Macrostrat is more than an overlay of maps and columns. Its value comes from links between records of different kinds, which let information flow from one to another: a map unit gains a precise age from a column, a column unit gains a detailed description from a map, a fossil or a geochemical sample is placed in its stratigraphic context. Together these links are the identity-carrying elements of a geologic framework model.
Nearly all links pass through the Geologic lexicon, above all through stratigraphic names, constrained by location and age.
Map legends to the lexicon
When a map is ingested, each legend entry is matched against Macrostrat's vocabularies (see Map ingestion):
- Stratigraphic names are looked for in the legend's stratigraphic name field, and also in the unit name, description and comments. A candidate name counts only if it is plausible where the map is: Macrostrat records whether a match is supported by a column unit at that location, by an adjacent column, by the footprint where the name is known to occur, or by nothing beyond the name itself. This is what keeps the Admiral Formation of the United States from being confused with the unrelated Admiral Formation of Australia.
- Column units are matched by name, space and time: a map unit is linked to the units of the columns beneath it that carry the same name and overlap it in age.
- Lithologies named in the legend are matched to Macrostrat's lithology terms.
The matches are then rolled up onto each legend entry: the stratigraphic names, concepts, column units and lithologies it corresponds to, a best age that combines the map's stated intervals with the ages of linked column units, and a display color. Each match records the basis on which it was made, so links can be reviewed and their strength weighed.
Columns and maps
Linking map units to column units runs in both directions. Map units inherit the precise ages of the Age model, so a polygon labelled only by period gains ages from the units it matches. Column units, in turn, gain the extent and detailed lithologic descriptions recorded on maps.
Outside records
Records from other data systems attach to Macrostrat units through the same strategies:
- Fossil collections from the Paleobiology Database are matched to column units using their stratigraphic names and locations, connecting the rock and fossil records.
- Geochemical samples, for example from the Sedimentary Geochemistry and Paleoenvironments Project (SGP), are matched to units so that each measurement carries its stratigraphic and age context.
- Ocean-drilling cores enter as columns of their own (see Stratigraphic columns).
- Literature: descriptions of units extracted from geologic papers are linked to the lexicon through the Knowledge graph.
Each integration adds a new kind of data to the framework, and a new way to check it: a sample that does not fit the age of the unit it matches points to a problem in one record or the other.
