What is permineralization ?

One of the common types of fossils is permineralization. This occurs when the pores of the plant materials, bones, and shells are impregnated by mineral matter from the ground, lakes, or ocean. In some cases, the wood fibers and cellulose dissolve and some minerals replace them. Sometimes the mineral substance of the fossils will completely dissolve and some other minerals replace them. The common minerals that form this kind of fossils are calcite, iron, and silica.

Since the pores of the organic tissues are filled with minerals or the organic matter is replaced with minerals, the fossils are formed in the original shape of the tissue or organism, but the composition of the fossils will be different and they will be heavier.

Petrification (petros means stone) occurs when the organic matter is completely replaced by minerals and the fossil is turned to stone. This generally occurs by filling the pores of the tissue, and inter and intra cellular spaces with minerals, then dissolving the organic matter and replacing it with minerals. This method reproduces the original tissue in every detail. This kind of fossilization occurs in both hard and soft tissues. An example of this kind of fossilization is petrified wood.

The process of permineralization

The ground water generally do not contain pure water molecules alone. It is hard to some degree meaning it contains some minerals. The degree of hardness varies. The different minerals are found in the ground, and water dissolves them until saturation at which point water will not hold any additional mineral matter. This process is enhanced by the acidification of the water. For example, the rain water when pure in the beginning picks up carbon dioxide from air and becomes a weak carbonic acid. The organic matter in the ground, and other decaying materials also will make ground water more acidic. This acidic water dissolves more minerals.

Organic tissues like wood, bone, and shell contain pores and spaces. The mineralized water fills the pores of the organic tissues and moves through the cellular spaces. During this process the saturated water evaporates, and the excess minerals are deposited on the cells and tissues. This process creates many layers of mineral deposits creating hard fossilized record.

What can we tell from permineralization ?

Since permineralizations of organisms are three-dimensional fossils with organic matter replaced by minerals, what they mainly tell us are the about the internal structures of the organisms. The mineralization process itself helps to prevent tissue compaction, which could distort the actual size proportions of the various organs. Permineralizations are also not "limited" to hard body parts (such as bones or shells), but can also be found preserving soft body parts. This could be very important to researchers who wish to look at what life was like in the past in relation to what it is now in the present. An example are the fragile reproductive structures of many plants. Depending on the conditions for the fossilization process and the specific mineral that was used for the fossilization, however, varying degrees of detail do exist. Sometimes, only very differentiated cell types can be distinguished (such as between vascular tissue for conducting water and nutrients and ground tissue in plants), while in other fossils, the detail can be so fine as to distinguish between the different organelles within the various cells.

There are three subgroups of permineralizations: silicification, pyritization, and carbonate mineralizations.

As with almost all fossilization processes, the specific type of permineralization, silicification (because of its conditions for fossilization), tells us a much about what type of environment the organism most likely lived in. This is because specific fossil types occur in environments with certain features. Silicification is a fossilization process whereby the organism is penetrated by minerals that form on the cells and cell structures. In this case, the mineral is silica, and because the mineral "follows" the internal structures of the organism during mineralization, this accounts for the amazing amount of detail found in permineralizations. For example, (for silicification) fluids in volcanic terrain often contain silica that could be absorbed by the plants themselves. This would indicate that a volcano was near the plant in the past. An interesting point that this example presents is that the plant was already beginning its fossilization process when it was still living. The silica that is taken up by the plants become embedded within them and when they die, the material (silica) is already present within them to quickly mineralize the organism and fossilize it. The silicification process can often show very fine detail in this way.

Pyritization involves the mineral sulfur. Many of the plants are thus pyritized when they are in marine sediments since they often contain a large amount of sulfur. This could have been their natural habitat in the past or they could have been near enough to a marine environment to end up there to be pyritized (after being carried down by a river, flood, or some other method). Some plants are also pyritized when they are in a clay terrain, but to a lesser extent than in a marine environment.

Carbonate mineralizations occur both in marine and nonmarine environments. The most popular forms of carbonate mineralizations that are cited in biology are what are called "coal balls." Coal balls (which are often found in a round ball shape, which gives them their name) are often a fossilization of many different plants and their tissues. Often, they occur in the presence of seawater or acidic peat. Acetate peels can also usually be made to study the various organic material trapped within a coal ball. These peels may sometimes be fairly revealing of cellular detail.

 

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Speed and Conditions of Fossilization

Bonnie Blackwell


Tom Holtz referred the person who asked about fossilization processes to any elementary textbook on geology or paleontology to answer this question. I have found, however, that these books have one glaring error: the speed at which they assume these processes occur. My research has shown that secondary mineralization, remineralization, leaching of bone mineral, and biologically-induced mineralization begin very rapidly after the bone is exposed to the environment. If the bone is not buried or underwater within 1-2 years of defleshing, it will literally become dust in the wind. The bone fragments may persist for several more years, but they are unrecognizable as to species. If the bone is buried or underwater, diagenetic processes begin rapidly. A bone can be completely remineralized within 5-10 years. Secondary mineralization can fill all the porosity elements within a few months in some environments. These are the environments which preserve bone the best.

Hypersaline environments in which carbonates are precipitating favor bone remineralization and secondary mineralization. Saline environments also are good, but there the processes are slower. Caves may offer excellent preservation over the short term, but karst processes may attack the bone later destroying it along with the cave.

Soil is not a favorable environment generally because the bone mineral will tend to dissolve in the acidic conditions that occur in many soils, carbonate-rich soils of arid zones being the exceptions. It is the requirement of rapid burial/submergence that ensures that few vertebrates become fossilized.


Copyright © 1995 Bonnie Blackwell. This document was a public post to the dinosaur mailing list.

 

 

 

 

 

 

 

 

 

 

 

 

 

Speed and Conditions of Fossilization

Bonnie Blackwell


Tom Holtz referred the person who asked about fossilization processes to any elementary textbook on geology or paleontology to answer this question. I have found, however, that these books have one glaring error: the speed at which they assume these processes occur. My research has shown that secondary mineralization, remineralization, leaching of bone mineral, and biologically-induced mineralization begin very rapidly after the bone is exposed to the environment. If the bone is not buried or underwater within 1-2 years of defleshing, it will literally become dust in the wind. The bone fragments may persist for several more years, but they are unrecognizable as to species. If the bone is buried or underwater, diagenetic processes begin rapidly. A bone can be completely remineralized within 5-10 years. Secondary mineralization can fill all the porosity elements within a few months in some environments. These are the environments which preserve bone the best.

Hypersaline environments in which carbonates are precipitating favor bone remineralization and secondary mineralization. Saline environments also are good, but there the processes are slower. Caves may offer excellent preservation over the short term, but karst processes may attack the bone later destroying it along with the cave.

Soil is not a favorable environment generally because the bone mineral will tend to dissolve in the acidic conditions that occur in many soils, carbonate-rich soils of arid zones being the exceptions. It is the requirement of rapid burial/submergence that ensures that few vertebrates become fossilized.


Copyright © 1995 Bonnie Blackwell. This document was a public post to the dinosaur mailing list.

 

 

 

 



           So you want to know just why everything you've been told about the time consuming process of fossilization is a lie?
Read this brief article found here:

40 Million year old Cowboy boot found!
Everyone has heard the story. "We know absolutely for certain, it takes millions and millions of years for fossils to petrify." It's so obvious that no proof is necessary and of course no witnesses verify. The claim is just repeated over and over. So we hear, "Everybody knows that." Oh yea? How old do you think this boot could be? Millions and millions of years old? I suppose it could be made from T. Rex skin. Do you really think so? The rubber-soled boot with petrified cowboy leg, bones and all was found in a dry creek bed near the West Texas town of Iraan, about 1980 by Mr. Jerry Stone, an employee of Corvette oil company. The boot was hand made by the M. L. Leddy boot company of San Angelo, Texas which began manufacturing boots in 1936. Gayland Leddy, nephew of the founder, grew up in the boot business and now manages Boot Town in Garland, Texas. He recognized the "number 10 stitch pattern" used by his uncle’s company and concluded that the boot was made in the early 1950's. Only the contents of the boot are fossilized, not the boot itself, demonstrating that some materials fossilize more readily than others. The bones of the partial leg and foot within the boot were revealed by an elaborate set of C.T. Scans performed at Harris Methodist Hospital in Bedford, Texas on July 24, 1997. The Radiologic Technician was Evelyn Americus, AART. A complete set of these scans remains with the boot at the Creation Evidence Museum in Glen Rose, Texas. The fact that some materials can fossilize rapidly under certain circumstances is well known by experts in the field and is not really a scientific issue. However, the general public has been misled in order to facilitate the impression of great ages. The dramatic example of the "Limestone Cowboy" immediately communicates the truth of the matter. Fossilization proves nothing about long periods of time.


So what do you think? Could it be possible that those dino fossils aren't actually as old as you've been told they are?

Rick Balogh, professor of geology and science at Antelope Valley College, gave us an excellent presentation. Video tapes of his presentation is available. He gave permission to publish any of the material appearing in his handout, A Christian Apologetic for Creation and the Flood, for which we are very thankful.

August 1993

DOES FOSSILIZATION REQUIRE MILLIONS OF YEARS?

By Rick Balogh, MS

Have you ever observed the process of petrifaction (replacement of the normal cells of organic matter with other minerals)? According to evolutionary doctrine, petrifaction requires much time, usually millions of years, but how much time is really needed in this process? Have you or anyone else ever observed the formation of petrified wood? Evolutionists say that the petrifaction of wood takes a very long time, but like the rapid formation of stalactites and stalagmites under the Lincoln Memorial, chemical and physical conditions determine how long it will take to fossilize something. Time plays only a small part in the equation. Consider this excerpt from Scientific American of March 23, 1889, page 181:

"There is a well known petrifying stream of water at Knaresborough, Yorkshire, England, three miles from Harrowgate, the well known sanitarium. It is a cascade from the River Nidd, about 15 feet high and twice as broad, and forms an aqueous curtain to a cave know as Mother Shipton’s Cave. The dripping waters are used for the purposes of petrifying anything sent to be hung up in the drip of the water ledge, which flows over, as it were, the eaves of the cave. This ledge of limestone rock is augmented unceasingly by the action of the waters which flow over it. This cascade has an endless variety of objects hung up by short lengths of wire to be petrified by the water trickling over them, as sponges, books, gloves, kerchiefs and veils, hunter’s cap, fox, cat, dog, bird, boots, etc., just as fancy prompts people to seek petrifying results. A sponge is petrified in a few months, a book or cap in a year or two, cat or bird a little longer....One cat shown in the museum had the head broken off at the neck showing the whole was limestone throughout, with not a trace of organic structure of the original cat."

Recorded in Scientific American of March 17, 1855, page 211:

"On the 20th of August, 1847, Mrs. Phelps, wife of our informant, Abner P. Phelps, died, and was buried at Oak Grove, in Dodge Co. On the 11th of April inst., she was taken up to be removed to Strong’s Landing. The coffin was found to be very heavy, and the body to retain its features and proportions. After its removal to Strong’s Landing, a distance of some 45 miles, the body was examined, and found to be wholly petrified, converted to a substance resembling a light colored stone. Upon trial, edge tools made no more impression upon it than upon marble. In striking upon the body with metal, a hollow singing sound was produced....The ground in which she had been buried was a yellowish loam, and the body lay about three feet above the lime rock....A few years ago a lady died in the neighborhood of Felicity, in this County, and was buried in the orchard on the farm. About four years, after she was disinterred, for the purpose of removal to a public graveyard, she was found to be completely petrified, being as solid as stone and fully as heavy. Every feature was distinct and perfect."

Not only are there examples of rapid petrifaction, but there are also examples of fossils that were preserved remarkably well and not petrified. Consider this statement from Jame E. Francis’ article "Arctic Eden," Natural History, January 1991, p.57 and 60:

"The remains of lush forests near the North Pole give a glimpse of the Arctic’s subtropical past....Despite the passage of 45 million years, the wood retains its original color and is still flexible and burns easily. I quickly discovered that my geologic hammer was useless for collecting samples of the fossil wood; the next season I came better prepared with wood saws."

How do you think a magnolia leaf would change as the result of having been buried for 17-20 million years? Consider this remark from Nature, V.344, April 12, 1990, p. 587:

"When rocks containing these fossils are cleaved open, the freshly exposed leaf tissues are often bright green or ‘deep autumnal’ in colour, though they rapidly curl away from the substrate as they oxidize and dry out."

The author say that it was even possible to isolate the DNA of the leaves:

"But even the most optimistic estimate of the longevity of this molecule would not have predicted that fragments of substantial length would survive after tens of millions of years at the bottom of an ancient lake." (p. 587)

THINK! Does petrifaction require lots of time or just the right conditions? The same could be asked of many processes to which evolutionists have assigned long ages: mountain building, the bending and buckling of geologic layers, the deposition of sediments many kilometers thick, and deep canyon formation.

DOES THE GEOLOGIC COLUMN REPRESENT HUNDREDS OF MILLIONS OF YEARS?

Long before the discovery of radioactivity and radiometric dating of rocks, the hundreds of millions of years of time needed for the deposition of the geologic column was reasoned as shown below, which is taken from James Dana’s book Manual of Geology, 1880, page 591:

"The rate at which coral reefs increase in height affords another mode of measuring the past. From calculations elsewhere stated by the author, it appears that the rate of increase of a coral reef probably is not over a sixteenth of an inch a year. Now, some reefs are at least 2,000 feet thick, which, at one sixteenth of an inch a year, corresponds to 384,000, or very nearly a thousand years for five feet of upward increase....The use of these numbers is simply to prove the proposition that Time is long, - very long, - even when the earth was hastening on toward its last age."

This reasoning is based on the principle of uniformitarianism which can be summarized as "the present is the key to the past." That is, the rate of sediment accumulation measured today can be used to determine how much time was needed for the geologic column to be deposited assuming the same rate was acting then as today. This is a big assumption which cannot be tested. Was anyone there to verify the sedimentation rate then? God was, but He asks Job:

"Where were you when I laid the foundation of the earth? Tell Me if you have understanding." (Job 28:4)

This question of "Were you there?" may seem trite but it serves to remind us that unless someone was there to accurately record just what happened, we simply have conjecture. Is a guess always correct, sometimes correct, or never correct? Only God was there to observe the deposition of all rock layers, everyone else is simply guessing.

Let’s imagine that you are standing at the base of a cliff where rock layers are clearly visible. Can any conclusion regarding time be deduced from what you see?

THINK! There is obviously an order to the deposition of layers. The one on the bottom must have been deposited before the one immediately above and, so on, to the top layer. This is obvious, common sense reasoning that does not require verification by someone who saw the layers form. Of course, there is the possibility that God created them instantly that way, but if we confine our possibilities to the natural, excluding the supernatural, we can accept this as fact.

Evolutionists go through similar reasoning based on the fossils. They see similarities in anatomical structures and the seeming order in which fossils are found in the geologic column and conclude that evolution occurred. How does their reasoning differ from that which we have used for deciding that the oldest layer is at the bottom of our imaginary pile and the youngest is at the top? The deposition of sedimentary layers has been observed many times (the geologic activities at Mount St. Helens provided us with a remarkable natural field model of significant volcanic and aqueous depositions, as well as deep canyon formation), we can repeat the process at will, and we can even predict certain characteristics that will form during the deposition. The French creationary geologist, Guy Berthault has conducted such experiments and next month we will look at his work in this area. The evolutionary process, however, has never been observed, it cannot be repeated at will, and we cannot predict which characteristics would evolve. Furthermore, it is important to realize that the order of rock layers says nothing about the length of time for deposition.

THINK! When a fish dies is it immediately buried and subsequently become fossilized as silt slowly covers it? Of course not! It is more likely to float than sink and to be eaten by scavengers. There is a great abundance of fossil fish, whole schools that were obviously buried rapidly in the midst of their daily activities, some caught in the act of swallowing other fish, indicating clearly that huge submarine mud flows or turbidity currents overtook them and instantly buried them. A beautiful fossil specimen of one fish swallowing another is seen on the cover of Creation Research Society Quarterly (CRSQ), vol. 26, June 1989 (available through the Creation Research Society P.O. Box 14016, Terre Haute, IN 47803).

THINK! Fossil trees have been discovered in several localities around the world whose trunks vertically span rock layers for dozens of feet, such as this photo shows (from CRSQ, vol. 14, p. 153, December 1977). Similar photos and drawings are seen in Why Not Creation, edited by Walter Lammerts (CRS), 1970, pp. 153-155 and in Neglected Geologic Anomalies by William Corliss, 1990, pp. 254-260.

What do you think—slow or rapid burial? Could the flood of Noah’s day have been responsible for depositing the geologic column? If so, the time period of its formation would be months, not hundreds of millions of years.

Types of Preservation

How To Become a Fossil

Uniformitarianism. We observe that organisms are commonly buried by these types of processes today. No reason not to think that fossils in the geologic record were buried under similar circumstances.

 

II. Processes of Fossilization Print section


Many factors can influence how fossils are preserved. Remains of an organism may be replaced by minerals, dissolved by an acidic solution to leave only their impression, or simply reduced to a more stable form. The fossilization of an organism depends on the chemistry of the environment and on the biochemical makeup of the organism. As a result, not all organisms in a community will be preserved.

A. Carbonization Print section

      

 Plants are most commonly fossilized through carbonization.

 

 

 

 

 

 

 

 

 

 

 

 

In this process, the mobile oils in the plant's organic matter are leached out and the remaining matter is reduced to a carbon film. Plants have an inner structure of rigid organic walls that may be preserved in this manner, revealing the framework of the original cells. Animal soft tissue has a less rigid cellular structure and is rarely preserved through carbonization. Although paleontologists have found the carbonized skin of some ichthyosaurs, marine reptiles from the Mesozoic Era (240 to 65 million years before present), the microscopic structure of the skin was not preserved.

B. Petrifaction Print section


Another common mode of preservation of plants is petrifaction, which is the crystallization of minerals inside cells. One of the best-known forms of petrifaction is silicification, a process in which silica-rich fluids enter the plant's cells and crystallize, making the cells appear to have turned to stone (petrified). Famous examples of silicification may be found in the petrified forests of the western United States (see Petrified Forest National Park). Petrifaction may also occur in animals when minerals such as calcite, silica, or iron fill the pores and cavities of fossil shells or bones.

C. Replacement Print section


Replacement occurs when an organism is buried in mud and its remains are replaced by sulfide (pyrite) or phosphate (apatite) minerals. This process may replace soft tissue, preserving rarely seen details of the organism's anatomy. X-ray scanning of some German shales from the Devonian Period (410 million to 360 million years before present) have revealed limbs and antennae of trilobites (extinct ocean-dwelling arthropods) and tentacle arms of cephalopods (highly developed mollusks) that have been pyritised (replaced by pyrite). Paleontologists have used mild acids to etch the phosphatized fossil remains of ancient fish found in Brazil to reveal structures such as gills and muscles. Although mineral replacement is rare, fossils created in this way are important in helping paleontologists compare the anatomical details of prehistoric organisms with those of living organisms.

D. Recrystallization Print section


Many animal shells are composed of the mineral aragonite, a form of calcium carbonate that breaks down over millions of years to form the more stable mineral calcite.
This method of preservation, called recrystallization, destroys the microscopic details of the shell but does not change the overall shape. Snail shells and bivalve shells from the Jurassic Period (205 million to 138 million years before present) and later are still composed principally of aragonite. Most older shells that have been preserved have recrystallized to calcite.


E. Soft-Tissue Preservation Print section


The soft tissues of animals are preserved only under extremely unusual conditions, and the preserved tissue usually lasts for only a short period of geological time. In the Siberian permafrost (earth that remains frozen year-round), for example, entire mammoths have been preserved in ice for thousands of years. The remains of the mammoths' last meals have sometimes been preserved in the stomachs, allowing paleontologists to study the animals' diet.

Mummification may occur in hot, arid climates, which can dehydrate organisms before their soft tissue has decayed fully. The skin itself is preserved for only a short time, but the impressions of the skin in the surrounding sediment can be preserved much longer if the sediment turns to rock. Paleontologists have found skin impressions of dinosaurs preserved by this method.

F. Organic Traps Print section


Whole organisms may become trapped and preserved in amber, natural asphalt, or peat (decaying organic matter). Amber is the fossilized remaining part of tree sap. When sap first flows from the tree, it is very thick and sticky, so as it runs down the trunk, it may trap insects, spiders, and occasionally larger animals such as lizards. These organisms can be preserved for millions of years with details of their soft tissue, such as muscles and hair-like bristles, still intact.

Natural asphalt (also called tar) is a residue from oil that has seeped to the earth's surface from deposits in the rock below. When an asphalt pit is covered by water, thirsty animals that come to the pit to drink may become trapped in the sticky substance and be preserved. One well-known example of such an area is the La Brea Tar Pits of the Pleistocene Epoch (1.6 million to 10,000 years before present) in Los Angeles, California.

Animals may also be preserved in peat, although the acidic environment of this decaying organic matter may cause bones to lose their rigidity. Some human remains have been found in peat bogs in Denmark (2000 years old) and England (2200 years old).

G. Molds and Casts Print section


Acidic conditions may slowly dissolve away the skeleton of fossil animals preserved in rock, leaving a space where the organism used to be. The impression that is left in the rock becomes a mold. This process commonly occurs in fossil shells where the calcite shell dissolves easily. The impression of the outside of the shell is the external mold. Sometimes the inside of the shell is filled with sediment before the shell is dissolved, leaving an internal impression of the shell called an internal mold. If the space where the shell used to be is then filled with a new mineral, the replica of the shell forms a cast.

H. Tracks and Trails Print section

      
When animals walk through soft sediment such as mud, their feet, tails, and other body parts leave impressions that may harden and become preserved. When such an impression is filled with a different sediment, the impression forms a mold and the sediment that fills the mold forms a cast. Molds and casts of dinosaur tracks are relatively common and help paleontologists understand how these creatures moved.

 

 

The Petrifaction of Remains

Petrifaction is another method of preservation of both plant and animal remains. This can occur in several ways. Mineral matter from underground water may be deposited in the interstices of porous materials, e.g., bones and some shells, making the material more compact and more stonelike and thus protecting it against disintegration. The original material may be entirely replaced with mineral matter, molecule by molecule, so that the original appearance and the microscopic structure are retained, as in petrified wood. Sometimes, on the other hand, all details of structure are lost in the replacement of organic matter by minerals, and only the form of the original is retained. In shales are sometimes found the silhouettes of plant tissues (more rarely of animals) formed by the carbon residue of the organism that remains after the volatile elements have been driven off.

Sections in this article:



The Formation of Fossils

Conditions conducive to the formation of fossils include quick burial in moist sediment or other material that tends to prevent weathering and to exclude oxygen and bacteria, thereby preventing decay. Shells and bones embedded in sediment in past geologic time, under conditions suitable for preservation, left exact reproductions of both external and internal structures. Skeletal remains have been preserved as a result of the engulfment of an animal's body in ancient asphalt pits, bogs, and quicksand. At Rancho La Brea, near Los Angeles, Calif., asphalt deposits have yielded a rich variety of skeletons of birds and mammals. Some fossils have been found buried in volcanic ash; such fossil deposits exist in the Cenozoic rocks of the W United States.

Mineral Coloration in Petrified Wood


Different elements, compounds, and minerals will color the petrified wood different colors. Here's a quick summary of what minerals you could see:

There are four different ways that something can become fossilized:

A cast is an impression of the organism left in the rock. For example, if you take clay, press a shell into it, and carefully remove the shell. What you have in the clay is an impression of the shell, or a cast when it hardens.

A mold is the result of filling in a cast, and having it harden. For example, if you took the hardened cast described above, and filled it with clay, after that filled area hardens, you have something that looks almost exactly like the original shell, but has none of the biological properties of a once living organism. It's like a rock copy.

Permineralization is when minerals enter the chemical make up of an organism, and take it over, creating a hard, preservable object. These minerals are leached into the buried object from the ground, lakes, and oceans. When this occurs in wood, it creates petrified wood.

Replacement is the occurance of materials replacing the original fossil piece by piece. In this case, the original fossil dissolves, and all interior detail is lost. This can sometimes be confused with permineralization, but the main difference between the two is with permineralization, internal structures are usually still visible.


How Does Wood Become Petrified?


Before petrification can begin, there usually has to be plenty of wood near a water source. The second step to petrification involves an event that causes the trees to be knocked over, usually into a water source. Most of the time that event is a volcanic eruption, as shown in this picture. The third step to petrification involves the wood being saturated with water, and eventually, as the wood moves downstream, it becomes bunched together and buried by mud, silt, and ash. The logs that have travelled downstream now need to become buried by mud and sediment, as well as being covered with some of the ash from the volcanic eruption. This fairly rapid burial allows the process of permineralization to begin. This picture shows the minerals and elements, like silica (from the volcanic ash), entering the wood either from water or the ground, and filling in the "pores". This step in the process is permineralization, and is what causes the wood to become petrified. When all the pores of the wood have been filled, it changes the colors of the wood. These colors change depending on the minerals presentIn this step, the wood begins to be exposed on the surface due to weathering such as rain. Because the "pores" of the wood have been filled with minerals, it has become resistant to weathering, and rotting, allowing it to stand on the surface virtually undisturbed This finally step has the wood fully exposed on the surface, and it is now considered both a fossil and a rock, because of it's mineralized state.

The U.S. Environmental Protection Agency’s water programs and their counterparts in states and pollution control agencies are increasingly emphasizing watershed and water quality-based assessment and integrated analysis of point and nonpoint sources. Better Assessment Science Integrating point and Nonpoint Sources (BASINS) is a system developed to meet the needs of such agencies. It integrates a geographic information system (GIS), national watershed and meteorologic data, and state-of-the-art environmental assessment and modeling tools into one convenient package.

Originally released in September 1996, BASINS addresses three objectives: (1) to facilitate examination of environmental information, (2) to provide an integrated watershed and modeling framework, and (3) to support analysis of point and nonpoint source management alternatives.

BASINS supports the development of total maximum daily loads (TMDLs), which require a watershed-based approach that integrates both point and nonpoint sources. It can support the analysis of a variety of pollutants at multiple scales, using tools that range from simple to sophisticated.

 

 

Overcoming the lack of integration, limited coordination, and time-intensive execution typical of more traditional assessment tools, BASINS makes watershed and water quality studies easier by bringing key data and analytical components together "under one roof."

Beside BASINS' primary role in creating TMDL analysis, it has been useful in identifying impaired surface waters from point and nonpoint pollution, wet weather combined sewer overflows (CSO), storm water management issues, and drinking water source protection. BASINS also has been used in urban/rural landuse evaluations, animal feeding operations, and habitat management practices. Another unexpected use of BASINS is providing schools and educational institutions with a quick, free resource of GIS and surface water data for the United States.

The heart of BASINS is its suite of interrelated components essential for performing watershed and water quality analysis. These components are grouped into several categories:

1.     nationally derived environmental and GIS databases (the 48 continuous states and the District of Columbia);

2.     assessment tools (TARGET, ASSESS, and DATA MINING) for evaluating water quality and point source loadings at a large or small scales;

3.     utilities including local data import and management of local water quality observation data;

4.     two watershed delineation tools;

5.     utilities for classifying elevation (DEM), landuse, soils, and water quality data;

6.     an in-stream water quality model (QUAL2E);

7.     a simplified GIS based nonpoint source annual loading model (PLOAD);

8.     two watershed loading and transport models (HSPF and SWAT);

9.     a postprocessor (GenScn) of model data and scenario generator to visualize, analyze, and compare results from HSPF and SWAT; and

10. many mapping, graphing, and reporting formats for documentation.

BASINS’ databases and assessment tools are directly integrated within an ArcView GIS environment. By using GIS, a user can fully visualize, explore, and query to bring a watershed to life. The simulation models run in a Windows environment, using data input files generated in ArcView.