For paleoclimate or geologic data, <Paleo_Temporal_Coverage> is the length of time represented by the data collected. <Paleo_Temporal_Coverage> should be used when the data spans time frames earlier than yyyy-mm-dd = 0001-01-01.

<Paleo_Start_Date> is the number of years furthest back in time including units Ga, Ma, ka or ybp.
<Paleo_Stop_Date> is the number of years closest to the present time including units Ga, Ma, ka or ybp.
<Chronostratigraphic_Unit> is a controlled keyword describing Geologic Time of the form:

• <Eon> is the primary and largest division of geologic time.  Limits correspond with major, global crustal events, changes in sea level and/or climate, or biotic changes.
• <Era> is a major division of geological time, tens or hundreds of millions of years long, usually distinguished by significant changes in the plant and animal kingdoms; also used to denote later archaeological periods, such as the prehistoric era. Five geologic eras have been established: Archeozoic [before 2500 million years ago (Ma)], Proterozoic (2500 to 570 Ma), Paleozoic (570 Ma to ca. 250 Ma), Mesozoic (ca. 250 to ca. 70 Ma), and Cenozoic (since ca. 70 Ma). All eras are divided into at least two geologic periods.
• <Period> is the secondary division of geologic time, delimited by moderate but usually global crustal events, changes in sea level and/or climate, or biotic changes, sometimes in a relatively localized area. Two or more periods are required to make up a geologic era, and each period comprises two or more geologic epochs.
• <Epoch> is the third-order division of geologic time, delimited by partial withdrawal of the sea from land masses and by gentle crustal disturbances in localized areas.  Two or more epochs are required to make up a geologic period, and, in turn, two or more periods are needed to constitute a geologic era.

• <Stage> is a smaller unit of time. An Epoch usually has 1 or more Stages.