#stratigraphic boundaries table

1	name:		name of the stratigraphic boundary, ID
2	age:			age of the stratigraphic boundary, in Ma, measured
3	error:		absolute error of the age, in Ma
4	def:			definition of the stratigraphic boundary
5	GSSP:		Global Stratotype and Point
6	within:		ID of the ICS unit (usually stage) which the stratigraphic boundary falls in
7	proportion:	relative proportion of the time span of the unit defined by 'within', from its base to the boundary defined by 'name'
8	calculated:	age calculated from the 'proportion' and 'within' fields