Thank you for the informative thread, Dub-Dub! And for that detailed geologic Time Chart, eta! I rarely see thew chart broken down into the smaller sub-divisions. And, usally, being more concerned with the organic aspects of the geologic time periods most paleontological charts simply designate everything before the trilobite fossil record as Pre-Cambrian.

However, this discussion reminded me of a post I've been meaning to make about the current, and increasingly-proliferous use of the term dead dinosaurs as a kind of euphemism in referring to oil. First of all, the bulk of the oil deposits were formed during the Carboniferous period, almost 50 million years before the appearance of the dnosaurs, from the remains of decayed plant life, the lush tropical forests, including giant ferns, that covered the earth at that time on what was mostly an expansive swamp. It is estimated that at least 70% of all extant oil deposits were created at this time. There were amphibians and sea life, and some reptiles did begin to appear at the end of this period, and *some of their remains may account for a minisule portion of the oil deposits of this period, but the bulk were formed from decaying flora (including alagae). Oil was formed from the organic matter that collected at the bottom of the swamps and sea (and other bodies of water), and coal was formed from plants that died on land. But "dead dinosaurs" to describe oil seems to have been adopted by the print and broadcast media, and it's use is gaining much frequency. It probably started when some ill-educated reporter decided it made for a cute and nifty turn of phrase (akin to "dead presidents" for US money), and some clueless editor let it go. But for a phrase of such geologic and scientific inaccuracy to be gaining popularity (and seeing as how that most people don't bother to study or delve into paleontologic or geologic data in this post-literate society), the adoption of this phrase will likely turn the misinformation that oil is "dead dinosaurs" into a "scientific" fact in most people's minds.

Here's the clearest breakdown of the formation of oil I could find:

http://www.gcsechemistry.com/o1.htm

And here's a bit more extensive look that attributes most of the oil deposits to the Carboniferous period:

http://www.energyquest.ca.gov/story/chapter08.html

A much smaller percentage of oil depostis is said to have formed later, right on into the Mesozoic era. So there is probably a small percentage that came from *some remains of pleisiosaurs and other sea dinosaurs. So the coiners and users can point to that to rescue the use of their phrase as *partially accurate. But it is *largely inaccurate.

And to say that oil is "dead dinosaurs" is just wrong.