The Chronostratigraphy tree shows the names of geologic time in a nested format. Erathem/Era, System/Period, Series/Epoch, Sub-System/Period and Stage/Age are formal divisions. Sub-Series/Epoch was added to allow for handling data from historic databases.
The Chronostrat tree shows the relationships of these divisions. Expanding the Cenozoic (an Erathem/Era), we see it contains 3 Systems/Periods- Neogene, Paleogene and Quaternary. These Periods can be expanded to show which Series/Epochs and Stages/Ages are associated with it.
Entries in this tree control the available options in the Chronostrat and Biostrat fields in the Paleo Context section of the main data entry form.