In older sections , there is insufficient fossil record or well preserved sections to identify the key events necessary for a GSSP so GSSAs are defined based on fixed dates .
In contrast to GSSAs , GSSPs are based on important events and transitions within a particular stratigraphic section .
In older sections , there is insufficient fossil record or well preserved sections to identify the key events necessary for a GSSPs so GSSAs are defined based on fixed dates .
In contrast to GSSAs , GSSPs are based on important events and transitions within a particular stratigraphic section .