DIFFERENT TYPES OF FOSSILSThe term fossil is used to refer to more than one type of plant or animal remains.
1. First there are the actual remainsof the plant or animal that can be preserved. An insect enclosed in amber is an example. The actual biological material still remains encased inside the amber.
2. Next there is the case where a structure of the animal may be preserved but the actual tissues and bones have been replaced by new material. An example would be fossil trees in Arizona. The wood has been replaced by silica. The rings and structure however are still present.
3. The next type fossil type is where the shape has been preserved but the material is gone. An example of this is a fossil footprint (called ichnite). The animal steps in soft limy mud that sets up quickly like concrete so to speak which then hardens to rock . This leaves the impression of the object so size, shape and aspect ratio can be measured. An example would be a footprint of a dinosaur or of a man in hard mudstone.
HOW ARE FOSSILS FORMEDThere are many processes by which plants and animals or their impressions can be preserved. Most living things after death decay or are eaten by scavengers. Teeth and bones which are very hard last much longer. The processes where fossils can be formed can happen in different ways.
- FREEZING: The best example of this is in Siberia where thousands of mammoths have been found frozen. Their flesh and skin are still present. The meat has been thawed and eaten for centuries. What catastrophe caused thousands of animals to be frozen across vast areas of the continent is up for debate. Many theories abound. Many frozen mammals have also been discovered in Alaska as well.
- DESICATION: We probably have all seen examples of dried out mice or flies found in the desert or perhaps in your hot attic. All it takes is a hot dry environment and the right conditions and the life form dries out and its parts are still there minus the water that evaporated from the object. Maybe you have found an old lemon in your refrigerator that dried out and is as hard as a rock.
ENTOMBMENT: Common examples are insects encased in amber. An insect lands on some tree sap and struggles to escape.
It is stuck and it dies while more sap from the tree engulfs its body. The tree dies and must experience some catastrophe
where it is buried under water or earth. If it were not covered it would decay and the amber would decay. Microbes
would destroy both. But if buried and preserved from scavengers and bacteria it would survive. The tree sap hardens over
the years and amber results. No one is sure how long this takes because no one seems to be performing experiments to find out.
Lots of amber is found in and around the Baltic seacoast. It is assumed that the salt water undercuts the strata at the bottom of the
sea and the lighter amber floats to the surface, washes ashore and is found along the beaches.
Another good example is the La Brea tar pits in los Angeles; mammals, birds, and insects found there have mostly bones preserved. Carbon 14 dating shows ages in thousands of years (saber tooth tigers, Smilodon 12,000 to 28,000 C-14 years). In this case all of the skin and tissue are gone. Bones, shells, teeth and some hard nut casings are found. One interesting theory is that a watery catastrophe (s) drowned the animal life and moved the disarticulated bones into a depression where an earthquake later released the underground tar to engulf and preserve the bones and their collagen content. Evidence for several theories will be discussed in a future article. Similar collections of bones are found in Peru and France as well.
- PERMINERALIZATION: This typically is what most people think of as a fossil. In their hand they hold a piece of petrified tree that is now made of stone. The woody material was replaced by silicon material over time. It was thought that the process took millions of years. Recently scientists have shown that woody materials can be rapidly turned into stone. All it takes is the wood to be immersed in hot silicon rich water for a few years.  Such conditions can be found in the Yellowstone hot springs as an example. As with any chemical reaction the temperature of the fluid and the concentration of the minerals would determine how much it took. Fossils have also been created by paraffin deposits and volcanic ash (Pompeii, Italy) and by dripping mineralized water in caves.
- CARBONIZATION: This process appears to be what causes coal seams to form. For hundreds of years scientists thought that coal took millions of years to form using heat and pressure. Now scientists know better. Under the right conditions coal can be formed in a matter of months. Oil also can be formed in a matter of months under the right conditions. Soft organic material may be preserved by carbonization or distillation where nitrogen, oxygen, and hydrogen are lost and a carbon replica of the organism is produced. Jellyfish and parts of trees have been preserved this way. These fossils are usually found in black shale that deposited under oxygen free conditions. X-Rays of black shale have revealed carbonized films of the soft parts of organisms which would not otherwise be visible (4).
- IMPRESSIONS: This process would involve a plant or animal being encased in some rock like material that hardens with time. Such events could be from volcanic lava flows, pyroclastic flows, fumoroles, etc. When the material hardens it takes the shape of the plant or animal inside. Possibly while it is hardening the material inside is decomposing or burning. The end result is only an impression of the object and a small amount of carbon sometimes left inside. Many scientists report that fossils often have a layer of carbonized material on them.
HOW OLD IS A FOSSIL:
How do you put a date to a fossil? there are actually 4 dates one has to be concerned with when evaluating how old a fossil is. There are 4 ages to be associated with any fossil and where it is found. Usually you will not be able to determine all 4 dates. Sometimes all some of the dates will be of similar age. Sometimes all 4 dates will have to be guessed at. Sometimes the dating method used to determine the age is subject to a high degree of doubt. Lets look a little closer at this problem. Here are the following 4 dates to keep in mind.
1. How old was the fossil when it died. Most animals would be hundreds of years old at most. For example Gallopogos turtles may live to be 200 years old or more. Plant material however can be thousands of years old. As an example Bristlecone pines living in the Nevada mountains have been found to be growing for over 4000 years. Anyone with an appropriate magnifier can count tree rings to determine the age of a tree with a very high degree of accuracy.
2. How long has the fossil been sitting entombed before being excavated. It may have been buried or entombed into the geological formation long after the geological formation was originally formed.
3. What is the alledged age of the geological formation it is found in. When was the geological sediment laid down. Nothing is actually measured just an assumption is made based on previous theory.
4. What is the age or how old is the sediment or particles entombing the fossil ( clay, limestone, mudstone,volcanic ash, etc )that the fossil was found in.
HOW ARE FOSSILS TYPICALLY DATED:
AGE 1:Directly dating the fossil itself is best when it can be done. Typical examples are dating desicated mummies, freeze dried wood, buried wood historical organic artifacts, charcoal, and plant material. This is most commonly done with carbon 14 dating. Anything truly over 100,000 years old should not contain enough carbon 14 to be measured. If scientists assume that the material they found is over 100,000 years old they will not consider using carbon 14 dating.
AGE 2:Usually this age is never given or determined. Instead the age of the formation is given as being this age. Mostly the assumption is made that the fossil was entombed when the formation was made geologically. Consider however that a creature could have fallen into a nook or cranny of the formation then be covered by the same material as the formation is made of and at a much later time frame. Therefore the plant/animal could have died and been covered up eons later than when the geologic formation is considered to have been formed. The faulty reasoning resulting is that if dinosaur bones are discovered in the Morrison formation in Colorado then the dinosaur must have been buried at the time of the formation and is as old as the geologic formation that it was found in. I hope you can see the possible flaw in this logic.
AGE 3:Most dinosaurs are given an age that is the supposed age of the rocks where they were found, They are given the age of the formation. This is referred to above as method 3. As an example the Morrison formation is a name given long ago to describe a type of soil and sediment found throughout parts of Colorado and Utah. If the fossil was found in this rock it is assumed that the fossil was buried when the geologic formation was originally built.
The age of this formation age was given to it long ago and is based mostly on what fossils are found in it. So here we have the age of a fossil is figured by what formation it is in. How do they determine the age of the formation...by what fossils are found in it. As a discerning reader can tell we have what is called circular reasoning. This is a very unscientific method and can lead to all kinds of error and erronious assumption. The assumption that a geologic formation can be dated is subject to doubt.
AGE 4:Another way a fossil age is determined is by measuring the age of the material that enclosed the fossil. This of course assumes at least two things. First it assumes that the. material encasing the fossil can be dated accurately. Second it assumes that the material encasing the fossil had its beginning at the time it encased the fossil. .. It is past history a one time event. Scientists can only observe in the present and speculate about the past.
The first assumption that the material entombing a fossil can be dated is a belief but can not be thoroughly verified in the lab as a repeatable scientific experiment. If I present a piece of sandstone or mudstone to a laboratory and dont tell them where i found it, they will tell me they will tell you that there are no well accepted lab test that can be performed on that rock to determine its age. What few test that exist are very limited in scope and accuracy. So how do scientists determine the age of this material? They can not be based on any lab test, so they resort to asking what geologic formation it was found in and tell you the material age as the age of the geologic formation. For example they may tell you since it is found in glacial till (rubble left by passing glacier) it must be 10-100,000 years old since it was left there. They did not tell you how old the sandstone was just when it was left behind. They have in fact given you age 3 or age 2 described above. Some minerals such as zircon can be formed during a volcanic event and scientists measure the amount of argon trapped inside the zircon to try to measure now old the zircon crystal is. This determination of zircon age for example is not accepted by many scientists as reliable. Other radiometric ages calculated by uranium dating are also now suspect as haveing serious problems. With these uranium dating methods they can not be verified by any other method than another radioactive dating method. Lately radioactive decay rates have been determined not to be constant always which makes the whole method subject to doubt. Radioactive Decay
AGE DETERMINING METHODS:Age determining methods can be grouped into direct and indirect methods:
INDIRECT METHODS: When you can not perform a direct measurement of the age of a speciman you can guess at its age by examining where it was found. Measuring the material surrounding the buried bone or speculating on when the material covered the bone are examples of indirect methods . Indirect methods are inferior and often quite misleading. See Radioactive Decay
DIRECT METHODS: These methods measure some characteristic of the actual material itself. Take the bone and date it. Don't date the surrounding rocks or speculate on when the rocks covered up the bone. For example carbon 14 dating measures radio active carbon 14 and from this it calculates how long ago since the organic speciman say animal bone died. When an animal dies it stops taking in carbon 14 into its bones and the carbon 14 that is already there start to decay into normal carbon 12.
BEST WAY TO DATE A FOSSIL:The very best way to date a fossil is to date the actual material, dont date the actual entombing material, dont date the supposed age when the entombing material buried the fossil, dont date for the geologic material it was found in. Lets take a hypothetical example. A paleontologist comes across a group of dinosaur eggs in the Gobi desert laying exposed out in the open. The very best way to directly date the eggs would be to radiocarbon date the eggs. But the paleontologist believes that every last dinosaur in existance died out 65 million years ago and none survived beyond that. Therefore the eggs have to be 65 million years old or more so he never tries to carbon date the eggs. He may also assume that the organic (carbon containing) material has all been replaced with inorganic material so there would never be any carbon left in the eggs. So how does he come up with a date for the dinosaur? He looks at the rocks, mineral, it was found among. He consults his references and sees that that is called the xyz formation formed xx million years ago Therefore he gives the age of the fossil as the age of the formation. I hope you can see the shaky assumptions made in this process. What he should have done is first determine if there is carbon present in the fossil. If there is he should carbon date the fossil. All radio carbon dates are done by licensed labs, follow strict rules to avoid contaminated material and record every date for every material tested. No other dating method comes close to this in its accuracy and usablility. Another important reason for this being the best methond is that it is independantly verifiable by other means. When our group took unmineralized dinosaur bones and tested them by the radiocarbon dating method they came out to be thousands of years old. There the phrase used in the movie Jurassic Park....65 Million years ago....is not true for the bones the paleogroup tested. See Carbon 14 Dating
CARBON DATING INDEPENDANTLY VERIFIABLE METHOD:
There is a simple way to verify that carbon dating is accurate. Take a core sample from a 4000 year old Bristlecone pine tree. Count back 4000 rings and take a sample of that ring material. Then carbon date it. The carbon 14 date and the tree ring dates will agree quite well. For very old dates >10,000 years we must extrapolate and make certain assumptions not as important with younger dates. Other radioactive dating methods depend on other radioactive dating methods to provide a cross check. All other radioactive methods are prone to much doubt. So why use them when carbon dating is the most accurate. If a paleontologist comes across any dinosaur bone they immediately write it off as 65 million years or older.
- The picture at the top was taken in the Morrison formation in Colorado from a recent road cut. It exposed a buried petrified log and branches. The curious thing was the center mineralized material was surrounded by a 1/4 inch thick layer of carbon in the form of a low grade coal. The carbon was tightly bonded to the mineralized material. What happened? Did the tree bark turn to coal under heat and pressure while the woody material absorbed hot mineral soaked water? It is quite common for mineralized fossils to have a layer of carbon on them. Do you have some knowledge of the subject you would like to share?  Email us.
- A careful examination of the picture will show that the dark black to the bottom and left is carbon and not a shadow of the mineralized material as some suggested after seeing the picture. We also have other photographic views as evidence.
- Whenever available our Paleo Group collects this carbon and has it carbon dated. Surprising to many people is that this carbon always turns out to be dateable implying that the carbon and the organism from which the carbon came is thousands not millions of years old!
- Earth History and Plate Tectonics an introduction to historical geology by Carl Seylert and Leslie Sirkin 1973 Lcc card number 72-8262
- See RadioCarbon Journals published monthly from 1960's through the present and available at any university geological library.
- How do Paleontologists know how old a fossil is http://www.ucmp.berkeley.edu/faq.php#dating