C'mon, post it anyway.
You know you want to!
Well, it'll be of no help regarding YEC scammers and their blind followers, but since there's always a chance that it will help cure or ease the symptoms of someone's religion-induced ignorance...
Follow the linkie thingie below to the geological time scale.
http://www.geosociety.org/science/timescale/timescl.pdf
Before we move on, please note its not in scale. Precambrian is the largest division (~4Gy) but is relegated to a single collumn, same space used by the pesky Cenozoic, a mere 65My (0.065Gy) time span.
Now, note the number of "-ians" each larger unit ("Eon") is divided and how many "-ians" subdivide the Periods and Epochs.
It all begun back in the XVII century, when people realized that not only (sedimentary) rock beds could be followed along large horizontal distances, but also that as you move upwards or downwards across a cliff, the fossil contents of rocks change and in some cases, quite fast and dramatically. Some fossils had widespread vertical span while others had very short ones, say, like restricted to a single thin bed. Then they noticed parts of a given fossil assemblage say, from a limestone in England could be present at a sandstone in Portugal, across a large horizontal distance and that at these two assemblages, some of those fossils with a small vertical span were included. This meant the limestone from England and the sandstone from Portugal were deposited at the same time, when that particular species of critters lived. That species had a large habitat area but lived for a short (in human terms) time. Good for correlation. Tiny critters such as foramnifera, dinoflagelates, ostracods and diatoms are excellent for such purpose, allowing very narrow definitions of time intervals.
So, most of those "whateverthefwordians" divisions and subdivisions actually represent fossil assemblages of different sizes distributed through time. No wonder some of those dividions will correspond to mass extinction events. Now, Mr. Rockhound found a given fossil assemblage at a given rock layer at a given site. Among them, a number are from unknown species, but since the assemblage includes other known critters, wich we know are restricted to the Cenomanian time division, then Mr. Rockhound can conclude the unknown fossils and the rocks hosting them are from that particular time.
Cool, aint it? But wait, this is simply a relative dating, we still don't know how many years ago those critters lived. So how can Mr. Rockhound know when those sediments were deposited?
Mr. Rockhound can do this because before him, other people working at several other parts of the world located volcanic rocks interbedded within sediments containing fossils wich are restricted to the geologic time division called Cenomanian. They not only found them - they also assayed minerals which compose those volcanic rocks, looking for unstable isotopes and the products of their decay. Based on the relative concentrations of parent and daughter isotopes and the decay constant, they managed to calculate the absolute ages of crystallization of those voclanic rocks. This allowed Mr. Rockhound to conclude the unknown fossils date back from the Cenomanian, a time slice ranging from 100 to 93.9My ago. This will allow geologists and paleontologists to establish absolute dates for a sedimentary rock based on their fossil contents.
Suck it up, creationist scammers.