Fossils are preserved remains of once-living organisms. They are usually formed when mineral-rich water makes its way into the organism's body. The minerals within the water aggregate within the spaces within the body and solidify. Once the organism's tissues have dissolved away, all that is left behind is a rock mold of the creature's shape.
Biblical creationists (such as Gary E. Parker (creationist pastor) see most of the fossil record as a record of the burial of creatures during Noah's Flood, wherein the creatures dwelling on the seafloor were buried first, then other marine creatures, amphibians, slow-moving reptiles, faster-moving mammals and birds, and finally, humans, the most able to escape the floodwaters the longest.
Atheistic paleontologists, geologists and evolutionists believe that the fossil record is a record of the evolution of life on Earth, with the oldest fossils, those of the earliest and simplest creatures, being at the base of the fossil record, and more recent and more advanced creatures higher up. This assumes no folding or bending of the geological strata.
Fossils are usually not able to be directly dated by any radiometric dating method. Carbon dating can only be used if carbon remains, which is not the case with most fossils. Most other dating methods work on volcanic rock, whereas most fossils are contained in sedimentary rock.
Instead, fossils are often dated by evolutionists according to ages that have already been assigned to various rock layers. Radiometric dating may be used to narrow this down, by dating available volcanic layers above and/or below the fossil-containing layer. However, radiometric dating is not a reliable method of dating fossils, and is rejected by creationary scientists.
Organic matter in fossils
Organic matter has been found in some fossils. In 1997 Dr. Mary Schweitzer of Montana State University reported finding red blood cells inside a Tyrannosaurus rex bone. And in 2005 the same scientist reported finding blood vessels that were still "soft and stretchy" in another Tyrannosaurus rex bone claimed to be 65 million years old.
It is well-accepted that biological matter cannot last anything like 65 million years. 
Creationists argue that this constitutes evidence that the fossils are not that old., whilst evolutionists argue either that this constitutes evidence that it can last that long, or that the apparent blood cells (which passed several tests for blood) were not really blood cells.
- Catchpoole, David, and Sarfati, Jonathan, ‘Schweitzer’s Dangerous Discovery’, 19 July 2006 (Creation Ministries International).
- Wieland, Carl, Sensational dinosaur blood report!, Creation 19(4):42–43, September 1997.
- Wieland, Carl, Still soft and stretchy 25 March 2005 (Creation Ministries International).
- Wieland, Carl, Squirming at the Squishosaur 16 May 2005 (Creation Ministries International)
- Wile, Jay L. Exploring Creation With Biology. Apologia Educational Ministries, Inc. 1998
- Wile, 1998
- What does the fossil record teach us about evolution?, Christian Answers, accessed 2009-05-03
- Books by Gary E. Parker, May be confused with another Gary E. Parker (Christian author), a Christian author.
- Web Geological Time Machine, University of California - Berkeley, Museum of Paleontology, accessed 2009-05-03
- Wieland, 1997.
- Wieland, 2005.
- Schweitzer herself expressed surprise that the blood cells could last that long:
It was exactly like looking at a slice of modern bone’. But, of course, I couldn’t believe it. I said to the lab technician: ‘The bones, after all, are 65 million years old. How could blood cells survive that long? —Wieland, 2005a
I just got goose bumps, because everyone knows these things don’t last for 65 million years.—Catchpoole and Sarfati
- Schweitzer had difficulties getting her research published because others didn't believe that blood cells could last that long. One reviewer didn't believe her, saying that what she was finding was not possible. Schweitzer commented:
If you take a blood sample, and you stick it on a shelf, you have nothing recognizable in about a week, ... So why would there be anything left in dinosaurs? —Catchpoole and Sarfati
- The reason that they won't last that long is known:
As Dr Aw Swee Eng (former professor of biochemistry, Singapore University) confirmed to me personally, complex biomolecules such as proteins are thermodynamically destined to fall apart eventually (from the random motion of molecules) even were they to be protected from all outside influences such as air, moisture, bacteria, etc. —Wieland, 2005b