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Discussion: Geologic Time Scale

Also see GeologicTime


Issues and change requests

Readers are invited to add issues to this table - select [Edit Table] below. It is not mandatory to enter a solution, but change requests are more likely to be implemented if a concrete solution is proposed.

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# By Timestamp Component(s) Description of issue Proposed solution Resolution
1 SimonCox 03 May 2004 xmml:TimeOrdinalEra xmml:GeologicalTimeScale Different subdivisions of eras may be used in different regions. The eras may then be composed into Systems in various ways. 1. Add domainOfValidity property to xmml:TimeOrdinalEra
2. Add support for TimeOrdinalEras to be recorded as top-level objects with identifiers in xmml:GeologicalTimeScale, to enable their re-use by-reference
2. era properties added to GTS

Discussion

GeologicTime package

  • Add GeologicEvent class (subtype of Event in OM:event package), with eventAge, eventEnvironment, and eventProcess attributes (after NADM, to give content for Genesis). Stratigraphic event is subtyped from GeologicEvent

Gssp diagram

  • Remove target association from DateMeasurement to Stratigraphic point; a DateMeasurement is always based on one or more specimens (more than one in the case of various isochron methods) (an Observation has a single featureOfInterest, so this is probably better modelled as a specimen-collection ... -- SimonCox - 29 Sep 2005).
  • Remove association from GeochronSpecimen to Site; this association is inherited from association of Specimen to Site. (though it is difficult to show such inherited relations on the diagram ... -- SimonCox - 29 Sep 2005)

Correlations diagram:

  • Deprecate StratigraphicUnit class, doesn’t fit in standard geologic unit hierarchy. StratigraphicSection is attribute of AbstractGeologicUnit, devolve constraints on when it makes sense to application logic
  • Introduce text constraint that the stratigraphic section that contains the GeochronologicEra stratotype must sample the ChronostratigraphicUnit that fills the manifestedBy link to GeochronologicEra
  • Model StratigraphicPoint (SP) (sample) association to GeologicContact (container), so the association of StratigraphicPoint to StratigraphicBoundary is inherited, and not shown in this diagram. Add text constraint stating that StratigraphicPoint that is prototype for StratigraphicEvent must sample the ChronostratigraphicBoundary (CB) (as subtype of GeologicContact) that is the manifestedBy attribute of the Stratigraphic event. SP is a specialization of Station. However, SP has particular status in the context of stratigraphy. I doubt if we would need a superclass between Station and SP, which would correlate with contact as a superclass of CB. -- SimonCox - 20 Oct 2005
  • GeologicEvent is parent type for StratigraphicEvent
  • Need definition of chemostratigraphic unit.

Dating diagram:

  • StratigraphicDateEstimate changed from kind of TimeInstant to kind of AbstractObservation. The TimeInstant that is the position attribute of TimeOrdinalEra boundary is the result of the StratigraphicDateEstimate observation. One or more DateMeasurements are relatedObservations used to determine a StratigraphicDateEstimate; the estimation procedure (linear extrapolation, averaging, etc.) is the procedure for the observation. (follows pattern discussed under ObservationPropertySpecification to allow both observation and feature views of data) (disagree - SDE should remain a specialization of TimeInstant; this retains the link to a general model for TORS where the boundarys have positions which are givan by TimeInstants - the related DateMeasurement(s) is metadata, obtained by following the observationalBasis association ... -- SimonCox - 29 Sep 2005)

Dating SMR diagram

  • This is an alternate view of relationship of dated specimens to a StratigraphicDateEstimate associated with a TimeOrdinalEra Boundary.
  • StratigraphicSection is modeled as an ordered collection of StratigraphicSectionIntervals. Each interval may have a StratigraphicPoint defined as the baseOf the interval. (In principle both profile composition and profiles containing stations is already allowed for via the "member" association from Site to Site. My feeling was that the "hostSection" association needed to be promoted, since it appears in the ICS guidelines, but perhaps the "containedPoint" association end can be dropped in favour of "member". Not clear to me that a two-layer hierarchy (Section/Interval) is useful, unless Intervals are atomic in some way, and that seems dangerous - you can always subdivide, right? Also, my understanding is that the ends of a section are not necessarily special, so I just allowed it to inherit the begin and end Points from Profile. -- SimonCox - 29 Sep 2005)
  • GeochronSpecimens are located in a StratigraphicSectionInterval.
  • The target of a StratigraphicDateEstimate is a StratigraphicPoint. (No - the SDE provides the (temporal) position of a Boundary. The StratigraphicPoint is the stratotype for the Boundary. Measurements are made on specimens correlated with the StratigraphicPoint. Measurements are the observationalBasis for the SDE ... -- SimonCox - 29 Sep 2005)
  • The target of a DateMeasurement observation is a GeochronSpecimen. Geologically this corresponds the situation described in published GSSP definitions in which the stratotype section is subdivided very finely—commonly into individual beds. Establishing the time position of the actual geochronBoundary is typically based on one or more dates from samples of particular beds with known stratigraphic position relative to the GSSP point of interest. The relative position of the samples with respect to the microstratigraphy around the boundary is key information for determining the reliability of the boundary time position determination.

GeoTime diagram:

  • Move ChronostratigraphicUnit, LithostratigraphicUnit, BiostratigraphicUnit, ChronostratigraphicBoundary, LithostratigraphicBoundary, StratigraphicBoundary, StratigraphicPoint, StratigraphicSection to GeologicUnit application schema. (though arguably the stratigraphy components might be treated as specializations of the "generic" geologic unit components, and live in their own package ...? -- SimonCox - 29 Sep 2005)

  • Deprecate StratigraphicUnit.
Topic revision: r4 - 15 Oct 2010, UnknownUser
 

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