Tiny fossils unlock clues to Earth's climate half a billion years ago

originally posted by: Mach2
You do realize that the dating was a large part if their conclusion as it relates to the Cambrian explosion?

How else do you establish a correlation between historical events, besides dating?

It can be done without knowing exact dates. For example if a layer is identified as a "Cambrian Explosion" layer, and if a group of researchers takes samples from that same layer and says their results are related to the Cambrian explosion, it would be hard to argue with saying there's a correlation regardless of how old the layer actually is.

The exact dates really aren't that critical, when examining the fossil record, where it's more important to know that deeper layers are usually older, the fossil record changes over time (depth in a given record), and similar fossil records can be found with index fossils which correlate timelines without necessarily having precise dates.

Index Fossil

Index fossil, any animal or plant preserved in the rock record of the Earth that is characteristic of a particular span of geologic time or environment. A useful index fossil must be distinctive or easily recognizable, abundant, and have a wide geographic distribution and a short range through time. Index fossils are the basis for defining boundaries in the geologic time scale and for the correlation of strata. In marine strata, index fossils that are commonly used include the single-celled Protista with hard body parts and larger forms such as ammonoids.

So they compare fossil records with other fossil records and find unique signatures that correlate the fossils in time, like the index fossils. There is some uncertainty in the age estimate of the index fossils, but paleontologists are fairly certain they existed at the same time, whatever their exact age, and this allows them to make correlations they believe are reliable, without necessarily knowing exact dates. I hope that answers your question.