Epochs and ages?

I've just uploaded a PDF featuring the Geologic Time Periods of the earth, from the earliest, the Hadean (when the earth was still a molten ball of rock) to the present day, the Quaternary Period.

http://volcanoseven.com/DinosaurDiggersClub/Downloads/GeologicTimePeriods.pdf

The Quaternary Period, our period, is divided into two epochs, the Pleistocene and the Holocene.

In the science of geochronology, an epoch is a subdivision of the geologic timescale.  It is longer than an "age" and shorter than a "period".

We are currently living in the Holocene Epoch of the Quaternary Period.

Rock layers deposited during an epoch are called a "series". "Series" are subdivisions of the stratigraphic column that, like epochs, are subdivisions of the geologic timescale. 

"Series" are futher subdivided into "stages."

Epochs are normally separated by, and usually named referring to the y significant changes in the rock layers to which they correspond.

Epochs are most commonly used for the younger Cenozoic Era. This is because this era has a great collection of fossils has been found and paleontologists have more detailed knowledge of the events that occurred during those times.

Since less fossil evidence exists for the other eras and eons, it is difficult to form a clearer view of those time periods, and the term epoch is therefore not used.