Add instructions for geologic dates

[laijasmine]

Special guidance for:

model output

• future dates

geologic dates

alternativeTimeScale/timeScaleAgeEstimate

description: Either an absolute date or a relative age name describing an
                    event or period in an alternative time scale such as the Geologic Time
                    Scale.

example: For example, '300 Ma' (300 million years before present) is a
                    Geologic_Age_Estimate based on the Absolute Geologic_Time_Scale, 'C28r' is a
                    chron name from the Geomagnetic Polarity Time Scale, and 'Maastrichtian' and
                    'Jurassic' are names from the International Geological Time Scale. Since
                    different relative geologic time scales are often not aligned, multiple geologic
                    dates may need to be specified. For example, the Geomagnetic Polarity Time Scale
                    chron 'C29r', at the K/T boundary lies in both the 'Maastrichtian' and the
                    'Danian' stages from the International Geological Time Scale, thus if you were
                    documenting this event using the International Geological Time Scale, both
                    'Maastrichtian' and 'Danian' should be included here.

alternativeTimeScale/timeScaleName

summary: Name of a recognized alternative time scale.
description: Name of a recognized alternative time scale. This includes
                    'Absolute' as the name of the time scale for measuring geologic dates before the
                    present and names of geologic dating systems that are arrangements of symbols or
                    names in order of relative geologic time.

example: 'Absolute', 'Geomagnetic Polarity Time Scale', 'International
                    Geological Time Scale', 'Oxygen-Isotope'

alternativeTimeScale/timeScaleAgeExplanation alternativeTimeScale/timeScaleAgeUncertainty alternativeTimeScale/timeScaleCitation