Well if a dinosaur bone has been fossilized at all . . . with calcium carbonate replacing organic bone material . . . you wouldn't be dating the dinosaur's carbon alone, you'd be dating the intruded carbon as well.
Actually, from what I understand, they were pretty careful to look at different sections of the bones, some that was collagen -- no petrification- and some that was at least partly petrified, and both sections showed up with carbon 14. Here is an extract from the website
http://www.sciencevsevolution.org/Holzschuh.htm.
"Summary of supporting evidence for accuracy and reliability for the significant presence of C-14 in dinosaur bones and therefore young RC ages
Short Summary: The most obvious scientific justification for accepting the RC ages for dinosaurs in the thousands of years is the concordance of RC ages between bone collagen and bone bio-apatite. If the date for a particular specimen is questionable or controversial RC dating labs recommend that the C-14 testing be repeated on several fractions using AMS and/or on larger samples using both AMS and conventional C-14 methods. We have made such repetitive tests and we obtain dates in the 22,000-33,000 range for dinosaur bones each time a different dinosaur bone or portion of the bone was tested for C-14. For example: Triceratops collagen was 30,080 ± 200 using AMS and 33,830 +2910/-1960 using the conventional method with a large sample (See Table 1).
Collagen and soft tissue were detected in dinosaur bones which is "
exceptional preservation" and should not be there after so long a time period as 65 M years.39
Harvard scientists have confirmed that proteins from the collagen detected in the famous T-Rex (2005) was definitely collagen as determined by sequencing the fraction. Thus there is no reason to believe that what our lab has extracted is NOT collagen.40
Collagen, inside Triceratops and Hadrosaur femur bones was tested successfully for C-14. Collagen from a second Triceratops femur bone from Montana likewise contained collagen and C-14 in 2008. 41
Bio-apatite was also successfully tested for AMS C-14 after careful pretreatment w/HAc (acetic acid) to remove possible old and young CaCO3 contamination.
Bone collagen and bone bioapatite and/or total bone organics gave concordant C-14 dates after careful extraction and purification of those fractions as noted in Table 1.
W. Libby, who received the Nobel Prize for his C-14 research showed there is no possible way that bone collagen can be contaminated.42
T. Stafford's data has shown that weak acid insoluble collagen and total Carbon, HAc and alkali treated Domebo Mammoth bone agreed within about 5% of the most expensive purification treatment methods for obtaining the oldest RC ages. 43
Collagen content for the Triceratops femur was same as that for Kennewick man's first metatarsal, namely 0.3% as shown by F. P. McManamon. 44 The former gave an RC age of 30,890 ± 200, the latter 8,410 ± 40 years BP. Collagen was extracted from the dinosaur femur and purified by the widely used "Modified Longin method" (weak acid insoluble collagen method).
Crushed bone containing bio-apatite was treated with mild HAc (acetic acid) to remove surficial carbonates that could give false younger or older ages before the final dilute HCl treatment to evolve CO2 for testing. Bio-apatite is calcium carbonate that replaces bone calcium phosphate during the life of the dinosaur or other animal.
In essence RC dating methods could give major false old RC ages rather than false young RC ages because labs have eliminated sources of major young contamination. Also, we really don't know the actual C-14 concentration during the period when dinosaurs and some magafauna lived together. In other words the ratio of formation of cosmogenic C-14 is not known in the past. But, major young contamination is most unlikely. Why? RC laboratories have mastered the techniques of removing young or old humic acids with alkaline pre-treatments or acetic acid pre-treatments under vacuum for young or old surficial calcium carbonates. So, young contamination is most unlikely for dinosaur and megafauna bones.
Of course the most important point or results of this research is that there are measurable amounts of C-14 in samples supposedly free of C14. Calculated RC dates are not absolute dates but they do correspond to the official C14 procedures as noted above. It can then be argued that it is far more probable that the atmosphere could have been much more depleted of C-14 content 1000's of years ago compared to today's content. Why? Because the protective quality of a much stronger magnetic field strength 1000's of years ago could have caused a much lower rate of C-14 formation compared to the current rate. In other words a half life of 1400 years implies a stronger magnetic field 1000's of years ago which would have inhibited the formation of C-14 in the upper atmosphere; this could make the dinosaurs and many megafauna seem much older than reality."
